Targeting the Transcription Factor c-Jun in Cervical Cancer Cells
Grace Pei Chien Yee
Centre for Vascular Research, School of Medical Sciences, University of New South Wales, Australia
A thesis submitted to the University of New South Wales for the degree of Doctor of Philosophy (PhD) September 2013
ORIGINALITY STATEMENT
‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.’
Signed ……………………………………………......
Date ……………………………………………......
i
ABSTRACT
Despite the development of vaccines for human papillomaviruses (HPV) in cervical cancer and other efforts to improve therapy, deaths still average 275,000 annually worldwide, with most women succumbing to recurrent or metastatic disease. The c-Jun oncogene is a subunit of the activating protein-1 (AP-1) transcription factor and is strongly expressed in cervical cancer, regulating the expression of HPV16 and 18 genes.
AP-1 plays a major role in cell growth, migration and apoptosis in many cell types. This work examined the role of c-Jun in modulating cervical cancer cell line (HeLa) proliferation, migration, apoptosis, invasion, susceptibility to cisplatin and the underlying mechanisms.
c-Jun protein and mRNA levels were reduced by c-Jun siRNA. c-Jun silencing inhibited cell proliferation. Significantly, c-Jun suppression dramatically reduced HeLa migration and invasion and targeted down-regulation of cyclooxygenase-2 (Cox-2), intracellular adhesion molecule 1 ( ICAM-1), matrix metalloproteinases (MMP)-1 and -9 genes highly expressed in cervical cancer and associated with metastatic growth. siRNA knockdown of Cox-2 also reduced HeLa migration and invasion as well as MMP-1 expression suggesting an intermediary link. In transfected cells over-expressing c-Jun, cell proliferation was not significantly increased but cell invasiveness was markedly enhanced in parallel with enhanced Cox-2 and MMP-1 expression as well as MMP-2 activity. Modulation of c-Jun expression did not synergistically combine with cisplatin to increase the susceptibility of HeLa cells to apoptosis or cell cycle disruption. In vivo, c-Jun siRNA pre-transfected HeLa-luc solid tumor growth and size were significantly retarded compared to the control groups. siRNA targeting another transcription factor,
ii
Early Growth Response-1 (Egr-1) demonstrated significant inhibition of HeLa cell migration and invasion as well as reduced MMP-1 expression and MMP-9 activity, with concomitant blockade of c-Jun and Cox-2 expression, suggesting pivotal link of these genes to HeLa cell migration and invasion.
Reduced invasion potential of HeLa cells after c-Jun, Egr-1 and Cox-2 knockdown, respectively suggests the potential of these genes as targets in treatment of metastatic and recurrent cervical cancer. Data also suggest a m echanism involving c-Jun, Egr-1 and Cox-2 in the regulation of MMP-1.
iii
PUBLICATIONS AND CONFERENCE PRESENTATIONS
Publications
Grace Pei Chien Yee, Paul de Souza, Levon M. Khachigian. Current and Potential Treatments for Cervical Cancer. Current Cancer Drug Targets. 2013 Feb;13(2):205- 20
Grace Pei Chien Yee, Paul L. De Souza, and Levon M. Khachigian. Reducing invasion potential of cervical cancer cells via targeted knockdown of c-Jun. ASCO MEETING ABSTRACTS Jun 17, 2013:e22005
Conference Presentations
1. May 2013, “c-Jun silencing reduces the invasion potential of cervical cancer cells”, poster in 2nd Lowy Cancer Symposium, Sydney.
2. September 2012, “Silencing the transcription factor c-Jun in cervical cancer”, oral presentation in Centre for Vascular Research Symposium, Sydney.
3. September 2012, “Silencing the transcription factor c-Jun in cervical cancer cells”, poster in Australian Vascular Biology Society Scientific Meeting, Queensland.
4. June 2012, “Targeting the transcription factor c-Jun in cervical cancer cells”, poster in the Australian Society for Medical Research, 20th NSW Scientific Meeting, Sydney.
Award
Runner-up for best poster presentation, “Silencing the transcription factor c-Jun in cervical cancer cells”, poster in Australian Vascular Biology Society Scientific Meeting, Queensland, September 2012.
iv
ACKNOWLEDGEMENTS
I would like to thank my supervisor, Professor Levon Khachigian and co-supervisor, Professor Paul de Souza, for their guidance and support throughout my PhD studies.
I would also like to thank all past and present members of the Khachigian lab, especially to Dr. Fernando Santiago, for mentoring me at the beginning of my PhD studies; to Dr. Lucinda McRobb, for peer reviewing my thesis and intellectual contribution to my work; to Dr. Leonel Prado-Lourenco, for his guidance in animal work and always willing to answer my many questions; and to Margaret, for her moral support especially during the beginning of my motherhood. Thank you again for all the support and encouragement particularly during my hard time.
I would also like to thank those who helped me with the work related to this thesis, especially to Professor Wendy Jessup from ANZAC Research Institute, for her kind gift of HeLa cells; Dr Maaike Kockx from ANZAC Research Institute, for her advice and positive control for zymography; and to Fei Shang from the Histology and Microscopy Unit, for her help with immunohistochemistry.
Last but not least, I would like to thank my dearest family: Dad, Seng Hoy, Mum, Lee Lee, Alex and Richard for always giving me endless love and support throughout my life; to my husband, Henry, for his great understanding and effort in sharing the household chores throughout my PhD; to my daughter, Claire, for being a good girl most of the time. I love you all.
v
LIST OF FIGURES
Figure 1.1: The cervical transformation zone ------4
Figure 1.2: Schematic image of HPV 16 genome and integration into host
chromosome ------9
Figure 1.3: The HPV life cycle ------10
Figure 1.4: HPV E6 and E7 regulated pathways and genes ------12
Figure 1.5: Current treatments for cervical cancer ------18
Figure 1.6: Potential future therapy for cervical cancer ------22
Figure 1.7: Schematic representation of the antigene or antisense approach ---- 26
Figure 1.8: Schematic representation of the ribozyme or DNAzyme approach -- 29
Figure 1.9: Schematic representation of the aptamer approach ------30
Figure 1.10: Schematic representation of the siRNA approach ------31
Figure 1.11: Mechanisms which enable rapid accumulation of IEGs ------44
Figure 1.12: Formation of AP-1 transcription factor from c-Jun and c-Fos
heterodimerization ------46
Figure1.13: Regulation of c-Jun transcriptional activity by de-repression
model ------47
Figure 1.14: The effects of c-Jun in apoptosis ------50
Figure 3.1: Molecular mechanisms of cell migration ------85
Figure 3.2: Serum induces the expression of c-Jun in HeLa cells ------89-90
Figure 3.3: Uptake of FITC-siRNA by HeLa cells ------91-92
Figure 3.4: c-Jun-targeting siRNA inhibits HeLa c-Jun mRNA & protein
expression ------93-94
Figure 3.5: c-Jun siRNA reduces HeLa cell proliferation ------95
Figure 3.6: c-Jun siRNA inhibits HeLa cell migration ------96-97
Figure 3.7: c-Jun siRNA inhibits HeLa cell invasion ------98-99 vi
Figure 3.8: c-Jun siRNA inhibits HeLa cell migration and regrowth in a
scratch wound assay ------100-101
Figure 3.9: c-Jun siRNA downregulates mRNA levels of c-Jun target genes
in HeLa cells ------103-104
Figure 3.10: c-Jun siRNA downregulates the protein expression of Cox-2
but does not significantly inhibit ICAM-1 ------105
Figure 3.11 c-Jun siRNA does not inhibit the activity of MMP-1, MMP-2
or MMP-9 in HeLa cells ------107-108
Figure 3.12: c-Jun siRNA inhibits HPV18 E6 and HPV18 E7 mRNA expression -109
Figure 3.13: Serum inducibility of Cox-2 mRNA and protein expression ------111-112
Figure 3.14 Cox-2 siRNA inhibits Cox-2 mRNA and protein expression
in HeLa cells ------113-114
Figure 3.15: Cox-2 siRNA significantly inhibits HeLa cell migration
and invasion ------115-116
Figure 3.16: Cox-2 siRNA reduces MMP1 mRNA expression in HeLa cells --- 117
Figure 3.17: Cox-2 siRNA does not inhibit MMP-1, MMP-2 and MMP-9
activities ------118-119
Figure 3.18 Uptake of GFP plasmid by HeLa cells ------120
Figure 3.19: c-Jun mRNA and protein levels are significantly increased by c-Jun
expression vector ------121-122
Figure 3.20: Overexpression of c-Jun enhances HeLa cell invasiveness but not cell
proliferation ------124-125
Figure 3.21: Overexpression of c-Jun increases MMP1 and Cox-2 mRNA
expression ------126-127
Figure 3.22: Overexpression of c-Jun increases Cox-2 protein expression ---- 129-130
Figure 3.23: Overexpression of c-Jun increases the enzymatic activity
of active MMP-2 ------131-132 vii
Figure 3.24: HeLa cell viability was inhibited by cisplatin in a
dose-dependent manner ------134
Figure 3.25: Combination treatment of c-Jun siRNA and cisplatin (CDDP)
does not show synergism in an MTT assay ------136
Figure 3.26: Combination treatment of c-Jun siRNA followed by cisplatin
does not increase HeLa cell apoptosis ------139-141
Figure 3.27: Combination treatment of c-Jun siRNA followed by cisplatin
diminishes the effect of cisplatin on cell cycle progression ------143-144
Figure 3.28: Cisplatin induces c-Jun expression ------146-148
Figure 3.29: Combination of c-Jun siRNA and cisplatin reduces cyclin A
and induces cyclin E protein expression ------149-151
Figure 4.1: Time course of Egr-1 expression in serum-induced HeLa cells ---- 171-172
Figure 4.2: Egr-1 siRNA inhibits HeLa Egr-1 mRNA & protein expression ---- 173-175
Figure 4.3: Egr-1 silencing does not reduce HeLa cell proliferation ------176
Figure 4.4: Egr-1 siRNA inhibits HeLa cell migration ------178
Figure 4.5: Egr-1 siRNA inhibits HeLa cell invasion ------180
Figure 4.6: Egr-1 silencing inhibits expression of MMP-1 and MMP-9 ------181
Figure 4.7: Egr-1 siRNA inhibits MMP-9 activitiy ------182-183
Figure 4.8: The differential serum-inducible profiles of Egr-1, c-Jun
and Cox-2 ------185-186
Figure 4.9: Egr-1 siRNA inhibits c-Jun and Cox-2 but not expression of
other AP-1 subunits ------188-190
Figure 5.1: c-Jun siRNA inhibits HeLa-luc c-Jun protein expression ------208
Figure 5.2: c-Jun siRNA retards HeLa-luc pre-transfection subcutaneous
tumor growth and weight ------210-212
Figure 5.3: BLI of c-Jun siRNA pre-transfected subcutaneous tumours ---- 214-215 viii
Figure 5.4: c-Jun expression was significantly reduced in c-Jun siRNA
pre-transfection subcutaneous tumours ------216-217
Figure 6.1: Proposed mechanism for HeLa cell migration and invasion ------232
ix
LIST OF TABLES
Table 1.1: Stages of cervical cancer according to FIGO ------4
Table 1.2: Common anti-cancer compounds and their mode of action ------16
Table 1.3 Targets for siRNA therapy in cervical cancer ------35
Table 1.4: The role of IEGs in cancers ------41
Table 2.1: Sequences of siRNAs ------67-68
Table 2.2: qPCR conditions and primer sequences used for mRNA
gene expression analysis ------71-72
Table 2.2: Primary antibodies for western blotting ------74-75
x
ABBREVIATIONS
AC Adenocarcinoma
AGO2 Argonaute2
AIG Anchorage independent growth
APCs Antigen-presenting cells
APS Ammonium persulphate
As2O3 Arsenic trioxide
AS-ODNs Antisense oligodeoxynucleotides bZIP Basic leucine-zipper
BAP31 B cell receptor-associated protein 31
CC Cervical cancer
CDDP Cisplatin c-FLIP Cellular Fas-associated death domain-like interleukin-1beta-converting enzyme inhibitory protein
CO2 Carbon dioxide
Cox-2 Cyclooxygenase-2
CRE CAMP-response element
CRT Calreticulin
CSK C-terminal Src kinase
DAPI 4',6-diamidino-2-phenylindole
DEGs Delayed early genes
DMEM Dulbecco's Modified Eagle Medium
DOPE Dioleyl phosphatidyl ethanolamine
xi
DOTAP N -[1-(2,3-dioleoyloxy)-propyl]- N , N , N -trimethylammonium methyl sulfate
ECM Extra-cellular matrix
EDTA Ethylenediaminetetraacetic acid
EGF Epidermal growth factor
EGFR Epidermal growth factor receptor
EGFR-TKI EGFR tyrosine kinase inhibitor
Egr-1 Early growth response -1
EMT Epithelial–mesenchymal transition
ERK Extracellular-signal-regulated kinase
FBS Fetal bovine serum
FDA Food and Drug Administration
FIGO International Federation of Gynaecology and Obstetrics
FITC Fluorescein Isothiocyanate
FOV Field of view
GBM Glioblastoma multiforme
GFP Green fluorescence
GRP9 Glucose regulated protein 94
GAPDH Glyceraldehyde 3-phosphate dehydrogenase
HDACs Histone deacetylases hNIS Human sodium/iodide symporter hTR Human telomerase
HIF Hypoxia-inducible factor
xii
HIF-1α Hypoxia inducible factor 1α
HPV Human papillomavirus
HSP Heat shock protein
HTLF Helicase-like transcription factor
H202 Hydrogen peroxide
ID-miRs Immediately down-regulated microRNAs
IEGs Immediate early genes
IEX-1 Immediate early response gene X-1
KRF-1 Keratinocyte-specific transcription factor
LB Luria-Bertani
LBL Layer-by-layer
MAPK Mitogen activated protein kinase
MEM Minimum Essential Media
MMP Matrix metalloproteinases
NAB1 NGF1-A binding protein 1
NAB2 NGF1-A binding protein 2
NCoR HDAC3-nuclear receptor corepressor
NIS Sodium/iodide symporter
NSCLC Non-small-cell lung cancer
OS Overall survival
PDGF Platelet-derived growth factor
PEI Polyethylenimine
PI Propidium iodide xiii
Pol II RNA polymerase II
Ps-S-Oligo Psoralen-conjugated oligo(nucleotide phosphorothiate)s
PVDF Polyvinylidene fluoride
PTEN Phosphatase and tensin homolog qPCR Quantitative real-time polymerase chain reaction rAAV Recombinant adeno-associated virus rhTRAIL Recombinant human TRAIL
RAR2 Retinoic acid receptor 2
RAS Rat sarcoma
Rb Retinoblastoma protein
RISC RNA-induced silencing complex
ROI Region of interest siCtrl non-targeting siRNA siJun c-Jun siRNA siRNA Short interfering ribonucleic acid
SCC Squamous cell carcinoma
SDS Sodium dodecyl sulfate
SELEX Systematic evolution of ligands by exponential enrichment
Src Sarcoma
TEMED Tetramethylethylenediamine
TERT Telomerase reverse transcriptase
TFOs Triplex-forming oligonucleotides
TPA 12-O-tetradecanoyl phorphol 13-acetate xiv
TRE TPA responsive element
TRAIL Tumour necrosis factor-related apoptosis inducing ligand
TRBP TAR-RNA binding protein
TXNIP Thioredoxin interacting protein
URR Upstream regulatory region
Veh. Vehicle
VEGF Vascular endothelial growth factor
xv
TABLE OF CONTENTS
ORIGINALITY STATEMENT ------i ABSTRACT ------ii PUBLICATIONS AND CONFERENCE PRESENTATIONS ------iv ACKNOWLEDGEMENT ------v LIST OF FIGURES ------vi LIST OF TABLES ------x ABBREVIATIONS ------xi
Chapter 1: Cervical Cancer, c-Jun and Early Growth Response Protein (Egr-1) ------1
1.1 Cervical cancer ------2
1.2 Pathophysiology of cervical cancer ------3 1.2.1 Adenocarcinoma versus Squamous Cell Carcinoma ------6
1.3 Human papillomavirus (HPV) in cervical cancer ------7
1.4 Current Treatments for Cervical Cancer ------14 1.4.1 Targeted therapies for cervical cancer ------19
1.5 Emerging Potential of Molecular Therapeutics for Cervical Cancer ------21 1.5.1 Immunotherapy in cervical cancer ------22 1.5.2 Antigene and antisense approaches ------24 1.5.3 Ribozymes ------27 1.5.4 DNAzymes ------27 1.5.5 Aptamer approach ------29 1.5.6 Short interfering (siRNA) targeting in cervical cancer ------31 1.5.6.1 siRNA delivery ------35
1.6 Novel Molecular Targets in Cervical Cancer ------38 1.6.1 Immediate early genes as molecular/ therapeutic targets in cervical cancer ------38 1.6.2 c-Jun and the AP-1 transcription factor ------44 1.6.3 Regulation of c-Jun expression and activity ------46 1.6.4 Importance of c-Jun to AP-1-driven oncogenesis ------48 1.6.4.1 c-Jun and proliferation or cell growth ------48 1.6.4.2 c-Jun and apoptosis ------48 1.6.4.3 c-Jun and invasion/ metastasis ------50 1.6.5 c-Jun and cervical cancer ------52 1.6.5.1 c-Jun and HPV ------53 1.6.6 Egr-1 ------54 1.6.6.1 Egr-1 – a tumour promoter or suppressor? ------55 1.6.6.2 Egr-1 and cervical cancer ------57
1.7 Hypothesis and Aims ------58 xvi
Chapter 2: Materials and Methods ------60
2.1 Media, Buffers and Solutions ------61 2.1.1 Dulbecco's Modified Eagle Medium (DMEM) ------61 2.1.2 Minimum Essential Media (MEM) ------61 2.1.3 RIPA Buffer ------61 2.1.4 4x SDS protein loading sample buffer ------62 2.1.5 Resolving gel ------62 2.1.6 Stacking gel ------62 2.1.7 Mini-PROTEAN® TGXTM Precast Gels ------62 2.1.8 SDS Running Buffer ------62 2.1.9 Transfer Buffer ------63 2.1.10 Phosphate Buffered Saline (PBS) (10X) ------63 2.1.11 Phosphate Buffered Saline (PBS) (1X) ------63 2.1.12 PBS-T ------63 2.1.13 Luria-Bertani (LB) - Ampicillin medium ------63 2.1.14 Frozen glycerol stocks ------64 2.1.15 N -[1-(2,3-dioleoyloxy)-propyl]- N , N , N -trimethylammonium methyl sulfate (DOTAP)/ dioleyl phosphatidyl ethanolamine (DOPE) Mixture ------64 2.1.16 MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) solution ------64
2.2 Cell culture ------64
2.3 Plasmid Purification ------65 2.3.1 Transformation of competent cells ------65 2.3.2 Maxi-prep: large scale DNA purification ------66
2.4 Transfection ------66 2.4.1 siRNA transfection ------66 2.4.2 Plasmid transfection ------68
2.5 Gene Expression Analysis ------69 2.5.1 Total RNA extraction ------69 2.5.2 cDNA synthesis from total RNA ------70 2.5.3 Quantitative real-time polymerase chain reaction (qPCR) ------70
2.6 Western blotting ------73
2.7 Cell Counting ------75
2.8 Wound Scratch Assay ------76
2.9 Dual-chamber transwell assay ------76
2.10 Matrigel dual-chamber transwell assay ------77
2.11 Flow cytometry ------78 xvii
2.11.1 Annexin V staining apoptosis assay ------78 2.11.2 Cell cycle analysis ------79
2.12 MTT assay ------79
2.13 FITC-siRNA and plasmid uptake studies ------80
2.14 MMP Activity Analysis ------81 2.14.1 Concentration of cell culture medium ------81 2.14.2 Gelatin Zymography ------81
2.15 Statistical analysis ------82
Chapter 3: The role of c-Jun in Cervical Cancer Cells in vitro ------83
3.1 Introduction and aims ------84
3.2 Results ------88 3.2.1 Serum induces c-Jun mRNA & protein expression in growth-quiescent HeLa cells ------88 3.2.2 Efficient uptake of Fluorescein Isothiocyanate (FITC) -siRNA by HeLa cells------91 3.2.3 c-Jun siRNA inhibits HeLa c-Jun mRNA and protein expression ------93 3.2.4 c-Jun siRNA reduces HeLa cell proliferation ------95 3.2.5 c-Jun siRNA inhibits HeLa cell migration ------96 3.2.6 c-Jun siRNA inhibits HeLa cell invasion ------98 3.2.7 c-Jun siRNA inhibits HeLa cell migration and regrowth in a scratch wound assay ------100 3.2.8 c-Jun siRNA downregulates mRNA levels of Cox-2, ICAM-1, MMP-1 and MMP-9 ------102 3.2.9 c-Jun siRNA downregulates the protein expression of Cox-2 but does not significantly inhibit ICAM-1 ------104 3.2.10 c-Jun siRNA does not inhibit the activity of MMP-1, MMP-2 or MMP-9 in HeLa cells ------106 3.2.11 c-Jun siRNA inhibits HPV18 E6 and HPV18 E7 mRNA expression ------108 3.2.12 Serum induces Cox-2 mRNA and protein expression in HeLa cells ------110 3.2.13 Cox-2 siRNA inhibits Cox-2 mRNA and protein expression in HeLa cells ------113 3.2.14 Cox-2 siRNA reduces HeLa cell migration and invasion ----- 115 3.2.15 Cox-2 siRNA reduces MMP1 mRNA expression in HeLa cells ------117 3.2.16 Cox-2 siRNA does not inhibit MMP-1, MMP-2 or MMP-9 activity in HeLa cells ------118 3.2.17 HeLa cells efficiently take up green fluorescence (GFP) plasmid ------120 3.2.18 c-Jun expression vector highly overexpresses c-Jun mRNA xviii
and protein levels ------121 3.2.19 Overexpression of c-Jun enhances HeLa cell invasiveness but not cell proliferation ------123 3.2.20 Overexpression of c-Jun increases MMP-1 and Cox-2 mRNA expression but has no effect on MMP-9 and ICAM-1 mRNA expression ------126 3.2.21 Overexpression of c-Jun increases Cox-2 protein expression ------128 3.2.22 Overexpression of c-Jun increases active MMP-2 and MMP-9 activities ------131 3.2.23 Cisplatin reduces HeLa cell viability in a dose-dependent manner ------133 3.2.24 Combination treatment of c-Jun siRNA and cisplatin does not show synergism in an MTT assay ------135 3.2.25 Combination treatment of c-Jun siRNA and cisplatin does not lead to increased apoptosis ------137 3.2.26 Combination treatment of c-Jun siRNA and cisplatin shows increased G1 of cell cycle and reduced G2/M phase of the cell cycle ------142 3.2.27 Cisplatin induces c-Jun expression ------145 3.2.28 Combination of c-Jun siRNA and cisplatin reduces cyclin A and induces cyclin E protein expression ------149
3.3 Discussion ------152
3.4 Conclusion and Future Directions ------162 3.4.1 Summary and Conclusions ------162 3.4.2 Future directions ------163
Chapter 4 The role of Egr-1 in Cervical Cancer Cells in vitro ------167
4.1 Introduction and aims ------168
4.2 Results ------170 4.2.1 Serum induced Egr-1 mRNA & protein expression in HeLa cells ------170 4.2.2 Egr-1 siRNA inhibits HeLa Egr-1 mRNA & protein expression ------173 4.2.3 Egr-1 siRNA does not reduce HeLa cell proliferation ------176 4.2.4 Egr-1 siRNA reduces HeLa cell migration ------177 4.2.5 Egr-1 siRNA reduces HeLa cell invasion ------179 4.2.6 Egr-1 siRNA downregulats the mRNA expression of MMP-1 and MMP-9 ------181 4.2.7 Egr-1 siRNA inhibits MMP-9 activity ------182 4.2.8 Egr-1 mRNA and protein expression is induced by serum earlier than c-Jun and Cox-2 ------184 4.2.9 Egr-1 siRNA inhibits c-Jun mRNA and protein expression as well as Cox-2 protein expression ------187
xix
4.3 Discussion ------193
4.4 Conclusion and Future Directions ------199 4.4.1 Summary and Conclusions ------199 4.4.2 Future directions ------199
Chapter 5 The role of c-Jun in Cervical Cancer Cells in vivo ------202
5.1 Introduction and aims ------203
5.2 Materials and methods ------205 5.2.1HeLa-luc Subcutaneous In Vivo Model of CC ------205 5.2.2 Bioluminescent Imaging (BLI) ------206
5.3 Results ------207 5.3.1 c-Jun siRNA inhibits HeLa-luc c-Jun protein expression ---- 207 5.3.2 c-Jun siRNA retards pre-transfected HeLa-luc subcutaneous tumour growth ------209 5.3.3 BLI of c-Jun siRNA pre-transfected subcutaneous tumours ------213 5.3.4 c-Jun expression is significantly reduced in c-Jun siRNA pre- transfected subcutaneous tumours ------216
5.4 Discussion ------218
5.5 Summary and Conclusions ------224
6 Final conclusions ------226
7 References ------234
8 Appendix ------259
xx
1
Chapter 1:
Cervical Cancer, c-Jun and Early
Growth Response-1 (Egr-1) 2
INTRODUCTION
1.1 Cervical Cancer
Cervical cancer (CC) is the third leading cancer in women worldwide (Source:
GLOBOCAN 2008 database (version 1.2) http://globocan.iarc.fr). Each year there are
529,000 new cases and 275,000 deaths (Ferlay et al., 2010). Most of these cases occur in developing countries where the awareness of cytologic screening (Papanicolaou or
PAP smear) and vaccination is still limited. The management of invasive CC remains particularly challenging in resource-limited and developing countries, especially in many sub-Saharan African countries, due to a lack of surgical facilities and radiotherapy services as well as expertise in the clinical field (Steward et al. 2003). Even in the developed world, recurrent and metastatic CC occurs in about one-third of patients and causes considerable morbidity and mortality, despite treatment for early disease (Thun et al., 2010). While the newly Food and Drug Administration (FDA)-approved preventive human papillomavirus (HPV) vaccines, Gardasil and Cervarix, are projected to reduce CC incidence, they do not have any therapeutic effect on established HPV infection or HPV-associated CC. Therefore, there is still a need to develop treatments for CC.
This work aims to investigate the therapeutic potential of molecular approaches in targeting two major transcriptional regulators, the c-Jun oncogene and the early growth response -1 (Egr-1) protein, in CC. In this chapter, the pathophysiology of CC will be described as well as a review of current treatments and their limitations, emerging treatments and the benefits of targeting specific proteins, and the evidence that the transcriptional regulators, Egr-1 and c-Jun, may be molecular targets in CC. 3
1.2 Pathophysiology of Cervical Cancer
CC is primarily caused by infection with the human papillomavirus (HPV). However, women infected with HPV variants can be asymptomatic and can immunologically clear the infection without specific therapy. Given that many years can elapse from the time of infection before cancer diagnosis, it is hypothesised that a triggering mechanism may be a necessary requirement for the eventual development of CC. CC usually arises from a ring of mucosa in the cervix called the cervical transformation zone (Schiffman et al.,
2007). For unclear reasons, transformation zones between different types of epithelium are the main sites where persistent HPV infections cause cancers. Over years, the position of the cancer-susceptible transformation zone shifts towards and into the endocervical canal (Castle et al., 2006) as stratified squamous epithelium replaces the mucus-producing glandular epithelium (Figure 1.1) (Jacobson et al., 1999).
Cervical cancer is classified into a number of stages according to International
Federation of Gynaecology and Obstetrics (FIGO) and the extent of tumour invasion
(Table 1.1).
4
Figure 1.1: The cervical transformation zone
The glandular epithelium of the endocervix is progressively replaced by stratified squamous epithelium of the ectocervix. This active squamous metaplasia is called cervical transformation zone and is especially susceptible to persistent HPV infections
(Schiffman et al., 2007).
Table 1.1: Stages of cervical cancer according to FIGO.
FIGO
Stages
0 Carcinoma in situ (preinvasive carcinoma)
I Cervical carcinoma confined to uterus
IA Invasive carcinoma diagnosed only by microscopy.
IA1 Stromal invasion no greater than 3.0 mm in depth and 7.0 mm or less in 5
horizontal spread
IA2 Stromal invasion more than 3.0 mm and not more than 5.0 mm with a
horizontal spread 7.0 mm or less
IB Clinically visible lesion confined to the cervix or microscopic lesion
greater than IA2
IB1 Clinically visible lesion 4.0 cm or less in greatest dimension
IB2 Clinically visible lesion more than 4 cm in greatest dimension
II Tumour invades beyond the uterus but not to pelvic wall or to lower
third of the vagina
IIA Without parametrial invasion
IIB With parametrial invasion
III Tumour extends to pelvic wall and/or involves lower third of vagina
and/or causes hydronephrosis or non-functioning kidney
IIIA Tumour involves lower third of vagina, no extension to pelvic wall
IIIB Tumour extends to pelvic wall and/or causes hydronephrosis or non-
functioning kidney
IVA Tumour invades mucosa of bladder or rectum and/or extends beyond
true pelvis
IVB Distant metastasis
6
1.2.1 Adenocarcinoma versus Squamous Cell Carcinoma
The two major histologic variants of CC are squamous cell carcinoma (SCC) and adenocarcinoma (AC). Eighty percent of cervical carcinoma consists of SCC and 20% is AC (Greer et al., 2010). SCC arises in the squamous (flattened) epithelial cells that line the cervix (exocervix), whereas AC develops from the mucus producing gland cells of the endocervix. The incidence of AC is increasing in comparison to SCC, which is also apparent in developed countries, despite cervical screening programs (Seoud et al.,
2011). The reasons behind the rising incidence could involve a lack of clear criteria for the appearance of endocervical gland dysplasia (AC) in situ and microinvasive AC on colposcopy (Hayes et al., 1997), as well as difficulties in the interpretation of morphologic abnormalities of glandular cells histologically (Boon et al., 1981).
SCC differs from AC in regards to risk factors, survival rates, prognosis, patterns of recurrence and response to treatment. The significantly higher incidence of lymph node involvement in AC leads to poorer survival rate compared to SCC (Irie T. et al., 2000).
AC is more likely to metastasize than SCC (Shimada et al., 2006). It also has a worse prognosis as it often escapes detection and is more likely to progress rapidly (Davy et al., 2003; Kleine, 1989). There are also differences in terms of epidemiologic co-factors for AC and SCC. Smoking is a risk factor for SCC (International Collaboration of
Epidemiological Studies of Cervical, 2007), while obesity is a risk factor for AC (Lacey et al., 2003). Due to the relative rarity of AC compared to SCC, evidence for the optimal management of AC is lacking.
7
1.3 HPV in cervical cancer
There are more than 100 variants of HPV, however, only a small subgroup are associated with CC development. The relationships between HPV genotypes can be expressed in the form of phylogenetic trees based on DNA sequences and protein homologies (Schiffman et al., 2005). Based on their preferred tissue tropism, HPVs can be generally classified into cutaneous and mucosal types. The cutaneous types are normally found in the general population and cause common warts or are found in immunosuppressed individuals. The mucosal types are further grouped into low-risk and high-risk types of HPV (zur Hausen, 1996). The most common low-risk types are
HPV 6 and 11 which are detected most often in benign genital warts. HPV 16 and 18 are considered the most highly pathogenic but the high-risk types include HPV 16, 18,
31, and 45 which are the predominant types found in cervical SCC, accounting for more than 90 per cent of cases (Bosch et al., 2002), with HPV 16 alone accounting for approximately half the cases worldwide (Clifford et al., 2003). HPV 18 is the most prevalent type in cervical AC (55%), followed by HPV 16 (32%) and HPV 45 (10%)
(Zielinski et al., 2003). Consistently high levels of integration of HPV 18 in CC samples may explain its greater transforming efficiency in vitro and its reported clinical association with more aggressive AC. On the other hand, integration of HPV 16 may not be essential for malignant transformation due to its absence in some CC samples
(Vinokurova et al., 2008).
HPVs contain approximately 8,000 base pairs of circular double-stranded DNA in small non-enveloped 55-nm-diameter icosahedral capsids (Munger et al., 2004). Only one of the two strands of the circular papillomavirus DNA genome is actively transcribed. 8
There are 3 major sections of the HPV genome: a ~1 kilobase (kb) non-coding long control region (LCR) that contains a variety of cis elements for regulation of viral replication and gene expression: a ~4kb early (E) region (E1, E2, E4, E5, E6 and E7) that encodes non-structural proteins; and a ~3-kb late (L) region (L1 and L2) that encodes the two capsid proteins. The higher the E or L number, the smaller the open reading frame (Figure 1.2). Viral E6 and E7 are constitutively expressed and appear essential, whereas the expression of the other genes can be deleted or disrupted (Baker et al., 1987). Moreover, high expression of HPV E6 and E7 is displayed in invasive cervical lesions where most lesions have integration of viral DNA into the host cell genome (von Knebel Doeberitz, 2002). Integration of high-risk HPV genomes is significantly linked with the progression from pre-neoplastic lesions to invasive CC
(Pett and Coleman, 2007). The event of integration causes loss of expression of the E2 transcriptional repressor which then leads to increased HPV E6 and E7 expression (Jeon and Lambert, 1995). Re-expression of E2 in CC cell lines causes growth inhibition, proving the importance of E2 repressor ability in cancer progression (Thierry and
Yaniv, 1987). Furthermore, cells that express E6/E7 from integrated HPV sequences have positive growth benefits over cells with episomal HPV genomes (Jeon et al.,
1995).
9
Figure 1.2: Schematic image of HPV 16 genome and integration into host chromosome. (A) Schematic image of the HPV-16 double-stranded circular DNA genome. The long control region (LCR) as well as early (E) and late (L) genes, are shown. The arrow indicates the major early promoter (P97). Transcription occurs from one strand only in a clockwise orientation in this image. (B) Schematic representation of integration of HPV-16 genome fragment (red) into a host chromosome (blue) (Munger et al., 2004).
HPVs are exclusively epitheliotropic and their replication is closely associated to the differentiation process of the host cells. Normal stratified epithelium consists of squamous epithelial cells. The basal layers of cells divide as stem cells of transient amplifying cells. Upon cell division, one of the daughter cells remains in the basal layer as a slow-cycling, self-renewing population while another cell moves upward and begins to undergo terminal differentiation (Watt, 1998). The HPV infection cycle begins with the entrance of infecting viral particles to the basal layer of epithelium, presumably through tiny tears of the mucosa (Munoz et al., 2006). The early HPV genes E1 and E2 support viral DNA replication and its segregation so that the viral genome is maintained in these cells as a stable episome at low copy number. Viral late gene products are produced to increase amplification of the viral genome as the infected daughter cells migrate towards the epithelial surface. The re-initiation of infection begins when the viral DNA is packaged into capsids and progeny virions are released in the outer layers of the epithelium (Figure 1.3). In addition to viral helicase E1, the host cell environment and host replication factors are crucial elements and have to be coordinated for viral DNA replication before virion synthesis. The coordination of host cell environment suitable for viral replication is achieved by HPV early genes E6 and E7, 10
where they induce unscheduled re-entry into S-phase of the cell cycle and activate the host replication machinery.
Figure 1.3: The HPV life cycle. Shown is the coordinate expression of the different viral proteins during the course of a productive infection ( Doorbar, 2006).
HPV E6 and E7 act through activation of Telomerase reverse transcriptase (TERT), binding to histone deacetylases (HDACs) and inactivation of the Retinoblastoma protein (Rb), respectively, which contributes to cell immortalization (Howie et al.,
2009). Telomerase reverse transcriptase (TERT) plays an important role in maintaining the length of telomeres in cells which further leads to cell immortalization (Akutagawa et al., 2008). Histone deacetylases (HDACs) determine the acetylation status of histones which affects the regulation of gene expression (Marks et al., 2001). In addition, HPV
E6 and E7 regulate proliferation and apoptosis through regulation of several important cell cycling proteins, as well as regulators of apoptosis. For high-risk HPV types, the E7 11
protein binds to and degrades phosphorylated Rb (p-Rb) (Hebner and Laimins, 2006), leading to disruption of its association with the E2F family of transcription factors. This disruption then causes transactivation of the expression of cellular proteins required for
DNA replication, such as DNA polymerase and thymidine kinase. HPV E7 also controls cell cycle progression from G1 to S phase by binding to the cell cycle regulators p21 and p27 at the carboxyl-termini, efficiently neutralizing the inhibitory effects on cyclin
E- and cyclin A-associated kinase activities (Deshpande et al., 2005; Jones et al., 1997).
The function of the HPV E7 protein is complimented by the function of the HPV E6 protein. These two proteins are expressed together from a single polycistronic mRNA species (Stacey et al., 2000). HPV E6 itself is capable of increasing cell proliferation independently of E7, through its C-terminal PDZ ligand domain by dissociating the cell proliferation and polarity control (Nguyen et al., 2003). The anti-apoptotic role of HPV
E6 is associated with Bak (Thomas and Banks, 1998). The inhibition of apoptosis is also mediated through the binding of HPV E6 to the tumor suppressor protein, p53, which results in degradation of p53 via the ubiquitin pathway (Thomas et al., 1999).
Although E6 and E7 can act without the other viral early region proteins, their transforming potential are further enhanced by HPV E5 by interacting with factors such as B cell receptor-associated protein 31 (BAP31) (Regan and Laimins, 2008), aberrant epidermal growth factor receptor (EGFR) signalling (Leechanachai et al., 1992) and activation of the MAPK pathway (Gu and Matlashewski, 1995).
Other than the typical apoptotic genes and cell cycle regulators mentioned above, HPV
E6 and E7 also regulate immediate early genes (c-Jun and Cox-2) and matrix metalloproteinases (MMP-2 and MMP-9) which are involved in extra-cellular matrix 12
(ECM) degradation. For instance, HPV E7 forms a complex with c-Jun and this interaction is essential for the E7 transformation pathway (Antinore et al., 1996). HPV
E6 and E7 oncoproteins regulate the expression of Cox-2 by co-activator and co- repressor exchange. These induce the recruitment of phosphorylated c-Jun and other co- factors to the Cox-2 promoter. On the other hand, these oncoproteins inhibit the binding of the HDAC3-nuclear receptor corepressor (NCoR) complex to the Cox-2 promoter.
This may cause the overexpression of Cox-2 and lead to cervical carcinogenesis
(Subbaramaiah and Dannenberg, 2007a). Moreover, HPV E6 up-regulates MMP-2 and
MMP-9 expression and activities in lung adenocarcinoma, which promote growth, angiogenic and metastatic phenotypes (Shiau et al., 2013). The pathways and genes regulated by HPV E6 and E7 are summarized in Figure 1.4.
A
MMP-2, E6 Invasion MMP-9
Bak
E6 c-Jun/ AP-1 Apoptosis HPV E6, E7
E6 p53
E6 hTERT Cell immortalization
13
B
c-Jun/ AP-1 HPV E6, E7
E7 E7 E7 E6 E7 E7 HDAC p21 p27 c-Jun Other co- c-Jun factors p-Rb
Cox-2 Cyclin Cyclin Cell transformation A E E2F
Invasion/ Inflammation DNA polymerase and Cell cycle progression thymidine kinase
Figure 1.4 HPV E6 and E7 regulated pathways and genes. c-Jun/ AP-1 binds to the upstream regulatory region (URR) of HPV E6 and E7. This leads to the expression of
HPV E6 and E7 which in turn controls pathways in HPV-induced carcinogenesis.
1.4 Current Treatments for Cervical Cancer
Management of cervical cancer (CC) is dictated by the clinical stage at presentation as defined by the International Federation of Gynecology and Obstetrics Cervical Cancer
Staging (FIGO) and described earlier in Table 1.1. Surgery is adequate for patients with stage 0 disease (carcinoma in situ). Patients with stage IA1, IA2, IB1 and IIA are treated with surgery or radiotherapy. A multidisciplinary treatment approach is undertaken for patients with stage IB2, IIB, IIIA, IIIB and IVA. Patients with metastatic CC (stage
IVB) have very limited treatment options. Palliation, along with chemotherapy or participation in a clinical trial, is the usual approach for these patients [6]. In 14
comparison to radiotherapy, surgery has the advantage of possible preservation of fertility and vaginal integrity which improves quality of life (Ercoli et al., 2009).
Following the publication of five trials in 1999 (Keys et al., 1999; Morris et al., 1999;
Peters, 2000; Rose et al., 1999; Whitney CW et al., 1999), each demonstrating a substantial survival benefit associated with concomitant cisplatin-based chemoradiation, the US National Cancer Institute (NCI) recommended the addition of concurrent chemotherapy to radiotherapy for treating invasive CC. This approach has since become the gold standard management for locally advanced or invasive CC. Current treatment options for CC are outlined in Figure 1.5.
The use of chemotherapy before and concurrent with radiotherapy could sensitize the tumour to radiotherapy, reduce tumour size and control micrometastases (Tierney et al.,
2008) prior to surgery (Benedetti-Panici et al., 1998; Buda et al., 2005). Neoadjuvant chemotherapy followed by radical surgery has been used extensively for the treatment of locally advanced CC in European and Latin American countries and regions where radiotherapy facilities are not generally available (Basile et al., 2006). However, this is not standard treatment for locally advanced CC in the US (Legge et al., 2010), where it is still considered investigational. The optimal chemotherapy regimen is yet to be defined in this setting.
Landoni and colleagues showed that surgery (and salvage radiotherapy for high risk patients) is about equivalent to radiation alone (Landoni et al., 1997). However, the combination of surgery and adjuvant radiotherapy can cause long-term complications.
On the other hand, radical surgery after chemoradiation has the potential advantage of better local control, especially in patients with bulky or very advanced-stage tumours 15
that are more likely to contain chemo- and radio-resistant clones. However, the morbidity associated with surgery after chemoradiation remains a major concern
(Ferrandina et al., 2007).
Cisplatin is the standard chemotherapy for CC, especially in the advanced stage. The response rate to single agent cisplatin is around 50% in chemo-naïve and 17% in chemoresistant patients (Moore et al., 2004; Tewari and Monk, 2009; Thigpen et al.,
1981), while overall survival (OS) is around 6-7 months. However, some patients are intolerant to cisplatin or develop chemoresistance after recurrence of CC. Patients with recurrent disease who have failed platinum-based therapy are treated with different non- platinum-based regimens, including paclitaxel, irinotecan, topotecan, etoposide, liposomal doxorubicin, vinorelbine, isofamide, capecitabine and pemetrexed. As single agents however, all of these drugs generally have lower response rates than cisplatin.
The general mechanisms of action of these drugs are summarized in Table 1.2.
16
Table 1.2: Common anti-cancer compounds and their mode of action
Type of anti-cancer compound Generic name
Alkylating agents:
Nitrogen mustard derivative Isofamide
Heavy metal alkylator Cisplatin
Anti-metabolites:
Pyrimidine analogs Capecitabine
Folic acid antagonist Pemetrexed
Mitotic/ spindle inhibitors Paclitaxel
Vinorelbine
Topoisomerase inhibitors Irinotecan
Topotecan
Etoposide
Signal transduction inhibitors Bevacizumab
Erlotinib
Cetuximab
Lapatinib
Pazopanib
Antitumor antibiotics Doxorubicin
The mechanism of action of cisplatin is by formation of DNA adducts of 1,2-intrastrand
ApG and GpG crosslinks, which interferes with DNA replication and transcription
(Basu and Krishnamurthy, 2010). It also increases cytotoxicity through binding of mismatch repair proteins and damage-recognition proteins with the cisplatin-GG 17
adducts (Ishibashi and Lippard, 1998). Cisplatin can induce apoptosis via a number of pathways: by increasing the Bax:Bcl-2 ratio by induction of Bax and activation of the intrinsic caspase 9-caspase 3 apoptosis pathway or cleavage of Bcl-2 (Liu et al.,
2005b); by activating the extrinsic caspase8-caspase 3 apoptosis pathway via Fas/FasL dependent and independent mechanisms (Muscolini et al., 2008);or via p53, p73 or p53 and p73-dependent parallel pathways (Chaney et al., 2005). Additionally, cell death is triggered by cisplatin via induction of reactive oxygen species (ROS) (Brozovic et al.,
2004a), degradation of telomere repeats, as well as reduction of miR-106 and miR-150 which lead to up-regulation of Rb and p53 expression (Splettstoesser et al., 2007).
Cisplatin also causes G1, S and G2/M cell cycle arrest, respectively, depending on the conditions and concentrations used (Ishibashi and Lippard, 1998; Wang and Lippard,
2004).
In order to enhance the efficacy of single-agent drugs and improve their toxicity profiles, combination chemotherapy has been investigated in many clinical trials
(Moore et al., 2004; Nagao et al., 2005). So far, only the topotecan / cisplatin combination has shown an overall survival (OS) advantage with a median OS of 9.4 months compared to 6.5 months for the single agent (Long et al., 2005). In 2006, the US
Food and Drug Administration (FDA) approved the combination of topotecan + cisplatin in treating women with stage IVB, recurrent or persistent cervical cancer not curable by surgery or radiotherapy (Legge et al., 2010). Triplet regimens have not proved to be beneficial in comparison to single-agent therapy (Bloss et al., 2002). More aggressive regimens such as MVAC (methotrexate, vinblastine, doxorubicin and cisplatin) have demonstrated excessive toxicity (Long et al., 2006). 18
Administration of cisplatin often causes severe side effects and toxicities such as nephrotoxicity, neurotoxicity, ototoxicity, myelotoxicity, hemolytic anemia, nausea and vomiting (Levi et al., 1981; Loehrer and Einhorn, 1984; Milosavljevic et al., 2010;
Windsor et al., 2012). Furthermore, paclitaxel and cisplatin cause severe side effects such as female infertility by ovarian damage (Ozcelik et al., 2010). Application of topotecan also leads to myelosuppression, diarrhea, low blood counts and susceptibility to infection. Due to the side effects of conventional chemotherapy and the development of chemoresistance in advanced and metastatic cervical cancer, new therapies and better targeting of drugs to reduce off-target effects and the associated toxicity are urgently needed.
Current
treatment options
Surgery Chemotherapy
Radiotherapy Chemoradiotherapy
Figure 1.5: Current treatments for cervical cancer.
19
1.4.1 Targeted therapies for cervical cancer
Current chemotherapeutic drugs generally have high toxicity and side effects. Specific target-based inhibitors, which may be small molecule drugs or targeted antibodies, have been developed to overcome the general effect of the standard chemotherapeutic drugs.
Combination therapy and target-based therapy may improve specificity and reduce toxicity. Currently, several inhibitors on the market have more specific targets, for instance bevacizumab, erlotinib, lapatinib and pazopanib, which target growth factors and/or their receptors as well as angiogenesis (VEGF, EGFR, HER2 and VEGFR) and are generally described as signal transduction inhibitors (Trigg and Flanigan-Minnick,
2011).
Epidermal growth factor receptor (EGFR) is another protein currently being targeted in
CC. Immunohistochemical analysis has demonstrated overexpression of EGFR in 64% of primary CC and 60% of the corresponding lymph node metastases (Shen et al.,
2008). EGFR is overexpressed in 85% of SCC cases. EGFR regulates a network of signal transduction pathways including promotion of proliferation, invasion, motility, and angiogenesis. Noordhuis et al. suggested that the expression of EGFR and activated
EGFR predicts poor response to chemoradiation and survival in CC (Noordhuis et al.,
2009). To test the validity of EGFR as a target, cetuximab, an anti-EGFR antibody, is being added concurrently to cisplatin and radiotherapy in ongoing Phase I clinical trials
(ClinicalTrials.gov Identifier: NCT00104910). In a Phase II trial of single agent cetuximab in persistent or recurrent carcinoma of the cervix, the drug was found to be well tolerated but had limited activity in this population; the median duration of PFS and OS was 1.97 and 6.7 months, respectively (Santin et al., 2011). Erlotinib, an EGFR 20
tyrosine kinase inhibitor (EGFR-TKI) was inactive in recurrent squamous cell carcinoma of the uterine cervix (Schilder et al., 2009). Cetuximab did not have additional benefit beyond cisplatin treatment in recurrent and persistent CC (Farley et al., 2011).
Angiogenesis is an important hallmark for many malignancies including CC. This process occurs mainly through the up-regulation of hypoxia-inducible factor (HIF) 1 alpha, leading to the induction of growth factors including vascular endothelial growth factor (VEGF) (Noguera et al., 2009). Therefore, VEGF is a promising therapeutic target in advanced and recurrent CC. Bevacizumab is a humanized monoclonal antibody targeting VEGF-A. It is the first clinically available anti-angiogenic agent in the United
States. It has been approved in the US for the treatment of colon, breast, non-small-cell lung cancer (NSCLC), and glioblastoma multiforme (GBM) (Grothey and Galanis,
2009). In a Phase II multicentre trial evaluating single agent bevacizumab therapy among 46 women with persistent or recurrent SCC of the cervix, bevacizumab has been found to be safe and active; in this study, the median progression free survival (PFS) and median OS was 3.40 and 7.29 months, respectively, whereas the response rate was
10.9 percent and median response duration was 6.21 months (Monk et al., 2009).
Pazopanib, an oral tyrosine kinase inhibitor targeting the VEGF receptor (VEGFR) as well as the platelet-derived growth factor receptor (PDGFR) and c-Kit is a promising therapy that has improved PFS and OS (Monk et al., 2010) and in women with advanced or recurrent CC has been found to be superior to an oral EGFR and HER2 inhibitor, lapatinib, in a head-to-head randomized Phase II trial. 21
Another protein that has been used as a target in cancer is the pro-apoptotic tumour necrosis factor-related apoptosis inducing ligand (TRAIL). Recombinant human TRAIL
(rhTRAIL) has been shown to enhance irradiation-induced apoptosis via death receptor
4 (DR4) (Maduro et al., 2008). The combination of rhTRAIL and luteolin, a naturally occurring flavonoid, has been shown to increase apoptosis of HeLa cells through up- regulation of death receptor 5 (DR5). This has proven useful for tumour cells that are resistant to TRAIL-induced apoptosis (Horinaka et al., 2005).
1.5 Emerging Potential of Molecular Therapeutics for Cervical Cancer
Targeted, molecular–based therapies have potential in the future treatment of CC, given their specific mechanisms of action, reduced off-target effects and therefore lesser likelihood of toxicity relative to traditional chemotherapy treatments. These molecular- based approaches may take various forms as summarized in Figure 1.6 including immunotherapy, antigene, antisense, ribozyme, DNAzyme, aptamer and short interfering RNA (siRNA) approaches.
22
Future treatment
Local cervical delivery Target-based device (CerviPrep™) therapies
Hyperthermia adjunt to Other radiotherapy/ immunotherapy Gene therapy chemotherapy approaches
Therapeutic Human VEGF EGFR Dendritic cells vaccines recombinant antibody anitbody TRAIL
Antigene Aptamer
Ribozyme / Antisense siRNA DNAzyme
Figure 1.6: Potential future therapy for cervical cancer.
1.5.1 Immunotherapy in Cervical Cancer
Existing FDA-approved preventive HPV vaccines, Gardasil and Cervarix, do not have any therapeutic effect on established HPV infection or HPV-associated CC. However, there are various therapeutic HPV vaccines in development for CC including live vector-based (bacterial and viral vectors), peptide or protein-based, nucleic acid-based
(DNA-based and naked RNA replicon) and cell-based (dendritic cell-based and tumor cell-based) vaccines targeting the HPV E6 and/or E7 antigens (Su et al., 2010), and vaccines targeting cervical intraepithelial neoplastic (CIN-2/3) lesions. ZYC-101, a microencapsulated DNA vaccine that encodes multiple HLA-A2-restricted, E7-specific
CTL epitopes appears to be well-tolerated in patients (Sheets et al., 2003). Another
Phase I clinical trial investigating the Sig/E7detox/ HSP70 DNA vaccine has been shown to be feasible and tolerable (Trimble et al., 2009). This vaccine encodes a signal sequence linked to a mutated form of HPV-16 E7 with an abolished Rb binding site 23
(E7detox) fused to heat shock protein 70. Other ongoing trials include DNA vaccine trials employing a DNA vaccine encoding modified E6 and E7 proteins of HPV16 and
18 delivered via intramuscular injection followed by electroporation (See http://clinicaltrials.gov/ct2/show/NCT00685412), or a DNA vaccine encoding calreticulin (CRT) fused to HPV-16 E7 (E7detox). Combination trials involving heterologous E7 DNA prime (Sig/E7detox/HSP70) followed by recombinant vaccinia boost (TAHPV) in combination with topical treatment with imiquimod are also being conducted (see http://clinicaltrials.gov/ct2/show/NCT00788164). The potency of therapeutic DNA vaccines can also be enhanced when used in combination with chemotherapy, radiation (Tseng et al., 2009) or other biotherapeutic agents (Tseng et al.,
2008).
Dendritic cells (DCs) have been used as an immunotherapy in various cancer types such as colon cancer and prostate cancer (Finkelstein et al., 2012; Hong et al., 2012). In vivo,
DCs are potent antigen-presenting cells (APCs) that stimulate helper and killer T-cells
(CD4 and CD8 T cells) which play an important role in cancer immunotherapy. This is particularly useful in CC as HPV E6/E7 is a tumour-specific antigen that could be identified by DCs (Ardavin et al., 2004). However, due to cytokine imbalance or regulatory T-cell hindrance in the host, DCs are not always effective in stimulation of tumour-specific or tumour-associated immune responses and anti-tumour effects
(Gilboa, 2007). The expression of sodium iodide symporter (NIS), a specialized active iodide transporter that co-transports sodium and iodide (Chung, 2002), causes accumulation of therapeutic radioisotope (Re-188 and I-131). NIS gene therapy has led to successful production of therapeutic effects in various cancer models (Kang et al.,
2004; Spitzweg et al., 2001). By using combined dendritic cells with HPV E7 insert 24
(DC-E7) vaccination and human sodium/iodide symporter (hNIS) radioiodine gene therapy in a mouse model with E7-expressing uterine cervical cancer, complete disappearance of the tumour has been noted (Jeon et al., 2011).
The combination of a vascular disrupting agent, DMXAA, with therapeutic HPV-16 E7 peptide-based vaccination significantly induces E7-specific CD8+ T-cell immune responses and antitumor effects in a subcutaneous and cervicovaginal tumour model
(Zeng et al., 2011). DMXAA is a synthetic flavonoid that selectively destroys the established tumour vasculature and shuts down blood supply to solid tumours, causing extensive tumour cell necrosis (Baguley, 2003; Cai, 2007).
1.5.2 Antigene and Antisense Approaches
Triplex-forming oligonucleotides (TFOs) recognize specific sequences and bind in a major groove at the polypurine-rich region of double-stranded DNA (Moser and
Dervan, 1987). The TFO approach functions at the level of genomic DNA by blocking mRNA elongation by polymerases (Hacia et al., 1994) or by inducing site-specific DNA damage (Vasquez et al., 1996). A 27 base pair TFO targeted at the human c-myc oncogene was shown to inhibit HeLa cell growth; however, a non-specific reduction in cell number was also found in the control oligonucleotide, suggesting more work needs to be done to understand the mechanisms of this approach (Helm et al., 1993). Target genes can also be silenced through DNA molecules (antisense) binding complementary
RNA. Degradation of RNA is mediated through RNase H upon activation by the formation of DNA-RNA heteroduplexes (Keller and Crouch, 1972). This hinders 25
translation of the gene into protein and subsequent downstream cellular events. A schematic representation of the antigene or antisense approach is shown in Figure 1.7.
Yatabe and colleagues developed 2-5A (5’-phosphorylated 2’-5’–linked oligoadenylate)–linked antisense oligonucleotides against human telomerase (hTR) in
ME180 and SiHa cervical cancer cells (Yatabe et al., 2002). Degradation of hTR, inhibition of telomerase activity, cell viability, colony formation and induction of apoptosis was achieved by the 2-5A anti –hTR antisense therapy. HPV16 E6 and E7 antisense RNA caused repression of HPV16 E6 and E7 oncogenes. In addition, significant increases of both p53 expression and hypophosphorylated Rb level which led to the increased apoptosis and senescence in SiHa cells, was also observed (Sima et al.,
2007). The insulin-like growth factor I receptor (IGF-IR) reversed the transformed phenotype of C33a, SiHa and HeLa S3 cells as well as inhibited tumour volume
(Nakamura et al., 2000). Compared to single antisense oligodeoxynucleotides (AS-
ODNs), an additive effect of the combined treatment of two AS-ODNs targeting adjacent targets within the HPV16 E6/E7 mRNA (419-434) was observed on the anchorage independent growth (AIG) of CaSki and SiHa cells. The combined treatment could be used to overcome the inherent variability of the HPV genome (Marquez-
Gutierrez et al., 2007). HPV16 E6 antisense induced apoptosis in CaSKi cells by causing inhibition of E6 splicing, upregulation of p53, a p53-responsive protein,
GADD45, release of cytochrome c into the cytoplasm, followed by activation of procaspase-9 and procaspase-3 (Cho et al., 2002). Photodynamic antisense therapy inhibited human CC cell, C4II cell growth using psoralen-conjugated oligo(nucleotide phosphorothiate)s (Ps-S-Oligo). C4II cells were pre-treated with Ps-S-Oligos for 6 hours followed by UVA-irradiation. As a result, accumulation of p53 occurred which 26
led to increased cellular apoptosis (Yamayoshi et al., 2003). Retrovirus vector containing the reverse orientation of full-length HPV16 E7 cDNA caused the reduction of HPV16 E7 protein expression. It decreased cell proliferation in CaSki cells through cell cycle arrest, up-regulation of Rb, and down-regulation of E2F-1 and bcl-2 proteins.
This antisense oligonucleotide also retarded the growth of tumour in vivo (Choo et al.,
2000). Antisense HPV16 E6 delivered by recombinant adeno-associated virus (rAAV) vector inhibited cell proliferation and migration, induced apoptosis, and reduced tumour growth in a CaSKi subcutaneous model (Wu et al., 2006).
Figure 1.7: Schematic representation of the antigene or antisense approach.
27
1.5.3 Ribozymes
Ribozymes are RNA molecules with enzymatic cleavage and ligation activities that catalyze highly sequence-specific reactions (Puerta-Fernandez et al., 2003).
Hammerhead ribozymes consist of a highly conserved 22 nucleotide-catalytic domain, a recognition sequence on the target RNA and a base pairing sequence flanking the sessile phosphodiester bond (DiPaolo and Alvarez-Salas, 2004). The consensus sequence for the cleavage site of these ribozymes has been established as 5’-NHH ↓ (N = any nucleotide and H=A, C or U; ↓= the cleavage site) (Kore et al., 1998). Hairpin ribozymes catalyse a reversible, site-specific reaction and the substrate sequence for cleavage must contain a 5’-BN↓GUC-3’ motif (↓= the cleavage site) (DeYoung et al.,
1995).
A hammerhead ribozyme, Rz170, targeting HPV16 E6/ E7, has been shown to reduce cell growth and increase apoptosis in CaSKi cells via the downregulation of E6, E7, c- myc and bcl-2 expression as well as up-regulation of p53 and Rb. Rz170 transfected cells also demonstrate higher sensitivity to cisplatin and radiation (Zheng et al., 2004).
A chimeric ribozyme targeting the anti-apoptotic gene survivin, pRNA/RZ (Sur), has also been shown to dose-dependently reduce cell viability of HeLa T4 cells (Liu et al.,
2007).
1.5.4 DNAzymes
DNAzymes or deoxyribozymes are synthetic catalytic DNA-based enzymes that cleave their target RNA between an unpaired purine (A or G) and a paired pyrimidine (C or U).
The most well-characterized DNAzyme is the 10-23 subtype, so-called because it was the twenty-third clone of the tenth cycle in the selection process, comprised of a cation- 28
dependent catalytic core of 15 deoxyribonucleotides (Santoro and Joyce, 1997). The catalytic core is flanked by 6 to12 nucleotide-long hybridization arms which target and bind to complementary RNA through Watson-Crick base-pairing (Silverman, 2005). A schematic representation of the ribozyme or DNAzyme approach is shown in Figure
1.8.
Several structural modifications have been made to improve the stability of DNAzymes.
The most commonly used modification is the incorporation of a 3’-3’ inverted nucleotide at the 3’ terminus of the DNAzyme, which creates a 5’-end on the 3’- terminus. This modification increases the resistance of an oligonucleotide to serum or cellular exonucleases that degrade oligonucleotide in a 3’ to 5’ direction. This modification can increase the stability of DNAzyme by extending half-life from ~70 minutes to >21 hours in human serum (Dass et al., 2002). Phosphorothioate linkage improves stability by rendering the oligonucleotide more resistant to endogenous nucleases (Lu et al., 2005). However, this is becoming less popular for DNAzymes because of its association with immunological responsiveness (Wahlestedt et al., 2000) and increased affinity for cellular proteins causing sequence-independent effects
(Guvakova et al., 1995; Rockwell et al., 1997). Locked nucleic acids are monomers comprising a 2’-O4-C methylene bridge that locks in a C3’-endo conformation
(Koshkin and Wengel, 1998); thus, enhancing the binding affinity (Braasch and Corey,
2001). Nevertheless, both catalytic activity under single turnover conditions (Fahmy and Khachigian, 2004) and biological potency (Fluiter et al., 2005) of DNAzymes have been found to be influenced by the incorporation of locked nucleic acids. 29
A DNAzyme targeting the polycistronic mRNA from the E6 and E7 genes of HPV16 was chemically modified to produce a stable locked nucleic acid (LNA)-modified DXZ
(Dz434-LNA) with significant cleavage activity of full E6/E7 transcripts. Dz434-LNA was shown to cause a dramatic reduction in E6/E7 mRNA levels in HPV-16-positive cells leading to decreased proliferation and cell death in a specific manner (Reyes-
Gutierrez and Alvarez-Salas, 2009). In another study, DNAzyme containing 2’-O, 4’-C locked nucleotides has higher ability to cleave HPV16 E6, and inhibits cell viability and
E6/E7 mRNA (Benítez-Hess et al., 2011).
Figure 1.8: Schematic representation of the ribozyme or DNAzyme approach.
1.5.5 Aptamer Approach
Aptamers are single-stranded nucleic acids that recognize a particular target with high specificity and affinity. Oligonucleotide aptamers can fold into a variety of secondary and tertiary structures and bind to their targets through an adaptive recognition process
(Stoltenburg et al., 2007). Systematic evolution of ligands by exponential enrichment 30
(SELEX) technology is a common in vitro selection method to develop aptamers
(Ellington and Szostak, 1990). A schematic representation of the aptamer approach is shown in Figure 1.9.
An RNA aptamer (G5a3N.4) binding the HPV16 E7 oncoprotein has been isolated and characterized however, limited binding and cross reactivity with HPV18 suggested the need for further investigation toward its application (Toscano-Garibay et al., 2011).
Figure 1.9: Schematic representation of the aptamer approach. 31
1.5.6 SiRNA targeting in CC
SiRNAs are double-stranded RNA fragments consisting of 21–23 nucleotides. The exogenous administration of synthetic siRNAs can be used to silence a given mRNA.
These siRNAs can be loaded directly onto the RNA-induced silencing complex (RISC) that includes Dicer, TAR-RNA binding protein (TRBP), Argonaute2 (AGO2) and other members of the Argonaute family. The activated RISC complexes containing the guide strand hybridize, cleave and degrade the complementary mRNA (Bernstein et al., 2001;
Meister et al., 2004; Nykanen et al., 2001). A schematic representation of the siRNA approach is shown in Figure 1.10. Alternatively, short hairpin or small hairpin RNA
(shRNA), a sequence of RNA that forms a tight hairpin loop, can be used to stably knock down the expression of a target gene through the RNAi pathway. Expression of shRNA can be achieved by delivery of plasmids, viral or bacterial vectors (Wang et al.,
2011). Table 1.3 summarises recent studies using siRNA and shRNA to target specific genes in CC.
Figure 1.10: Schematic representation of the siRNA approach. 32
E6 and E7 siRNAs are promising therapeutic agents for treatment of virus-related cancer (Yamato et al., 2008). Studies have shown that siRNA targeting HPV16 E6 and
E7 inhibits cell proliferation and colony formation as well as induces apoptosis in vitro
(Chang et al., 2010; Hong et al., 2009; Lea et al., 2007; Zhou et al., 2012). Application of siRNA targeting E6 and E7 of HPV16 and HPV18 resulted in significant inhibition of tumour growth in BALB/c nude mice (Chang et al., 2010; Lea et al., 2007; Zhou et al., 2012). HPV16 E6 silencing sensitizes CC cells which specifically contain the
HPV16 sequence (SiHa cells) to cisplatin, a combination of cisplatin with rhTRAIL or anti-Fas antibody, but not to irradiation-, rhTRAIL-, or anti-Fas antibody alone (Tan et al., 2012). In addition, the combination of E6/E7-specific siRNA and cisplatin therapy was significantly more efficient especially in inducing cellular senescence in vitro as well as apoptosis, cellular senescence and reducing angiogenesis in vivo (Jung et al.,
2012; Putral et al., 2005).
Synergistic toxicity and reduced tumour growth was observed in the SiHa xenograft model when the combination of paclitaxel and siRNA targeting HPV16 E6 and E7 was used (Liu et al., 2009). As described earlier, HPV E6 binds to the p53 tumour suppressor, leading to its degradation and thus increased cancer cell survival. It has been demonstrated that transient activation of p53 can be achieved by using siRNA targeting
E6. Further, this activation can be sustained if the endogenous p53 antagonists c-Jun-
NH2-kinase, COP1, MDM2, and Pirh2 are inhibited by their complementary siRNAs
(Koivusalo et al., 2006).
Disparate results have been obtained for shRNA targeting HPV E6 and E7. A lentiviral vector was used to carry two copies of the same shRNA (HPV E6 or E7) or two shRNAs targeting at two different but closely related genes (HPV E6 and vascular 33
endothelial growth factor, VEGF) (Gu et al., 2011). These constructs showed increased effectiveness at suppressing the gene targets, inhibiting cell and tumour growth compared to their single shRNA counterparts. Transduction of dual shRNA sensitizes
HeLa cells to the signal transduction inhibitors including the mTOR-pathway inhibitor, rapamycin, and the HDAC inhibitor, SAHA, in comparison to single shRNA-treated cells. Qi et al. cloned two synthetic double-stranded oligonucleotides, encoding short hairpin transcripts corresponding to HPV-18 E6 and E7 genes into pGenesilence (pGS)
1.0 vectors individually and in combination, namely [pGS-E6, pGS-E7, and pGS-
(E6+E7)] and demonstrated that simultaneous inhibition of HPV18 E6 and E7 had a stronger therapeutic effect compared with the inhibition of HPV18 E6 or HPV18 E7 alone (Qi et al., 2010). Controversially, Yamato and colleagues suggested E6-specific suppression may induce more potent anticancer activity than simultaneous E6 and E7 suppression for HPV positive CC (Yamato et al., 2006).
E6 and E7 are not the only siRNA targets in CC that have shown potential. Other targets that have been tested include clusterin, helicase-like transcription factor (HTLF), survivin, stathmin and arsenic trioxide (As2O3), cellular Fas-associated death domain- like interleukin-1beta-converting enzyme inhibitory protein (c-FLIP), glucose regulated protein 94 (GRP94), heat shock protein (HSP) and human telomerase RNA (hTR).
SiRNAs have also been designed to target cell cycle regulators such as CDK4 and cyclin B1. These siRNAs have been shown to be effective in causing significant G1 cell cycle arrest and the inhibition of HeLa cell proliferation and tumour growth in vivo
(Androic et al., 2008; Wang et al., 2011). Additionally, siRNAs against clusterin,
HLTF, survivin, stathmin, As2O3 and c-FLIP have also demonstrated decreased cell growth, increased apoptosis and cell cycle arrest in a number of CC cell lines (Chen et 34
al., 2009; Cho et al., 2011; Li et al., 2006; Luo et al., 2008; Park et al., 2006; Song et al.,
2008; Wang et al., 2010).
SiRNA or shRNA have also been shown to play a role in the sensitization of CC cells to chemotherapy and radiotherapy. Silencing of clusterin using siRNA increases the apoptotic effect and cytotoxicity of chemotherapeutic drugs, particularly paclitaxel
(Park et al., 2006). HLTF and survivin knockdown by siRNA enhances radiosensitivity of HeLa cells (Cho et al., 2011; Li et al., 2006). Suppression of GRP94 using siRNA reverses radio-resistance prior to radiation in CC (Kubota et al., 2005). Vector-based shRNA against c-FLIP significantly sensitizes HeLa cells to cisplatin, irinotecan and radiotherapy (Luo et al., 2008). A combination of local hyperthermia and systemic administration of cisplatin has been successfully trialled in Phase I/II studies. However, thermotolerance and chemoresistance from heat-induced expression of HSP, a complication of hyperthermia, could be counterproductive. Silencing heat shock transcription factor 1 (HSF1) enhanced hyperthermo-chemotherapy efficacy in CC
(Rossi et al., 2006).
Application of siRNA has also been successfully tested in CC in vivo models. siRNA and shRNA against survivin, stathmin and As2O3 demonstrated anti-tumour effects in
HeLa subcutaneous models (Chen et al., 2009; Li et al., 2006; Song et al., 2008). Down- modulation of hTR mRNA, telomerase activity and subcutaneous tumour was achieved by delivery of adenovirus carrying the hTR-targeting siRNA (Ad-hTR-siRNA) in HeLa cells (Li et al., 2007).
35
1.5.6.1 SiRNA Delivery
While siRNA treatments appear to have significant potential, the major challenges of siRNA as a therapy include rapid degradation of the naked oligonucleotides by endonucleases, quick clearance by liver and kidneys and the activation of interferon response upon systemic administration that could potentially lead to toxicity (Kim et al.,
2004; Soutschek et al., 2004). The advances of nanomedicine technologies have provided more useful approaches for the delivery of siRNA. SiRNA can be encapsulated in liposomes (Wang et al., 2011; Wu et al., 2011), dendrosomes (Dutta et al., 2010), lentivirus (Gu et al., 2006), atelocollagen (Kuroda et al., 2005), or polyethylenimine (PEI) (Urban-Klein et al., 2005) to prevent destruction by nucleases.
Further, siRNA can be deposited onto nanoparticles, for instance gold in a layer-by- layer (LBL) approach to fabricate well-defined and homogenously distributed nanocarriers for siRNA delivery (Elbakry et al., 2009). Localized and targeted delivery by cervical delivery devices (Hodge et al., 2012) or ultrasound-mediated microbubble destruction of siRNA could minimize systemic mediated toxicity and clearance by the liver and kidneys.
Table 1.3 Targets for siRNA therapy in cervical cancer
Gene of Cell type Effect Reference
interest
HPV16 E6, E7, SiHa Inhibition of cell proliferation and (Hong et al., E6/E7 inducing cell death, particularly 2009) senescence. SiHa Reduction of cell growth, induced (Zhou et al., apoptosis, inhibited tumour formation. 2012) 36
HeLa, C4I Reduction of cell growth and colony (Lea et al., formation, significantly increased 2007) apoptosis and reduced tumour growth in BALB/c nude mice. SiHa Sensitization of SiHa cells to cisplatin, (Tan et al., combination of cisplatin with 2012) rhTRAIL or anti-Fas antibody. Combination of SiHa Paclitaxel: synergistic toxicity and (Liu et al., HPV E6, E7 reduction of tumour growth of the 2009) with xenograft model. chemotherapy HeLa Cisplatin: sensitization of cells to (Putral et cisplatin treatment. al., 2005) HeLa, HeLa- Cisplatin: induction of cellular (Jung et al., luc, SiHa, senescence in vitro as well as 2012) CaSki apoptosis, cellular senescence and antiangiogenesis in vivo. Clusterin HT3, CaSki, Induction of anti-apoptotic effect and (Park et al., HeLa, C33A, cytotoxicity of chemotherapeutic 2006) HeLaS3, drugs, particularly paclitaxel. and SiHa
Cyclin HeLa G1 cell cycle arrest. (Wang et dependent al., 2011) kinase 4 (CDK4) Helicase-like HeLa Inhibition of cell proliferation, (Cho et al., transcription induction of apoptosis and 2011) factor (HLTF) enhancement of radiosensitivity. Glucose HeLa, SKG-I, Reversal of radio-resistance prior to (Kubota et regulated SKG-IIIb, radiation in CC. al., 2005) protein 94 QG-U, Caski, (GRP94) SiHa and C33A Survivin HeLa Reduction of cell proliferation, (Chen et al., 37
induced apoptosis and antitumour 2009) effect in a subcutaneous model. HeLa Reduction of cell growth, increased (Li et al., apoptosis and many cells were 2006) arrested at G0/G1 phase. HeLa Inhibition of tumour growth and (Song et al., declined cloning efficiency was 2008) observed especially when combined with radiotherapy. Human HeLa Inhibition of subcutaneous tumour. (Li et al., telomerase 2007) RNA (hTR) c-FLIP HeLa Inhibition of cell proliferation, (Luo et al., induced apoptosis as well as 2008) sensitizing cells to cisplatin, iritican and radiotherapy.
Stathmin HeLa, SiHa Enhancement of As2O3-triggered (Wang et apoptosis in cell culture and in mouse al., 2010) models. Cyclin B1 HeLa Inhibition of cell proliferation and (Androic et tumour growth. al., 2008) Heat shock HeLa Enhancement of (Rossi et al., transcription hyperthermochemotherapy efficacy. 2006) factor 1 (HSF1)
1.6 Novel Molecular Targets in Cervical Cancer
Recent advances in nanomedicine have shed light on the delivery of target-based molecular therapy, providing a better platform for the translation of these therapies to patient treatment. The potential use of such molecular techniques as gene silencing 38
offers an almost unlimited choice of gene targets. It is now important to identify what may be significant therapeutic targets in CC and test their validity using gene silencing techniques. The role of various transcription factors that are master regulators of many genes involved in tumourigenesis and in metastasis has not been examined in CC. These transcription factors can often target multiple growth factors and signalling pathways and therefore have significant impact on cancer cell growth. Further, they can be frequently over-expressed in many cancer cell types, signifying their potential importance to the pathogenesis of disease. Transcription factors such as the proto- oncogene c-Jun and early growth response-1 (Egr-1) are classified as immediate early genes that are known to be over-expressed in many cancer types including CC (Huang et al., 2008; Pérez-Plasencia et al., 2007; Shin et al., 2010). The significance of c-Jun and Egr-1 to CC and their potential as therapeutic targets will be discussed.
1.6.1 Immediate early genes as molecular/ therapeutic targets in cervical cancer
Immediate early genes (IEGs) are a class of genes which encode for a variety of transcription factors, cytoplasmic enzymes and secreted proteins which regulate many cellular processes including proliferation, differentiation, migration, invasion, immune response and apoptosis. IEGs are rapidly and transiently up-regulated within 1-2 hours of stimulation and do not require an initial round of protein synthesis prior to transcription initiation (Lau and Nathans, 1987). The expression of IEGs are typically induced following an extracellular signal, such as growth factors (e.g. platelet-derived growth factor, PDGF; epidermal growth factor, EGF), phorbol esters (e.g. 12-
Otetradecanoylphorbol- 13-acetate, TPA), developmental and immunological signals, mitogens and stress (e.g. UV, toxins) (Herschman, 1991). IEGs are found to have 39
similar core structures which are distinct from other genes, including delayed early genes (DEGs). Stimulation of IEGs leads to the activation of DEGs which are up- regulated after a lag of 2 to 4 hours. DEGs often lead to subsequent down-regulation of
IEG expression. IEGs are often constitutively activated in diverse cancer types concomitant with reduced expression of DEGs (Amit et al., 2007).
The rapid accumulation of IEGs in response to stimulation is regulated by both transcriptional and post-transcriptional mechanisms. At the transcriptional level, DNA accessibility to transcriptional machineries which facilitate gene expression is increased when chromatin encoding for IEGs tends to “loop out” and reside near edges of chromatin territories (Chambeyron and Bickmore, 2004) (Figure 1.11A). Moreover, reduction of nucleosomal occupancy by the presence of CpG islands in the promoters of
IEGs renders the chromatin accessible to DNA binding components, such as RNA polymerase II (Pol II) (Figure 1.11B). Activation of the poised pre-assembled Pol II at the promoters of IEGs results in a dramatic increase in production of mRNAs which are pivotal for efficient accumulation of IEGs (Hargreaves et al., 2009) (Figure 1.11C).
The recruitment of transcription factors to the promoters of these IEGs depends on rapid post-transcriptional modifications, such as phosphorylation, along with subcellular translocations. Pre-existing transcription factors accelerate the initiation of the transcription of IEGs (Sas-Chen et al., 2012) (Figure 1.11D). Subsequently, synthesis of IEG mRNA is regulated at the level of transcription elongation. The respective pre- mRNAs show a short pulse of production that significantly exceeds the eventual rise in mature mRNA levels, leading to a strong and transient production overshoot and 40
thereby fast accumulation of mature mRNAs (Zeisel et al., 2011). This production overshoot shortens the response time of cells to stimuli (Figure 1.11E).
At the post-transcriptional level, stimulant driven down-regulation of immediately down-regulated microRNAs (ID-miRs) relieves the suppression of basally transcribed
IEGs, thereby promoting rapid accumulation of the respective transcripts (Sas-Chen et al., 2012) (Figure 1.11F). RNA-protein granules, such as the processing bodies (P- bodies), function as reservoirs that sequester AU-rich mRNAs of IEGs from polysomes
(Franks and Lykke-Andersen, 2007). Upon stimulation, untranslated mRNA is released from these cellular reservoirs to the cytosol to undergo translation (Zeisel et al., 2011)
(Figure 1.11G). The rate of translation is influenced by the signalling network (Staber et al., 2007) and the number of ribosomes linked to a single transcript in response to stimuli (Piques et al., 2009) (Figure 1.11H).
As previously mentioned, IEG expression is transient and rapidly returns to undetectable levels after stimulation. However, IEG expression is found to be abnormally high and sustained in many cancer types, typically due to specific mutations in the Rat sarcoma (RAS) gene or in growth factor-binding receptors or kinases such as
Sarcoma (Src) which may ultimately lead to constitutively active MAP kinase (MAPK) signalling. Overexpression of IEGs such as c-Fos, c-Jun, Egr-1, cyclooxygenase-2
(Cox-2), immediate early response 1(Ier2), immediate early response gene X-1 (IEX-1) and nuclear receptor subfamily 4, group A (NR4A) is often associated with cancer progression, poor prognosis and tumourigenic resistance. For instance, Egr-1, c-Fos,
FosB, JunB and c-Jun are up-regulated in inflammatory breast cancer (Bièche et al.,
2004). Levels of c-Fos, Cox-2 and thioredoxin interacting protein (TXNIP) are increased in invasive and metastatic breast cancer (Gilhooly and Rose, 1999; Milde-
Langosch et al., 2004; Turturro et al., 2007). The role of IEGs in cancers is summarized 41
in Table 1.4. These are also described in greater detail below. IEGs function as major players in deregulated signalling pathways. Therefore, inhibition of IEGs can lead to reduction in cancer phenotypes. IEGs of particular interest are c-Jun and Egr-1. They are master regulators of genes involved in proliferation, migration, invasion, apoptosis and angiogenesis. Overexpression of c-Jun and Egr-1 has been found in CC (Pérez-
Plasencia et al., 2007; Shin et al., 2010). Therefore targeting these genes may provide a potential method to inhibit cancer growth, especially cervical carcinogenesis.
Table 1.4: The role of IEGs in cancers
IEGs Cancer Type Promoter/ Reference
suppressor
Cox-2 Breast cancer Promoter (Hou et al., 2011) Pancreatic ductal Promoter (Hill et al., 2012) adenocarcinoma Cervical cancer Promoter (Eichele et al., 2008; Ferrandina et al., 2002; Khunamornpong et al., 2009; Kulkarni et al., 2001; Ryu et al., 2000; Settakorn et al., 2009) TXNIP Breast cancer Promoter (Turturro et al., 2007)
Ier2 Carcinoma of cervix, breast, Promoter (Neeb et al., 2012) endometrium, liver, intestine and pancreas
IEX-1 Cervical cancer Promoter (Arlt et al., 2008; Kruse et al., 2005; Wu et al., 42
2013) Egr-1 Fibrosarcoma Suppressor (Lucerna et al., 2006) Uterine leiomyoma Suppressor (Shozu et al., 2004) Glioma Suppressor (Calogero et al., 2004) Lung carcinoma Suppressor (Sakaue et al., 2001) Thyroid cancer Suppressor (Tell et al., 2004) Breast cancer Suppressor (Huang et al., 1997) Lymphoma Suppressor (Bouchard et al., 2010) Skin tumors Suppressor (Krones-Herzig et al., 2005) Melanoma Suppressor (Nair et al., 1997) Non–small-cell lung cancer Suppressor (Ferraro et al., 2005) Cervical cancer Suppressor (Akutagawa et al., 2008; de Wilde et al., 2010) (Abdulkadir et al., Prostate cancer Promoter 2001a; Abdulkadir et al., 2001b; Yang et al., 2006) (Baron et al., 2003; Lung adenocarcinoma Promoter Shimoyamada et al., 2010) Wilms’ tumors Promoter (Scharnhorst et al., 2000) Gastric cancer Promoter (Sun et al., 2013) Bladder cancer Promoter (Egerod et al., 2009) Cervical cancer Promoter (Shin et al., 2010) c-Jun Glioblastoma Promoter (Potapova et al., 2001) Osteosarcoma Promoter (Dass et al., 2008b) Hepatocellular carcinoma Promoter (Eferl et al., 2003) Liposarcoma Promoter (Dass et al., 2008a; Mariani et al., 2007) Breast cancer Promoter (Huang et al., 2004b; Jiao et al., 2010; Smith 43
et al., 1999; Vleugel et al., 2006) Melanoma Promoter (Lopez-Bergami et al., 2007; Zhang et al., 2004) Squamous cell carcinoma Promoter (Cai et al., 2012; Zhang et al., 2006b) Prostate cancer Promoter (Chen et al., 2006; Ouyang et al., 2008) Cervical cancer Promoter (Huang et al., 2008; Nrnberg et al., 1995)
44
Figure 1.11 Mechanisms which enable rapid accumulation of IEGs (Sas-Chen et al., 2012)
1.6.2 c-Jun and the AP-1 transcription factor c-Jun is the cellular homolog of the retroviral v-Jun oncogene (Vogt, 2001). c-Jun is a basic leucine-zipper (bZIP) protein which is a subunit of the AP-1 transcription factor.
The AP-1 transcription factor (Figure 1.12) is a dimeric complex of bZIP domain protein subunits and may be formed through the leucine zipper motif by homodimerisation of proteins from the JUN family of proteins (c-Jun, JunB or JunD) or 45
heterodimerisation of Jun proteins with the FOS (c-Fos, Fos B, Fra-1 and Fra-2), MAF
(c-Maf, MafB, MafA, MafG/F/K and Nrl) or ATF (ATF-2, ATF-a, JDP1and JDP2) families of proteins (Leppä and Bohmann, 1999; Shaulian and Karin, 2002). AP-1 recognizes and binds DNA at specific sequences termed the TPA responsive element
(TRE) as well as the CAMP-response element (CRE). TRE and CRE promoter binding sites are almost ubiquitous throughout the genome, however, AP-1 binding at specific promoters under certain stimuli is determined by relative levels of subunit transcription, dimer composition, post-translational modification of subunits, and interactions with other proteins which is dependent upon promoter context. Binding to the TRE sequence is rapidly induced by a variety of physical and chemical stresses, oncoproteins, growth factors, oxidative and other forms of cellular stress, UV irradiation, cytokines, cell– matrix interactions as well as bacterial and viral infections (Eferl and Wagner, 2003;
Wisdom et al., 1999). The MAPK pathway is activated by these stimuli which then enhance AP-1 activity through the phosphorylation of its subunits. Induction of AP-1 by serum and growth factors is mediated through extracellular-signal-regulated kinase
(ERK) subgroup of MAPKs (Hill et al., 1994). Pro-inflammatory cytokines and genotoxic stress stimulate AP-1 activity through JNK and p38 MAPK cascades (Chang and Karin, 2001). Activation of c-Jun is required for the formation of a dimer. The activity of c-Jun is regulated post-translationally by phosphorylation of c-Jun on its N- terminal transactivation domain at serine (Ser) 63 and 73 by kinases of the JNK/SAPK family (Dérijard et al., 1994) (Cao et al., 2010) (Figure 1.13). AP-1 activated through these MAPK cascades then in turn regulates multiple genes involved in cell proliferation, apoptosis, differentiation, angiogenesis and tumour invasion. Most AP-1 components require “cooperating” oncoproteins, for instance, activated RAS or MEK1
(MAPK kinase) to fully elicit their oncogenic potential. These “cooperating” 46
oncoproteins induce Jun and Fos proteins as well as supporting AP-1-mediated cell transformation by post-transcriptional mechanisms (Westwick et al., 1994).
c-JUN
c-FOS
TGACTC A
Figure 1.12: Formation of AP-1 transcription factor from c-Jun and c-Fos heterodimerization (Eferl and Wagner, 2003).
1.6.3 Regulation of c-Jun expression and activity
Stabilization of c-Jun is achieved by reduced c-Jun ubiquitination, as a result of phosphorylation by JNK and ERKs. By contrast, phosphorylation of c-Jun by C- terminal Src kinase (CSK) promotes c-Jun degradation and reduced stability. This helps to maintain a low steady-state level of c-Jun, thereby inhibiting AP-1 activity and c-Jun induced transformation (Zhu et al., 2006). On the other hand, regulation of c-Jun transcriptional activity by a de-repression model has also been proposed. c-Jun is repressed by a titratable inhibition complex which functionally interacts with the epsilon and delta domains in the absence of phosphorylation. HDAC3 and co-factors interfere with c-Jun transactivation only at the epsilon domain (Weiss et al., 2003). This 47
repressor binding and inhibition by HDAC3 could be abrogated by signal dependent phosphorylation of c-Jun, thus promoting transactivation. On the other hand, in addition to phosphorylation, abundance of c-Jun protein level can relieve suppression by auto- titration of repressor components. As c-Jun is commonly elevated in cancers, this mechanism can lead to constitutive activation of c-Jun in cancer cells (Weiss and
Bohmann, 2004) (Figure 1.13). The binding of HPV E7 to HDAC (as shown in Section
1.3 Figure 1.4) could also inhibit the suppressive activity of HDAC on c-Jun transactivation, leading to overexpression of c-Jun in CC.
Figure1.13: Regulation of c-Jun transcriptional activity by de-repression model
(Weiss and Bohmann, 2004).
48
1.6.4 Importance of c-Jun to AP-1-driven oncogenesis
1.6.4.1 c-Jun and proliferation or cell growth
There is much evidence in the literature describing the links between c-Jun and cellular growth in multiple cell types. A null mutation at the c-Jun locus leads to embryonic lethality and reduced cell growth in vitro (Johnson et al., 1993). Microinjection of antibodies directed against c-Jun and c-Fos in Swiss 3T3 cells results in G1 arrest of the cell cycle, whereas anti-c-Jun antibody prevented DNA synthesis more effectively than did any of the anti-Fos antibodies (Kovary and Bravo, 1991). Tumour-prone K5-SOS-F transgenic mice harbouring an allele of Jun (JunAA) that cannot be phosphorylated by
JNK, develop smaller papillomas in the absence of c-Jun (Jochum et al., 2001; Zenz et al., 2003). Retarded growth rate of fibroblasts from c-Jun null embryos showed that c-
Jun is required for progression through the G1 phase of the cell cycle via direct transcriptional control of the cyclin D1 gene (Wisdom et al., 1999). The role of c-Jun in cell proliferation is cell type dependent. Contrary to that seen in fibroblasts, growth rates are not affected in c-Jun-/- embryonic stem cells ( Hilberg and Wagner, 1992).
1.6.4.2 c-Jun and apoptosis
The role of c-Jun in apoptosis is controversial. In c-Jun knockout fibroblast cells, p53- independent cell cycle arrest and apoptosis as well as JunB levels are induced (Gurzov et al., 2008). In vitro, increased c-Jun activity promotes apoptosis in neuronal cells
(Behrens et al., 1999). Furthermore, c-Jun is required for the survival of fetal hepatocytes as apoptosis occurred in fetal hepatocytes from c-Jun-deficient mouse embryos (Eferl et al., 1999). On the contrary, phosphorylated c-Jun plays a selective role in protecting human cancer cells from apoptosis induced by DNA damage. 49
Phosphorylation-deficient dominant negative mutant c-Jun in T98G glioblastoma cells greatly enhances the cytotoxic effects of DNA-damaging agents associated with increased apoptosis but not other non-DNA-damaging cytotoxic compounds (Potapova et al., 2001).
Two models can explain the diverse effects of c-Jun on survival and cell death. The first model (Figure 1.14A) suggests that the induction of c-Jun by UV results in activation of various genes, such as FasL, Bcl3 or Bim whose products are either positive or negative regulators of apoptosis. It is the balance between the pro-apoptotic and anti- apoptotic target genes that decides the final cell fate. This balance depends on cell type, duration and type of stimulus used to activate c-Jun as well as activation of other transcription factors. The second model suggests the function of c-Jun as a homeostatic regulator that keeps cells in a certain proliferative steady state. Constitutive activation of c-Jun by changes in the environment causes defective cell cycle progression and may trigger apoptosis in cells containing damaged DNA (Figure 1.14B) (Shaulian and
Karin, 2002). 50
Figure 1.14: The effects of c-Jun in apoptosis. (a) The direct effects of c-Jun on apoptosis through transcriptional regulation of pro- and anti-apoptotic gene products, like FasL, Bim Bcl3 and Fas. (b) The indirect effects of c-Jun on apoptosis by down- regulation of p21Cip1 expression to allow growth-arrested cells to proliferate. However, the final fate of cells exposed to UV will be determined by the extent of the UV-induced cell damage (Shaulian and Karin, 2002).
1.6.4.3 c-Jun and invasion/ metastasis c-Jun–c-Fos complexes might regulate genes that are important for invasion and metastasis. Reduction of c-Jun-/- 3T3 cell migration and invasion by suppression of c-
Jun is mediated through inhibition of c-Src and hyperactivation of ROCK II kinase (Jiao 51
et al., 2008). Ectopic expression of the dominant-negative c-Jun mutant TAM67 has been shown to inhibit the invasiveness of several cell types (Lamb et al., 1997). TAM67 is a mutant form of c-Jun in which the COOH-terminal DNA binding and dimerization domain are intact but the transactivation domain (amino acids 3–122) has been deleted.
TAM67 is able to bind to AP-1 recognition elements in promoter regions of target genes and competitively quench the transactivation activity of endogenous wild-type Jun and its dimerization partners. In addition, the development of breast cancer invasion and invasive spindle-cell carcinomas in mouse skin tumourigenesis models is associated with overexpression of c-Jun/ AP-1 family members as well as its transcription factor activity (Sankpal et al., 2011; Zoumpourlis et al., 2000). Maximal activation of MMP expression in stress conditions present in the tumour is determined by MAPK-mediated activation of AP-1 and ETS transcription factors (Westermarck and Kahari, 1999).
MMPs play a role in extra-cellular matrix (ECM) degradation which facilitates cell invasion.
In the process of metastasis and invasive growth, c-Jun can induce epithelial– mesenchymal transition (EMT), which is the transition of tumour cells from an epithelial to a mesenchymal morphology. An epithelium is formed by a relatively thin layer of cells which adhere laterally by cell-to-cell junctions. Mesenchymal cells typically have only points on their surface engaged in adhesion to their neighbors, forming a more diffused and relaxed organization of tissue network. This provides the mesenchymal cells more flexibility and motility, thus leading to migration and invasion
(Thompson et al., 2005).
52
1.6.5 c-Jun and cervical cancer
High c-Jun expression has been found consistently in CC tissue samples (Huang et al.,
2008; Perez-Plasencia et al., 2008). For example, in 9 out of 12 CC tissue samples in the human protein atlas c-Jun has been shown to be highly expressed. Overexpression of c-
Jun has been demonstrated by microarray studies in fresh biopsies of invasive squamous
CC Stage IIB HPV16 relative to normal cervical tissues (Pérez-Plasencia et al., 2007) and shown to be enhanced in a separate study in non-invasive squamous CC patient tissue samples (Huang et al., 2008). In contrast to normal-appearing cervical mucosa, all cervical patients’ tumours (n=9) showed a strong expression of c-fos and c-Jun by in situ hybridization in comparison to normal-appearing cervical mucosa (Nrnberg et al.,
1995). c-Jun expression was mainly observed in the lower layers of epithelia or throughout the undifferentiated cells in high-grade CIN and invasive cancer but weak signals were also observed in more differentiated layers in normal cervix and low-grade
CIN II which retain markers of terminal differentiation ( Kyo et al., 1997).
In CC cell lines, high c-Jun expression has also been demonstrated in vitro. In HeLa cells, an HPV-18 positive CC cell line, c-Jun was present and found together with c-Jun,
JunB, JunD and c-Fos in the composition of activated AP-1 complex by supershift assays (Thierry et al., 1992). AP-1 is a major transcription factor essential for efficient transcription and gene expression of HPV16/18 (Butz and Hoppe-Seyler, 1993; Rösl et al., 1997; Thierry et al., 1992). Binding sites for AP-1 and SP-1 are found in the non- coding upstream regulatory region (URR) of all HPV types studied (Longworth and
Laimins, 2004). Thus AP-1 composition may be pivotal in determining the in vivo phenotype of HPV-positive cells and in some cases other AP-1 subunits may play a preferential role (de Wilde et al., 2008; Offord and Beard, 1990; Soto et al., 1999; Soto et al., 2000) [3, 4, 13, 14]. For example, c-Fos and JunB in one study was shown to be 53
highly expressed in malignant CC tissues whereas c-Jun expression remained constant from normal tissues to cancer tissues and a preferential heterodimer of c-Fos and JunB was observed in supershift analysis of HeLa cells instead of its canonical dimerization partner c-Jun (Prusty and Das, 2005). In another study, conversion of HPV 18 positive non-tumourigenic HeLa-fibroblast hybrids to tumourigenic cells required modification of the active AP-1 complex from Fra-1/c-Jun to c-Fos/c-Jun heterodimerization, suggesting a critical role for c-Fos in tumourigenesis in some cases.
1.6.5.1 c-Jun and HPV
As stated above, AP-1 is a major transcription factor essential for efficient transcription and gene expression of HPV16/18 (Butz and Hoppe-Seyler, 1993; Rösl et al., 1997;
Thierry et al., 1992). Binding sites for AP-1 and SP-1 are found in the non-coding upstream regulatory region (URR) of all HPV types studied (Longworth and Laimins,
2004). The activation of transcription from the HPV-18 constitutive (C) enhancer by
AP-1 occurs only in combination with keratinocyte-specific transcription factor (KRF-
1) and possibly other unidentified factors (Mack and Laimins, 1991). For example, p300 was shown to cooperate with c-Jun to activate the activity of HPV-16 long coding region (LCR) (Fontaine et al., 2001). On the other hand, selective degradation of c-Jun by ectopic expression of retinoic acid receptor 2 (RAR2) caused down-regulation of
HPV-18 transcriptional activity in HeLa cells (De-Castro Arce et al., 2004a; De-Castro
Arce et al., 2004b). Further, physical interaction of HPV E7 with the c-Jun protein leads to enhancement of AP-1 activity, which may be part of the mechanism by which HPV transforms cells (Antinore et al., 1996). Interaction between c-Jun and the E6 protein may also be responsible for the prolonged c-Jun mRNA peak observed in G1 phase in 54
both HPV16 and HPV18 E6 cells (Fogel and and Riou, 1998). In recent work, Maritz and colleagues demonstrated that inhibition of AP-1 activity using the c-Jun dominant negative inhibitor, TAM67, significantly reduces cell proliferation and anchorage independent colony formation in HPV positive CC cells, CaSki and is associated with p21 (Maritz et al., 2011). The evidence of the relationship between c-Jun/ AP-1 and
HPV16 E7 can also be found in other cell types. RT-PCR, immunoblotting and immunofluorescence staining of rat fibroblast cells which constitutively express HPV16
E7 showed that c-Jun is required for the restoration of N-cadherin. N-cadherin-mediated adhesion is suppressed by HPV16 E7 via ERK/ AP-1 c-Jun pathway (Yuan et al., 2009).
The expression of dominant negative c-Jun (TAM67) in the mouse skin protects the mice against HPV16E7 oncogene-induced tumourigenesis, without affecting E7- induced deregulation of cell cycle and proliferation (Young et al., 2002a).
Clearly, c-Jun is highly expressed and closely associated with HPV transcription as well as cervical tumourigenesis. However, its role in the phenotypes and the underlying mechanism needs to be further elucidated.
1.6.6 Egr-1
Egr-1 is a nuclear protein that contains three zinc fingers of the C2H2 subtype. It is an immediate early gene as well as DNA-binding transcription factor which is rapidly expressed and activated in response to a wide variety of stimuli, including serum, growth factors, UV, gamma-radiation, X-ray radiation and stress. Egr-1 contains DNA- binding domains, activation domains and inhibitory domains. Egr-1 binds to the GC- rich consensus DNA sequences of promoters and its DNA-binding activity can be modulated by phosphorylation (Huang and and Adamson, 1994). Egr-1 binding 55
proteins, such as NGF1-A binding protein 1 (NAB1) and NGF1-A binding protein 2
(NAB2) (Miano and Berk, 1999; Russo et al., 1995), also contribute to the regulation of
Egr-1 activity. NAB2 is itself transcriptionally regulated by Egr-1 and acts as a repressor in a negative feedback loop to limit expression of Egr-1 and its target genes
(Kumbrink et al., 2010). Egr-1 null mice are viable and display a rather mild phenotype without any obvious defects in cell differentiation (Lee et al., 1996). Egr-1 has been shown to have anti-proliferative, anti-angiogenic, anti-apoptotic and pro-apoptotic roles in various cellular contexts. For example, sustained expression of Egr-1 by recombinant adenoviruses in endothelial cells inhibits angiogenesis through downregulation of
VEGF and bFGF (Lucerna et al., 2006). Egr-1 induces apoptosis via phosphatase and tensin homolog (PTEN) in UV-induced apoptosis (Virolle et al., 2001), while upon exposure to ionizing radiation, Egr-1 inhibits the functions of radiation-induced pro- survival genes (NFκB activity and bcl-2 expression) and activates pro-apoptotic genes
(such as bax) to achieve a significant radio-sensitizing effect (Ahmed, 2004).
1.6.6.1 Egr-1 – a tumour promoter or suppressor?
Unlike c-Jun, Egr-1 can act as either a tumour promoter or suppressor depending on the cellular context. In uterine leiomyoma, Egr-1 has been found to be down-regulated in comparison to its relatively high expression in the normal myometrium, suggesting more of a role as a tumour suppressor (Shozu et al., 2004). In glioma cells, constitutive expression of Egr-1 using a recombinant adenovirus system drastically reduces cell growth regardless of the mutational status of the p53 gene (Calogero et al., 2004).
Constitutive Egr-1 expression has also been shown to inhibit cell invasion and vessel formation in a murine Matrigel model as well as suppression of tumour growth in a 56
murine fibrosarcoma model (Lucerna et al., 2006). In HT1080 fibrosarcoma cells, Egr-1 expressing clones regain a more normal phenotype through increased transactivation of fibronectin and plasminogen activator inhibitor, which in turn enhance cell attachment
(Liu et al., 1999).
Egr-1 also plays a tumour suppressor role in thyroid cell transformation (Tell et al.,
2004). Weak or no Egr-1 expression has been reported in several breast cancer cell lines compared to their normal counterparts (Huang et al., 1997). The reduced Egr-1 expression in rat mammary tumours was increased to normal levels in tumours that regressed after tamoxifen treatment. The tumour suppressor role of Egr-1 was demonstrated when EGF-induced Egr-1 activation suppressed MMP-9 expression and lymphoma growth (Bouchard et al., 2010). In an in vivo two-step skin carcinogenesis study, Egr-1 null mice displayed uniformly accelerated development of skin tumours via regulation of p53 (Krones-Herzig et al., 2005).Apoptosis was induced in human
A375-C6 melanoma cells stably transfected with Egr-1 expression vector via p53
(Nair et al., 1997). Low levels of Egr-1 were found in NSCLC compared with normal lung (Ferraro et al., 2005). The low expression of Egr-1 in NSCLC is associated with poor survival, high recurrence and resistance to therapy.
In other cancer types however, Egr-1 appears to play a role as tumour promoter. In prostate cancer, Egr-1 is highly expressed and serves as a positive regulator in prostate tumourigenesis. Evidence for the latter comes from in vivo experiments with Egr-1- deficient mice which demonstrate retarded prostate tumour growth (Abdulkadir et al.,
2001b). Egr-1 appears to promote translocation of the androgen receptor into the nucleus, a key factor which drives prostate cancer development (Yang and Abdulkadir,
2003). Egr-1 was also shown to be able to induce prostate cancer progression independent of androgen in vitro and in vivo (Yang et al., 2006). Interestingly, most of 57
the prostate carcinoma specimens exhibit a loss of the negative feedback of NAB2- regulated Egr-1 protein expression, indicating that high levels of Egr-1 with low levels of NAB2 promotes the onset of prostate cancer (Abdulkadir et al., 2001a).
Elevated Egr-1 expression and a tumour promoter role have also been described in lung adenocarcinoma cells carrying mutant K-RAS or EGFR genes (Shimoyamada et al.,
2010). Binding of Egr-1 to the proximal region of VEGF-A promoter leads to activation of VEGF-A expression and enhances hypoxia inducible factor 1α (HIF-1α) mediated
VEGF-A expression. Relative elevation of EGR-1 and VEGF-A expression in mutant
K-RAS- or EGFR-carrying adenocarcinomas and correlations between EGR-1/HIF-1α and VEGF-A expressions is further confirmed in human lung adenocarcinoma by immunohistochemistry. High expression of Egr-1 was found in Wilms’ tumors, suggesting a tumour promoter role (Scharnhorst et al., 2000). Moreover, Egr-1 overexpression increased baby rat kidney cell proliferation in nude mice. In gastric cancer, Egr-1 enhanced cell proliferation and invasion (Sun et al., 2013). The frequency of tumour cells with nuclear Egr-1 immuno-labelling correlated positively to bladder cancer stage, grade and metastasis (Egerod et al., 2009).
1.6.6.2 Egr-1 and cervical cancer
To date, limited and conflicting findings confound the role of Egr-1 in CC. Suppressor evidence demonstrated that overexpression of Egr-1using an expression plasmid inhibited hTERT promoter activity, mRNA and protein expression, suggesting Egr-1 down-regulates telomerase (Akutagawa et al., 2008). In CC cells however, the repressive activity of Egr-1 may be inhibited by DNA methylation, relieving the inhibition on hTERT expression, because in approximately half of the alleles in the 58
HPV-immortalized cell lines and CC cell lines, the Egr-1 site was methylated (de Wilde et al., 2010).
On the other hand, Egr-1 expression was shown to be much higher in CC tissues than in the normal cervix (Shin et al., 2010). Egr-1 is essential for MMP-9 transcription. In
HeLa cells, it directly binds to the MMP-9 promoter and together with NF-κB can synergistically activate both basal and TNFα-induced MMP-9 promoter activities in the presence of p300 (Shin et al., 2010). Clearly, the role of Egr-1 in CC remains controversial and needs to be further elucidated.
1.7 Hypothesis and Aims
The need for new alternative treatments for CC is crucial despite the recent advent of preventive vaccines and cervical screening. The high toxicity, side effects and development of resistance to existing drugs, further urges the requirement for new therapies. To overcome this, gene targeting and molecular approaches are emerging.
IEGs such as c-Jun and Egr-1 are known to be up-regulated in CC and contribute to cancer growth and progression and thus may provide novel gene targets for therapy.
Therefore, the work in this thesis is based on the following hypotheses:
1) That molecular targeting of the IEG c-Jun will prevent or reduce CC cell growth
and CC progression;
2) That molecular targeting of the IEG Egr-1 will prevent or reduce CC cell growth
and CC progression.
59
The overall aim of this study is therefore to examine the ability of molecular siRNA approaches targeting c-Jun and Egr-1 to attenuate CC cell growth. Specifically, the aims of this thesis are:
1) To silence c-Jun gene expression in HeLa cervical cancer cells using siRNA
targeting c-Jun and determine the phenotypic effect on cellular proliferation,
migration and invasion.
2) To silence Egr-1 gene expression in HeLa cervical cancer cells using siRNA
targeting Egr-1 and determine the phenotypic effect on cellular proliferation,
migration and invasion.
3) To use siRNA techniques to silence Egr-1 and c-Jun gene expression in HeLa
CC cells and examine the effect on downstream gene expression.
4) To overexpress c-Jun in HeLa cervical cancer cells using c-Jun expression
vector and determine the phenotypic effect on cellular proliferation and
invasion.
5) To overexpress c-Jun in HeLa cervical cancer cells using c-Jun expression
vector and examine the effect on downstream gene expression.
6) To determine the potential of synergism of c-Jun siRNA and cisplatin
combination treatment.
7) To examine the efficacy of c-Jun silencing with targeted siRNA to attenuate
tumour growth in a pretransfected subcutaneous model of CC. 60
Chapter 2:
Materials and Methods
61
2 Materials and Methods
2.1 Media, Buffers and Solutions
2.1.1 Dulbecco's Modified Eagle Medium (DMEM)
Five hundred millilitres DMEM (Gibco®, Life Technologies, Australia) with low glucose (1g/mL) was supplemented with 10U/mL penicillin, 10U/mL streptomycin and
10% (v/v) fetal bovine serum (FBS) (JRH Biosciences, Australia).
2.1.2 Minimum Essential Media (MEM)
Five hundred millilitres MEM (Gibco®, Life Technologies, Australia) was supplemented with 10U/mL penicillin, 10U/mL streptomycin, 5mL of 100x MEM non- essential amino acids (Gibco®, Life Technologies, Australia) and 10% (v/v) FBS (JRH
Biosciences, Australia).
2.1.3 RIPA Buffer
Five hundred microlitres of 1 x RIPA buffer was prepared by mixing 150nM NaCl
(Sigma, USA), 50nM Tris-HCl pH 7.5 (Sigma, USA), 1% deoxycholate (w/v) (ICN,
Biomedicals, Inc, France), 0.1% (v/v) sodium dodecyl sulfate (SDS), 1% (w/v) Triton
X-100 (Sigma, USA), 1% (v/v) aprotinin-Trasylol (Bayer, Germany), 5mg/ mL leupeptin (Sigma, USA), together with 100nM phenylmethylsulfanyl (PMSF) (Sigma,
USA).
62
2.1.4 4x SDS protein loading sample buffer
Five hundred microlitres 1M Tris-HCl (pH 6.8) (Sigma, USA), 800µL 100% (v/v) glycerol (Merck, Germany), 900µL 20% (w/v) SDS and 400µL 0.05% (w/v) bromophenol blue (Sigma, USA) were added to 500µL of dH2O.
2.1.5 Resolving gel
Ten percent SDS-PAGE resolving gel was prepared with 2.5mL of 1.5M Tris (pH 8.8),
2.5mL of 40% (v/v) acrylamide (Bio-Rad Laboratories, Inc), 100µL of 10% (w/v) SDS,
5µL Tetramethylethylenediamine (TEMED) (Sigma, USA), 50µL of 10% (w/v) ammonium persulphate (APS) (Sigma, USA) and 4.86mL of dH2O.
2.1.6 Stacking gel
The stacking gel was prepared with 1.26mL of 0.5M Tris (pH 6.8), 700µL of 40% (v/v) acrylamide, 50µL of 10% (w/v) SDS, 5µL TEMED, 25µL of 10% (w/v) APS and
3.6mL of dH2O.
2.1.7 Mini-PROTEAN® TGXTM Precast Gels
Four to twenty percent Mini-PROTEAN ® TGXTM Precast Gels (Bio-Rad, USA) were also used for western blotting.
2.1.8 SDS Running Buffer
Six grams Tris-base (ICN, Biomedicals, Inc, France), 28.8g glycine (Sigma, USA), 2g
SDS were made up to 1L with dH2O.
63
2.1.9 Transfer Buffer
Six grams Tris-base (ICN, Biomedicals, Inc, France), 28.8g glycine (Sigma, USA) were mixed with 200mL methanol and made up to 1L with dH2O.
2.1.10 Phosphate Buffered Saline (PBS) (10X)
One vial of Dulbecco’s PBS (Gibco®, Life Technologies, Australia) was made up to 5L with dH2O.
2.1.11 Phosphate Buffered Saline (PBS) (1X)
Sterile Dulbecco’s 1 x PBS (Gibco®, Life Technologies, Australia) was purchased for cell culture use.
2.1.12 PBS-T
Zero point zero five percent (v/v) Tween-20 (Sigma, USA) was added to 1 x PBS (1:10 dilution from 10 x PBS) for western blotting.
2.1.13 Luria-Bertani (LB) - Ampicillin medium
LB growth medium was prepared using 7 LB pellets (BIO101, USA), dissolved in
250mL of dH2O. Medium was sterilized by autoclaving. For preparation of agar plates,
5g of bacteriological agar (Gibco) was added to LB medium prior to autoclaving. For plasmid selection, Ampicillin (Austrapen, Australia) at a concentration of 200µg/mL was added to growth medium and plates prior to culture or pouring of plates.
64
2.1.14 Frozen glycerol stocks
Six hundred microlitres of bacterial culture was mixed with 400µL of 50% (v/v) glycerol (Sigma, USA) and stored at -80°C.
2.1.15 N -[1-(2,3-dioleoyloxy)-propyl]- N , N , N -trimethylammonium methyl sulfate (DOTAP)/ dioleyl phosphatidyl ethanolamine (DOPE) Mixture
DOTAP and DOPE were dissolved in sterile absolute ethanol and sterile water was added to make up to 80% ethanol, respectively. The final concentration of each DOTAP and DOPE was 1mg/mL. The mixture of DOTAP/ DOPE was prepared by mixing equal volumes of each lipid and was stored at -20°C in 1mL aliquots.
2.1.16 MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) solution
MTT (Sigma) was weighed and dissolved with 1 x PBS to a final concentration of
4mg/mL. The solution was filtered sterilized in a tissue culture hood using a 0.22μm syringe filter unit (Millipore, USA) attached to a syringe with BD Luer-Lok Tip (BD
Biosciences, USA) and stored at -20°C in the dark.
2.2 Cell Culture
HeLa cells were a gift from Professor Wendy Jessup (Concord Repatriation General
Hospital/ANZACRI, Australia). HeLa-luc cells were obtained from Caliper Life
Sciences, Inc., USA. HeLa cells were cultured in DMEM in 75cm2 flasks (T75, Nunc,
Denmark) and incubated at 37°C in a humidified atmosphere of 5% carbon dioxide
(CO2), using an Air Jacket CO2 incubator (Model 60A0100a, Thermoline). At 90% cell confluency, culture medium was removed and cells were rinsed twice with pre-warmed 65
1 x PBS. Trypsinization of the cells was performed by addition of 2mL 0.05% Trypsin and 0.02% ethylenediaminetetraacetic acid (EDTA) in Hank’s balanced salt solution
(BioWhittaker) followed by incubation at 37°C, 5% CO2 for 1-2 minutes. Flasks were tapped to dislodge the cells. Cells were re-suspended in 10% FBS DMEM and seeded onto T75 flask with 10mL of medium. The cells were swirled gently to ensure proper and even cell distribution, followed by incubation in the incubator. The split ratio for
HeLa cells was 1:10 once a week. HeLa-luc cells were cultured in 10% FBS MEM and split at a ratio of 1:15 once a week. Cell culture conditions and trypsinization processes were the same with HeLa cells.
2.3 Plasmid Purification
2.3.1 Transformation of competent cells c-Jun expression vector, pCMV6-Jun and its control vector, pCMV6-XL4 were obtained from OriGene Technologies, Inc. (USA). Each plasmid was transformed into
XL10-Gold Ultracompetent Cells (Stratagene, USA), respectively. Four microlitres of the β-Mercaptoethanol (provided with this kit) was added to 50μl of thawed competent cells in pre-chilled 14mL BD Falcon polypropylene round-bottom tubes. The tubes were swirled gently and incubated on ice for 10 minutes, swirling gently every 2 minutes. Fifty nanograms of each plasmid were added to the cells and the tubes were incubated on ice for 30 minutes. The suspension was heat-shocked at 42°C in a water bath for 30 seconds and incubated on ice for 2 minutes. Four hundred and fifty microlitres of pre-heated S.O.C. medium (Gibco, USA) was added to the cell suspension and incubated at 37°C for 1 hour with shaking at 225-250 rpm using a vertical rotator (Bioline orbital shaker incubator model BL 4600, Edwards Instrument 66
Company, Australia). The transformation mixture was spread on LB-ampicillin agar plates and incubated overnight at 37°C.
2.3.2 Maxi-prep: large scale DNA purification
A single colony was selected from LB- Ampicillin plate and inoculated into 5mL LB/
Ampicillin broth. The bacterial culture was incubated in a 37°C shaking incubator for approximately 6 hours. The suspension was then poured into 200mL LB/ Ampicillin broth and shaken at 37°C overnight at 225-250 rpm. The next day, a small aliquot was used to make frozen glycerol stocks (Section 2.1) while the rest of the suspension was centrifuged at 4000rpm in a pre-cooled centrifuge for 10 minutes. The pellet was subjected to large scale plasmid purification using PureLink® HiPure Plasmid Filter
Purification Kits (Invitrogen, USA) following the manufacturer’s manual. Plasmid
DNA was dissolved in 500μl of sterile water. DNA concentration was determined by reading absorbance at 260nm on a Nanodrop 1000 spectrophotometer (Thermo Fisher
Scientific, USA).
2.4 Transfection
2.4.1 SiRNA transfection
Dharmacon ON-TARGETplus SMARTpool siRNAs (Thermo Scientific, USA) to c-
Jun, Egr-1 and Cox-2 as well as ON-TARGETplus Non-targeting Pool siRNA were used in the experiments. The sequences of the siRNAs are listed in Table 2.1. HeLa cells were seeded in 6cm2 or 10cm2 petri dishes in 10% FBS DMEM. After 24 hours, cell culture medium was removed and serum-free medium was added. Six hours later, the serum-starved cells were transfected with 50nM c-Jun or 100nM Egr-1 siRNA in serum-free medium. Sixteen hours later, culture medium was removed and cells were 67
transfected again with 50nM c-Jun or 100nM Egr-1 siRNA in serum-free medium. After
24 hours, the cells were stimulated with 10% FBS DMEM for various time points, depending on the experiment. For Cox-2 siRNA transfection, HeLa cells were serum- starved for 24 hours. The culture medium was removed and cells were transfected with
100nM Cox-2 siRNA for 24 hours. After 24 hours, the cells were stimulated with 10%
FBS DMEM for various time points, depending on the experiment. For zymography, cells were stimulated with 50ng/ mL 12-O-tetradecanoyl phorphol 13-acetate (TPA) containing DMEM for 24 hours. The transfection mixture for all siRNA experiments was prepared at the ratio of 1µg siRNA to 1µL DOTAP/DOPE. DOTAP/ DOPE was added to serum-free medium followed by addition of siRNA. The transfection formulation was mixed well by pipetting up and down a few times and incubated at room temperature for 30 minutes before adding drop-wise to the cells.
Table 2.1: Sequences of siRNAs
ON-TARGETplus SMARTpool, human JUN siRNA
ON-TARGETplus SMARTpool siRNA J-003268-10, JUN
Target sequence: GAG CGG ACC UUA UGG CUA C
ON-TARGETplus SMARTpool siRNA J-003268-11, JUN
Target sequence: GAA CAG GUG GCA CAG CUU A
ON-TARGETplus SMARTpool siRNA J-003268-12, JUN
Target sequence: GAA ACG ACC UUC UAU GAC G
ON-TARGETplus SMARTpool siRNA J-003268-13, JUN
Target sequence: UGA AAG CUC AGA ACU CGG A
68
ON-TARGETplus SMARTpool, human EGR-1 siRNA
ON-TARGETplus SMARTpool siRNA J-006526-06, EGR-1
Target sequence: GAU GAA CGC AAG AGG CAU A
ON-TARGETplus SMARTpool siRNA J-006526-07, EGR-1
Target sequence: CGA CAG CAG UCC CAU UUA C
ON-TARGETplus SMARTpool siRNA J-006526-08, EGR-1
Target sequence: GGA CAU GAC AGC AAC CUU U
ON-TARGETplus SMARTpool siRNA J-006526-09, EGR-1
Target sequence: GAC CUG AAG GCC CUC AAU A
ON-TARGETplus SMARTpool, human COX-2 siRNA
ON-TARGETplus SMARTpool siRNA J-004557-06, COX-2
Target sequence: GGA CUU AUG GGU AAU GUU A
ON-TARGETplus SMARTpool siRNA J-004557-07, COX-2
Target sequence: GAU AAU UGA UGG AGA GAU G
ON-TARGETplus SMARTpool siRNA J-004557-08, COX-2
Target sequence: GUG AAA CUC UGG CUA GAC A
ON-TARGETplus SMARTpool siRNA J-004557-09, COX-2
Target sequence: CGA AAU GCA AUU AUG AGU U
ON-TARGETplus Non-targeting Pool
Sequence was not provided by the supplier.
2.4.2 Plasmid transfection
HeLa cells were seeded in 6cm2 or 10cm2 petri dishes in 10% FBS DMEM. After 24 hours, cell culture medium was removed and serum-free medium was added. Cells were 69
serum-starved for 24 hours before plasmid transfection. The transfection mixture was prepared at the ratio of 1µg plasmid to 3µL Fugene (Roche). Fugene was added to serum-free medium followed by addition of plasmid. The transfection formulation was mixed well by pipetting up and down a few times and incubated at room temperature for
30 minutes before adding drop-wise to the cells. Twenty-four hours after transfection, culture medium was removed and cells were stimulated with 10% FBS DMEM at various time points for gene expression studies.
2.5 Gene Expression Analysis
2.5.1 Total RNA extraction
After transfection and stimulation with 10% FBS DMEM for various time points, HeLa cells were rinsed twice with 1 x ice-cold PBS. Immediately after removal of PBS,
600µL of lysis buffer from Qiagen RNeasy Mini Kit (Qiagen, USA) was added to each petri dish. Cells were lifted with a Costar cell lifter (Corning Incorporated, Mexico) and passed through an insulin syringe 5 times for homogenization, followed by pipetting up and down several times to ensure complete cell lysis. Cell lysate was then frozen at -
80°C until required. Before RNA extraction, cell lysate was thawed at 37°C. RNA was extracted following the protocols from Qiagen RNeasy Mini Kit. RNA was resuspended in 30µL RNase-free water and stored at -80°C. RNA concentration was determined by reading absorbance at 260nm on a Nanodrop 1000 spectrophotometer. RNA purity was determined by the A260/ A280 ratio. RNA with an A260/ A280 ratio of greater than 1.8 was used for cDNA synthesis.
70
2.5.2 cDNA synthesis from total RNA
Reaction mix was composed of 1µg of total RNA, 1µL of 0.5µg/ mL Oligo (dTs)
(Sigma), 1µL of 10mM deoxyribonucleoside triphosphate mix (dNTPs) (Roche) (10mM each dATP, dGTP, dCTP and dTTP) and dH2O to a final volume of 20µL. Reaction tubes were incubated at 65°C for 5 minutes, then immediately chilled on ice and quick spun. To each sample, 7µL of the master mix was added. Master mix was composed of
4µL 5 x First Strand Buffer (Invitrogen, USA), 2µL of 0.1M dithiothreitol (DTT)
(Invitrogen, USA) and 1µL RNAsin (Promega, USA). The contents were quick spun and incubated at 42°C for 2 minutes. One microlitre of Superscript II (Invitrogen, USA) was added and mixed by gently pipetting. Samples were incubated at 42°C for 50 minutes. The reaction was inactivated at 70°C for 15 minutes. cDNA was either stored at -20°C or used immediately as template for quantitative real-time polymerase chain reaction (qPCR).
2.5.3 Quantitative real-time polymerase chain reaction (qPCR) qPCR was performed using Corbett RotorGene 6000 Sequence Detection System
(Corbett Life Science, Australia). Reaction mixture consisted of 10µL of 2 x SYBR®
Green PCR Master Mix (Applied Biosystems, USA), 1µL of cDNA, 0.3µL of 10µM forward and reverse primers (Sigma) (Table 2.2) and RNase-free water to a final volume of 20µL. qPCR cycling conditions were listed in Table 2.2. Glyceraldehyde 3- phosphate dehydrogenase (GAPDH) mRNA expression served as an internal control. Its expression was measured simultaneously with gene of interest for each sample in triplicate. Relative gene expression was calculated using the Delta-Delta Ct method.
71
Table 2.2: qPCR conditions and primer sequences used for mRNA gene expression analysis
qPCR cycling condition for c-Jun, Egr-1, GAPDH, ICAM-1 and MMP-2
Initial hold: 50°C for 2 minutes
Hold: 94°C for 10 minutes
Cycling condition: 94°C for 20 seconds, 60°C for 45 seconds, 72°C for 20 seconds
Number of cycles: 40 x
Human c-Jun
Forward: 5’- AGA GGA AGC GCA TGA GGA A -3’
Reverse: 5’- CCA GCC GGG CGA TTC -3’
Human Egr-1
Forward: 5’- CTT CAA CCC TCA GGC GGA CA -3’
Reverse: 5’- GGA AAA GCG GCC AGT ATA GGT -3’
Human GAPDH
Forward: 5’- GAA GGC TGG GGC TCA TTT -3’
Reverse: 5’- CAG GAG GCA TTG CTG ATG AT -3’
Human ICAM-1
Forward: 5’- TGC CCG AGC TCA AGT GTC TA -3’
Reverse: 5’- GCC TGC AGT GCC CAT TAT -3’
Human MMP-2
Forward: 5’- TAT GAC AGC TGC ACC ACT GAG -3’
Reverse: 5’- ATT TTG TTG CCC AGG AAA GTG -3’
qPCR cycling conditions for MMP-1, MMP-9 and Cox-2
Initial hold: 50°C for 2 minutes
Hold: 94°C for 10 minutes 72
Cycling conditions: 94°C for 30 seconds, 58°C for 30 seconds, 72°C for 30 seconds
Number of cycles: 40 x
Human MMP-1
Forward: 5’- TTC CCA GCG ACT CTA GAA ACA -3’
Reverse: 5’- AGA ATT CCT GCA TTT GCT TCA -3’
Human MMP-9
Forward: 5’- TTG ACA GCG ACA AGA AGT GG -3’
Reverse: 5’- GCC ATT CAC GTC GTC CTT AT -3’
Human Cox-2
Forward: 5’- CCC TTG GGT GTC AAA GGT AA-3’
Reverse: 5’- GCC CTC GCT TAT GAT CTG TC-3’
qPCR cycling conditions for HPV18 E6 and E7
Initial hold: 50°C for 2 minutes
Hold: 94°C for 10 minutes
Cycling conditions: 94°C for 20 seconds, 62°C for 45 seconds, 72°C for 20 seconds
Number of cycles: 40 x
Human HPV18 E6
Forward: 5’- CCA GAA ACC GTT GAA TCC -3’
Reverse: 5’- AGT CGT TCC TGT CGT GCT C -3’
Human HPV18 E7
Forward: 5’- CGA ACC ACA ACG TCA CAC AAT -3’ 73
Reverse: 5’- TGG AAG CTC GTA AGG TCG T-3’
2.6 Western blotting
After transfection and stimulation with 10% FBS DMEM for various time points, HeLa cells were rinsed twice with 1 x ice-cold PBS. Immediately after removal of PBS,
200µL of RIPA buffer was added to the cells (Section 2.1.3). Cells were lifted using a
Costar cell lifter and pipetted up and down several times. Cell lysates were frozen at -
80°C and thawed on ice to ensure complete cell lysis. The samples were then centrifuged for 10 minutes at 4°C. The supernatant was used for determination of protein estimation by the BCA Protein Assay Kit (Pierce, USA). Quantification was performed on a FLUOstar Omega (BMG LABTECH, Germany) at an absorbance of
562nm using Omega data analysis.
Protein samples along with 6µL 4 x SDS protein loading buffer and 2µL of 0.5M DTT were denatured for 5 minutes at 100°C followed by placing on ice for 1 minute and quick spun. One microlitre of 0.5M iodoacetamide (IAM) was added to each tube.
Samples were loaded onto SDS-PAGE gel at the specified percentage of acrylamide.
Gels were subjected to electrophoresis at 100V for 1.5 hours in SDS running buffer.
Kaleidoscope protein ladder (Promega, USA) was loaded alongside samples.
After electrophoresis, protein on the gel was transferred onto pre-soaked (absolute ethanol and thoroughly rinsed) Immobilon-P polyvinylidene fluoride nylon transfer membrane (PVDF) (Millipore, USA) in pre-cooled Transfer buffer. The transfer was done by the assembly of “gel-membrane sandwich”, which in a pre-established order consisted of sponge, blotting paper, gel, PVDF membrane, blotting paper and sponge. 74
This was set up in a cassette and placed in the electrophoresis apparatus with ice block and run at 100V for 2 hours.
After transfer and apparatus disassembly, the gel was stained with GelCode Blue
(Pierce, USA) for 1 hour and de-stained in dH2O overnight. Meanwhile, the membrane was air-dried, washed with 100% (v/v) ethanol and rinsed with dH2O followed by immersion in blocking buffer consisting of 5% (w/v) skim milk powder in PBS-T for 1 hour. Primary antibodies diluted in 5% (w/v) skim milk-PBS-T according to Table 2.3 were added to the membranes and incubated overnight at 4°C with constant gentle shaking. On the next day, the membranes were washed 3 times with PBS-T for 15 minutes each at room temperature prior to incubation with appropriate secondary antibody conjugated to horse radish peroxidase (HRP) (Dako Corporation, USA) for 1 hour at room temperature. Secondary antibodies were diluted in 5% skim milk (w/v) –
PBS-T. Membranes were washed 3 times with PBS-T for 15 minutes each. Then, membranes were incubated with Renaissance chemilumescent reagents (ECLTM
Western Blotting Detection Reagent, GE Healthcare, UK) (mixing equal parts of oxidizing and enhanced luminol) for 1 minute with gentle swirling. Membranes were blotted twice with blotting paper to remove excess reagent and placed between transparent films. Membranes were exposed to X-Ray Hyperfilm (Amersham Life
Sciences, UK) for various lengths of time before manual development.
Table 2.3: Primary antibodies for western blotting
Primary antibody Supplier Dilution factor c-Jun (ab32137) Abcam, UK 1: 5000
Egr-1 (sc-189) Santa Cruz Biotechnology, Inc., USA 1: 2000 75
HPV18 E6 (ab70) Abcam, UK 1: 1000
HPV18 E7 (ab100953) Abcam, UK 1: 1000
Cyclin A (sc-751) Santa Cruz Biotechnology, Inc., USA 1: 1000
Cyclin E (sc-247) Santa Cruz Biotechnology, Inc., USA 1: 1000
Cox-2 (sc-1745) Santa Cruz Biotechnology, Inc., USA 1: 1000
ICAM-1 (sc-7891) Santa Cruz Biotechnology, Inc., USA 1: 1000 c-Fos Santa Cruz Biotechnology, Inc., USA 1: 1000
Jun D Santa Cruz Biotechnology, Inc., USA 1: 1000
Jun B Santa Cruz Biotechnology, Inc., USA 1: 1000
Fra-1 Santa Cruz Biotechnology, Inc., USA 1: 1000
Fra-2 Santa Cruz Biotechnology, Inc., USA 1: 1000
Fos B Abcam, UK 1: 1000
Beta actin Sigma 1: 30 000
2.7 Cell Counting
Three thousand HeLa cells were seeded in 96-well plates in 10% FBS DMEM. After 24 hours, cell culture medium was removed and serum-free medium was added. Six hours later, the serum-starved cells were transfected with 50nM c-Jun or 100nM Egr-1 siRNA in serum-free medium. Sixteen hours later, culture medium was removed and cells were transfected again with 50nM c-Jun or 100nM Egr-1 siRNA in serum-free medium. After
24 hours, the cells were stimulated with 10% FBS DMEM for 72 hours. At endpoint, the cells were rinsed twice with pre-warmed 1 x PBS and trypsinized by addition of
100µL 0.05% Trypsin and 0.02% EDTA in Hank’s balanced salt solution
(BioWhittaker) followed by incubation at 37°C, 5% CO2 for 1-2 minutes. The cells were 76
dislodged from the plate by pipetting up and down several times. One hundred microlitres of the cell suspension was transferred to 10mL IsoFlow solution (Beckman
Coulter, Australia) and automated cell counting was performed using Beckman Coulter
Particle Counter Z1 (GMI, Inc). Each group was done in triplicate wells.
2.8 Wound Scratch Assay
HeLa cells were seeded in 6-well plates in 10% FBS DMEM and transfected as described in Section 2.3.1 for c-Jun siRNA. Twenty-four hours after the second transfection, cell monolayers were scratched using a P20 micropipette tip. Medium was replaced with 10% FBS DMEM to remove cell debris and stimulation of cells. Cell migration and regrowth in the denuded zone was monitored and images were taken at
10 x magnification at 72 hours after serum stimulation.
2.9 Dual-chamber Transwell Assay
HeLa cells were seeded in 10cm2 petri dishes in 10% FBS DMEM and transfected as mentioned in Section 2.4.1 for c-Jun siRNA. Twenty-four hours after the second transfection, the cells were rinsed twice with pre-warmed 1 x PBS and trypsinized by addition of 1mL 0.05% Trypsin and 0.02% EDTA in Hank’s balanced salt solution
(BioWhittaker) followed by incubation at 37°C, 5% CO2 for 1-2 minutes. The cells were dislodged from the plate by pipetting up and down several times and subject to centrifugation. The cells were resuspended in serum-free medium before cell counting using Innovatis CASY Cell Counter and Analyzer System Model TTC (Roche). Fifty microlitres of cell suspension was added to 5mL of CASY ton (Roche) and mixed well.
50,000 cells/ 200µL were seeded onto the top chamber of the insert (Millipore, USA).
The inserts were then placed in a 24-well plate filled with 10% FBS DMEM as chemo- 77
attractant. The cells were allowed to migrate from the top chamber to bottom chamber for 24 hours. At endpoint, the culture medium on the top chamber was removed followed by addition of 500µL of 1 x PBS. The top chamber was cleaned with a cotton swab (to dislodge the cells which did not migrate) and rinsed twice with 1 x PBS while transferring the inserts to a new 24-well plate filled with 500µL of 1 x PBS. Then, the inserts were transferred to another 24-well plate filled with 5% formalin neutral buffered solution (Sigma) and incubated at room temperature for 1 hour to fix the cells on the bottom side of the insert membrane. The insert membranes were washed twice as mentioned above before air-drying on the glass slides. The bottom side of the membrane was placed facing upward. One drop of ProLong® Gold antifade reagent with 4',6-diamidino-2-phenylindole (DAPI) (Invitrogen, USA) was added to each insert membrane (to stain the nucleus of the cells for easier quantification) and covered immediately with glass cover slip. Bubbles were removed from the slides and the slides were sealed with nail polish. Ten random fields of images per membrane were taken at
10x magnification using Olympus BX 53 Microscope (Japan). Quantitation of the number of cells migrated per field was performed using ImageJ.
2.10 Matrigel Dual-chamber Transwell Assay
BD Matrigel™ Basement Membrane Matrix (BD Biosciences, USA) was diluted to
3.33mg/ mL with serum-free medium. Fifty microlitres of the diluted Matrigel was added to the top chamber of dual-chamber transwell (Millipore, USA) and incubated at
37°C for 30 minutes (to solidify the Matrigel). Once the Matrigel coating was solidified,
HeLa cells were subjected to trypsinization and seeding on the top chamber as well as endpoint fixation and staining of the cells as shown in Section 2.9.
78
2.11 Flow Cytometry
2.11.1 Annexin V staining apoptosis assay
HeLa cells were seeded in 10cm2 petri dishes in 10% FBS DMEM and transfected as mentioned in Section 2.4.1 for c-Jun siRNA. Twenty-four hours after the second transfection, the culture medium was replaced with 10% FBS DMEM containing 2µM cisplatin (Sigma) and incubated at 37°C, 5% CO2 for 48 and 72 hours, respectively. At endpoint, the culture medium was transferred to 15mL Falcon tube and the cells were washed twice with pre-warmed 1 x PBS. Trypsinization of cells was performed as shown in Section 2.9 and supernatant was removed after centrifugation. Cells were resuspended in cold 1 x PBS and subjected to centrifugation. This step was repeated again. After the 2 washes, cells were resuspended in 800µL cold 1 x PBS and cell counting was performed as mentioned in Section 2.9. Cells were prepared to a final concentration of 1 x 106 cells/ mL in 1 x Annexin V Binding Buffer (BD Biosciences,
USA). One hundred microlitres of cell suspension was transferred to 5mL round bottom tubes (BD Biosciences, USA) followed by addition of 5µL of Annexin V FITC (BD
Biosciences, USA ) and 1µL of 0.5mg/ mL propidium iodide (PI) (Calbiochem,
Millipore, USA). The mixture was gently vortexed to mix and incubated at room temperature for 15 minutes in the dark. Then, 400µL of 1 x Annexin V Binding Buffer was added to each tube, flicked mixed and kept on ice in the dark. The mixture was analyzed by flow cytometer (BD FACSVerseTM and BD FACS suite software, BD
Biosciences, USA) as soon as possible (within 1 hour). In this experiment, 150µL hydrogen peroxide (H2O2) 30% (Univar, USA) was added to cells 2 hours prior to cell harvesting as a positive control for apoptosis.
79
2.11.2 Cell Cycle Analysis
The same samples used for the apoptosis assay were used for cell cycle analysis. Three hundred microlitres of cell suspension in cold 1 x PBS from Section 2.11.1 was gently vortexed while adding 1200µL of ice-cold absolute ethanol and stored at 4°C overnight.
On the next day, the cells were washed twice and resuspended in 300µL of 1 x PBS. For each sample, 50µg/ mL of PI and 0.1mg/ mL RNaseA were added to the fixed cells and incubated at 37°C for 40 minutes in the dark. The cells were then washed once with cold 1 x PBS and resuspended in 300µL 1 x PBS. Cell cycle analysis was performed for at least 20 000 events on a low flow rate by flow cytometer (BD FACSVerseTM and
BD FACS suite software, BD Biosciences, USA).
2.12 MTT Assay
Three thousand HeLa cells were seeded in a 96-well plate in 10% FBS DMEM. After
24 hours, cell culture medium was removed and serum-free medium was added. Cells were transfected with c-Jun siRNA and treated with 2µM cisplatin as shown in Section
2.11.1. Twenty-four hours after the second transfection, the culture medium was replaced with 10% FBS DMEM and incubated for 72 hours before MTT assay. Twenty microlitres of MTT (Section 2.1) was added into each well and incubated at 37°C, 5%
CO2 for 4 hours. The culture medium was removed followed by addition of 180µL of dimethyl sulfoxide (DMSO) (Sigma) to each well and incubated at room temperature for 15 minutes with gentle orbital shaking. The absorbance of A560 and A670 was read using FLUOstar Omega. MTT values were obtained by substraction of A670 from A560.
80
2.13 FITC-siRNA and GFP plasmid uptake studies
HeLa cells were seeded on glass cover slips placed in a 6-well plate in 10% FBS
DMEM. Twenty-four hours later, the culture medium was replaced with serum-free medium. Six hours after serum starvation, the cells were transfected with control siRNA
(Fluorescein Conjugate)-A (Santa Cruz Biotechnologies, Inc., USA) in serum-free medium with 1µg siRNA to 1µL DOTAP/ DOPE ratio. The same transfection was performed again on the next morning. 24 hours later, the cells were washed twice with 1 x PBS followed by fixation for 30 minutes at room temperature using fresh 4% formaldehyde diluted from 16% formaldehyde (Electron Microscopy Sciences, USA) with 1 x PBS. Fixed cells were washed twice with 1 x PBS. One drop of ProLong®
Gold antifade reagent with DAPI was placed on a glass slide, the cover slip with monolayer of cells was placed face down onto the DAPI reagent. Air bubbles were removed gently from the slides and nail polish was applied on the edge of the cover slip to seal it. Three random images were taken from each sample at 40 x magnification using an Olympus Fluoview FV1000 microscope (Japan).
HeLa cells were seeded on glass cover slips placed in a 6-well plate in 10% FBS
DMEM. 24 hours later, the culture medium was replaced with serum-free medium.
Twenty-four hours after serum starvation, the cells were transfected with 1µg of pEGFP-C3, (Clontech, USA) in serum-free medium with 1µg plasmid DNA to 3µL
Fugene ratio. Twenty-four hours later, the cells were fixed and stained as mentioned above. Six random fields were taken at 40 x magnification using an Olympus BX53 microscope (Japan).
81
2.14 MMP Activity Analysis
2.14.1 Concentration of cell culture medium
HeLa cells were seeded in 10cm2 petri dishes in 10% FBS DMEM and transfected as mentioned in Section 2.4.1 for c-Jun siRNA. Twenty-four hours after the second transfection, the culture medium was replaced with 50ng/ mL TPA. Twenty-four hours later, culture medium was transferred to a 15mL Falcon tube. At the same time, centrifugal filter units (Millipore, USA) were filled with 3mL of 1 x PBS and centrifuged alongside with the culture medium at 4000rpm for 10 minutes in a pre- cooled centrifuge. The centrifugal units were decanted followed by an addition of 4mL of centrifuged culture medium. The medium was spun at 4000rpm for 1.5 hours in a pre-cooled centrifuge. Then, the concentrated medium was transferred to eppendorf tubes in 50µL aliquots and stored at -80°C.
2.14.2 Gelatin Zymography
Sixteen point five microlitres of concentrated medium from each sample was mixed with 5.5µL of 4 x SDS protein loading buffer and loaded onto 10% Novex® zymogram
(gelatin) gels (Invitrogen, USA). The gels were subjected to electrophoresis in 1 x SDS running buffer at 125V for 2 hours using an XCell SureLock™ Mini-Cell system
(Invitrogen, USA). After electrophoresis, the gels were removed and incubated in 1 x
Novex® Zymogram Renaturing Buffer for 30 minutes at room temperature with gentle agitation. Zymogram Renaturing Buffer was decanted and 1 x Zymogram Developing
Buffer was added to equilibrate gel for 30 minutes at room temperature with gentle agitation. The buffer was replaced with fresh 1 x Zymogram Developing Buffer and gels were incubated at 37°C overnight for maximum sensitivity. On the next day, the 82
® gels were rinsed with dH2O and stained with GelCode Blue Stain Reagent (Thermo
Scientific, USA) until the bands were clear against the dark background.
2.15 Statistical analysis
Results were expressed as mean values ± SEM from tri- or quadruplicate measurements performed in 2 to 3 independent experiments producing similar results. For gel-based display items, the data is representative of 2 to 3 independent experiments. Statistical analysis was performed using GraphPad Prism 6 One-Way or two-way ANOVA with
Bonferroni post-hoc analysis and differences considered significant at P<0.05 (*P<0.05,
**P<0.01, ***P<0.001, ****P<0.0001, ns=not significant). Unpaired Student t-test was also performed and differences considered significant at P<0.05 (*P<0.05, **P<0.01,
***P<0.001, ****P<0.0001, ns=not significant). 83
Chapter 3:
The role of c-Jun in HeLa Cervical
Cancer Cells in vitro
84
3.1 Introduction and Aims c-Jun is an immediate-early gene and transcription factor that is overexpressed in many cancer types. It plays a major regulatory role in many cellular processes including transformation (Treinies et al., 1999), proliferation (Wisdom et al., 1999), apoptosis
(Potapova et al., 2001), invasion (Fialka et al., 1996) and angiogenesis (Zhang et al.,
2004).
Strong c-Jun expression has been detected in CC cells and tissues compared with normal cervical counterparts. c-Jun/AP-1 is pivotal in the regulation of HPV gene expression, which is the major cause for CC. Despite the implementation of PAP test and vaccination, many CC patients still suffer from and die of recurrent and metastatic
CC. Therefore, in addition to CC cell proliferation and apoptosis - classic aspects that are typically investigated in siRNA studies (as listed in Chapter 1, Table 1.2) - processes such as migration and invasion that underpin metastasis will also be examined in this work.
Metastasis is a two-phase process (Chaffer and Weinberg, 2011). The first phase involves the migration and invasion of cancer cells to a distant organ, whereas the second encompasses the ability of the cancer cell to develop into a metastatic lesion at that distant site. Cell migration involves five main steps (Figure 3.1) (Friedl and Wolf,
2003). These include the protrusion of the leading edge of the cancer cells by cytoskeletal re-organization, cell-matrix interaction via binding with adhesion molecules and formation of focal contacts, recruitment of surface proteases like MMPs to ECM contacts and degradation of ECM, cell contraction by actomyosin and detachment of the trailing edge. Hence, it is logical to target cell migration and invasion 85
to prevent the first phase of cancer metastasis. Various molecular targets of c-Jun involved in adhesion (eg. intracellular adhesion molecule-1, ICAM-1) and ECM degradation (eg. MMP-1, MMP-2 and MMP-9) will be studied in this chapter.
Figure 3.1 Molecular mechanisms of cell migration (Adapted from Friedl and
Wolf, 2003)
Cyclooxygenase-2 (Cox-2) is another immediate-early gene that has been implicated in cancer cell invasion that is also known to be regulated by c-Jun (Reddy et al., 2000;
Subbaramaiah et al., 1998). Cox-2 expression is closely associated with increasing angiogenesis, cell proliferation, tumour invasion, lymph node metastatic status, tumour size, HPV expression and stage of CC but independent of apoptosis (Fitzgerald et al., 86
2011; Lee et al., 2004; Ryu et al., 2000; Settakorn et al., 2009). The efficacy of a Cox-2 inhibitor (celecoxib) in combination with chemoradiotherapy has been tested in a clinical trial of CC (Gaffney et al., 2007b), where the estimated disease-free survival and overall survival rate for patients with advanced CC was 69% and 83% at two years, respectively. However, loco-regional control continues to be problematic and a high incidence of acute toxicities was observed (Gaffney et al., 2007a), possibly due to non- specific, Cox-2 independent effects of celecoxib (Grosch et al., 2006). Therefore, it is hypothesized that targeting c-Jun may suppress the expression of Cox-2 in a targeted manner and may ultimately prove to be a useful approach in CC therapy.
Synergistic combinations of two or more chemotherapeutic agents may improve treatment outcome, yet reduce toxicity compared to large doses of a single agent alone.
Silencing of molecular targets like the HPV oncogenes or the anti-apoptotic inhibitor
Livin by siRNA has been shown to sensitize CC cells to the standard chemotherapeutic drug, cisplatin (Putral et al., 2005; Yu and Wang, 2009). Thus, the role of c-Jun inhibition in sensitization of CC cells to cisplatin will be elucidated.
HeLa cells originated from a patient named Henrietta Lacks, who died from cervical adenocarcinoma in 1951. HeLa was the first human cell line established in culture (Gey et al., 1952). Recently, a German virologist, Harald zur Hausen was awarded the Nobel
Prize for a discovery in which HeLa cells played a central role in demonstrating the link between HPV and CC. HeLa is a CC cell line that contains the HPV18 sequence, an important discovery that led to the development of a CC vaccine in 2006. HeLa has become a well-established cell line that is used widely in CC research. It also offers the advantage of the development of a CC xenograft model. 87
The hypothesis for the work performed in this chapter is that c-Jun serves as a positive regulator of CC HeLa cell proliferation, migration and invasion. Further, it is hypothesized that c-Jun exerts its effect through HPV18 E6 and E7 as well as its target genes responsible for cell migration and invasion. Based on these hypotheses, the specific aims of this study were to substantiate a role for c-Jun in CC HeLa cell proliferation, apoptosis, migration and invasion as well as discern any underlying mechanisms. Two approaches were undertaken to achieve this: c-Jun silencing via siRNA and c-Jun overexpression via an expression vector. The potential of c-Jun siRNA to sensitize HeLa cells to cisplatin was also evaluated in a combined treatment setup.
88
3.2 Results
3.2.1 Serum induces c-Jun mRNA & protein expression in growth-quiescent
HeLa cells
To determine the profile of c-Jun induction as an immediate-early gene by serum, HeLa cells were deprived of serum for 24 hours and then stimulated with 10% FBS- containing medium for various times. For mRNA analysis, HeLa cells were stimulated with 10% FBS and total RNA harvested after 15, 30, 45, 60, 120 and 240 minutes. For protein analysis, HeLa cells were stimulated with 10% FBS and protein harvested after
0.5, 1, 2, 6 and 24 hours. c-Jun mRNA levels increased after 15 minutes incubation with
10% FBS and peaked at 120 minutes. Expression of c-Jun mRNA was then returned to a level similar to serum-free cells at 4 hours after serum induction (Figure 3.2A). At the protein level, after 30 minutes exposure to serum containing medium, c-Jun protein expression increased after 30 minutes serum stimulation and continued to increase from
1 hour to 6 hours. Its expression was significantly reduced at 24 hours post-serum induction (Figure 3.2B). GAPDH and beta actin were used to show unbiased cDNA and protein loading, respectively. 89
A
______n s 1 0 ______**** 8 ______** ______** 6 ______** ___* 4 Fold Change (c-Jun/GAPDH) 2
0
1 5 3 0 4 5 6 0 1 2 0 2 4 0 SFM ______1 0 % F B S
Time (minutes)
B 10%FBS
50kDa c-Jun 37kDa 50kDa Beta actin 37kDa
90
C
______n s
2 .5 ______**
______** 2 .0 ______** 1 .5 _____*
1 .0
(c-Jun/0 Beta .5 actin) Relative band intensity
0 .0
5 1 2 6 4 M 0 . 2 SF ______1 0 % F B S
Time (minutes)
Figure 3.2 Serum induces the expression of c-Jun in HeLa cells. HeLa cells were serum-starved for (A) 24 hours before induction with 10% FBS and harvesting of total
RNA at 15, 30, 45, 60, 120 and 240 minutes. qPCR was performed in triplicates (B)
HeLa cells were serum-starved for 24 hours before induction with 10% FBS and harvesting of protein at 0.5, 1, 2, 6 and 24 hours. (C) ImageJ quantitation of western blots. Data represent mean +/- SEM of 2 independent experiments. Statistical analysis of qPCR was performed using One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05 (*P<0.05; **P<0.01, *** P<0.001, ns
= not significant). 91
3.2.2 Efficient uptake of Fluorescein Isothiocyanate (FITC) -siRNA by HeLa cells
To examine the efficiency of HeLa cells in taking up siRNA for the following experiments, a FITC-labelled siRNA cell incorporation study was performed. HeLa cells were serum-starved for 6 hours followed by transfection of 50 nM FITC-labelled siRNA. Eighteen hours later, HeLa cells were transfected again with 50 nM FITC- labelled siRNA. On the next day, HeLa cells were fixed and nuclei were counter-stained with DAPI. The confocal image demonstrates that green fluorescence staining was observed in the cytoplasm of 99% HeLa cells, showing efficient uptake of the FITC- labelled siRNA by HeLa cells (Figure 3.3A and B).
A
B 92
1 5 0
______**** 1 0 0
5 0
% cells with FITC0 staining
h . V e A + V e h .
T C -s iR N FI
Figure 3.3 Uptake of FITC-siRNA by HeLa cells. HeLa was serum-starved and transfected twice at 50 nM with FITC-labelled siRNA. Images were taken using confocal microscopy. (A) Green fluorescence staining shows efficient uptake of FITC- siRNA by HeLa in the cytoplasm; blue staining indicate nuclei counterstained with
DAPI. (B) Quantitation of the transfection efficiency of FITC-siRNA. Data represent mean +/- SD and statistical analysis was performed using unpaired Student T-Test analysis and differences considered significant at P<0.05 (****P<0.001). 93
3.2.3 c-Jun siRNA inhibits HeLa c-Jun mRNA & protein expression
To determine the role of c-Jun in HeLa CC cells, the siRNA silencing approach was used. Serum-starved cells were transfected twice with 50 nM siRNA and the expression of c-Jun was induced with serum for 1 hour before RNA extraction. Double transfection of 50 nM siRNA was carried out and cells were stimulated with 10% FBS for 2 hours before protein extraction. Both c-Jun mRNA and protein expression was induced by
10% FBS compared to the serum-free control. c-Jun mRNA levels were significantly reduced by c-Jun siRNA, relative to levels of the housekeeper control, GAPDH (Figure
3.4A). At the protein level, c-Jun siRNA suppressed the expression of c-Jun dramatically at 50 nM, relative to the levels of beta actin (Figure 3.4B).
A
6 ______n s ______**
______* 4
2 Fold Change (c-Jun/GAPDH)
0
n r l C t SFM h ic le s iJ u s i V e ______1 0 % F B S
94
B 10%FBS
50kDa c-Jun 37kDa 50kDa Beta actin
37kDa
C
1 .5
______* ______* 1 .0
0 .5 (c-Jun/ Beta actin) Relative band intensity
0 .0
tr l J u n S F M h ic le s i s iC ______V e 1 0 % F B S
Figure 3.4 c-Jun-targeting siRNA inhibits HeLa c-Jun mRNA & protein expression. HeLa cells were serum-starved and double transfected with 50 nM Jun siRNA. mRNA and protein was extracted 1 hour and 2 hours after serum stimulation, respectively. (A) qPCR and (B) western blotting were performed. Representative western blot is shown. (C) ImageJ quantitation of western blot. Data represent mean +/-
SEM of 3 independent experiments. Statistical analysis was performed using One-Way
ANOVA with Bonferroni post-hoc analysis and differences considered significant at
P<0.05 (*P<0.05; **P<0.01, ns=not significant). 95
3.2.4 c-Jun siRNA reduces HeLa cell proliferation
To determine the effect of c-Jun siRNA on HeLa cell proliferation, synthetic siRNA targeting c-Jun was introduced twice to serum-starved HeLa cells using DOTAP/DOPE.
After double transfection of siRNA, HeLa cells were stimulated with 10% FBS for 72 hours before cell counting. There was significantly less cell growth in the presence of c-
Jun siRNA compared to its non-targeting counterpart, siCtrl and the vehicle controls
(Figure 3.5).
6 0 0 0 ______n s ______* ______*
4 0 0 0
C e ll c2 o u n t 0 0 0
0 l tr FM ic le J u n S iC s i s V e h ______1 0 % F B S
Figure 3.5 c-Jun siRNA reduces HeLa cell proliferation. HeLa cells seeded in 96- well plates were serum-starved for 6 hours then transfected twice with 50 nM c-Jun siRNA. Automated cell counting was performed after 72 hours of serum stimulation. c-
Jun silencing resulted in a reduction in cellular proliferation. Data represent mean +/-
SEM of 3 independent experiments. Statistical analysis was performed using One-Way
ANOVA with Bonferroni post-hoc analysis and differences considered significant at
P<0.05 (*P<0.05; ns = not significant). 96
3.2.5 c-Jun siRNA inhibits HeLa cell migration
The capacity of c-Jun siRNA to block cell migration was evaluated by quantifying the number of cells that migrated from the upper chamber of a dual-chamber transwell to the lower chamber in the presence of 10% FBS containing medium as chemo-attractant.
Nuclei of HeLa cells were stained with DAPI for quantitation of the number of cells.
Serum stimulated the migration of HeLa cells to the lower chamber of the dual-chamber transwell compared to the serum-free control. c-Jun siRNA significantly inhibited HeLa cell migration relative to its controls (Figure 3.6A). The number of HeLa cells that migrated to the lower chamber was quantitated using ImageJ (Figure 3.6B).
A SFM Vehicle + 10%FBS
siJun + 10%FBS siCtrl + 10%FBS
97
B
n s 8 0 ______* ______*** 6 0
4 0
2 0 Average number of cells m igrated/ field
0 l tr SFM iJ u n iC e h ic le s s V ______
1 0 % F B S
Figure 3.6 c-Jun siRNA inhibits HeLa cell migration. (A) Serum-starved HeLa cells were double transfected with 50 nM c-Jun siRNA, seeded onto the upper chamber of a dual-chamber transwell with 10% serum containing medium at the bottom of the chamber as chemoattractant. Cells were allowed to migrate through the membrane for
24 hours, followed by fixing and staining of the cells with DAPI. (B) Migrated cells were counted under 10X magnification in 10 random fields of view and quantitated using ImageJ. Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05 (*P<0.05; ***P<0.001, ns = not significant). 98
3.2.6 c-Jun siRNA inhibits HeLa cell invasion
To examine the effect of c-Jun siRNA on the invasiveness of HeLa cells, a Matrigel dual-chamber transwell assay was performed. The top chamber of the transwell was coated with Matrigel to act as a matrix barrier for HeLa cell invasion. Serum stimulated the invasion of HeLa cells to the lower chamber of the dual-chamber transwell compared to the serum-free control. The ability to invade the Matrigel and migrate to the lower chamber of the transwell was impaired by the c-Jun siRNA. The invasiveness of the HeLa cells in the presence of non-targeting siRNA was indistinguishable from the vehicle control (Figure 3.7A). The number of HeLa cells invaded to the lower chamber of the transwell was quantified using ImageJ (Figure 3.7B).
A SFM Vehicle + 10%FBS
siJun + 10%FBS siCtrl + 10%FBS
99
B
5 0 ______n s ______* ______** 4 0
3 0
2 0
1 0 Average number of cells m igrated/ field
0 l tr SFM iJ u n iC h ic le s s V e ______1 0 % F B S
Figure 3.7 c-Jun siRNA inhibits HeLa cell invasion. Matrigel (3.3 mg/ml) was coated on the top chamber of the transwell before cell seeding for the invasion assay (A)
Serum-starved HeLa cells were double transfected with 50 nM c-Jun siRNA, seeded onto the upper chamber of a dual-chamber transwell with 10% serum containing medium at the bottom of the chamber as chemoattractant. Cells were allowed to invade and migrate through the membrane for 24 hours, followed by fixing and staining of the cells with DAPI. (B) Invaded cells were counted under 10X magnification in 10 random fields of view and quantitated using ImageJ. Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05
(*P<0.05; **P<0.01, ns = not significant).
100
3.2.7 c-Jun siRNA inhibits HeLa cell migration and regrowth in a scratch wound assay
To further determine the ability of c-Jun siRNA to inhibit HeLa cell proliferation and migration, a scratch wound assay was performed. Serum-starved HeLa cells were transfected twice with c-Jun siRNA and a scratch wound was created by scraping the tip of a 200ul pipette tip across the cell monolayer. After 72 hours, stimulation with 10%
FBS, the number of cells in the denuded zone was quantified. In the vehicle and non- targeting control groups, HeLa cells migrated and proliferated into the denuded area of the scratch wound and eventually closed the scratch wound. However, c-Jun siRNA suppressed the regrowth of cells into the denuded zone (Figure 3.8). These results complement the proliferation and migration assays as shown in Figure 3.5 - 3.7.
A
SFM Veh. +10%FBS
siJun +10%FBS siCtrl+10%FBS
101
B
______n s 4 0 0 ______** ______** 3 0 0
2 0 0
1 0 0 the denuded area Num ber of cells in
0
e n r l J u C t SFM i h ic l s i s V e ______1 0 % F B S
Figure 3.8 c-Jun siRNA inhibits HeLa cell migration and regrowth in a scratch wound assay. Serum-starved HeLa were double transfected with 50 nM c-Jun siRNA, followed by scraping to create a denuded area and stimulation with 10% FBS for 72 hours. Photographs of the wound area were taken at 10x magnification (A) and number of cells determined in denuded region using Image J (B). Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using One-Way
ANOVA with Bonferroni post-hoc analysis and differences considered significant at
P<0.05 (**P<0.01, ns=not significant).
102
3.2.8 c-Jun siRNA downregulates mRNA levels of Cox-2, ICAM-1, MMP-1 and
MMP-9
As a transcription factor, c-Jun plays an important role in regulating the transcription of a myriad of genes involved in many cellular processes including cell proliferation, migration, invasion and inflammation. qPCR was performed to determine the expression of several c-Jun-regulated genes which are highly expressed in CC and known to be involved in metastasis and inflammation. HeLa cells were transfected twice with 50 nM c-Jun siRNA and stimulated with 10% FBS for 1 hour before total
RNA extraction. In comparison to vehicle and non-targeting siRNA controls, c-Jun siRNA significantly down-regulated the expression of Cox-2, ICAM-1, MMP-1 and
MMP-9 at the level of mRNA (Figure 3.9A, B, C, D). No significant change was observed for MMP-2 mRNA expression in response to c-Jun siRNA (Figure 3.9E). 103
A B
______n s 2 .0 ______* 6 ______** ______***
1 .5 ______** 4
1 .0 Fold Change
2 (ICAM-1/GAPDH) Fold Change
(Cox2/GAPDH) 0 .5
0 0 .0 e n n r l tr l FM C t iJ u iC SFM S h ic l h ic le s iJ u s i s s V e ______V e ______1 0 % F B S 1 0 % F B S
C D
______n s 3 1 .5 ______* ______n s * ______* * 2 1 .0 Fold Change
Fold Change 1 0 .5 (MMP-9/GAPDH) (MMP-1/GAPDH)
0 .0 0
n l r l tr FM FM ic le J u n C t S iC S h ic le s iJ u s s i s i V e h ______V e ______1 0 % F B S 1 0 % F B S
E
______n s 1 .5 ______n s n s
1 .0
0 .5 Fold Change (MMP-2/GAPDH)
0 .0
M n r l J u C t SF h ic le s i s i V e ______1 0 % F B S
104
Figure 3.9 c-Jun siRNA downregulates mRNA levels of c-Jun target genes in
HeLa cells. Serum-starved HeLa cells were transfected twice with 50nM c-Jun siRNA and stimulated with 10% FBS for 1 hour prior to total RNA extraction. The mRNA expression of c-Jun target genes was determined by qPCR. Relative expression of (A)
Cox2 (B) ICAM-1 (C) MMP-1 (D) MMP-9 and (E ) MMP-2 mRNA levels. Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05 (*P<0.05; **P<0.01, ***P<0.001, ns=not significant).
3.2.9 c-Jun siRNA downregulates the protein expression of Cox-2 but does not significantly inhibit ICAM-1
To determine the protein expression of the genes that may be involved in the inhibition of HeLa cell proliferation and migration as well as invasion, western blotting was performed for Cox-2 and ICAM-1. HeLa cells were serum-starved and transfected twice with 50 nM siRNA. These cells were then stimulated with 10% FBS for 6 hours. At 6 hours after serum induction, protein expression of Cox-2 was reduced significantly by c-Jun siRNA compared to the vehicle and non-targeting siRNA controls (Figure
3.10A). However, ICAM-1 protein expression was not significantly reduced by c-Jun siRNA compared to the vehicle control. 105
A
10%FBS
75kDa Cox-2
50kDa Beta actin 37kDa 100kDa ICAM-1 75kDa 50kDa Beta actin 37kDa
B C
n s 2 .0 ______1 .5 ______n s ______* ______* * 1 .5 1 .0 ______n s 1 .0
0 .5 0 .5 (Cox-2/ Beta actin) (ICAM -1/ Beta actin) Relative band intensity Relative band intensity
0 .0 0 .0
tr l r l J u n S F M h ic le s i s iC S F M h ic le iJ u n iC t V e s s ______V e ______1 0 % F B S 1 0 % F B S
Figure 3.10 c-Jun siRNA downregulates the protein expression of Cox-2 but does not significantly inhibit ICAM-1. (A) Serum-starved HeLa cells were transfected twice with 50 nM c-Jun siRNA and stimulated with 10% FBS for 6 hours before protein extraction. (B, C) ImageJ quantitation of western blots. Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using One-Way
ANOVA with Bonferroni post-hoc analysis and differences considered significant at
P<0.05 (*P<0.05; **P<0.01, ***P<0.001, ****P<0.0001, ns=not significant).
106
3.2.10 c-Jun siRNA does not inhibit the activity of MMP-1, MMP-2 or MMP-9 in
HeLa cells.
To elucidate the mechanism of reduced HeLa cell migration and invasion by c-Jun siRNA, gelatin zymography was performed to determine the activity of MMP1, 2 and 9.
HeLa cells were transfected twice with 50 nM c-Jun siRNA and stimulated with 50 ng/mL 12-O-tetradecanoylphorbol 13-acetate (TPA) for 24 hours. TPA has been shown to induce c-Jun mRNA and protein expression (Przybyszewski et al., 2001) and was used as a stimulant in place of FBS as the latter contains endogenous gelatinases that co-migrate with the human gelatinases and interfere with the visualization of MMP bands in a zymogram (Frankowski et al., 2012). The cell culture medium was collected and concentrated using centrifugal filter units before loading in equal volume onto 10% gelatin-infused zymogram gels. In the presence of MMP activity, the gelatin is digested by the MMP and appears as clear bands against the dark background of the commassie- stained gel. The zymogram demonstrates that MMP-1, MMP-2 and MMP-9 activity was not affected by c-Jun silencing where there was no significant change in terms of the intensity of the MMP-1, MMP-2 and MMP-9 bands compared to the counterpart controls (Figure 3.11A). The band intensities of the MMPs were quantitated using
ImageJ (Figure 3.11B, C and D). 107
A
50ng/mL TPA
Pro MMP9→ Active MMP9→
Pro MMP2→ Active MMP2→
MMP1→
B C
3 0 0 0 0 8 0 0 0 0 ______n s n s ______n s 6 0 0 0 0 2 0 0 0 0 ______n s 4 0 0 0 0 ( M M P - 9 ) 1 0 0 0 0 ( M M P - 2 ) 2 0 0 0 0 Relative band intensity Relative band intensity
0 0 l l J u n SFM iC tr J u n ______s i s SFM iC tr V e h ic le s i s V e______h ic le 50ng/mL TPA 50ng/mL TPA
D
5 0 0 0 0 ______n s ______n s 4 0 0 0 0
3 0 0 0 0
2 0 0 0 0 ( M M P - 1 )
1 0 0 0 0 Relative band intensity
0 l J u n C tr SFM h ic le s i s i V e ______50ng/mL TPA
108
Figure 3.11 c-Jun siRNA does not inhibit the activity of MMP-1, MMP-2 or
MMP-9 in HeLa cells. Double transfection of 50 nM c-Jun siRNA was performed on serum-starved HeLa cells. The cells were then stimulated with 50 ng/ mL TPA for 24 hours before the cell culture medium was collected, concentrated 20-fold and loaded in equal volumes onto a 10% gelatin-infused zymogram gel and stained with GelCode blue stain. (A) Bands represent pro-MMP-2 (72kDa), active MMP-2 (62kDa), proMMP-9 (92kDa), active MMP-9 (72kDa) and MMP-1 (54kDa). Relative intensity of bands was determined using Image J and shown in (B) total MMP-9, (C) total MMP-2 and (D) MMP-1. Data represent mean +/- SEM of 3 independent experiments. Ns= not significant.
3.2.11 c-Jun siRNA inhibits HPV18 E6 and HPV18 E7 mRNA expression
HPV is the main cause of CC and c-Jun/AP-1 has been shown to regulate the expression of HPV E6 and E7 (De-Castro Arce et al., 2004a; De-Castro Arce et al., 2004b; Mack and Laimins, 1991). HeLa is a CC cell line which contains the HPV18 sequence. Here, the c-Jun siRNA approach was used to determine its effect on HPV18 E6 and E7 transcription as well as protein expression. At the transcriptional level, c-Jun siRNA significantly inhibited the mRNA expression of HPV18 E6 and E7 in contrast to the vehicle and non-targeting siRNA controls (Figure 3.12A, B). However, at the protein level, c-Jun siRNA did not cause significant reduction of the protein levels of HPV18
E6 and E7 as compared to its counterpart controls (Figure 3.12C). 109
A B
1 .5 1 .5 ______n s ______n s ______* ______*** 1 .0 1 .0 ______** ______*
0 .5 0 .5 Fold Change Fold Change (HPV18 E6/GAPDH) (HPV18 E7/GAPDH)
0 .0 0 .0
r l r l iJ u n C t C t SFM h ic le SFM iJ u n s s i h ic le s s i V e ______V e ______1 0 % F B S 1 0 % F B S
C 10%FBS
15kDa HPV18 E6
15kDa HPV18 E7
50kDa Beta-actin 37kDa
Figure 3.12: c-Jun siRNA inhibits HPV18 E6 and HPV18 E7 mRNA expression
Serum- starved HeLa cells were transfected twice with 50 nM c-Jun siRNA. RNA and protein was harvested 2 and 24 hours after serum stimulation, respectively. qPCR for
(A) HPV18 E6 and (B) E7 as well as (C) western blotting were performed.
Representative images of western blots were shown. Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05
(*P<0.05; **P<0.01, ***P<0.001, ns=not significant). 110
3.2.12 Serum induces Cox-2 mRNA and protein expression in HeLa cells
Having demonstrated that c-Jun siRNA could down-regulate Cox-2 at the mRNA and protein levels (Figures 3.2.8A and 3.2.9A), it was of interest to elucidate whether Cox-
2 plays an intermediary role in c-Jun-mediated HeLa cell migration and invasion. The time course Cox-2 induction by 10% FBS was first evaluated. HeLa cells were deprived of serum for 24 hours and then stimulated with 10% FBS for 15, 30, 45, 60, 120 and
240 minutes before total RNA extraction. HeLa cells were stimulated with 10% FBS for
0.5, 1, 2, 6 and 24 hours before protein extraction. Consistent with its status as an immediate early gene, Cox-2 mRNA levels increased after 15 minutes incubation with
10% FBS and peaked at 45 minutes. Expression was then returned to the level similar to serum-free cells at 4 hours (Figure 3.13A). After 2 hours exposure to serum, Cox-2 protein expression was induced and sustained to 24 hours post-serum induction (Figure
3.13B). GAPDH and beta actin were used to show unbiased cDNA and protein loading, respectively. 111
A
______n s ______** ______* 1 0 ______*** ______*** 8
6
n s 4 _____ Fold Change (Cox-2/GAPDH) 2
0
1 5 6 0 3 0 4 5 1 2 0 2 4 0 SFM ______1 0 % F B S
Time (minutes)
B 10%FBS
75kDa Cox-2
50kDa Beta actin 37kDa
112
C
______** 3 ______* ______* ______n s 2 _____ n s
1 (Cox-2/ Beta actin) Relative band intensity
0
5 1 2 6 4 M 0 . 2 SF ______1 0 % F B S
Time (minutes)
Figure 3.13 Serum inducibility of Cox-2 mRNA and protein expression. HeLa cells were serum-starved for (A) 24 hours before induction with 10% FBS and harvesting of total RNA at 15, 30, 45, 60, 120 and 240 minutes. qPCR was performed in triplicates (B) HeLa cells were serum-starved for 24 hours before induction with 10%
FBS and harvesting of protein at 0.5, 1, 2, 6 and 24 hours. (C) ImageJ quantitation of western blots. Data represent mean +/- SEM of 2 independent experiments. Statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc analysis and considered significant at P<0.05 (*P<0.05, **P<0.01, ***P<0.001, ****P<0.0001, ns = not significant). (B) Protein was harvested and western blotting was performed.
Representative image of western blot was shown. (C) ImageJ quantitation of western blotting.
113
3.2.13 Cox-2 siRNA inhibits Cox-2 mRNA and protein expression in HeLa cells
Next, the inhibition of Cox-2 mRNA and expression in HeLa cells was examined by using the siRNA approach targeting Cox-2. HeLa cells were serum-starved for 24 hours and then transfected with 100 nM Cox-2 siRNA for another 24 hours. On the next day, transfected HeLa cells were stimulated with 10% FBS for 1 and 12 hours for RNA and protein analysis, respectively. Cox-2 mRNA and protein expression was significantly increased in the HeLa cells stimulated with 10% FBS as opposed to the serum-free control. In contrast to the vehicle and non-targeting siRNA controls, Cox-2 siRNA significantly reduced Cox-2 mRNA (Figure 3.14A) and protein expression (Figure
3.14B).
A
______n s 4 ______***
3 ______*
2 Fold change
(Cox-2/1 GAPDH)
0
r l
SFM h ic le iC t C o x 2 s V e ______s i
1 0 % F B S
T r e a t m e n t
114
B 10%FBS
75kDa Cox-2
50kDa ß-actin 37kDa
C
______n s
1 .5 ______**
______** 1 .0
0 .5 (Cox-2/ Beta actin) Relative band intensity
0 .0
r l ic le S F M iC t C o x -2 s V e______h s i 1 0 % F B S
Figure 3.14 Cox-2 siRNA inhibits Cox-2 mRNA and protein expression in HeLa cells. HeLa cells were serum-starved for 24 hours followed by transfection with 100 nM Cox-2 siRNA for 24 hours. The transfected HeLa cells were stimulated with 10%
FBS for (A) 1 hour prior to RNA extraction or (B) 24 hours prior to protein extraction. qPCR and western blotting were performed. (C) ImageJ quantitation of western blotting. All values were normalized against beta actin followed by normalization against vehicle control. Data represent mean +/- SEM of 3 independent experiments.
Statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc 115
analysis and differences considered significant at P<0.05 (*P<0.05; ***P<0.001, ns=not significant).
3.2.14 Cox-2 siRNA reduces HeLa cell migration and invasion
To determine the effect of Cox-2 siRNA on HeLa cell migration and invasion, dual- chamber transwell and Matrigel dual-chamber transwell assays were performed as previously described (Section 3.2.5 and 3.2.6). As previously shown, 10% FBS stimulated HeLa cell migration and invasion relative to serum-free controls. The ability of HeLa cells to migrate (Figure 3.15A) and invade Matrigel (Figure 3.15B) was significantly impaired by siRNA targeting Cox-2 in comparison to vehicle and non- targeting siRNA controls.
A
______***
______**** 2 5 0
2 0 0
______**** 1 5 0
1 0 0
5 0
Num ber of cells0 m igrated/ field
l FM S iC tr h ic le C o x 2 s V e ______s i 1 0 % F B S
T r e a t m e n t
116
B
______n s
8 0 ______****
______**** 6 0
4 0
2 0
Num ber0 of cells invaded/ field
l
SFM ic le o x 2 iC tr s V e h______s iC 1 0 % F B S
T r e a t m e n t
Figure 3.15 Cox-2 siRNA significantly inhibits HeLa cell migration and invasion.
Transfection of 100 nM Cox-2 siRNA was performed on serum-starved HeLa for 24 hours. Then, these cells were typsinized and seeded on the top chamber of the dual- chamber transwell with 10% FBS as chemoattractant in the lower chamber. (A) The cells were allowed to migrate for 24 hours. (B) Matrigel was coated on the top chamber of the transwell for invasion assay. Migrated and invaded cells were counted under 10X magnification in 10 random fields of view and quantitated using ImageJ. Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using
One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05 (****P<0.0001, ns = not significant).
117
3.2.15 Cox-2 siRNA reduces MMP-1 mRNA expression in HeLa cells
As shown in Section 3.2.8, c-Jun siRNA down-regulated the mRNA expression of
MMP-1. To elucidate whether Cox-2 siRNA also plays a role in the regulation of MMP-
1 mRNA expression, qPCR was performed. HeLa cells were serum-starved for 24 hours before transfection with 100 nM siRNA. The day after transfection, HeLa cells were serum-stimulated for 1 hour before RNA extraction. SiRNA targeting Cox-2 significantly down-regulated MMP-1 mRNA expression compared to its counterpart controls (Figure 3.16).
1 .5 ______n s
______**
______* 1 .0
0 .5 Fold change (MMP-1/ GAPDH)
0 .0
l
SFM iC tr h ic le s iC o x -2 V e ______s
1 0 % F B S
T r e a t m e n t
Figure 3.16 Cox-2 siRNA reduces MMP1 mRNA expression in HeLa cells.
Serum-starved HeLa cells were transfected with 100 nM Cox-2 siRNA for 24 hours and then stimulated with serum containing medium for 1 hour before RNA extraction. qPCR was performed. Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05 (*P<0.05; **P<0.01, ns = not significant). 118
3.2.16 Cox-2 siRNA does not inhibit MMP-1, MMP-2 or MMP-9 activity in HeLa cells.
As shown in Section 3.2.10, c-Jun siRNA inhibited MMP-1 activity. To determine whether Cox-2 siRNA also controls MMP-1 activity, zymography was performed on
Cox-2 siRNA transfected HeLa cells. Briefly, HeLa cells were serum-starved for 24 hours and transfected with 100 nM siRNA for another 24 hours. Then, HeLa cells were stimulated with 50 ng/mL TPA (as previously discussed, Section 3.2.10) for 24 hours.
Concentrated culture medium was loaded in equal volumes on a 10% gelatin-infused zymogram gel. There was no significant change observed in the activity of MMP-1,
MMP-2 and MMP-9 by Cox-2 silencing compared to its counterpart controls (Figure
3.17).
A
50ng/mL TPA
MMP9→
MMP2→
MMP1→
119
B C
2 0 0 0 0 1 5 0 0 0 ______n s ______n s ______n s 1 5 0 0 0 n s 1 0 0 0 0 ______
1 0 0 0 0
5 0 0 0
Band intensity5 0 0 0 Band intensity
0 0
r l r l SFM SFM h ic le iC t h ic le iC t iC o x -2 s iC o x -2 s V e ______s V e ______s 50ng/mL TPA 50ng/mL TPA
D
2 0 0 0 0
______n s 1 5 0 0 0 ______n s
1 0 0 0 0
Band intensity5 0 0 0
0
r l SFM h ic le iC t iC o x -2 s V e ______s 50ng/mL TPA
Figure 3.17 Cox-2 siRNA does not inhibit MMP-1, MMP-2 and MMP-9 activities. Serum-starved HeLa cells were transfected with 100 nM Cox-2 siRNA for 24 hours and then stimulated with 50ng/mL TPA for 24 hours. The culture medium was concentrated 20-fold and loaded in equal volume to the 10% gelatin zymogram gel and stained with GelCode blue stain. (A) Bands represent pro MMP-2 (72kDa), pro-MMP-9
(92kDa) and MMP-1 (54kDa). Relative intensity of bands was determined using ImageJ and shown in (B) total MMP-9, (C) total MMP-2 and (D) MMP-1. Data represent mean
+/- SEM of 2 independent experiments. ns=not significant. 120
3.2.17 HeLa cells efficiently take up green fluorescence (GFP) plasmid
The preceding results demonstrated that c-Jun plays a role in HeLa cell proliferation, migration and invasion and regulates multiple genes involved in these processes. To further determine the role of c-Jun in CC cells, an overexpression approach was used.
Prior to this however, the efficiency of plasmid uptake into HeLa cells in the presence of the transfection reagent Fugene was tested. HeLa cells were transfected with a GFP- tagged plasmid (pGFP-C3) in DOTAP/DOPE for 24 hours. HeLa cells were then fixed and the nuclei counter-stained with DAPI. Fluorescence was visualized with an
Olympus BX53 microscope. Representative image shows that HeLa cells efficiently take up GFP plasmid mainly in the cytoplasm (green) (Figure 3.18).
Figure 3.18 Uptake of GFP plasmid by HeLa cells. HeLa was serum-starved and transfected with 1µg GFP plasmid for 24 hours. Images were taken using an Olympus
BX53 microscope. Green fluorescence staining shows efficient uptake of GFP plasmid 121
by HeLa in the cytoplasm; blue staining indicate nuclei counterstained with DAPI.
Representative images shown.
3.2.18 c-Jun expression vector highly overexpresses c-Jun mRNA and protein levels
The role of c-Jun in CC cells was investigated using an overexpression approach. HeLa cells were serum-starved for 24 hours followed by transfection with the c-Jun expression vector, pCMV6-Jun or vector control, pCMV6-XL4, for another 24 hours.
On the next day, serum-starved HeLa cells were stimulated with 10% FBS for 1 or 2 hours before RNA and protein extraction, respectively. c-Jun mRNA expression was significantly increased by the c-Jun expression vector, pCMV6-Jun, compared to the serum-free control and the control vector, pCMV6-XL4 (Figure 3.19A). Similarly, c-
Jun protein expression was dramatically increased by pCMV6-Jun in contrast to the counterpart controls (Figure 3.19B).
A
______**** 1 6 0 0 **__****______
1 2 0 0
8 0 0 6 ______n s
Fold change 4 (c-Jun/ GAPDH)
2
0
M L 4 u n SF c -J
C M V 6 -X M V 6 - p p C ______1 0 % F B S
122
B 10%FBS
50kDa c-Jun 37kDa 50kDa Beta actin 37kDa
C
1 .5 ______**** ______****
1 .0
0 .5 ______n s (c-Jun/ Beta actin) Relative band intensity
0 .0
J u n SFM
M V 6 -X L 4 M V 6 - p C______p C 1 0 % F B S
Figure 3.19 c-Jun mRNA and protein levels are significantly increased by c-Jun expression vector. HeLa cells were serum-starved for 24 hours followed by transfection of the expression vectors for another 24 hours. Then, the transfected cells were stimulated with serum before RNA extraction for 1 hour and protein extraction for
2 hours. (A) qPCR and (B) western blotting were performed. (C) ImageJ quantitation of western blotting. Data represent mean +/- SEM of 3 independent experiments.
Statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc 123
analysis and differences considered significant at P<0.05 (****P<0.0001, ns = not significant).
3.2.19 Overexpression of c-Jun enhances HeLa cell invasiveness but not cell proliferation
To determine the effect of c-Jun expression vector on HeLa phenotypes, cell proliferation and Matrigel dual-chamber transwell invasion assays were performed. For the latter, HeLa cells were seeded onto Matrigel-coated dual-chamber transwells after transfection of the pCMV6-Jun or pCMV6-XL4 vectors. After 24 hours stimulation with 10% FBS these cells were then fixed in 5% formalin for an hour and stained with
DAPI for quantitation. HeLa cell invasion was greatly enhanced by pCMV6-Jun in comparison to the serum-free control and control vector (Figure 3.20A). The number of cells invaded to the lower chamber of the transwell was quantitated using ImageJ
(Figure 3.20B).
In the proliferation assays, HeLa cells were serum-starved for 24 hours and then transfected with pCMV6-Jun for 24 hours in 96-well plates. These cells were then stimulated with 10% FBS for 72 hours before automated cell counting was performed.
HeLa cell proliferation was significantly increased when the cells were stimulated with
FBS compared to the serum-free control. However there was no significant increase in proliferation between cells treated with pCMV6-Jun and its vector control (Figure
3.20C). 124
A
SFM pCMV6-XL4
pCMV6-c-Jun
B
6 0 ______*** ______***
4 0
______***
2 0
Num ber 0of cells m igrated/ field
FM S X L 4 c -J u n
M V 6 - p C M V 6 - p C ______1 0 % F B S
125
C
5 0 0 0 0
_____n s 4 0 0 0 0 _____n s
3 0 0 0 0
2 0 0 0 0 Num ber of cells 1 0 0 0 0
0
L 4 J u n SFM -c -J u n 6 -c - C M V 6 -X L 4 C M V 6 -X
p C M V 6 p C M V 0 n g p 0 n g p 0 n g 1 0 0 0 n g 1 5 1 1 5 ______1 0 % F B S
Figure 3.20 Overexpression of c-Jun enhances HeLa cell invasiveness but not cell proliferation. HeLa cells were serum-starved for 24 hours followed by transfection of the expression vectors for another 24 hours. (A) For the invasion assay, transfected
HeLa cells were allowed to invade and migrate for 24 hours after seeding on the top chamber of the dual-chamber transwell. (B) Migrated and invaded cells were counted under 10X magnification in 10 random fields of view and quantitated using ImageJ. (C)
For the proliferation assay, HeLa cells were stimulated with serum containing medium and incubated for 72 hours before automated cell counting. Data represent mean +/-
SEM of 3 independent experiments. Statistical analysis was performed using One-Way
ANOVA with Bonferroni post-hoc analysis and differences considered significant at
P<0.05 (***P<0.001, ns=not significant).
126
3.2.20 Overexpression of c-Jun increases MMP-1 and Cox-2 mRNA expression but has no effect on MMP-9 and ICAM-1 mRNA expression
To determine whether the c-Jun target genes previously shown to be down-regulated by c-Jun siRNA (Section 3.2.8) could be up-regulated by overexpression of c-Jun, qPCR was performed for serum stimulated HeLa cells examining MMP-1, MMP-9, Cox-2 and
ICAM-1 expression. Overexpression of c-Jun by pCMV6-Jun significantly up-regulated
MMP-1 and Cox-2 mRNA expression compared to the serum-free control and vector control, pCMV6-XL4 (Figure 3.21A and B). Overexpression of c-Jun did not however up-regulate the mRNA expression of MMP-9 and ICAM-1 (Figure 3.21C and D).
A B
______*** ______**** 6 8 ______** ______*
______**** 6 4
4 ______n s
2 Fold Change (Cox2/GAPDH)2
0 0 4 Fold change (MMP-1/ GAPDH) 4 u n M SFM SF -c -J c -J u n C M V 6 -X L M V 6 p C M V 6 -X L p C p C M V 6 - ______p ______1 0 % F B S
1 0 % F B S T r e a t m e n t
127
C D
n s 2 .5 ______8
n s 2 .0 ______6
1 .5 4 1 .0 Fold Change Fold change (ICAM-1/GAPDH)0 .5 2 (MMP-9/ GAPDH)
0 .0 0 4 J u n SFM L 4 SFM M V 6 - -c -J u n C M V 6 -X L p p C ______C M V 6 -X p C M V 6 1 0 % F B S ______p T r e a t m e n t 1 0 % F B S
Figure 3.21 Overexpression of c-Jun increases MMP1 and Cox-2 mRNA expression. HeLa cells were serum-starved for 24 hours followed by transfection of the expression vectors for another 24 hours. The transfected cells were then stimulated with serum and harvested 1 hour later for RNA. (A) MMP-1, (B) Cox-2, (C) ICAM-1 and
(D) MMP-9. Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05 (*P<0.05; **P<0.01, ***P<0.001.
****P<0.0001, ns=not significant).
128
3.2.21 Overexpression of c-Jun increases Cox-2 protein expression
To determine the genes which may be involved in the enhanced invasiveness of HeLa by overexpression of c-Jun, western blots were performed for Cox-2 and ICAM-1.
HeLa cells were serum-starved and transfected with the c-Jun expression vector pCMV6-Jun and its control vector, pCMV6-XL4, for 24 hours before stimulation by
10% FBS for 24 hours. At 24 hours upon serum induction, the protein expression of
Cox-2 was significantly increased by overexpression of c-Jun (Figure 3.22 A). No change was observed in the expression of ICAM-1 24 hours post-serum stimulation.
Furthermore, the expression of HPV18 E6 and E7 was not increased by overexpression of c-Jun (Figure 3.22 C). 129
A
10%FBS
75kDa Cox-2 100kDa ICAM-1 75kDa 50kDa ß-actin 37kDa
B
______****
1 .0 ______**
0 .8 * *__ _****______
0 .6
0 .4
(Cox-2/0 Beta .2 actin) Relative band intensity
0 .0
4 J u n SFM V 6 -X L M V 6 - p C______M p C 1 0 % F B S
130
C
10%FBS
15kDa HPV18 E6
15kDa HPV18 E7 50kDa ß-actin 37kDa
Figure 3.22 Overexpression of c-Jun increases Cox-2 protein expression but not
ICAM-1, E6 and E7. HeLa cells were serum-starved for 24 hours followed by transfection of the expression vectors for another 24 hours. The transfected cells were then stimulated with serum and harvested at 24 hours. Western blotting was performed for (A) Cox-2 and ICAM-1 as well as (C) HPV18 E6 and E7. (B) ImageJ quantitation of western blots. Data represent mean +/- SEM of 2 independent experiments. Statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05 (*P<0.05, **P<0.01, ****P<0.0001).
131
3.2.22 Overexpression of c-Jun increases active MMP-2 activity
The activity of MMP2 and MMP9 by overexpression of c-Jun was also determined using 10% gelatin zymograms. The gelatin in the zymogram gel was digested by MMP, leaving a clear band when stained with GelCode Blue stain. Overexpression of c-Jun using Jun expression vector significantly increased the activity of active MMP-2 compared to the control vector. No change was observed for pro- MMP-2 between Jun expression vector and its control vector (Figure 3.23A). The faint bands of the MMP-9 on the zymogram gel was difficult to demonstrated on the photograph convincingly.
The band intensities were quantitated using ImageJ (Figure 3.23B, C and D).
A
Pro MMP2 → Active MMP2 →
132
B C
1 0 0 0 0 2 5 0 0 0 n s ______*
2 0 0 0 0 8 0 0 0
1 5 0 0 0 6 0 0 0
1 0 0 0 0 4 0 0 0 (Pro- MMP-2) (Active MMP-2) 5 0 0 0 2 0 0 0 Relative band intensity Relative band intensity
0 0
4 J u n -J u n
M V 6 -X L 4 M V 6 M V 6 - C M V 6 -X L p C p C p p C
Figure 3.23 Overexpression of c-Jun increases the enzymatic activity of active
MMP-2. (A) Serum-starved HeLa cells were transfected with c-Jun expression vector for 48 hours. Then, the culture medium was concentrated and loaded in equal volumes onto a 10% gelatin-infused zymogram gel (A). ImageJ was used to quantitate MMP-2 and MMP-9 in the zymogram (B) pro-MMP-2 (C) active MMP-2. Data represent mean
+/- SEM of 3 independent experiments. Statistical analysis was performed using
Unpaired student T-test and differences considered significant at P<0.05 (*P<0.05, ns=not significant).
133
3.2.23 Cisplatin reduces HeLa cell viability in a dose-dependent manner
To test the potency of cisplatin as a chemotherapeutic drug, HeLa cells were treated with varying concentrations of cisplatin, from 0.5 µM to 10 µM for 72 hours before cell counting or MTT assay. The MTT assay is a common method to determine cell viability and metabolism for a variety of drugs. It is a colourimetric assay for measuring the activity of cellular enzymes that reduce the tetrazolium dye, MTT. The automated cell counting result demonstrated that there was a dose-dependent response of HeLa cells to cisplatin. Serum stimulated HeLa cell growth compared to serum-free control was attenuated by 0.5 µM cisplatin, causing about 50% cell growth inhibition. HeLa cell growth was further reduced by 1 µM and 2 µM cisplatin, but higher concentrations of cisplatin (i.e. 5 µM and 10 µM) had no further effect. (Figure 3.24A).
Results from the MTT assay showed that serum stimulated HeLa cell growth compared to the serum-free control and that there was a slight reduction in the formation of MTT formazan observed for 0.5 µM and 1 µM cisplatin. About 50% of the formation of formazan was observed for 2 µM cisplatin, but higher concentrations of cisplatin did not have additional effects on HeLa cell viability or metabolism (Figure 3.24B). 134
A
5 0 0 0 0
4 0 0 0 0
3 0 0 0 0 ****
2 0 0 0 0
Cell num ber **** 1 0 0 0 0 **** **** **** ****
0
0 5 0 0 0 0 . 1 .0 2 . 5 . SFM ______1 0 . C is p la tin
T re a tm e n t ( µ M )
B
3
n s *
2 **** **** **** 1 **** Corrected Abs
0
0 5 0 0 0 0 . 1 .0 2 . 5 . SFM ______1 0 . C is p la tin
Treatment (µM)
Figure 3.24 HeLa cell viability was inhibited by cisplatin in a dose-dependent manner. Cells were serum-starved for 24 hours before treating with different concentrations of cisplatin for 72 hours in 10% FBS medium. 72 hours later, HeLa cell viability was determined by (A) automated cell counting and (B) MTT assays. Data 135
represent mean +/- SEM of 3 independent experiments. Triplicates were performed for each experiment. Statistical analysis was performed using One-Way ANOVA with
Bonferroni post-hoc analysis and differences considered significant at P<0.05
(****P<0.0001, ns = not significant).
3.2.24 Combination treatment of c-Jun siRNA and cisplatin does not show synergism in an MTT assay
The MTT assay is one of the most common methods used to screen synergism of combination drugs in a high-throughput manner. Therefore, it was used to test the synergism of c-Jun siRNA and cisplatin. Serum-starved HeLa cells were transfected twice with 50 nM c-Jun siRNA followed by 2 µM cisplatin treatment for 72 hours and incubation with MTT for 4 hours to allow colour development. A series of c-Jun siRNA and cisplatin concentrations were tested. All of them yielded similar results. A representative set of data is shown in Figure 3.25. A combination of c-Jun siRNA and cisplatin reduced absorbance values compared to siRNA treatment alone indicating lower cell viability or metabolic rate. However, there was no difference when c-Jun siRNA was compared with its counterpart controls in the presence of cisplatin (Figure
3.25). 136
4
____n s ____n s 3
2 ______n s n s
Corrected1 Abs
0
c le u n DP SFM iC tr l s iJ s CDDP V e h i + C D e + C D D P J u n + C tr l h ic l s i s i ______V e 1 0 % F B S
T r e a t m e n t
Figure 3.25 Combination treatment of c-Jun siRNA and cisplatin (CDDP) does not show synergism in an MTT assay. Serum-starved HeLa cells were transfected twice with c-Jun siRNA followed by 2 µM cisplatin treatment for 72 hours. These cells were then analyzed using a MTT assay. Triplicates were performed. Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using
One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05, ns=not significant. 137
3.2.25 Combination treatment of c-Jun siRNA and cisplatin does not lead to increased apoptosis
The MTT assay is a method which primarily determines the metabolic rate of cells in response to the drug given. It may not be the most sensitive way to determine synergism. As cisplatin acts to induce apoptosis in cancer cells, it was examined whether c-Jun siRNA could sensitize HeLa cells to cisplatin-induced apoptosis. HeLa cells were transfected twice with 50 nM c-Jun siRNA and treated with 2 µM cisplatin for 48 and 72 hours in 10% FBS medium. Flow cytometry of Annexin V and Propidium iodide (PI) stained cells was performed. The membrane phospholipid phosphatidylserine (PS) is translocated from the inner to the outer leaflet of the plasma membrane in apoptotic cells, thereby exposing PS to the external cellular environment.
Annexin V, typically conjugated to a fluorochrome such as FITC, binds to PS for easy identification of apoptotic cells (early apoptosis) by flow cytometry. It is typically used in conjunction with a vital dye such as PI to distinguish early apoptotic cells [Annexin
V–FITC positive, PI negative (lower right, LR quandrant)] from necrotic cells [Annexin
V–FITC negative, PI positive (upper left, UL quandrant)]. Late apoptotic cells will be
Annexin V–FITC positive and PI positive (upper right, UR quadrant) whereas viable cells will be negative for both staining (lower left, LL quadrant). c-Jun siRNA did not induce apoptosis compared to its vehicle and non-targeting controls. Hydrogen peroxide
(H202) treated cells served as positive controls for apoptosis and necrosis
After 48 hours of cisplatin treatment, most of the HeLa cells were still viable and there was no increase in either early or late apoptosis for the combination of c-Jun siRNA and cisplatin compared to the cisplatin combination with vehicle or non-targeting siRNA controls (Figure 3.26A). There was also no increase in apoptosis observed for single 138
siRNA treatment in HeLa cells compared to the combination treatment. Untreated HeLa cells were used as a negative control and hydrogen peroxide-treated cells and serum- free cells used as positive controls for apoptosis (Figure 3.26A).
After 72 hours of cisplatin treatment, less than 50% of the total HeLa cell population was viable. The other half of the HeLa cell population showed characteristics of early and late apoptosis. Similar trends were observed at 72 hours relative to 48 hours, but no increased apoptosis was seen for the combination of c-Jun siRNA and cisplatin compared to its counterpart controls. There was a slight increase of late apoptosis for the cisplatin-treated HeLa cells compared to the single siRNA treatment. Untreated
HeLa cells were used as a negative control and hydrogen-peroxide-treated as well as serum-free cells used as positive controls for apoptosis, as most of the HeLa cell population was undergoing apoptosis at this stage (Figure 3.26B). 139
A
140
B
141
C
1 0 0
______**
5 0 % Early + late apoptosis 0 l n M r l e c le tr l u n FM J u n C tr l S h ic le SF 2 O 2 s iJ us n iC s iJ us iC tr e h ic les iJ s iC te h ic ls i s i H V e h i V_____ e V V______C is p la tin ______C is p la tin ______1 0 % F B S ______1 0 % F B S 4 8 h r 7 2 h r
Figure 3.26 Combination treatment of c-Jun siRNA followed by cisplatin does not increase HeLa cell apoptosis. After serum starvation, HeLa cells were transfected twice with 50nM c-Jun siRNA followed by 2 µM cisplatin treatment in serum containing medium. (A) At 48 hours and (B) 72 hours after cisplatin treatment, the cells were stained with Annexin V and PI for apoptosis analysis by flow cytometer. Data are representative plots from 3 independent experiments. (C) Quantitation of percentage of population for early and late apoptosis. Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using unpaired student T-test and differences considered significant at P<0.05 (*P<0.05; **P<0.01). 142
3.2.26 Combination treatment of c-Jun siRNA and cisplatin shows increased G1 of cell cycle and reduced G2/M phase of the cell cycle
As shown in the previous section, no increased apoptosis was observed in HeLa cells with the c-Jun siRNA alone or c-Jun siRNA and cisplatin combination. Cisplatin has previously been reported to have an effect on cell cycle progression apart from inducing apoptosis (Wang et al. 2012). Cell cycle analysis was performed for the combination treatment as well as c-Jun siRNA alone.
HeLa cells were transfected twice with 50 nM c-Jun siRNA or control and treated with or without 2 µM cisplatin for 72 hours. These cells were then fixed with cold absolute ethanol and DNA content was stained with PI before flow cytometry (Figure 3.27A).
Treatment with c-Jun siRNA alone or the combination of c-Jun siRNA and cisplatin did not change the percentage of population of the subG1 phase of the cell cycle, whereas the serum-free control contained a higher percentage of the subG1 population (Figure
3.27B). Sub-G1 phase cells usually represent cells undergoing apoptosis and this is consistent with some cell death evident in HeLa cells held in serum–free medium for extended periods. Treatment with c-Jun siRNA alone did not cause significant changes in any cell cycle phases compared to its counterpart controls. Cisplatin treated cells exhibited G2/M arrest of cell cycle phase compared to the non-cisplatin treated cells
(Figure 3.27E). However, the combination of c-Jun siRNA and cisplatin caused a reduction in the cisplatin-induced G2/M cell cycle arrest. This was accompanied by an increase in G1 cell cycle arrest by the combination of c-Jun siRNA and cisplatin compared to its combination counterpart controls (Figure 3.27C).
143
A
144
B C
4 0 1 0 0
3 0 8 0 ______**
6 0 2 0
4 0 1 0 2 0
0 % Population 0of G1 Phase % Population of subG1 Phase e n u n tr l u n tr l tr l C tr l c le SFM a te d J u n s iJ s iC h ic le s iJ s i SFM a te d s i s iC e h ic le s iJ u s iC V e h ic l V______e V e h i V______n tr e n tr e C is p la tin U C is p la tin U ______1 0 % F B S 1 0 % F B S
D E
3 0 8 0
______* 6 0 2 0
4 0
1 0 2 0 % Population of S Phase 0 0 % Population of G2/M Phase n le r l tr l le r l n u n u n tr l SFM h ic le a te d SFM a te d s iJ s iC t s iJ u s iC s iJ s iC t h ic le s iJ u s iC V e h ic V______e V e h ic V______e n tr e n tr e C is p la tin U C is p la tin U ______1 0 % F B S 1 0 % F B S
Figure 3.27 Combination treatment of c-Jun siRNA followed by cisplatin diminishes the effect of cisplatin on cell cycle progression. (A) After serum starvation, HeLa cells were transfected twice with 50 nM c-Jun siRNA followed by 2
µM cisplatin treatment in serum containing medium for 72 hours. The cells were fixed in cold ethanol and stained with PI for cell cycle analysis by flow cytometer.
Distribution of population at (B) subG1 (P5), (C) G1 (P6), (D) S (P7) and (E) G2/M
(P8) phases. Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05 (*P<0.05; **P<0.01). 145
3.2.27 Cisplatin induces c-Jun expression
Cisplatin has previously been reported to induce c-Jun expression in other cell types
(Brozovic et al., 2004b; Rubin et al., 1992). Therefore, to determine whether cisplatin induces c-Jun in our experimental setup and the possibility that c-Jun silencing by c-Jun siRNA diminishes the effect of cisplatin, western blotting was performed. Using the same experimental setup as shown in Section 3.2.25 and 3.2.26, HeLa cells were harvested for protein extraction at 24, 48 and 72 hours after cisplatin treatment, respectively. At 24 and 48 hours, c-Jun protein expression was significantly induced by
10% FBS with no further increase in the presence of 2 µM cisplatin. However, after 72 hours the c-Jun level was sustained in the presence of cisplatin but not serum. Even though cisplatin induced sustained c-Jun expression, the effect of c-Jun siRNA was strong and sustainable to overcome the inducible effect of cisplatin in the combination of c-Jun siRNA and cisplatin compared to its counterpart controls (Figure 3.28A and
B). 146
A
10%FBS Cisplatin
50kDa c-Jun 24hr 37kDa 48hr
72hr
B 10%FBS Cisplatin
50kDa ß-actin 24hr 37kDa 48hr
72hr
147
C
______n s 1 .5 ______n s n s ______**** ______**** **** 1 .0 ___****
0 .5 (c-Jun/ Beta actin) Relative band intensity
0 .0
ic le C tr l S F M iJ u n C tr l h ic le iJ u n s s i s s i V e h V______e ______C is p la tin
1 0 % F B S
D
______****
1 .5 ______** ___**** ___**** ______n s 1 .0 ___**** ___****
0 .5 (c-Jun/ Beta actin) Relative band intensity
0 .0
ic le C tr l J u n C tr l S F M iJ u n s s i h ic le s i s i V e h V______e ______C is p la tin
1 0 % F B S
148
E
______n s 1 .5 ______**** ______**** ****
1 .0
______n s 0 .5 ___** ___n s (c-Jun/ Beta actin) Relative band intensity
0 .0
ic le C tr l C tr l S F M iJ u n h ic le iJ u n s s i s s i V e h V______e ______C is p la tin
1 0 % F B S
Figure 3.28 Cisplatin induces c-Jun expression. Serum-starved HeLa cells were transfected twice with 50 nM c-Jun siRNA followed by 2 µM cisplatin treatment in serum containing medium for 24, 48 and 72 hours. (A) c-Jun protein expression and (B) beta-actin was used as a loading control. ImageJ quantitation of the representative western blots, (C) 24 hours, (D) 48 hours and (E) 72 hours. Data represent mean +/-
SEM of 3 independent experiements. Statistical analysis was performed using One-Way
ANOVA with Bonferroni post-hoc analysis and differences considered significant at
P<0.05 (**P<0.01, ****P<0.0001, ns=not significant). 149
3.2.28 Combination of c-Jun siRNA and cisplatin reduces cyclin A and induces cyclin E protein expression
To investigate the expression of cell cycle regulators that play a role for the combination of c-Jun siRNA and cisplatin, western blots were performed. Using the same experimental setup as in Section 3.2.25 and 3.2.26, HeLa cells were harvested for protein extraction at 72 hours after cisplatin treatment. . In the absence of cisplatin, c-
Jun siRNA caused slight but not significant increase in cyclin E or cyclin A expression, consistent with no significant change observed in cell cycle analysis (Section 3.2.26)
(Figure 3.29). Treatment with cisplatin increased cyclin A expression but decreased cyclinE expression, in line with the increase in G2/M population of cell cycle phase and decrease in G1 phase cells. When combined with c-Jun siRNA however, there was a reduction of cyclin A and induction of cyclin E expression relative to its counterpart controls. This was also consistent with the reduction in G2/M population of cell cycle and increased G1 population for the combination treatment.
A
150
B
______** ______*
4 ___* ___n s ______n s 3 ______**
2
1 (Cyclin E/ Beta actin) Relative band intensity
0
+ + l + ic le C tr l S F M iJ u n s s i h ic le iJ u n iC tr V e h s s V______e ______C is p la tin
1 0 % F B S
C
______** 2 .5 ______**** ___**** 2 .0 ___* 1 .5 ______n s
1 .0 n s ___* ___
0 .5 (Cyclin A/ Beta actin) Relative band intensity
0 .0
+ + tr l l + ic le S F M iJ u n s s iC h ic le iJ u n iC tr V e h s s V______e ______C is p la tin
1 0 % F B S
Figure 3.29 Combination of c-Jun siRNA and cisplatin reduces cyclin A and induces cyclin E protein expression. Serum-starved HeLa cells were transfected twice with 50 nM c-Jun siRNA followed by 2 µM cisplatin treatment in serum containing 151
medium for 72 hours in 10% FBS medium. (A) Western blotting was performed and representative images of 3 independent experiments were shown. (B, C) ImageJ quantitation of representative western blots. Data represent mean +/- SEM of 3 independent experiements. Statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05
(*P<0.05; **P<0.01, ***P<0.001, ****P<0.0001, ns=not significant). 152
3.3 Discussion c-Jun may represent a novel molecular target for CC therapy. As indicated in Section
1.6, immediate-early genes like c-Jun are generally overexpressed and sustained in cancers. In the context of CC, c-Jun has been found to be highly expressed in CC tissue samples compared to normal cervical tissues and c-Jun/AP-1 has been shown to be important in the transcriptional regulation of HPV gene expression ( Rösl et al., 1997).
Here the siRNA approach was used to target c-Jun specifically in HeLa CC cells in order to investigate the pivotal role of c-Jun in CC tumourigenesis. In this chapter, it was demonstrated that upon serum induction, the mRNA and protein expression of c-
Jun was highly induced in HeLa cells within 15 minutes. This is consistent with c-Jun being an immediate-early gene that is rapidly and transiently induced by stimuli. c-Jun siRNA significantly reduced the serum-inducible mRNA and protein expression of c-
Jun in these cells.
As reviewed in Section 1.5.6, most of the siRNA silencing experiments performed in the literature targeted effects on HPV oncogene expression, cell proliferation and apoptosis in HeLa cells. However, the process of cancer cell migration and invasion can give rise to cancer metastasis, and because recurrent and metastatic CC occurs in about one-third of patients and causes considerable morbidity and mortality (Mack and
Laimins, 1991), it is important to develop a tool to reduce the incidence of CC metastasis. In this work, c-Jun siRNA significantly inhibited HeLa cell migration and invasion. Cell migration and invasion is a multistep process involving cytoskeletal reorganization and stimulation of the cell motility machinery as well as proteolysis of the extracellular matrix (ECM) surrounding cancer cells by MMPs. Following the re- 153
arrangement of cytoskeleton, the growing cell protrusions touch the adjacent ECM and initiate binding via adhesion molecules like ICAM-1 and integrins to form focal contacts. The interaction and binding of the cross-linker of plasma membrane and cytoskeleton, Ezrin and Moesin to ICAM-1 has been shown in leukocytes (Barreiro et al., 2002; Heiska et al., 1998). In this work, c-Jun siRNA significantly inhibited the mRNA expression of ICAM-1 in HeLa cells. The protein expression of ICAM-1 was not significantly reduced by c-Jun siRNA, possibly due to post-translational modification. ICAM-1 is a transmembrane glycoprotein as well as an adhesion molecule that has a role in mediating signal transduction (Etienne-Manneville et al.,
1999). High ICAM-1 immunoreactivity is found in primary sites of CC whereas it is absent in normal cervical tissues (Hayes and Seigel, 2009). Furthermore, serum levels of soluble ICAM-1 in patients with CC are significantly higher than normal and benign controls (Okamoto et al., 1999). ICAM-1 is implicated in enhanced invasion of metastatic human breast carcinoma cell lines (Rosette et al., 2005) and oral cancer cells
(Yang et al., 2010). AP-1 luciferase activity and binding of c-Jun to the AP-1 element on the ICAM-1 promoter has been demonstrated by Fong and co-workers in chondrosarcoma cells (Fong et al., 2012). Further, the application of an AP-1 inhibitor suppressed chondrosarcoma cell migration and ICAM-1 expression. Moreover, the expression of ICAM-1 and oral cancer cell migration has been shown to be inhibited by c-Jun siRNA (Yang et al., 2010). Our findings where c-Jun siRNA reduced HeLa cell migration and ICAM-1 expression, would appear to be consistent with the literature.
Degradation of ECM by MMPs allows cancer cells to invade local and distant tissues, thus contributing to cancer metastasis. Application of c-Jun siRNA significantly inhibited collagenase MMP-1 and gelatinase MMP-9 mRNA expression. Schröpfer and 154
co-workers found strong expression of MMP-1 mRNA and weak expression of active
MMP-1 in CC cell lines (Schropfer et al., 2010). MMP-9 is present in the tissue of cervical adenocarcinoma but is not found in the non-neoplastic endocervical epithelium
(Davidson et al., 1998). In addition, Ryzhakova and colleagues demonstrated that increased MMP-1 and MMP-9 contribute to the invasion potential of squamous cell cervical carcinoma (Ryzhakova et al., 2013). Unlike oncogenes, MMP expression is regulated at the transcriptional level rather than up-regulation by gene amplification or activating mutations (Egeblad and Werb, 2002). For instance, the transcriptional regulation of MMP-1 gene expression largely depends on the proximal AP-1 element located between positions -72 and -66 (Vincenti et al., 1996). The c-Jun protein is able to induce minimal promoter activity and gene expression of MMP-1. Moreover, expression of antisense mRNAs for c-Jun abrogates the induction of MMP-1 gene expression (Westermarck and Kahari, 1999). A single nucleotide polymorphism (SNP) in the promoter region of MMP-1 (at -1607) is associated with clinical stage of CC as well as the ability of CC invasion (Nishioka et al., 2003). On the other hand, it has been reported that MMP-9 is also regulated by c-Jun. MMP-9 expression is increased by JNK and c-Jun at the transcriptional level via the proximal AP-1 site (Crowe et al., 2001).
DNAzyme targeting c-Jun inhibited MMP-9 in skin tumours (Cai et al., 2012). A significant effect of c-Jun siRNA on the activity of MMP-1 was difficult to detect using the gelatin zymography method. This could be because gelatin is not the preferential substrate of MMP-1 (Beurden et al. 2005). The necessity of changing the stimulus to
TPA rather than serum, due to endogenous MMP levels in the latter, may have also changed the signalling pathway of c-Jun-regulated MMP-1 activity. Further investigations with a more sensitive method, for instance, collagenase zymography, could be used to further improve the visualization of MMP-1 activity and make a solid 155
conclusion regarding the c-Jun and MMP-1 relationship in these cells. Therefore, c-Jun regulated HeLa cell invasion may be mediated through MMP-1 and MMP-9 but this should be further investigated with more sensitive MMP-1 enzymatic assays. Besides, no significant change of MMP-2 expression and activity was observed using c-Jun siRNA. This result was different from Zhang and colleagues’ work where c-Jun siRNA significantly reduced MMP-2 expression and enzymatic activity in murine microvascular endothelial cells. The discrepancy from the literature could be due to differences in cell type and culture conditions ( Zhang et al., 2006a).
Cox-2 is also another target for cancer metastasis. Cox-2 is normally expressed at low levels in most tissues but is overexpressed in cancer and highly inducible by tumour promoters, growth factors and cytokines (Dubois et al., 1998). Strong Cox-2 expression has been found in CC tissues but is undetectable in normal cervical tissue. Cox-2 expression is closely related to increasing angiogenesis, cell proliferation, tumor invasion, lymph node metastatic status, tumour size, HPV expression and stage of CC but independent of apoptosis (Fitzgerald et al., 2011; Lee et al., 2004; Ryu et al., 2000;
Settakorn et al., 2009). c-Jun siRNA significantly inhibited the mRNA and protein expression of Cox-2 in HeLa cells in this study. The regulation of Cox-2 by c-Jun has been noted in other studies. The induction of Cox-2 and its promoter activity was shown to be controlled by c-Jun in mast cells and human mammary epithelial cells (Reddy et al., 2000; Subbaramaiah et al., 1998). It has been reported that inhibition of Cox-2 by a number of siRNA, selective Cox-2 inhibitors and synthetic small molecule inhibitors, significantly reduced the invasiveness of breast cancer cells (Yiu and Toker, 2006),
U2OS osteosarcoma (Lee et al., 2007), alveolar epithelial carcinoma cells (Huang et al.,
2004a) and laryngeal carcinoma cells ( Wang et al., 2008b). The use of siRNAs targeting 156
tumor antigen CML66 and selective Cox-2 inhibitor NS398 have also been shown to greatly inhibit Cox-2 expression and HeLa cell invasion (Shi et al., 2007; Wang et al.,
2008a). Nevertheless, the association of Cox-2 expression in c-Jun regulated HeLa cell migration and invasion has not been reported. Data are conflicting however with respect to any role that Cox-2 plays in regulation of MMP-1 expression. The selective Cox-2 inhibitor NS398 was shown to reduce latanoprost-induced MMP-1 mRNA and protein levels (Hinz et al., 2005). By contrast, inhibition of Cox-2 enhanced MMP-1 expression in an ERK dependent manner in fibroblast-like synoviocytes (Pillinger et al., 2003).
Thus, to elucidate whether Cox-2 plays a role in c-Jun regulated HeLa cell migration and invasion, siRNA targeting Cox-2 was used. SiRNA targeting Cox-2 significantly reduced Cox-2 mRNA and protein levels. In addition, Cox-2 siRNA significantly inhibited HeLa cell migration and invasion as well as MMP-1 mRNA. This strongly suggests that suppression of HeLa cell migration and invasion as well as MMP-1 expression by c-Jun siRNA is mediated through Cox-2. On the other hand, the serum inducible profile of Cox-2 mRNA and protein expression is similar to that of c-Jun, suggesting that Cox-2 may co-operate with c-Jun as a co-activator to form a complex which binds to the MMP-1 promoter region. However, further investigation is required to explain this hypothesis or another mechanism by which c-Jun and Cox-2 regulate
MMP-1. As mentioned earlier, more sensitive MMP enzymatic assays should be used to detect significant changes of MMP-1 by Cox-2 siRNA.
c-Jun/AP-1 plays an important role in the transcriptional regulation of HPV E6 and E7 gene expression. HPV E6 binds to p53 and inhibits apoptosis whereas E7 binds to Rb and causes cell cycle progression which leads to CC tumourigenesis. The inhibition of c-Jun in this study caused a significant reduction in the mRNA expression of HPV18 E6 157
and E7. However, the protein expression of HPV18 E6 and E7 was not significantly reduced by c-Jun siRNA. Other AP-1 subunits like c-Fos form heterodimers with c-Jun has been shown to be essential for HPV transcription and gene expression (Rösl et al.,
1997). Thus, significant inhibition of HPV18 E6 and E7 protein expression may be achieved by co-inhibition of both c-Fos and c-Jun expression. On the other hand, there may be post-translational modification which needs to be further elucidated.
Based on the findings above, c-Jun silencing using siRNA plays a crucial role in HeLa cell proliferation as well as migration and invasion. Hence, an overexpression approach was used to further determine the role of c-Jun in CC HeLa cells. The functionality of the c-Jun expression vector was proven by significantly high c-Jun mRNA and protein expression compared to the control vector. There was significant enhanced HeLa cell invasion and a trend of increased cell proliferation by overexpression of c-Jun. The result of enhanced HeLa cell invasion is similar to Smith and colleagues’ finding whereby overexpression of c-Jun in breast cancer cells contributed to a more invasive phenotype (Smith et al., 1999). The augmented HeLa cell invasiveness was associated with increased Cox-2 protein expression. The up-regulation of Cox-2 expression has been reported to increase breast cancer cell invasion through Matrigel and this effect can be attenuated by Cox-2 inhibitor (Yiu and Toker, 2006). Moreover, overexpression of Cox-2 also enhanced the invasiveness of human hepatocellular carcinoma cell, U2OS osteosarcoma and oral cancer cell invasion (Han et al., 2006; Lee et al., 2007; Yang et al., 2010).
Active MMP-2 activity was also increased with overexpression of c-Jun. Nevertheless, the mRNA and protein expression of ICAM-1 was not induced by overexpression of c- 158
Jun. The difference of gene expression responsible for the invasive phenotype of c-Jun overexpressed HeLa could be due to the difference of pathways involved in c-Jun siRNA and overexpression systems. In addition, the overexpression of c-Jun alone may be sufficient to induce the expression or activity of certain genes (eg. Cox-2, MMP-1 and MMP-2) but other co-factors may be needed for the induction of other genes (eg.
ICAM-1). For instance, Wang and colleagues demonstrated that co-expression of c-Jun and c-Fos was more efficient for the induction of ICAM-1 (Wang et al., 1999a). Up- regulation of MMP-1 mRNA expression was observed with the overexpression of c-
Jun. However, the detection of MMP-1 activity by gelatinase zymography in this context was not consistent, possibly because gelatinase zymography may not be the best or most sensitive method to detect MMP-1 activity in view of the fact that gelatin is not the preferential substrate (Snoek-van Beurden and Von den Hoff, 2005). On the other hand, overexpression of c-Jun did not up-regulate the expression of HPV18 E6 and E7. This could be due to the lack of co-expression of Fos with c-Jun to increase AP-
1 to threshold levels to the extent required for efficient transcription of HPV gene expression (De-Castro Arce et al., 2007; Kyo et al., 1997).
The combination of cisplatin and HPV E6/ E7 siRNA or shRNA against the HPV18 E6 gene (Jung et al., 2012; Putral et al., 2005) demonstrated synergistic therapeutic effect.
The increased sensitivity of CC cells to cisplatin may be mediated via enhanced apoptosis and senescence. Therefore, c-Jun siRNA was tested in combination with cisplatin to determine the possibility of a synergistic effect on HeLa cells. There was no increased apoptosis observed for the combination of c-Jun siRNA and cisplatin compared to single treatment. Cell cycle analysis demonstrated that this combined treatment diminished the chemotherapeutic effect of cisplatin. c-Jun siRNA and 159
cisplatin combination treatment caused G1 arrest and reduced the G2/M population of the cell cycle in HeLa cells. This result is consistent with the increased cyclin E and decreased cyclin A expression noted in these cells. Cyclin E is a regulator of G1 to S phase cell cycle progression whereas cyclin A plays a role in S to G2/M progression
(Schafer, 1998). Notably, cisplatin treatment alone increased the G2/M population, accompanied by increased cyclin A expression. This is consistent with the literature whereby cisplatin causes G2/M arrest (Wang et al., 2012). As demonstrated earlier,
HeLa cell growth was inhibited in a proliferation assay by c-Jun siRNA. The inhibition of HeLa cell growth was not due to apoptosis and no significant change of cell cycle was observed. The possibility of activation of interferon response via toll-like receptor
7/8 by the high dose of siRNA could be eliminated because there was no significant change of cell cycle by c-Jun and its control siRNA. Nevertheless, c-Jun siRNA caused slight increase in cyclin E and cyclin A expression, suggesting that these cells may be undergoing a change in cell cycle which may not be detectable by flow cytometry within the experiments defined here. This finding is different to another study where a dominant negative mutant of c-Jun, TAM67 was shown to significantly inhibit CaSki cell proliferation and anchorage-independent colony formation (Maritz et al., 2011). In that study, TAM67 caused cell cycle arrest at G2/M phase of the cell cycle through the suppression of cell cycle regulator p21. This suggests that the role of c-Jun in regulating cell cycle may be CC cell type specific. It could also due to the difference in the mode of action of TAM67 and siRNA against c-Jun. TAM67 competes with c-Jun and binds competitively with other AP-1 subunits to form non-functional protein whereas c-Jun siRNA binds to c-Jun mRNA and prevent the biosynthesis of the protein resulting in its absence altogether.
160
The expression of c-Jun was induced by cisplatin and the induction was sustainable up to 72 hours upon exposure to cisplatin. This is in line with reports demonstrating that increased JNK and its target gene c-Jun are observed in cisplatin treated cells (Brozovic et al., 2004b; Rubin et al., 1992). The role of c-Jun as pro or anti-apoptotic factor in cancer cells in response to cisplatin has been controversial and mainly dependent on cell type and treatment condition. For instance, T98G, U87 glioma cells, PC-3 prostate cancer cells and MCF-7 breast cancer cells expressing TAM67 exhibit decreased viability following treatment with cisplatin. This suggests that c-Jun is required for
DNA repair and viability following cisplatin treatment (Potapova et al., 1997). On the contrary, elevated c-Jun expression is involved in cisplatin-induced apoptosis (Brozovic et al., 2004b). Reduced c-Jun expression in cisplatin resistant cells suggests a possible role of c-Jun in cisplatin resistance (Brozovic et al., 2004b; Sanchez-Perez and Perona,
1999). Therefore, the attenuation of c-Jun expression by c-Jun siRNA which was sustained up to 72 hours could serve as the reason for no synergistic effect for the combination of c-Jun siRNA and cisplatin in terms of apoptosis and cell cycle.
On the other hand, transcription factors are generally considered as inferior durg targets
(Konstantinopoulos and Papavassiliou, 2011). This is largely due to their surfaces greatly exceeded the binding area of small molecules as well as lack of hot spots or deep binding sites for small molecules. The nuclear localization of transcription factors also render the nuclear biochemical events difficult to be selectively targeted. Novel approaches in drug design and delivery shed light in overcoming these challenges.
Artificial transcription factor mimics with the aid of an effective delivery systems are alternatives for targeting transcription factors. For instance, synthetic peptides targeting transcription factor NOTCH have been shown to have anti–proliferative effects in 161
leukaemia in vitro and in vivo (Moellering et al., 2009). Liposomal formulated
DNAzyme 13 which targets c-Jun was to be able to inhibit cancer growth in several tumour models (Tan et al., 2010). Transcription factor target-based therapy remains one of the highest priorities in cancer research although more work need to be done to achieve the translational outcome. The potential of c-Jun as a transcription factor target in CC needs to be further explored.
c-Jun is also found in normal cells and serve normal functions. Consequently, there could be potential undesirable side effects in targeting c-Jun in cancer treatment.
However, c-Jun is often highly expressed in several types of cancer as shown in Table
1.4, more specifically cervical cancer. By using an appropriate (usually low) concentration of drugs, one can inhibit c-Jun in cancer cells without suppressing c-Jun in the normal cells. 162
3.4 Conclusion and Future Directions
3.4.1 Summary and Conclusions
The work in this chapter aimed to determine the role of c-Jun in CC HeLa cells using siRNA silencing and overexpression approaches. The potential of c-Jun siRNA to sensitize HeLa cells to cisplatin was also determined. Overall, this work has demonstrated that c-Jun plays a positive role in regulating the proliferation, migration and invasion of HeLa cells and that c-Jun is a positive regulator of CC carcinogenesis.
Some evidence demonstrates that this may occur through regulation of genes such as
ICAM-1, MMP-1, MMP-9, HPV18 E6 and E7, and in particular Cox-2, which may be an intermediate in this regulatory process. In summary, the primary findings of work performed in this chapter are:
1) Significant inhibition of c-Jun expression by c-Jun siRNA can reduce HeLa cell
proliferation, migration and invasion while overexpression of c-Jun by
expression vector can significantly enhance HeLa cell invasiveness;
2) c-Jun siRNA can significantly down-regulate transcription of genes responsible
for cell invasion and ECM degradation including Cox-2, ICAM-1, MMP-1 and
MMP-9, and HPV gene expression including HPV18 E6 and E7, while
overexpression of c-Jun can significantly up-regulate Cox-2 and MMP-1 gene
expression as well as MMP-2 and MMP-9 activities;
3) Significant inhibition of Cox-2 expression by Cox-2 siRNA can reduce HeLa
cell migration and invasion as well as MMP-1 gene expression;c-Jun siRNA
diminishes the G2/M cell cycle arrest caused by cisplatin but does not sensitize
HeLa cells to cisplatin treatment.
163
3.4.2 Future directions
In addition to the work presented in this dissertation, there are a number of interesting areas for further investigation. These include the mechanisms of c-Jun, Cox-2, ICAM-1,
IL-6 and MMP-1 in the regulation of CC cell invasion and inflammation; as well as the role of c-Jun in epithelial–mesenchymal transition (EMT) which leads to metastasis.
Others are the exploration of novel c-Jun regulated genes; the importance of c-Fos as a co-factor in the regulation of HPV expression; as well as the potential synergism of c-
Jun and other CC treatments. Furthermore, HeLa cells that were used in this work are
CC cells containing the HPV18 sequence. It would be interesting to determine the role of c-Jun in HPV16 SiHa, HPV 16 and 18 CaSki, HPV negative C33A and normal cervical cells.
The interaction of c-Jun and Cox-2 as well as pathways involved in the regulation of
MMP-1 and HeLa cell migration and invasion should be further investigated. c-Jun may regulate MMP-1 by down-regulation of Cox-2 or by binding with Cox-2 to form a complex and bind to the MMP-1 promoter. Co-immunoprecipitation of c-Jun and Cox-2 may provide a better insight into how these genes work to regulate MMP-1. Moreover, in addition to c-Jun, Cox-2 has been demonstrated to regulate ICAM-1 in the context of cell motility (Bishop-Bailey et al., 1998; Dianzani et al., 2008; Yang et al., 2010).
Therefore, siRNA targeting Cox-2 could be used to determine the expression of ICAM-
1. The role of ICAM-1 in HeLa cell migration and invasion as well as MMP-1 regulation could be tested using siRNA targeting ICAM-1.
Apart from their roles in modulating cancer cell motility and invasion, c-Jun, Cox-2 and
ICAM-1 have been implicated in inflammation. The potential role of c-Jun in cervical 164
inflammation and CC would be another interesting area for investigation.
Approximately a quarter of all human cancer globally is associated with chronic inflammation, chronic infection, or both (Morrison, 2012). The correlation of inflammation and CC was demonstrated by Subbaramaiah and Dannenberg and Oh and co-workers (Oh et al., 2009; Subbaramaiah and Dannenberg, 2007b). In neoplastic cervical epithelial cells, HPV 16 E5, E6, and E7 oncogenes induce the inflammatory
Cox-prostaglandin axis, by increasing the expression of Cox-2. This inflammatory pathway is closely associated with many chronic inflammatory diseases and cancer.
HPV infection can persist for decades and it is non-inflammatory; most women eliminate it via an adaptive immune recognition of the virus. However, failure to clear the virus and concomitant elevated activation of inflammatory pathways can promote
CC. This coincides with the findings that cervical inflammation and other genital infections are co-factors which contribute to CC (Castle et al., 2001; Parashari et al.,
1995). The expression and levels of the major pro-inflammatory cytokine, IL-6, is significantly higher in CC compared to non-cancer tissues in early-stage CC patients.
High levels of IL-6 are closely related to tumour size, HPV infections and CC metastasis (Tartour et al., 1994; Wei et al., 2001). IL-6 stimulates cell growth and tumour development and plays a role in metastasis. Further, c-Jun co-operates with signal transducer and activator of transcription 3 (STAT3) or nuclear factor-κB (NK-
κB) to activate IL-6 expression (Chauhan et al., 1994; Ndlovu et al., 2009; Schuringa et al., 2001; Xiao et al., 2004). As another inflammatory gene, Cox-2, which is regulated by c-Jun, is also induced by IL-6 (Maihofner et al., 2003). The crosstalk of Cox-2 and
IL-6 pathways has been demonstrated in the enhancement of osteoclastogenesis (Liu et al., 2005a). On the other hand, ICAM-1 is inducible by cytokines including IL-6 (Lin et al., 2013) and is regulated by Cox-2 (Bishop-Bailey et al., 1998; Dianzani et al., 2008; 165
Yang et al., 2010). ICAM-1 is also associated with the infiltration of lymphocytes into inflammatory lesions. Taken together, c-Jun may be implicated in the process of cervical inflammation which contributes to CC. This involvement may be mediated through the cross-talk of c-Jun, Cox-2, IL-6 and ICAM-1 systems. Further investigation will be needed to prove the importance of c-Jun in the context of cervical inflammation leading to CC progression.
EMT is the transition of tumour cells from an epithelial to a mesenchymal morphology which contributes to the cancer invasion and metastasis. c-Jun has been shown to induce
EMT in tumour cells (Thompson et al., 2005). Moreover, ezrin and moesin expression is correlated with EMT by regulating adhesion and contractile elements for changes in actin filament organization (Haynes et al., 2011; Saito et al., 2013). Therefore, further studies are needed to explore the correlation of c-Jun, ezrin, moesin and EMT.
As a transcription factor, c-Jun regulates the transcription of a diversity of genes which play important roles in carcinogenesis. Hence, microarray or cDNA array in the context of cervical cancer cells could be performed to explore novel c-Jun regulated genes by both c-Jun siRNA and c-Jun overexpression approaches.
c-Jun and c-Fos form a heterodimer to regulate the expression of HPV. Hence, another area of investigation would include knockdown of c-Fos using siRNA targeting c-Fos as well as the combination of both c-Jun and c-Fos siRNA in CC cells to determine whether the work in this chapter is comparable or further enhanced by c-Fos siRNA.
This helps to recapitulate the role of AP-1 in CC and its potential as a target for CC therapy. 166
Apart from cisplatin, other common chemotherapeutic drugs or ionizing irradiation may be used in combination with c-Jun siRNA. The microtubule stabilizing agent, paclitaxel, topoisomerase 1 inhibitor, topotecan and ionizing irradiation exert their effect or induce apoptosis via JNK/ c-Jun pathway (Kim et al., 2008; McDaid and Horwitz, 2001;
Mialon et al., 2005; Wang et al., 1999b). Whether knockdown of c-Jun by c-Jun siRNA counters the effect of these agents when used in combination or whether synergistic activity results is unknown, and remains an area for future investigation. Anti- angiogenic drugs like bevacizumab and cetuximab, have undergone clinical trials and appear beneficial for persistent or recurrent carcinoma of the cervix, and could be used in combination with c-Jun siRNA. c-Jun is a positive regulator for VEGF-A and EGFR in the tumourigensis of skin tumours and human fibrosarcoma cell line HT-1080 (Cai et al., 2012; Mialon et al., 2005). c-Jun siRNA may therefore enhance the effects of bevacizumab and cetuximab.
In conclusion however, this study has primarily demonstrated that c-Jun plays a crucial role in CC cell activites and may therefore play a crucial role in cervical carcinogenesis and serves as a potential target for CC therapy. 167
Chapter 4:
The role of Egr-1 in Cervical Cancer
Cells in vitro
168
4.1 Introduction and Aims
Similar to c-Jun, Egr-1 is an immediate-early gene which is transiently and robustly stimulated in response to a wide variety of stimuli, including serum, growth factors,
UV, gamma-radiation, X-ray radiation and stress (Gregg and Fraizer, 2011; Hallahan et al., 1991; Hjoberg et al., 2004; You and Jakowlew, 1997). It is also a transcription factor which regulates a diverse array of genes crucial in cellular processes. Egr-1 plays a role in cell differentiation (Lee et al., 1996), angiogenesis (Lucerna et al., 2006), apoptosis (Virolle et al., 2001) and metastasis (Cermak et al., 2010). It can serve as a tumour suppressor or tumour promoter gene depending on cancer type (Abdulkadir et al., 2001b; Lucerna et al., 2006).
In CC, the role of Egr-1 is controversial and remains mostly unclear. Egr-1 acts as a transcriptional repressor of hTERT promoter-driven reporter constructs in CC cell lines
(de Wilde et al., 2010). On the other hand, Egr-1 expression is much higher in CC tissues than in the normal cervix (Akutagawa et al., 2008). It is essential for key effectors of ECM remodeling and controls MMP-9 transcription through interactions at the MMP-9 promoter in HeLa cells ( Shin et al., 2010).
It has been reported that a dominant negative inhibitor of Egr-1 suppresses activation of c-Jun in neurite outgrowth (Levkovitz and Baraban 2002). As demonstrated in Chapter
3 and 4, c-Jun plays an important role in cervical carcinogenesis. The association of
Egr-1 and c-Jun has not been described in the context of CC. Thus, it would be interesting to determine the relationship of Egr-1 and c-Jun in CC in this thesis.
169
Therefore, the hypothesis explored here is that Egr-1 serves as a positive regulator in
CC. The aims were to determine the role of Egr-1 using siRNA targeting Egr-1 in HeLa cell proliferation, migration and invasion as well as the underlying mechanisms which lead to these phenotypes. The possible association of Egr-1 and c-Jun was also explored. 170
4.2 Results
4.2.1 Serum induced Egr-1 mRNA & protein expression in HeLa cells
To determine the profile of Egr-1 induction as an immediate early gene by serum, HeLa cells were deprived of serum for 24 hours and stimulated with 10% FBS containing medium over time. For mRNA analysis, HeLa cells were stimulated with 10% FBS for
15, 30, 45, 60, 120 and 240 minutes prior to extraction of total RNA. HeLa cells were induced with 10% FBS for 0.5, 1, 2, 6 and 24 hours before protein extractions. Egr-1 mRNA levels increased dramatically after incubation for 15 minutes with 10% FBS, with a 100-fold change compared with the serum-free control. Egr-1 mRNA expression peaked at 30 minutes post-serum induction with a greater than 150-fold increase. The mRNA expression of Egr-1 was drastically reduced after 1 hour of serum induction and returned to a level similar to the serum-free control (Figure 4.1A). After 30 minutes’ exposure to serum, Egr-1 protein expression increased significantly and peaked at 1 hour. Expression was greatly reduced to a basal level at 6 hours post-serum induction
(Figure 4.1B). GAPDH and beta actin were used to show unbiased cDNA and protein loading, respectively. 171
A
______n s ______n s n s 2 5 0 ______*** 2 0 0
___* 1 5 0
1 0 0 Fold Change (Egr-1/GAPDH) 5 0
0
1 5 3 0 4 5 6 0 1 2 0 2 4 0 SFM ______1 0 % F B S
Time (minutes)
B 10%FBS
75kDa Egr-1
50kDa Beta actin 37kDa
172
C
______** ______*** ______n s ______*** 2 .5 _____***
2 .0
1 .5
1 .0
(Egr-1/0 Beta .5 actin) Relative band intensity
0 .0
5 1 2 6 4 0 . 2 S F M ______1 0 % F B S
Time (minutes)
Figure 4.1 Time course of Egr-1 expression in serum-induced HeLa cells. (A)
HeLa cells were serum-starved for 24 hours before induction with 10% serum. Total
RNA was harvested at 15, 30, 45, 60, 120 and 240 minutes upon serum induction. qPCR was performed to determine Egr-1 mRNA expression relative to GAPDH. (B)
HeLa cells were serum-starved for 24 hours before induction with 10% serum. Protein was harvested 0.5, 1, 2, 6 and 24 hours after stimulation. Western blotting was performed to determine Egr-1 protein expression and beta-actin level for normalization.
(C) ImageJ quantitation of representative western blots. Data represent mean +/- SEM of 2 independent experiments. Statistical analysis was performed using Graphpad Prism and One-way ANOVA with Bonferroni’s multiple comparison test against serum-free control and difference was considered significant at P<0.05 (*P<0.05, ***P<0.005, ns= not significant).
173
4.2.2 Egr-1 siRNA inhibits HeLa Egr-1 mRNA & protein expression
To determine the role of Egr-1 in HeLa cells, a siRNA silencing approach was used.
Serum-starved HeLa cells were double transfected with 100 nM Egr-1 siRNA and the cells were induced with 10% FBS for 1 hour before RNA extraction. For protein analysis, HeLa cells were double transfected with 100 nM Egr-1 siRNA then stimulated for 1 hour. Egr-1 mRNA and protein expression were induced by 10%FBS compared to the serum-free medium control. Egr-1 mRNA levels were significantly reduced by Egr-
1 siRNA relative to levels of GAPDH (Figure 4.2A ). At the protein level, Egr-1 siRNA suppressed the expression of Egr-1 dramatically, relative to the levels of ß-actin (Figure
4.2B). Dose response experiment was performed to determine the siRNA concentration and transfection method to achieve the optimal knock down of Egr-1 protein expression
(Figure 4.2D). HeLa cells were transfected once or twice with both 50 and 100 nM Egr-
1 siRNA.
A
______n s n s 5 0 ______*
4 0
3 0
2 0 Fold Change (Egr-1/GAPDH) 1 0
0
r l SFM iC t h ic le E g r -1 s V e ______s i 1 0 % F B S
174
B 10%FBS
75kDa Egr-1
50kDa Beta actin 37kDa
C
2 .0 ______n s
______**
1 .5 ______*
1 .0
0 .5 (Egr-1/ Beta actin) Relative band intensity
0 .0
r l S F M e h ic le iE g r -1 s iC t V ______s 1 0 % F B S
175
D Single transfection 10%FBS 50nM 100nM
75kDa Egr-1
50kDa Beta actin 37kDa
Double transfection
10%FBS 10%FBS 50nM 100nM
75kDa Egr-1
50kDa Beta actin 37kDa
Figure 4.2 Egr-1 siRNA inhibits HeLa Egr-1 mRNA & protein expression.
HeLa cells were serum-starved and double transfected with 100nM Egr-1 siRNA. Total
RNA and protein were extracted 1 hour after serum stimulation and qPCR and western blotting were performed to determine Egr-1 expression. (A) Egr-1 mRNA levels were determined relative GAPDH. (B) Western blots are representative of 3 independent experiments. (C) ImageJ quantitation of western blots. Data represent mean +/- SEM of
3 independent experiments. Statistical analysis was performed using Graphpad Prism and One-way ANOVA with Bonferroni’s multiple comparison test and difference was considered significant at P<0.05 (*P<0.05, **P<0.01, ns = not significant). (D) Dose response experiment of Egr-1 siRNA via single and double transfection of 50 and 100 nM siRNA. Western blots are representative of 2 independent experiments. 176
4.2.3 Egr-1 siRNA does not reduce HeLa cell proliferation
To determine the effect of Egr-1 siRNA on HeLa cell proliferation, synthetic siRNA targeting Egr-1 was transfected into serum-starved HeLa cells with DOTAP/DOPE.
After double transfection of siRNA, HeLa cells were stimulated with 10% FBS for 72 hours before automated cell counting. There was no influence on cell growth by the
Egr-1 siRNA compared to its non-targeting counterpart (siCtrl) and vehicle control
(Figure 4.3).
6 0 0 0 0
4 0 0 0 0
2 0 0 0 0 Cell num ber
0
r l SFM iE g r -1 s iC t s V e h______ic le 1 0 % F B S
Figure 4.3 Egr-1 silencing does not reduce HeLa cell proliferation. HeLa cells grown in 96-well plates were serum-starved and transfected twice with 100 nM Egr-1 siRNA. Automated cell counting was performed after 72 hours of serum stimulation.
Data represent mean +/- SEM of 3 independent experiments. 177
4.2.4 Egr-1 siRNA inhibits HeLa cell migration
The capacity of Egr-1 siRNA to block cell migration was evaluated by quantifying the number of cells migrated from the upper chamber of the dual-chamber transwell to the lower chamber using medium containing 10% FBS as the chemo-attractant. HeLa cell nuclei were stained with DAPI to facilitate quantitation of the number of cells. Serum containing medium stimulated migration of HeLa cells to the lower chamber of the dual-chamber transwell compared to the serum-free control. Egr-1 siRNA significantly inhibited HeLa cell migration to the lower chamber of the dual-chamber transwell
(Figure 4.4). HeLa cell migration to the lower chamber of the transwell was quantitated using ImageJ.
178
4 0 0 ______*** ______****
3 0 0 ______****
2 0 0
1 0 0
Num ber of cells0 m igrated/ field l h . C tr SFM V e iE g r 1 s i ______s 1 0 % F B S
Figure 4.4 Egr-1 siRNA inhibits HeLa cell migration. Serum-starved HeLa were double transfected with 100 nM Egr-1 siRNA and seeded onto the upper chamber of the dual-chamber transwell with 10% serum containing medium in the lower chamber as chemoattractant. Cells were allowed to migrate through the membrane for 24 hours, followed by fixing and staining the cells with DAPI. Ten random fields of images per membrane were taken under 10x magnification and quantitated using ImageJ. Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using Graphpad Prism and One-way ANOVA with Bonferroni’s multiple comparison test and difference was considered significant at P<0.05 (
***P<0.005****P<0.001).
179
4.2.5 Egr-1 siRNA inhibited HeLa cell invasion
To examine the effect of Egr-1 siRNA on invasiveness of HeLa cells, the Matrigel dual- chamber transwell assay was performed. The top chamber of the transwell was coated with Matrigel to act as a matrix barrier for HeLa cell invasion. Serum-containing medium stimulated the invasion of HeLa cells to the lower chamber compared with the serum-free control. The ability to invade the Matrigel and migrate to the lower chamber of the transwell was impaired by the Egr-1 siRNA. In contrast, invasiveness of the
HeLa cells in the presence of non-targeting siRNA was indistinguishable from the vehicle control (Figure 4.5). The number of HeLa cells invading to the lower chamber of the transwell was quantified using ImageJ.
180
2 5 0 ______*** ______**** 2 0 0
______1 5 0 ****
1 0 0
5 0
Num ber of cells0 invaded/ field . r l SFM V e h iC t iE g r 1 s ______s 1 0 % F B S
Figure 4.5 Egr-1 siRNA inhibits HeLa cell invasion. Serum-starved HeLa were double transfected with 100 nM Egr-1 siRNA and seeded onto the upper chamber of the dual-chamber transwell with 10% serum containing medium in the lower chamber as chemoattractant. The top chamber was coated with 3.33 mg/mL Matrigel prior to cell seeding. Cells were allowed to migrate through the membrane for 24 hours, followed by fixing and staining the cells with DAPI. 10 random fields of images per membrane were taken under 10x magnification and quantitated using ImageJ. Data represent mean +/-
SEM of 3 independent experiments. Statistical analysis was performed using Graphpad
Prism and One-way ANOVA with Bonferroni’s multiple comparison test and difference was considered significant at P<0.05 ( ***P<0.005, ****P<0.001).
181
4.2.6 Egr-1 siRNA downregulates the mRNA expression of MMP-1 and MMP-9
In other cell types Egr-1 plays an important role in regulating the transcription of a myriad of genes involved in many cellular processes including cell proliferation, migration, invasion and inflammation. Real-time PCR was performed to determine whether Egr-1 regulates genes which are implicated in ECM degradation. HeLa cells were transfected twice with 100 nM Egr-1 siRNA and stimulated with 10% FBS containing medium for 1 hour before RNA extraction. In comparison to the vehicle and non-targeting siRNA controls, Egr-1 siRNA significantly down-regulated the mRNA expression of MMP-1 and MMP-9 (Figure 4.6A and B).
A B
______n s
______* 4 ______n s 2 .0 ______** ______* ______* 3 1 .5
2 1 .0 Fold Change Fold change
(MMP-9/GAPDH)1
(MMP-1/0 GAPDH) .5
0 .0 0 l M l SF ic le g r -1 SFM iC tr h ic le iC tr s iE g r -1 s V e______h s iE V e ______s 1 0 % F B S 1 0 % F B S
Figure 4.6 Egr-1 silencing inhibits expression of MMP-1 and MMP-9. Serum- starved HeLa cells were transfected twice with 100 nM Egr-1 siRNA and stimulated with 10% FBS containing medium for 1 hour before RNA extraction. Real-time PCR was performed to determine the expression of MMP-1 and MMP-9 mRNA. Data represent mean +/- SEM of 3 independent experiments. Statistical analysis was performed using Graphpad Prism and One-way ANOVA with Bonferroni’s multiple comparison test and difference was considered significant at P<0.05 ( *P<0.05,
**P<0.01, ns = not significant). 182
4.2.7 Egr-1 siRNA inhibits MMP-9 activity
To provide insights into the mechanisms involved in reduced HeLa cell migration and invasion by Egr-1 siRNA, gelatin zymography was performed to determine the activities of MMP-1, -2 and -9. HeLa cells were transfected twice with 100 nM Egr-1 siRNA and stimulated with 50 ng/mL TPA for 24 hours (Hass et al., 1992). TPA was used as the agonist rather than serum because the presence of serum interferes with
MMP bands on a zymogram gel. The cell culture medium was collected and concentrated using centrifugal filter units before loading in equal volume onto 10% gelatin zymogram gels. In this assay, the presence of MMP activity digests the gelatin in the zymogram gel which appears as clear bands against the dark background of the stained gel. The zymogram demonstrates that there was no significant inhibition of
MMP-1 and MMP-2 activities by Egr-1 siRNA compared to the controls. However, there was significant inhibition of MMP-9 activity by the Egr-1 siRNA when compared to the vehicle and non-targeting siRNA controls (Figure 4.7A). MMP band intensity was quantitated using ImageJ (Figure 4.7B, C and D).
A
50ng/mL TPA
MMP9→
MMP2→
MMP1→
183
B C
______n s 8 0 0 0 2 0 0 0 0 ______n s ______** ______n s 6 0 0 0 1 5 0 0 0 ______**
4 0 0 0 1 0 0 0 0
2 0 0 0 5 0 0 0 Band intensity of MMP-2 Band intensity of MMP-9 0 0
l r l SFM SFM h ic le iC tr h ic le iC t iE g r -1 s iE g r -1 s V e ______s V e ______s 50ng/mL TPA 50ng/mL TPA
D
5 0 0 0 ______n s n s 4 0 0 0 ______
3 0 0 0
2 0 0 0
1 0 0 0 Band intensity of MMP-1 0
r l SFM ic le iE g r -1 s iC t V e h ______s 50ng/mL TPA
Figure 4.7 Egr-1 siRNA inhibits MMP-9 activitiy. (A) Double transfection of 100 nM Egr-1 siRNA was performed on serum-starved HeLa cells. The cells were then stimulated with 50 ng/mL TPA for 24 hours before the cell culture medium was concentrated and loaded in equal volume onto a 10% gelatin zymogram gel. ImageJ was used for quantitation of zymogram result (B) MMP-9, (C) MMP-2 and (D) MMP-1.
Data represent mean +/- SEM of 2 independent experiments. Statistical analysis was performed using Graphpad Prism and one-way ANOVA with Bonferroni’s multiple comparison test and difference was considered significant at P<0.05 ( **P<0.01, ns = not significant). 184
4.2.8 Egr-1 mRNA and protein expression is induced by serum earlier than c-Jun and Cox-2
The serum-inducible profile of the immediate early genes Egr-1, c-Jun and Cox-2 was next compared. Briefly, HeLa cells were serum-starved for 24 hours and stimulated with serum containing medium for various times before cell harvest. At the mRNA level,
Egr-1, c-Jun and Cox-2 were significantly induced by serum compared to serum-free control (Figure 4.8A-C). Egr-1 had the greatest fold change of 100 followed by c-Jun
(fold change of 4) and Cox-2 (fold change of 3). The mRNA expression of Egr-1 peaked at 30 minutes after serum stimulation, followed by Cox-2 at 45 minutes and c-
Jun at 120 minutes. The mRNA expression of Egr-1 was reduced after 30 minutes but c-
Jun and Cox-2 was sustained up to 120 minutes. Egr-1, c-Jun and Cox-2 mRNA levels were decreased to basal levels after 2 and 4 hours of serum stimulation, respectively
At the protein level, Egr-1 was dramatically induced at 30 minutes and peaked at 60 minutes after serum stimulation (Figure 4.8D ). Egr-1 protein expression returned to basal levels after 6 hours. On the other hand, c-Jun protein expression was induced after
30 minutes of serum induction and peaked at 120 minutes. However, like mRNA levels, c-Jun protein expression was not as dynamic as Egr-1. Moreover, c-Jun protein expression was sustained longer that Egr-1 and reduced to basal levels only at 24 hours of serum stimulation. The expression of Cox-2, on the other hand, was not induced by serum until 60 minutes and sustained up to 24 hours. In comparison to Egr-1 and c-Jun, the level of induction of Cox-2 was much lower. This is consistent with the mRNA result where the fold change of these genes at the same time point was significantly different. 185
A
______n s ______n s n s 2 5 0 ______*** 2 0 0
___* 1 5 0
1 0 0 Fold Change (Egr-1/GAPDH) 5 0
0
1 5 3 0 4 5 6 0 1 2 0 2 4 0 SFM ______1 0 % F B S
Time (minutes)
B
______n s 1 0 ______**** 8 ______** ______** 6 ______** ___* 4 Fold Change (c-Jun/GAPDH) 2
0
1 5 3 0 4 5 6 0 1 2 0 2 4 0 SFM ______1 0 % F B S
Time (minutes)
C
______n s ______** ______* 1 0 ______*** ______*** 8
6
n s 4 _____ Fold Change (Cox-2/GAPDH) 2
0
1 5 6 0 3 0 4 5 1 2 0 2 4 0 SFM ______1 0 % F B S
Time (minutes)
186
D 10%FBS
75kDa Egr-1
50kDa c-Jun 37kDa
75kDa Cox-2
50kDa Beta actin 37kDa
Figure 4.8 The differential serum-inducible profiles of Egr-1, c-Jun and Cox-2.
HeLa cells were serum-starved for 24 hours and stimulated with 10% serum containing medium for various times. For RNA extraction, HeLa cells were harvested at 15, 30, 45,
60, 120 and 240 minutes after serum stimulation. For protein extraction, HeLa cells were harvested at 0.5, 1, 2, 6 and 24 hours after serum stimulation. qPCR was performed using the same samples for (A) Egr-1, (B) c-Jun and (C) Cox-2. Western blotting was performed using the samples for (D) Egr-1, c-Jun and Cox-2.
Representative images of western blots shown. Data represent mean +/- SEM of 2 independent experiments. Statistical analysis was performed using Graphpad Prism and
One-way ANOVA with Bonferroni’s multiple comparison test and difference was considered significant at P<0.05 (*P<,0.05, **P<0.01, ***p<0.005, ****p<0.001, ns = not significant). 187
4.2.9 Egr-1 siRNA inhibits c-Jun mRNA and protein expression as well as Cox-2 protein expression
The pattern of expression of Egr-1, c-Jun and Cox-2 stimulated by serum suggested that
Egr-1 may play a role in the regulation of c-Jun and Cox-2. Therefore, serum-starved
HeLa cells were transfected with siRNA targeting Egr-1. qPCR and western blotting were then performed for c-Jun and Cox-2. c-Jun mRNA expression was significantly inhibited by Egr-1 siRNA compared to its counterpart controls (Figure 4.9A). There was no significant inhibition of Cox-2 mRNA expression compared to its counterpart controls (Figure 4.9B). c-Jun and Cox-2 protein expression showed significant down- regulation by Egr-1 siRNA compared with vehicle and non-targeting siRNA controls
(Figure 4.9C, E). c-Jun is a subunit of the AP-1 transcription factor. Hence, the effect of Egr-1 silencing on the regulation of other AP-1 subunits was also tested by Western blotting. The same samples used to determine c-Jun expression was used to probe for
JunB, JunD, Fra-1, Fra-2, FosB and c-Fos (Figure 4.9G). Egr-1 siRNA did not inhibit any of these other AP-1 subunits. 188
A
n s 6 ______****
______* 4
2 Fold change (c-Jun/ GAPDH)
0
r l SFM h ic le iC t iE g r -1 s V e ______s 1 0 % F B S
B
n s 8 ______n s
6 ______n s
4 Fold Change
(Cox-2/GAPDH)2
0
r l SFM h ic le iC t iE g r -1 s V e ______s 1 0 % F B S
189
C 10%FBS
50kDa c-Jun 37kDa 50kDa Beta actin 37kDa
D
______n s ______**** 0 .4 ______****
0 .3
0 .2
0 .1 (c-Jun/ Beta actin) Relative band intensity
0 .0
M r l SF ic le iC t E g r -1 s V e h ______s i 1 0 % F B S
190
E 10%FBS
75kDa Cox-2
50kDa Beta actin 37kDa
F
______n s 2 .5 ______*** ______2 .0 **
1 .5
1 .0
(Cox-2/0 Beta .5 actin) Relative band intensity
0 .0
r l F M ic le S iC t E g r -1 s V e h ______s i 1 0 % F B S
191
G 10%FBS
50kDa Jun B 37kDa 50kDa Jun D 37kDa 50kDa Fra-1 37kDa
50kDa Fra-2 37kDa 50kDa Fos B 37kDa 50kDa ß-actin 37kDa 75kDa c-Fos 50kDa 50kDa ß-actin 37kDa
Figure 4.9: Egr-1 siRNA inhibits c-Jun and Cox-2 but not expression of other AP-1 subunits. Serum-starved HeLa cells were transfected twice with 100 nM Egr-1 siRNA and stimulated with serum for (A, B, C) 1 hour and (E) 48 hours. (D and F) Quantitation of c-Jun and Cox-2 expression by ImageJ, repectively. Western blotting was performed for AP-1 subunits using the same samples. qPCR and western blotting results are representative data from 2 independent experiments for Cox-2 and 3 independent experiments for c-Jun and AP-1 subunits. Data represent mean +/- SEM of at least 2 independent experiments. Statistical analysis was performed using Graphpad Prism and
One-way ANOVA with Bonferroni’s multiple comparison test and difference was considered significant at P<0.05 (*p<,0.05, **p<0.01, ***p<0.005, ****p,0.001, ns = 192
not significant). 193
4.3 Discussion
Egr-1 is an immediate-early gene. Its expression is transiently and rapidly induced by various stimuli including growth factors (Hjoberg et al., 2004; You and Jakowlew,
1997) and irradiation (Hallahan et al., 1991). The serum response element (SRE) and radiation response element located in the promoter region of Egr-1 are essential for this induction. This is in line with the result shown earlier where Egr-1 mRNA and protein expression was dramatically induced by 10% serum in HeLa cells. The induction of
Egr-1 mRNA and protein was as early as 15 minutes and 30 minutes, respectively.
Moreover, the level of Egr-1 mRNA induction was considerable with a fold change of
100 at 15 minutes of serum stimulation. It reached a maximal induction of 150-fold at
30 minutes for mRNA expression and 1 hour for protein expression. The induction of
Egr-1 mRNA and protein expression was transient and reduced to basal level after 2 and
6 hours of serum stimulation, respectively. These findings are consistent with other reports where Egr-1 mRNA and protein expression had at least a 20-fold change and peaked at 1 hour after stimulation (Gregg and Fraizer, 2011; Hallahan et al., 1991;
Hjoberg et al., 2004; You and Jakowlew, 1997). This transient activation of Egr-1 is pivotal in the regulation of the expression of a variety of pro-cancerous genes via binding to their promoter regions (Fahmy et al., 2003; Lucerna et al., 2006).
Egr-1 serves as a tumour suppressor gene as well as tumour promoter gene, depending on cancer type. The role of Egr-1 in CC remains controversial and unclear. Therefore, a siRNA approach targeting Egr-1 was used to dissect the role of Egr-1 in CC. SiRNA to
Egr-1 significantly inhibited Egr-1 mRNA and protein expression, however no change in HeLa cell proliferation was observed. In contrast, it has been shown by others that 194
inhibition of Egr-1 using siRNA reduces breast and prostate cancer cell growth
(Mitchell et al., 2004; Parra et al., 2009).
Egr-1 has also been reported to play a crucial role in cancer cell migration and invasion
(Sun et al., 2013). Inhibition of Egr-1 using siRNA was previously shown to block breast cancer cell migration and invasion (Mitchell et al., 2004). This finding is in line with the dual-chamber transwell migration and invasion results reported here. HeLa cell migration and invasion was significantly inhibited by Egr-1 siRNA. Thus, the evidence presented here suggests that Egr-1 plays a more important role in HeLa cell migration and invasion compared to proliferation.
To elucidate the mechanisms which contribute to the reduced migration of HeLa by
Egr-1 siRNA, the role of MMPs in Egr-1 regulated HeLa cell invasion was also evaluated by real-time PCR and gelatinase zymography. SiRNA targeting Egr-1 significantly inhibited MMP-1 and MMP-9 at the transcriptional level. Egr-1 siRNA also significantly reduced MMP-9 activity. The regulatory actions of Egr-1 on MMP-9 reflects the findings of Shin and colleagues (Shin et al., 2010) which show Egr-1 controls MMP-9 expression by binding to its promoter. The relationship between Egr-1 and MMP-1 is somewhat controversial. Egr-1 has been implicated in elevated MMP-1 gene expression observed in rheumatoid synoviocytes (Vincenti and Brinckerhoff,
2001). On the other hand, Aicher and colleagues demonstrated that Egr-1 exerts its tumour-suppressing functions through the inhibition of MMP-1 in synovial fibroblasts
(Aicher et al., 2003). Moreover, MMP-1 has been shown to induce Egr-1 expression in macrophages (Faisal Khan et al., 2012). These indicate that the regulation of Egr-1 and
MMP-1 could be cell type and condition-dependent. A significant effect of Egr-1 195
siRNA on the activity of MMP-1 was difficult to detect using the gelatin zymography method. This could be because gelatin is not the preferential substrate of MMP-1
(Snoek-van Beurden and Von den Hoff, 2005). The necessity of changing the stimulus to TPA rather than serum, due to endogenous MMP levels in the latter, may have also changed the signalling pathway of Egr-1-regulated MMP-1 activity. Further investigations with a more sensitive method, for instance, collagenase zymography, could be used to further improve the visualization of MMP-1 activity and make a solid conclusion regarding the Egr-1 and MMP-1 relationship in these cells.
The time course studies performed in this chapter demonstrated that Egr-1 protein expression was dramatically induced by serum at 30 minutes, maximal at 1 hour, then reduced to basal levels by 6 hours. Interestingly, this serum-inducible Egr-1 expression was followed by a somewhat delayed time course of c-Jun and Cox-2 protein expression. Both c-Jun and Cox-2 had lower expression levels at 30 minutes and 1 hour compared to Egr-1. Their expression was maximal at 2 hours and sustained up to 24 hours. This differential serum inducible profile of Egr-1, c-Jun and Cox-2 suggests the hypothesis that in HeLa cells, Egr-1 may act upstream of c-Jun and Cox-2 as well as regulate the expression of these genes. Therefore, siRNA targeting Egr-1 was used to determine the role of Egr-1 in the regulation of c-Jun and Cox-2 expression. Egr-1 siRNA significantly inhibited c-Jun mRNA and protein expression, suggesting that Egr-
1 regulates c-Jun at the transcription level. This is consistent with the finding that dominant negative inhibition of Egr-1 suppresses activation of c-Jun in the context of neurite outgrowth (Levkovitz and Baraban, 2002). In the latter study, Egr-1 was shown to regulate c-Jun through protein-protein interactions, rather than via their classical mode of action, binding to the Egr-1 response element (ERE). However, Faour and 196
colleagues showed that Egr-1 causes the inhibition of c-Jun phosphorylation; blockade of c-Jun transcription by binding to its promoter; as well as disruption of ATF2/c-Jun enhancer complex in human macrophages (Faour et al., 2005). Remarkably, and in contrast to this Egr-1 regulation of c-Jun, c-Jun has also previously been shown to regulate Egr-1 by binding to its promoter in multiple myeloma and mouse embryonic fibroblast (Chen et al., 2010; Hoffmann et al., 2008). Thus there may be a complex relationship between these two factors. It is interesting that Egr-1 siRNA did not have any significant effect on the expression of the other Fos/Jun subunits of AP-1, suggesting its effect could be specific to c-Jun expression.
Egr-1 siRNA significantly inhibited Cox-2 protein expression but not the mRNA, suggesting that Egr-1 may regulate Cox-2 at post-translational level. This should be further determined by additional studies on Cox-2 promoter by Egr-1 siRNA.
Cycloheximide blocking experiment in the presence and absence of Egr-1 siRNA would also provide further information on the post-translational regulation of Cox-2 expression by Egr-1. In regard to the finding in this study that Egr-1 siRNA down- regulated Cox-2 protein expression, the literature has suggested that Egr-1 is downstream of Cox-2 (Faisal Khan et al., 2012; Faour et al., 2005; Moon et al., 2005).
For instance, Egr-1 has been shown to be a key transcription factor in promoting Cox-2- dependent prostaglandin E2 (PGE2) release in human macrophages (Faour et al., 2005).
Yet in this study, the down-regulation of Cox-2 by Egr-1 is consistent with the concurrent down-regulation of c-Jun, as it was previously shown in chapter 3 that c-Jun silencing could also down-regulate Cox-2 expression. Thus the down-regulation of c-
Jun by Egr-1 would be expected to have a flow on effect to Cox-2 given the earlier findings. This Egr-1/c-Jun/Cox-2 pathway is also supported by the earlier induction of 197
Egr-1 relative to c-Jun and Cox-2. Further studies using c-Jun overexpression in the presence of Egr-1 siRNA could investigate c-Jun as an intermediate between Egr-1 and
Cox-2 in this cell type. In general, these distinctive results indicate that the relationship of Egr-1, c-Jun and Cox-2 may be complex but also cell type and condition dependent.
All three siRNA targeting Egr-1, c-Jun and Cox-2 significantly inhibited HeLa cell migration and invasion as well as MMP-1 expression. This evidence suggests that there may be crosstalk involving Egr-1, followed by c-Jun and Cox-2 in the regulation of
HeLa cell migration and invasion, as well as MMP-1 expression. Further investigation is needed to confirm these findings. c-Jun siRNA inhibited HeLa cell proliferation and it has been shown in the literature that inhibition of Cox-2 by Cox-2 selective inhibitors significantly reduced proliferation of mouse colorectal cancer cells and human leukaemia cell lines (Nakanishi et al., 2001; Yao et al., 2004). Egr-1 siRNA did not reduce HeLa cell proliferation. Unlike c-Jun which is a tumor promoter in majority of cancers, Egr-1 plays a versatile role as a tumor suppressor or promoter in tumorigenesis depending on cancer type as shown in Chapter 1. This suggests that Egr-1 may exert its effects through c-Jun and Cox-2 specifically on HeLa cell migration and invasion but not cell proliferation.
Double transfection of 100nM Egr-1 siRNA was performed for all the phenotypic and gene expression experiments. This method of transfection consistently caused great reduction of Egr-1 protein expression in a dose response experiment, lower concentration of Egr-1 siRNA resulted in minimal or lesser reduction of Egr-1 protein expression. The non-specific inhibition of Cox-2 mRNA expression by non-targeting siRNA might be overcome by reducing the concentration of Egr-1 siRNA used in future 198
experiments. ON-TARGETplus siRNAs (Dharmacon) were used in these experiments.
The patented dual-strand modification of these siRNAs reduces off-target effects by up to 90% compared to unmodified siRNA. The pool of 4 individual siRNAs (19 base pair each) and the non-GU-rich motifs in the siRNA sequence also reduce the non-specific effect or innate immune response (Reynolds et al., 2006). However, the possibility of non-specific effects may occur at high concentration of siRNA as well as cell type and transfection condition dependent. In this chapter, the off-target effect of siRNA was not reflected in other experiments including cell proliferation. Nevertheless, to determine the possibility of activation of interferon pathway, a Toll-like receptor response assay or microarray could be performed.
199
4.4 Conclusion and Future Directions
4.4.1 Summary and Conclusions
The work in this chapter was to determine the role of Egr-1 in CC HeLa cell using siRNA silencing approach. Egr-1 may play an important role in CC carcinogenesis. In summary, the primary findings of work performed in this chapter are:
1) Significant inhibition of Egr-1 mRNA and protein expression by Egr-1 siRNA
can significantly reduce HeLa cell migration and invasion but not proliferation.
2) Egr-1 siRNA can significantly down-regulate MMP-1 and MMP-9 mRNA
expression as well as inhibit MMP-9 activity.
3) Egr-1 knock-down can significantly block c-Jun expression and possibly Cox-2.
The fact that Egr-1 induction occurs prior to c-Jun and Cox-2 induction suggests
that Egr-1 may positively regulate c-Jun and Cox-2 in HeLa cells.
4) Similarly, the collective data show that Egr-1, c-Jun and Cox-2 siRNA can
independently cause inhibition of HeLa cell migration and invasion as well as
MMP-1 expression. This implicates these genes in the regulation of HeLa cell
migration and invasion through regulation of MMP-1.
4.4.2 Future directions
Further investigation is required to confirm a regulatory pathway involving Egr-1-c-
Jun-Cox-2 in HeLa cells. A number of methods could be used to determine the mode of regulation of c-Jun and Cox-2 by Egr-1. For instance, a reporter assay system could be used to determine the transcriptional regulation by Egr-1. HeLa cells could be transfected with a reporter plasmid in which the c-Jun or Cox-2 gene promoters are fused upstream of a firefly luciferase reporter gene. This would be followed by 200
transfection of Egr-1 siRNA and incubation in the presence of serum for various times.
Cells transfected Egr-1 siRNA would be predicted to have reduced luciferase activity.
This would provide insight as to whether Egr-1 regulates c-Jun or Cox-2 at the level of transcription at the promoter. Moreover, an electrophoretic mobility shift assay (EMSA) could be performed to study whether Egr-1 protein binds directly to the c-Jun or Cox-2 promoter sequences. It may also indicate whether other proteins are involved in the binding complex using supershift analysis. In addition to protein-DNA interaction, co- immunoprecipiation (CoIP) is another useful method to determine the possibility of
Egr-1 and c-Jun and/or Cox-2 interactions (Levkovitz and Baraban 2002). Moreover a rescue experiment could be performed to further determine if Egr-1 lies upstream of c-
Jun and Cox-2. c-Jun or Cox-2 expression would be silenced using the corresponding siRNA in HeLa cells and the expression of these genes may be rescued by overexpression of Egr-1 with an Egr-1 expression vector. As mentioned above, c-Jun overexpression in the presence of siRNA against Egr-1 could also examine whether c-
Jun can rescue the Egr-1 effect on Cox-2 and whether c-Jun is an intermediate between the two. These strategies would provide more insight into the mechanisms underlying
Egr-1 regulation of c-Jun and Cox-2. Moreover, the use of an Egr-1 overexpression vector would help to confirm the role of Egr-1 in HeLa cells.
Given the great potential of c-Jun regulation by Egr-1, Egr-1 siRNA could also be used to determine the role of Egr-1 on some other c-Jun target genes like ICAM-1 and IL-6.
It has been reported that Egr-1 transcriptionally regulates ICAM-1 in human atherosclerotic lesions, B cells and mouse endotoxemia model (McCaffrey et al., 2000;
Pawlinski et al., 2003). Besides, Egr-1 also plays a role in the transcriptional regulation of IL-6 (Hoffmann et al., 2008; Pawlinski et al., 2003). The possible involvement of 201
Egr-1 in the modulation of ICAM-1 and IL-6 in HeLa cells would enhance the evidence that Egr-1 plays a crucial role in c-Jun-regulated HeLa cell migration and invasion as well as cervical inflammation as mentioned in Chapter 3.
In addition to the work presented in this dissertation, the role of Egr-1 in cytoskeletal re- modelling could be studied by western blotting and confocal imaging of immuno- fluorescence stained ezrin and moesin in HeLa cells. Sarver and co-workers demonstrated the correlation of Egr-1 and ezrin by microRNA-183 in the regulation of synovial sarcoma and rhabdomyosarcoma invasion (Sarver et al., 2010). A link between
Egr-1 and ezrin has also been suggested by Ilmonen and colleagues (Ilmonen et al.,
2005). Another cytoskeletal linker, moesin, has not been related to Egr-1 in the literature. Nevertheless, the relationship of Egr-1, ezrin and moesin should be further investigated especially in the context of HeLa cell migration.
Egr-1 has been implicated in colorectal cancer apoptosis (Kwona et al., 2012). In this study however, no reduction in cell counts was seen in the proliferation assays in response to Egr-1 siRNA, suggesting that there was also no cell loss through apoptosis. .
Despite this, silencing of Egr-1 may still have potential in sensitizing HeLa cells to current chemotherapeutic treatments through other means and should be evaluated as well. Finally, given the striking impact that Egr-1 siRNA had on the inhibition of HeLa cell migration and invasion, this should be applied in an in vivo animal model to determine the potential of Egr-1 siRNA as a novel therapy for CC metastasis.
Egr-1 regulated HeLa cell migration and invasion may be mediated through c-Jun and
Cox-2. It serves as a potential target for CC metastasis therapy. 202
Chapter 5:
The role of c-Jun in Cervical Cancer
Cells in vivo
203
5.1 Introduction and Aims
Various in vivo models have been used to study the efficacy of siRNA and drug response for cervical cancer (CC) (Cabral et al., 2007 ; Lin et al., 2009). Common models include subcutaneous injection of tumour cells to study the effect of drugs on solid tumour growth (Anzai et al., 2011; Yalcin et al., 2010) and an intravenous model to determine drug efficacy on tumour cell metastasis (Gao et al., 2009; Toyoshima et al., 2007). The orthotopic xenograft model for CC remains a challenging technique
(Chaudary et al., 2011). However, it is very useful for determination of micro- environmental effects on metastasis formation and drug response.
In this chapter, a commercially available validated firefly luciferase-expressing CC cell line, HeLa-luc, was utilized in the subcutaneous model. HeLa-luc is one of the earliest cell lines used to monitor tumour growth (Edinger et al., 1999). Detection of the firefly luciferase, which is a bioluminescent reporter gene, is achieved by bioluminescence imaging (BLI). This is a method which allows sensitive and quantitative detection of cells non-invasively in small research animals over many days (Contag et al., 2000;
Edinger et al., 2002). HeLa-luc cells have previously been used to determine drug response as well as the synergism of HPV E6/ E7 siRNA and cisplatin combinations
(Cabral et al., 2007; Jung et al., 2012). Apart from non-invasive imaging of tumour development, BLI can be used for cell trafficking (Chen et al., 2010), in vivo imaging of gene expression (Lehmann et al., 2009), for evaluation of gene therapy (Bartlett and
Davis, 2006) and for monitoring protein-protein interactions in living animals
(Paulmurugan et al., 2002).
204
The hypothesis of this chapter was that c-Jun siRNA plays an important role in inhibiting HeLa-luc tumour growth. Previously, c-Jun siRNA significantly inhibited
HeLa cell proliferation, migration and invasion. Therefore, the aim was to investigate whether the effect of c-Jun siRNA could be carried out into an in vivo model. As a proof of principle, c-Jun siRNA pre-transfection in the HeLa-luc subcutaneous mouse model of CC was performed. 205
5.2 Materials and methods
5.2.1 HeLa-luc Subcutaneous In Vivo Model of CC
All animal experiments were approved (UNSW ACEC approval #12/ 80B, see
Appendix 1) and conducted in accordance with the Animal Care and Ethics Committee guidelines, University of NSW (Sydney, NSW, Australia). Female balb/c nude mice
(n=15) were obtained from Animal Resource Centre (ARC), Perth and kept at the Lowy animal facility, University of NSW. Mice were randomly divided into 3 groups. Mice were given free access to normal chow and water. Mice were held for one week in the facility prior to commencement of experiments.
Treatment groups included: HeLa-luc cells with no treatment; HeLa-luc cells pretransfected with c-Jun siRNA; and HeLa-luc cells pretransfected with non-targeting control siRNA. For pre-transfected cell preparation, HeLa-luc cells were seeded in
10cm2 petri dishes in 10% FBS MEM and transfected as mentioned in Section 2.4.1 for c-Jun siRNA. 24 hours after the second transfection, the cells were rinsed twice with pre-warmed 1 x PBS and typsinized as described in Section 2.2. Trypsin was inactivated with 10% FBS MEM. After centrifugation, the cells were resuspended in serum-free medium and automated cell counting was performed using Innovatis CASY
Cell Counter and Analyzer System Model TTC (Roche) as described in Section 2.9.
The cells were resuspended to a final concentration of 1 x 107 cells/ mL in serum-free
MEM and injected as soon as possible to the mice. Prior to subcutaneous injection, the site of injection was cleaned with 70% ethanol. A 100µL volume of cell suspension containing 1 x 106 cells was then injected subcutaneously to the right flank of 8-10 week old female Balb/c nude mice (17-20g) using a 27G needle (Terumo, USA). The 206
mice were monitored every 2 days for body weight and tumour growth. Tumour growth was measured by 150mm digital Caliper (ProSciTech, Australia).
5.2.2 Bioluminescent Imaging (BLI)
Luciferin for BLI was prepared by reconstituting D-luciferin, Firefly, potassium salt,
1.0g/vial (GoldBiotech, USA) with 1 x PBS to a final concentration of 15mg/mL. The solution was filtered sterilized using a 0.22 µm filter (Millipore). Aliquots were made and stored at -80°C in the dark. Prior to BLI, the appropriate amount of luciferin was thawed at 37°C and kept in the dark. 10µL/ g of mouse body weight (final concentration of 150mg/kg) was injected intraperitoneally to each mouse using a 29G insulin syringe
(Terumo, USA) 10 minutes prior to imaging. At imaging, three mice were anaesthesized with 3% isoflurane gas with 1L of oxygen/minute for induction (in an induction chamber) then placed onto the warmed stage (37°C) of a Xenogen IVIS Lumina II
(Caliper Life Sciences, USA) which consists of a highly sensitive CCD camera, light- tight imaging chamber and full automation. Anaesthesia was maintained with nose cones supplied with 2.5% isoflurane gas with 1L of oxygen/minute. Ten minutes after the injection of luciferin, the luminescent image was acquired using 2 bin at field of view (FOV) 12.5 for 1 second. The mice were then returned to their respective cages and monitored for recovery. For image acquisition, “counts” were used. For quantitation using region of interest (ROI) measurement in Living lmage® Software Version 3.2
“counts” was converted to “photons”. In this mode, various settings of integration time, f/stop, binning and FOV were automatically taken into account.
The experiment was terminated when most of the mice had tumour volume exceeding the 1000mm3 or tumour ulceration was observed. At endpoint, the mice were 207
anaesthesized with 3% isoflurane gas with 1L of oxygen/minute for induction (in an induction chamber) and sacrificed by cervical dislocation. The tumours were quickly removed from the mice and weighed. Large tumours were cut in half for better fixation.
The tumours were rinsed with 1 x PBS and fixed in 10% neutral-buffered formalin solution for 24 hours and rinsed again with 1 x PBS before placing in 70% ethanol. The tumours were dehydrated and embedded in paraffin blocks and subject to c-Jun immunohistochemical staining (Abcam, UK) performed by the Histology and
Microscopy Unit (HMU, UNSW).
5.3 Results
5.3.1 c-Jun siRNA inhibits HeLa-luc c-Jun protein expression
To first validate whether c-Jun siRNA could inhibit c-Jun expression in HeLa-luc cells in vitro, the siRNA silencing approach was used. Serum-starved cells were transfected twice with 100 nM siRNA and the expression of c-Jun was induced with serum for 2 hours before protein extraction. Protein expression of c-Jun was induced by 10% FBS compared to the serum-free control while c-Jun siRNA suppressed this induction relative to the non-targeting control (Figure 5.1). Protein levels were normalized to beta actin.
208
A
10%FBS
50kDa ns c-Jun 37kDa 50kDa Beta actin
37kDa
B
______n s
0 .4 ______** ______* 0 .3
0 .2
0 .1 (c-Jun/ Beta actin) Relative band intensity
0 .0
M r l J u n SF ic le iC t s i s V e h ______1 0 % F B S
Figure 5.1 c-Jun siRNA inhibits HeLa-luc c-Jun protein expression. HeLa-luc cells were serum-starved and double transfected with 100 nM c-Jun siRNA. Protein were extracted 2 hours after serum stimulation. (A) Western blotting was performed to determine c-Jun expression. Ns = non-specific bands. Representative images of western blots are shown. (B) ImageJ quantitation of western blots. Data represent mean +/- SEM of 3 independent experiments, expression was normalized to beta actin levels. Statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05 (*P<0.05; **P<0.01, ns=not significant). 209
5.3.2 c-Jun siRNA retards pre-transfected HeLa-luc subcutaneous tumour growth
To evaluate the efficacy of c-Jun siRNA in an in vivo setting, a pre-transfection subcutaneous model was used (Section 5.2). Mice were randomly divided into 3 groups: mice receiving HeLa-luc cells with no treatment, c-Jun siRNA or non-targeting siRNA. One million HeLa-luc cells from each group were injected subcutaneously into
8- 10 weeks old Balb/c nude mice. The mice were monitored every 2 days and caliper measurements performed from when the tumours were palpable. Generally, the tumours from the no treatment and non-targeting siRNA control groups were palpable on day 14 to 16 after subcutaneous injection of HeLa-luc cells.
As shown in Figure 5.2, tumour growth in the c-Jun siRNA pre-transfected group was significantly retarded compared to the no treatment and non-targeting siRNA groups
(Figure 5.2A and B). This effect was observed up to 32 days post-subcutaneous injection of HeLa-luc cells. One mouse from the no treatment group and another from the non-targeting siRNA group were sacrificed before the endpoint because the tumours grew too large and exceeded the limit proposed in the animal ethics application. For the welfare of the mice, all animals were culled by 32 days when the tumours were starting to exceed the limit of tumour volume and necrosis or ulceration was observed. At this point tumours were harvested and weighed. The c-Jun siRNA pre-transfected group had tumours which were significantly lower in weight compared to the no treatment group.
There was no significant difference between the weight of tumours in the c-Jun siRNA pre-transfected group and the non-targeting siRNA group however a strong trend was observed (Figure 5.2C ). There was no significant change in body weight of mice between groups (no treatment: 18.7 +/- 0.58g; non-targeting siRNA: 17.9 +/- 0.33g; and 210
c-Jun siRNA 18.2 +/- 0.38g). On autopsy the mice were examined for gross metastasis in various organs. No such metastasis was observed in the control and other groups.
Figure 5.2 c-Jun siRNA retards HeLa-luc pre-transfection subcutaneous tumor growth and weight. Serum-starved HeLa-luc cells were transfected twice with 100nM c-Jun siRNA or non-targeting siRNA. These cells were trypsinized and one million
HeLa-luc cells were injected subcutaneously to Balb/c nude mice. (A) Tumour growth was monitored every 2 days by caliper measurement. (B) Images of each group of 4-5 mice bearing tumours. (C) Tumours were harvested and weighed at the endpoint. (D)
Images of harvested tumours. Data represent mean +/ - SEM and statistical analysis was performed using One-Way ANOVA with Bonferroni post-hoc analysis and differences considered significant at P<0.05 (*P<0.05; ****P<0.0001, ns=not significant).
A
8 0 0
6 0 0 s iC trl
No treatment 4 0 0
2 0 0 s iJ u n Tumor volume (mm3) ****
0
0 2 4 6 8 4 1 0 1 2 1 1 6 1 8 2 0 2 2 2 4 2 6 2 8 3 0 3 2
D a y s
211
B No treatment siCtrl
siJun
C
1 .5 n s ______* ______n s
1 .0
0 .5 W e ig h t (g )
0 .0 t
iJ u n C tr l s s i
tr e a tm e n
N o
G ro u p s
212
D
No treatment
siCtrl
siJun
213
5.3.3 BLI of c-Jun siRNA pre-transfected subcutaneous tumours
To obtain supportive data on solid tumour growth as well as to determine the incidence of metastasis of HeLa-luc cells in the subcutaneous model, BLI was performed on the tumour-bearing mice as described in Section 5.2.2. The instrument generates a heat map that correlates with the number of fluorescent HeLa-luc cells with red colour correlating with high numbers of cells and blue colour correlating with low numbers of cells. c-Jun siRNA pre-transfection tumours demonstrated reduced luciferase signal which was associated with smaller tumours compared to the no treatment and non-targeting siRNA controls (Figure 5.3A). However, statistical analysis showed that the reduction was not significant (Figure 5.3B). During BLI, 1 large tumour from the non-targeting siRNA group was observed with areas without luciferase signal, which did not correlate with the large size of the tumour by Caliper measurement, it may be misleading to include this animal in the analysis (Figure 5.3C). Data from this animal was excluded from the analysis.
214
A
siCtrl No treatment
siJun
B
______n s 2 .0 1 0 1 0
______n s 1 .5 1 0 1 0
1 .0 1 0 1 0
5 .0 1 0 0 9
0 Total Flux (photon/ second)
u n C tr l tm e n t s iJ s i
tr e a N o
G ro u p s
215
C
siCtrl
Figure 5.3 BLI of c-Jun siRNA pre-transfected subcutaneous tumours. Tumour- bearing mice were given an intra-peritoneal injection of D-luciferin 10 min prior to BLI and placed on a warmed stage of IVIS Lumina II under isoflurane anaesthesia during imaging. (A) Each time, BLI images were taken for three mice under anaesthesia.
Representative images are shown. (B) Quantitation of region of interest (ROI) using
Living Image® Software Version 3.2. No treatment, n=4; c-Jun siRNA, n=5; non- targeting siRNA, n=3. Data represent mean +/ - SEM and were analyzed using One-way
ANOVA Bonferroni’s multiple comparison test (p<0.005), ns = not significant. (C) The mice from the non-targeting siRNA group without correlation of tumour size and luciferase signal (n=1) were excluded from the analysis.
216
5.3.4 c-Jun expression is significantly reduced in c-Jun siRNA pre-transfected subcutaneous tumours
To confirm whether the inhibition of HeLa-luc solid tumour growth was associated with reduction of c-Jun expression in the tumours as expected from the c-Jun silencing approach, immunohistochemistry (IHC) was performed. Immunohistochemical analysis with an anti-c-Jun antibody demonstrated a significant reduction in c-Jun expression in the c-Jun siRNA pre-transfection solid tumours compared to the no treatment and non- targeting siRNA controls (Figure 5.4). IgG control served as negative control for IHC.
A
No treatment siCtrl
siJun IgG control
217
B
n s ______
4 0 0 0 ______*** ______**
3 0 0 0
2 0 0 0
Sum of Areac-Jun for Staining1 (µm 0 ²) 0 0
0
l e n t J u n iC tr s i s
tr e a tm
N o G ro u p s
Figure 5.4 c-Jun expression was significantly reduced in c-Jun siRNA pre- transfection subcutaneous tumours. At endpoint, HeLa-luc tumours were harvested and fixed in 10% formalin for 24 hours followed by 70% ethanol for another 24 hours.
The fixed tumours were then embedded in paraffin wax and 5µm sections used for immunohistochemistry of c-Jun staining. (A) Representative images of c-Jun staining for each group. 5 random fields were taken at 20x magnification for each tumour. (B)
Sum of area of c-Jun staining per field of view was combined from 4 mice per group and calculated as mean +/- SEM using the CellSense Dimension software (Olympus).
The fifth mouse from c-Jun siRNA group was excluded from quantificantion of c-Jun staining because it did not show HeLa-luc cells in the tumour- like structure on the IHC sections. Statistics were performed using Two -way ANOVA with Bonferroni’s multiple comparison test and difference was considered significant at P<0.05
(**P<0.001,***P<0.005, ns = not significant). Positive staining indicated by brown colour (DAB) (indicated by arrows) with haematoxylin counterstain. An appropriate rabbit IgG was used as a negative control. 218
5.4 Discussion
In Chapter 3 it was demonstrated that knockdown of c-Jun with siRNA had profound effects on HeLa cell proliferation, migration and invasion. Therefore, as a proof-of- principle, in vivo studies were performed to examine whether siRNA knockdown of c-
Jun in HeLa-luc cells could attenuate solid tumour growth in a pre-transfected subcutaneous mouse model of CC. Tumour growth and weight were significantly retarded in the c-Jun siRNA transfected group of mice compared to the no treatment and non-targeting siRNA controls over a 30 day period. The inhibition of tumour growth was accompanied by significant reduction of c-Jun expression by IHC, consistent with the in vitro findings that c-Jun silencing with siRNA can alter HeLa cell growth and migration characteristics.
The concept of subcutaneous injection of siRNA pre-transfected cancer cells has also been applied by other researchers. For instance, Androic and colleagues demonstrated that pre-transfection of HeLa cells with siRNA against the cell cycle regulator, cyclin
B1, significantly inhibited HeLa solid tumour growth in a the same model (Androic et al. 2008). Similarly, transient silencing of a prognostic marker for cancer progression, choline kinase, and Oral Cancer Overexpressed 1 (ORAOV1) using siRNA, respectively, abrogated the survival of HeLa xenografts in athymic mice (Jiang et al.,
2010; Yalcin et al., 2010). The effects of transient gene silencing using siRNA in xenograft models, such as in the current study and those just mentioned, with effects sustainable for at least 10-30 days, shows that siRNA pre-transfection in in vivo models is an effective way to study gene involvement in solid tumour growth apart from the use of shRNA stably transfected animal models.
219
The confirmation of c-Jun knockdown in the HeLa-luc tumours further suggests that c-
Jun plays a crucial role in HeLa-luc solid tumour growth. The importance of c-Jun in promoting solid tumour growth has not previously been reported in a CC model however has been reported in other cancer types. For instance, the expression of
TAM67 protected mice from HPV16 E7-induced papillomas in a K14-TAM67/K14-
HPV-16 E7 double-transgenic mice model (Young et al., 2002b). Knockdown of c-Jun using a DNAzyme targeting c-Jun significantly inhibited B16 melanoma, KMC basal cell carcinoma (BCC) and T79 squamous cell carcinoma (SCC) cells in the same xenograft model (Cai et al., 2012; Zhang et al., 2004). The reduction of c-Jun expression in the c-Jun siRNA pre-transfected group was still sustainable at endpoint,
32 days after the introduction of transfected cells into the mice, compared to the control groups. One would expect the effect of the siRNA to be gone 2 to 3 days after transfection. However, as demonstrated in Fig. 3.28, c-Jun protein expression was still significantly reduced even 4 days after the second transfection, suggesting that the effect of the c-Jun siRNA used in this study was sustainable and greater than we expected. To further determine how long the inhibitory effect of c-Jun siRNA can last, c-Jun siRNA transfected cells could be left longer in the petri dish and replenish with fresh serum containing medium after several days; and harvested at various time points for c-Jun expression. On the other hand, there might be a feed-back loop mechanism where c-Jun expression is constantly suppressed by other activated or suppressed genes in the c-Jun siRNA transfected cells. Also, the tumour micro-environment of the c-Jun siRNA pre-transfected group could vary from the control groups which support the continuous down-regulation of c-Jun expression. Further experiments are required to explain this phenomenon.
220
Due to time constraints, the expression of the c-Jun–regulated genes investigated in
Chapter 3 (Cox-2, ICAM-1, MMP-1 and MMP-9) were not examined here, however further work to examine this would nicely complement the findings in vitro and determine whether the association of c-Jun expression and micro-environment of the tumour might have differential effect in the regulation of these genes in vivo. In addition, IHC of the proliferation and apoptosis markers, Ki67 and cleaved caspase-3, and angiogenesis marker, VEGF as well as CD31 could be performed to examine these processes in vivo.
The advantage of using HeLa-luc cells rather than normal HeLa cell xenografts is that tumour growth and metastasis in response to a treatment can be easily monitored non- invasively by administering the luciferase substrate to produce a luminescent signal for bioluminescent imaging (BLI). In this study, BLI was used to monitor the tumour growth of c-Jun siRNA pre-transfection tumours in addition to the standard caliper measurements. While there was a trend consistent with the tumour sizes, a significant difference between the luciferase signal in each group was not found. This may have been limited by the final number of animals that could be analysed, as several were excluded because of a lack of luminescent signal, despite the presence of large tumours.
It is a limitation of this method that the generation of light by luciferase-expressing cells following administration of the substrate luciferin requires the presence of oxygen and
ATP (Khalil et al., 2013). Hypoxia is however common in solid tumours where the tumours outgrow the oxygen supply (Rockwell et al., 2009). Thus, hypoxic luciferase- expressing cells within a large tumour may not be able to produce luciferase signal. A similar observation of increased tumour size with reduction of BLI signal, potentially caused by hypoxia, was also reported by Khalil and colleagues (Khalil et al., 2013). The 221
lack of signal may also have been a result of tumour necrosis. Despite the overall external tumour size continuing to enlarge as determined by caliper measurement, tumour necrosis affects the optical properties of tissues and thus affects scattering and absorption of light (Khalil et al., 2013). These changes impact the interpretation of BLI, suggesting BLI may not be a good method to monitor solid tumour growth, especially in the presence of tumour hypoxia and necrosis. Tumour hypoxia was not examined in this study but further studies could examine this via immunohistochemistry using antibodies specific for hypoxic markers such as the endogenous proteins hypoxia inducible factor 1 alpha (HIF1α) and glucose transporter 1 (GLUT-1) (Young and Möller, 2009). Tumour necrosis could be examined by haematoxylin and eosin staining. Alternatively, a multi- camera system for BLI tomography may be used to improve for more accurate acquisition of images. It provides a 3-dimensional (3-D) image compared to the 2-D images generated by the Xenogen used in this dissertation, which would represent better tumour structure (Lewis et al., 2013).
The use of HeLa-luc cells also allows monitoring of the metastasis of cells from the injection site to other organs. However in this study it was found that there was no significant luminescence observed in any particular body region. In particular, the lungs showed no significant signal, the region of the body normally targeted by metastatic CC cells (D'Orsi et al., 1979). Further, no lung metastasis was observed by gross examination at endpoint harvesting. This was not surprising because the subcutaneous model used is not typically designed for metastasis study and the time frame was too short for the development of metastasis. However, Gao and colleagues used the subcutaneous model and observed lung metastasis six weeks after the subcutaneous injection of two million HeLa cells. This suggests that lung metastasis may still be 222
visible but a longer time frame (more than 30 days) is needed for the development of
HeLa cell metastasis. Longer time frame and subcutaneous inoculation of more than one million HeLa-luc cells may post a problem for future experiments as in the current model most tumours were reaching volume limit of 1000mm3 and displayed signs of tumour ulceration some before 30 days. The most common yet technically challenging method for cancer metastasis in animal is the intravenous model. In this model, cancer cells are injected through the tail vein of the mice and monitored using imaging systems or examination of the organs after at least 30 days. Another more relevant model would be the orthotopic xenograft model of CC for studying micro-environmental effects on metastasis formation (Chaudary et al., 2011). This method is very technically challenging. It involves surgical procedures to implant the tumour into the cervix of the mice and monitoring lymph node as well as lung metastasis via fluorescence imaging or
BLI. These models would be useful to complement the effect of c-Jun siRNA on HeLa cell migration and invasion seen in vitro in an in vivo setup.
There are several limitations of the pretranfection subcutaneous model used as described above, and the experiments performed here are essentially proof-of-concept that c-Jun may be important in tumour growth in vivo. The route and method of siRNA delivery to CC patients remains a challenge to be overcome. Therefore, it would be interesting to determine the efficacy of c-Jun siRNA in a therapeutic setup. This is being achieved in collaboration with a group of researchers from Massachusetts Institute of
Technology (MIT), US. In vivo, c-Jun siRNA will be delivered systemically with the aid of layer-by-layer (LBL) nanoparticles. LBL nanoparticles are ultra-thin films assembled based on the alternating adsorption of substances containing complementary charged or functional groups (Hammond, 2004). The charged substances include 223
nucleic acids, proteins, saccharides and virus particles (Ariga and Hill, 2008). To eliminate non-specific cellular uptake or gain tumour selectivity in systemic delivery, a number of approaches are used to coat the LBL nanoparticles (Cortez et al., 2007; Poon et al., 2011). For instance, positively charged nanoparticles with a poly(ethylene glycol)
(PEG) layer have been developed. The PEG layer can be selectively removed by acidity generated in the hypoxic tumour microenvironment (Poon et al., 2011). Moreover, nanoparticles could be coated with targeting ligands which enable nanoparticles to bind to cell-surface receptors that are increased on the surface of the cancer cells (Cortez et al., 2007). The efflux pump mediated drug resistance can be overcome by nanoparticles through the enhanced permeability and retention (EPR) effect (Davis et al., 2008). The leakiness of the tumour blood vessels and EPR allow nanoparticles to exit blood vessels in a tumour, target the receptor on tumour cells and enter the tumour cells via endocytosis before releasing their drug loads. More recently, Morton and colleagues observed significant reduction of liver accumulation for coated LBL nanoparticles within the first 30 min of systemic circulation (Morton et al., 2013). Furthermore, in their studies, the drug half-life was increased from 2-3 minutes to 4.54 hours. These advantages of LBL nanoparticles may provide more specific delivery of c-Jun siRNA via systemic route. This would be highly clinically-relevant and promising for CC therapy.
On the other hand, many nucleic acids including siRNA have been shown to induce innate immune response in mammals. This has been shown to be due to the GU-rich sequence of the siRNA (Judge et al., 2005). However, this non-specific event is not likely in this case with my studies because c-Jun siRNA does not contain GU-rich 224
sequence. Furthermore, c-Jun siRNA has been shown to knock down c-Jun expression
(Fig. 5.4) suggesting its specific effect is specific.
In future studies, to be certain that the retarded tumour growth in the c-Jun siRNA pre- transfected group is not due to non-specific effect, Toll-like receptor assay and cytokine
ELISA assays whould be performed. Immunohistochemical analysis of interferon pathway proteins could be carried out on harvested tumours to determine whether there is any interferon activation.
5.5 Summary and Conclusions
The work in this chapter was a preliminary study to prove in principle that the findings in chapter 3 which demonstrated that c-Jun siRNA could attenuate HeLa cellular growth in vitro could be demonstrated in vivo. In summary, the primary findings of work performed in this chapter are:
1) c-Jun siRNA pre-transfection of HeLa-luc cells can reduce expression of c-Jun
in tumour cells in vivo and sustain this for 30 days.
2) c-Jun siRNA pre-transfection of HeLa-luc cells can significantly retard solid
tumour growth in a subcutaneous model of CC.
225
Chapter 6:
Final conclusions 226
6 Final conclusions
Despite treatment for early disease, recurrent and metastatic CC occurs in about one- third of patients and causes considerable morbidity and mortality (Thun et al., 2010).
Moreover, the management of invasive CC remains particularly challenging in resource-limited and developing countries (Stewart B.W. and P., 2003). As described in
Chapter 1, the majority of the molecular targets in CC investigated using siRNA to date, have been shown to be effective in inhibiting HPV oncogene expression and CC cell growth as well as inducing apoptosis. In the literature however, there is a lack of molecular targets targeted using siRNA that address the issue of CC cell migration and invasion, pivotal processes for cancer metastasis. Two major transcriptional regulators, c-Jun and Egr-1 play crucial roles in cancer cell proliferation, migration and invasion. c-
Jun/ AP-1 is also important for HPV oncogenes, E6 and E7 transcription. However, the role of c-Jun and Egr-1, have not been investigated extensively in CC. Therefore, this work set out to investigate the therapeutic potential of molecular approaches in targeting the c-Jun oncogene and the Egr-1 protein, in CC.
By using a siRNA approach, c-Jun siRNA significantly inhibited HeLa (HPV18) cell proliferation. Similar results have been reported by Maritz and colleagues in the context of CaSki (HPV16) cell proliferation (Maritz et al., 2011). However, the role of c-Jun in migration and invasion has not been investigated in HeLa or any CC cell lines. In this dissertation, siRNA targeting c-Jun significantly inhibited HeLa cell migration and invasion through the down-regulation of c-Jun regulated genes, Cox-2, ICAM-1, MMP-
1 and MMP-9. The role of c-Jun in HeLa cell invasion was further confirmed by an overexpression approach. Overexpression of c-Jun using a c-Jun expression vector 227
significantly enhanced the invasiveness of HeLa cells. The enzymatic activity of MMP-
2 as well as Cox-2 and MMP-1 were increased by overexpression of c-Jun. Cox-2 and
MMP-1 appeared to be pivotal players in the c-Jun regulated invasion consistent in both c-Jun silencing and overexpression approaches. c-Jun has been implicated in regulation of Cox-2 promoter activity in CaSki cells by applying a dominant negative c-Jun and c-
Jun expression vector (Kulkarni et al., 2001). Nevertheless, the mRNA and protein regulation of Cox-2 by c-Jun in HeLa cells has not been reported. The involvement of
Cox-2 in c-Jun induced HeLa cell invasion has also not been suggested. Cox-2 is highly expressed and related to distant metastasis in CC (Kim et al., 2003). The application of a Cox-2 inhibitor (celecoxib) in a clinical trial for CC has shown high incidence of acute toxicities (Gaffney et al., 2007a), possibly due to non-specific, Cox-2 independent effects of celecoxib (Grosch et al., 2006). By using siRNA targeting Cox-2, HeLa cell migration and invasion were significantly inhibited, accompanied by down-regulation of MMP-1 transcription. This suggests a new mechanism whereby Cox-2 is an important player in c-Jun regulated migration and invasion as well as MMP-1 transcription. Therefore, targeting c-Jun which appears to act upstream of Cox-2 seems to be a reasonable approach in CC metastasis.
On the other hand, the role of Egr-1 is unclear in the literature in the context of CC. In this study, siRNA targeting Egr-1 significantly inhibited HeLa cell migration and invasion but did not have any effect on proliferation. Whether Egr-1 plays a role specifically in migration and invasion should be further investigated. Use of an in vivo model for metastasis using Egr-1 siRNA might enhance the significance of Egr-1 as a potential target for CC metastasis. In terms of the mechanism(s) underpinning the involvement of Egr-1, it was observed that expression of Egr-1 was more rapid and 228
transient at an earlier time compared to c-Jun and Cox-2. Further, silencing of Egr-1 significantly reduced c-Jun and Cox-2 expression, suggesting Egr-1 positively regulates c-Jun and Cox-2. Egr-1 has been demonstrated to regulate c-Jun in neurite outgrowth
(Levkovitz and Baraban, 2002) and human macrophages (Faour et al., 2005) and vice versa in multiple myeloma and mouse embryonic fibroblasts (Chen et al., 2010;
Hoffmann et al., 2008). Furthermore, Egr-1 was shown to be downstream of Cox-2
(Faisal Khan et al., 2012; Faour et al., 2005; Moon et al., 2005) which suggests a possible feedback loop. This regulation of Egr-1 on these two genes has not been described in CC.
The use of siRNA targeting Egr-1 and c-Jun as well as the c-Jun regulated gene, Cox-2, demonstrated significant inhibition of HeLa cell migration and invasion. Similarly, silencing of these genes was shown to significantly inhibit MMP-1 expression which is known to play a role in facilitating cell migration and invasion (Pulukuri and Rao,
2008). Molecular dissection suggested that Egr-1 may positively regulate c-Jun and
Cox-2 which is responsible for regulation of MMP-1 and this phenotype (Figure 6.1).
This is a novel finding implicated in CC cell migration and invasion. It provides encouraging insight and molecular targets for treatment of CC metastasis.
HPV infection is cleared by most women however can persist for many decades before progression to CC (Schiffman et al., 2007); suggesting a trigger may be needed for cervical carcinogenesis. Cervical inflammation is one of the co-factors for CC (Castle et al., 2001; Parashari et al., 1995). c-Jun may play a role in promoting cervical inflammation by regulating pro-inflammatory genes, such as Cox-2 (Deng et al., 2012), 229
ICAM-1 (Beck-Schimmer et al., 2002) and MMP-1 (Steenport et al., 2009).
Interestingly, Egr-1 has also been implicated in inflammation (Schmidt et al., 2008). In this dissertation, inhibition of Cox-2, ICAM-1 and MMP-1 by c-Jun and Egr-1 siRNA strongly suggests the potential implication or blockade of inflammatory pathways in CC cells. To date, c-Jun and Egr-1 have not been directly linked to cervical inflammation.
Further investigation is needed to prove this concept however this study shows that silencing of c-Jun or Egr-1 using siRNA could perhaps be used to improve cervical inflammation, thus reducing the incidence of CC progression.
The c-Jun/AP-1 complex plays a role in HPV oncogene transcription. c-Jun siRNA significantly inhibited the expression of HPV E6 and E7 at the transcriptional level.
However, the protein expression of the HPV oncogenes, as well as some c-Jun regulated genes investigated in this dissertation (e.g. ICAM-1) were not significantly down- regulated by c-Jun siRNA. This could be due to differences in the methods used. For example real-time PCR is a more sensitive method in detecting changes. However, quantitation of western blotting lacks precision as depends on the exposure time of western blot detection and the loading of the samples. These variables may mask the subtle inhibitory changes and cause insignificant results. Increased concentration of c-
Jun siRNA may further enhance the inhibitory effect on the protein expression of
ICAM-1 as well as HPV18 E6 and E7. There may also be post-translational modification to these genes which needs to be further elucidated.
Combination treatment in CC has shown improved progression-free survival (PFS) and overall survival (OS) as discussed in Chapter 1. Nevertheless, the combination of c-Jun 230
siRNA and cisplatin in this study did not show any synergism with regard to HeLa cell growth or apoptosis. This was most likely due to the fact that cisplatin appears to exert some of its effects through sustaining c-Jun expression as demonstrated in this study and also by others (Brozovic et al., 2004b; Rubin et al., 1992). Although the application of c-Jun siRNA could reduce this over-expression of c-Jun and change cell cycle patterns in the presence of cisplatin, no significant effect on apoptosis or proliferation was observed. This suggests that c-Jun siRNA may not be suitable to be used in conjunction with cisplatin for future clinical use. It could be used as a single agent, especially in the context of CC metastasis, or perhaps in combination with other chemotherapeutic drugs which do not exert their therapeutic effects through up- regulation of c-Jun.
To my current knowledge, the role of c-Jun in CC solid tumour growth in vivo has not previously been described. Subcutaneous injection of c-Jun siRNA pretransfected
HeLa-luc demonstrated significant retarded solid tumour growth in athymic nude mice compared to the control groups, accompanied by significant reduction in c-Jun expression. This is an exciting finding as it proves the principle that c-Jun is important in CC solid tumour growth and that c-Jun siRNA can sustain its anti-proliferative effect in vivo over 30 days which complements the in vitro findings. The limitation of this model is that pre-transfection of siRNA cannot be applied in CC patients. The mode of delivery of siRNA to patients in relevant clinical use has to be addressed. Therefore, the application of c-Jun siRNA in a therapeutic setup needs to be investigated to translate from bench to bedside. The collaboration with MIT as mentioned in Chapter 5 aims to determine the potential and further develop the systemic delivery of c-Jun siRNA in
LBL technology. This would provide more clinically relevant application of c-Jun 231
siRNA as a therapeutic for CC. Furthermore, to complement the in vitro finding where c-Jun plays an important role in CC metastasis should be investigated in in vivo metastasis models like intravenous as well as orthotopic models.
Taken together, immediate early genes like c-Jun, Egr-1 and Cox-2 are crucial regulators in cervical carcinogensis especially in the context of migration and invasion.
The involvement and relationship of these genes in the regulation of HeLa migration and invasion as well as MMP-1 provide crucial information on the possible mechanisms driving CC metastasis.
Transcription factor like c-Jun may not be a good drug target in the past. However, modern technology in nanomedicine improves the delivery of drugs such as siRNA into the cells to target and eliminate transcription factors. SiRNA can be formulated with a number of carriers like liposomes, PEI, dendrosomes or nanoparticles. In addition to siRNA, DNAzyme targeting c-Jun has been formulated with liposomal to reduce tumour growth in various tumour models (Tan et al., 2010). Even though transcription factors are found in normal cells and serve normal cell functions, they are often overexpressed in cancer. Appropriate usage of drug concentration could target cancer cells but spare normal cells.
c-Jun is overexpressed in CC. In addition to the importance of c-Jun in CC cell proliferation, migration and invasion in vitro, c-Jun also plays a role in CC solid tumour growth in vivo. Although other groups target the viral oncogenes, targeting transcription 232
factor c-Jun in CC is another novel approach. To avoid or minimize the side effects which may occur when targeting c-Jun clinically in vivo, CerviPrep, a device which can be used to delivery drug directly to the cervix could be used. LBL technology which was mentioned in Chapter 5 could also be used to target the receptor of cervical cancer cells. More work need to be done to make sure the feasibility of c-Jun as a CC therapy from bench to bedside.
Pro-angiogenic factors
Egr-1
MMP-9 c-Jun
MMP-1
Cox-2
ICAM-1
HeLa cell migration and invasion
Figure 6.1 Proposed mechanism for HeLa cell migration and invasion. Upon stimulation by pro-angiogenic factors, Egr-1 and c-Jun are stimulated. Egr-1 may act 233
upstream of c-Jun which further regulate the expression of Cox-2, ICAM-1, MMP-1 and MMP-9, playing a role in HeLa cell migration and invasion. 234
7 References Abdulkadir, S.A., Carbone, J.M., Naughton, C.K., Humphrey, P.A., Catalona, W.J., and Milbrandt, J. (2001a). Frequent and early loss of the EGR1 corepressor NAB2 in human prostate carcinoma. Hum Pathol 32, 935-939. Abdulkadir, S.A., Qu, Z., Garabedian, E., Song, S.K., Peters, T.J., Svaren, J., Carbone, J.M., Naughton, C.K., Catalona, W.J., Ackerman, J.J., et al. (2001b). Impaired prostate tumorigenesis in Egr1-deficient mice. Nature medicine 7, 101-107. Ahmed, M.M. (2004). Regulation of radiation-induced apoptosis by early growth response-1 gene in solid tumors. Curr Cancer Drug Targets 4, 43-52. Aicher, W.K., Alexander, D., Haas, C., Kuchen, S., Pagenstecher, A., Gay, S., Peter, H.H., and Eibel, H. (2003). Transcription factor early growth response 1 activity up-regulates expression of tissue inhibitor of metalloproteinases 1 in human synovial fibroblasts. Arthritis and rheumatism 48, 348-359. Akutagawa, O., Nishi, H., Kyo, S., Terauchi, F., Yamazawa, K., Higuma, C., Inoue, M., and Isaka, K. (2008). Early growth response-1 mediates downregulation of telomerase in cervical cancer. Cancer Sci 99, 1401-1406. Amit, I., Citri, A., Shay, T., Lu, Y., Katz, M., Zhang, F., Tarcic, G., Siwak, D., Lahad, J., Jacob- Hirsch, J., et al. (2007). A module of negative feedback regulators defines growth factor signaling. Nat Genet 39, 503-512. Androic, I., Kramer, A., Yan, R., Rodel, F., Gatje, R., Kaufmann, M., Strebhardt, K., and Yuan, J. (2008). Targeting cyclin B1 inhibits proliferation and sensitizes breast cancer cells to taxol. BMC Cancer 8, 391. Antinore, M.J., Birrer, M.J., Patel, D., Nader, L., and McCance, D.J. (1996). The human pailloma virus type 16 E7 gene product interacts with and transactivates the AP1 family of transcription factors. EMBO J 15, 1950-1960. Anzai, K., Sekine-Suzuki, E., and Ueno, M.e.a. (2011). Effectiveness of combined treatment using X-rays and a phosphoinositide 3-kinase inhibitor, ZSTK474, on proliferation of HeLa cells in vitro and in vivo. Cancer Science 102, 1176–1180. Ardavin, C., Amigorena, S., and Reis e Sousa, C. (2004). Dendritic cells: immunobiology and cancer immunotherapy. Immunity 20, 17-23. Ariga, K., and Hill, J.P. (2008). Layer-by-Layer (LbL) Assembly, A "Gentle Yet Flexible" Method Toward Functional Biomaterials. Material Matters 3. Arlt, A., Rosenstiel, P., Kruse, M.L., Grohmann, F., Minkenberg, J., Perkins, N.D., Folsch, U.R., Schreiber, S., and Schafer, H. (2008). IEX-1 directly interferes with RelA/p65 dependent transactivation and regulation of apoptosis. Biochim Biophys Acta 1783, 941-952. Baguley, B.C. (2003). Antivascular therapy of cancer: DMXAA. Lancet Oncol 4, 141-148. Baker, C.C., Phelps, W.C., Lindgren, V., Braun, M.J., Gonda, M.A., and Howley, P.M. (1987). Structural and transcriptional analysis of human papillomavirus type 16 sequences in cervical carcinoma cell lines. J Virol 61, 962-971. Baron, V., De Gregorio, G., Krones-Herzig, A., Virolle, T., Calogero, A., Urcis, R., and Mercola, D. (2003). Inhibition of Egr-1 expression reverses transformation of prostate cancer cells in vitro and in vivo. Oncogene 22, 4194-4204. Barreiro, O., Yanez-Mo, M., Serrador, J.M., Montoya, M.C., Vicente-Manzanares, M., Tejedor, R., Furthmayr, H., and Sanchez-Madrid, F. (2002). Dynamic interaction of VCAM-1 and ICAM-1 with moesin and ezrin in a novel endothelial docking structure for adherent leukocytes. J Cell Biol 157, 1233-1245. Bartlett, D.W., and Davis, M.E. (2006). Insights into the kinetics of siRNA-mediated gene silencing from live-cell and live-animal bioluminescent imaging. Nucleic acids research 34, 322- 333. Basile, S., Angioli, R., Manci, N., Palaia, I., Plotti, F., and Benedetti Panici, P. (2006). Gynecological cancers in developing countries: the challenge of chemotherapy in low- 235
resources setting. International journal of gynecological cancer : official journal of the International Gynecological Cancer Society 16, 1491-1497. Basu, A., and Krishnamurthy, S. (2010). Cellular responses to Cisplatin-induced DNA damage. Journal of nucleic acids 2010, 1-16. Beck-Schimmer, B., Madjdpour, C., Kneller, S., Ziegler, U., Pasch, T., Wuthrich, R.P., Ward, P.A., and Schimmer, R.C. (2002). Role of alveolar epithelial ICAM-1 in lipopolysaccharide-induced lung inflammation. The European respiratory journal 19, 1142-1150. Behrens, A., Sibilia, M., and Wagner, E.F. (1999). Amino-terminal phosphorylation of c-Jun regulates stress-induced apoptosis and cellular proliferation. Nat Genet 21, 326-329. Benedetti-Panici, P., Greggi, S., Scambia, G., Amoroso, M., Salerno, M.G., Maneschi, F., Cutillo, G., Paratore, M.P., Scorpiglione, N., and Mancuso, S. (1998). Long-term survival following neoadjuvant chemotherapy and radical surgery in locally advanced cervical cancer. European journal of cancer 34, 341-346. Benítez-Hess, M.L., Reyes-Gutiérrez, P., and Alvarez-Salas, L.M. (2011). Inhibition of Human Papillomavirus Expression Using DNAzymes. J Goodchild (ed), Therapeutic Oligonucleotides, Methods in Molecular Biology 764, 317-335. Bernstein, E., Caudy, A.A., Hammond, S.M., and Hannon, G.J. (2001). Role for a bidentate ribonuclease in the initiation step of RNA interference. Nature 409, 363-366. Bièche, I., Lerebours, F., and Tozlu, S.e.a. (2004). Molecular Profiling of Inflammatory Breast Cancer: Identification of a Poor-Prognosis Gene Expression Signiture. Clinical Cancer Research 10, 6789-6795. Bishop-Bailey, D., Burke-Gaffney, A., Hellewell, P.G., Pepper, J.R., and Mitchell, J.A. (1998). Cyclo-oxygenase-2 regulates inducible ICAM-1 and VCAM-1 expression in human vascular smooth muscle cells. Biochem Biophys Res Commun 249, 44-47. Bloss, J.D., Blessing, J.A., Behrens, B.C., Mannel, R.S., Rader, J.S., Sood, A.K., Markman, M., and Benda, J. (2002). Randomized Trial of Cisplatin and Ifosfamide With or Without Bleomycin in Squamous Carcinoma of the Cervix: A Gynecologic Oncology Group Study. J Clin Oncol. Boon, M.E., Baak, J.P., Kurver, P.J., Overdiep, S.H., and Verdonk, G.W. (1981). Adenocarcinoma in situ of the cervix: an underdiagnosed lesion. Cancer 48, 768-773. Bosch, F.X., Lorincz, A., Muñoz, N., Meijer, C.J.L.M., and Shah, K.V. (2002). The causal relation between human papillomavirus and cervical cancer. Journal of Clinical Pathology 55, 244–265. Bouchard, F., Belanger, S.D., Biron-Pain, K., and St-Pierre, Y. (2010). EGR-1 activation by EGF inhibits MMP-9 expression and lymphoma growth. Blood 116, 759-766. Braasch, D.A., and Corey, D.R. (2001). Locked nucleic acid (LNA): fine-tuning the recognition of DNA and RNA. Chem Biol 8, 1-7. Brozovic, A., Fritz, G., and Christmann, M. (2004a). Long-term activation of SAPK/JNK, p38 kinase and Fas-L expression by cisplatin is attenuated in human carcinoma cells that acquired drug resistance. Int J Cancer 112, 974–985. Brozovic, A., Fritz, G., Christmann, M., Zisowsky, M., Jaehde, U., Osmak, M., and Kaina, B. (2004b). LONG-TERM ACTIVATION OF SAPK/JNK, P38 KINASE AND FAS-L EXPRESSION BY CISPLATIN IS ATTENUATED IN HUMAN CARCINOMA CELLS THAT ACQUIRED DRUG RESISTANCE. Int J Cancer 112, 974-985. Buda, A., Fossati, R., Colombo, N., Fei, F., Floriani, I., Gueli Alletti, D., Katsaros, D., Landoni, F., Lissoni, A., Malzoni, C., et al. (2005). Randomized trial of neoadjuvant chemotherapy comparing paclitaxel, ifosfamide, and cisplatin with ifosfamide and cisplatin followed by radical surgery in patients with locally advanced squamous cell cervical carcinoma: the SNAP01 (Studio Neo-Adjuvante Portio) Italian Collaborative Study. J Clin Oncol 23, 4137-4145. Butz, K., and Hoppe-Seyler, F. (1993). Transcriptional control of human papillomavirus (HPV) oncogene expression: composition of the HPV type 18 upstream regulatory region. J Virol 67, 6476-6486. Cabral, H., Nishiyama, N., and Kataoka, K. (2007). Optimization of (1,2-diamino- cyclohexane)platinum(II)-loaded polymeric micelles directed to improved tumor targeting and 236
enhanced antitumor activity. Journal of controlled release : official journal of the Controlled Release Society 121, 146-155. Cai, H., Santiago, F.S., Prado-Lourenco, L., Wang, B., Patrikakis, M., Davenport, M.P., Maghzal, G.J., Stocker, R., Parish, C.R., Chong, B.H., et al. (2012). DNAzyme targeting c-jun suppresses skin cancer growth. Sci Transl Med 4, 139ra182. Cai, S.X. (2007). Small molecule vascular disrupting agents: potential new drugs for cancer treatment. Recent Pat Anticancer Drug Discov 2, 79-101. Calogero, A., Lombari, V., De Gregorio, G., Porcellini, A., Ucci, S., Arcella, A., Caruso, R., Gagliardi, F.M., Gulino, A., Lanzetta, G., et al. (2004). Inhibition of cell growth by EGR-1 in human primary cultures from malignant glioma. Cancer Cell Int 4, 1. Cao, H., Feng, Q., Xu, W., Li, X., Kang, Z., Ren, Y., and Du, L. (2010). Genipin induced apoptosis associated with activation of the c-Jun NH2-terminal kinase and p53 protein in HeLa cells. Biological & pharmaceutical bulletin 33, 1343-1348. Castle, P.E., Hillier, S.L., Rabe, L.K., Hildesheim, A., Herrero, R., Bratti, M.C., Sherman, M.E., Burk, R.D., Rodriguez, A.C., Alfaro, M., et al. (2001). An association of cervical inflammation with high-grade cervical neoplasia in women infected with oncogenic human papillomavirus (HPV). Cancer Epidemiol Biomarkers Prev 10, 1021-1027. Castle, P.E., Jeronimo, J., Schiffman, M., Herrero, R., Rodriguez, A.C., Bratti, M.C., Hildesheim, A., Wacholder, S., Long, L.R., Neve, L., et al. (2006). Age-related changes of the cervix influence human papillomavirus type distribution. Cancer Res 66, 1218-1224. Cermak, V., Kosla, J., Plachy, J., Trejbalova, K., Hejnar, J., and Dvorak, M. (2010). The transcription factor EGR1 regulates metastatic potential of v-src transformed sarcoma cells. Cellular and molecular life sciences : CMLS 67, 3557-3568. Chaffer, C.L., and Weinberg, R.A. (2011). A perspective on cancer cell metastasis. Science 331, 1559-1564. Chambeyron, S., and Bickmore, W.A. (2004). Chromatin decondensation and nuclear eorganization of the HoxB locus upon induction of transcription. Genes and Development 18, 1119-1130. Chaney, S.G., Campbell, S.L., Bassett, E., and Wu, Y. (2005). Recognition and processing of cisplatin- and oxaliplatin-DNA adducts. Critical reviews in oncology/hematology 53, 3-11. Chang, J.T., Kuo, T.F., Chen, Y.J., Chiu, C.C., Lu, Y.C., Li, H.F., Shen, C.R., and Cheng, A.J. (2010). Highly potent and specific siRNAs against E6 or E7 genes of HPV16- or HPV18-infected cervical cancers. Cancer gene therapy 17, 827-836. Chang, L., and Karin, M. (2001). Mammalian MAP kinase signalling cascades. Nature 410, 37- 40. Chaudary, N., Hedley, D.W., and Hill, R.P. (2011). Orthotopic xenograft model of cervical cancer for studying microenvironmental effects on metastasis formation and response to drug treatment. Current protocols in pharmacology / editorial board, SJ Enna Chapter 14, Unit 14 19. Chauhan, D., Kharbanda, S., Uchiyama, H., Urashima, M., Fragoso, R., Sen, J., Kufe, D.W., and Anderson, K.C. (1994). Identification of upstream signals regulating interleukin-6 gene expression during in vitro treatment of human B cells with pokeweed mitogen. Blood 84, 2243- 2252. Chen, L., Wang, S., Zhou, Y., and Wu, X.e.a. (2010). Identification of early growth response protein 1 (EGR-1) as a novel target for JUN-induced apoptosis in multiple myeloma Blood 115, 61-70. Chen, S., Cai, C., Fisher, C.J., Zheng, Z., Omwancha, J., Hsieh, C., and Shemshedini, L. (2006). c- Jun enhancement of androgen receptor transactivation is associated with prostate cancer cell proliferation. Oncogene 25, 7212–7223. Chen, Z.Y., Liang, K., Xie, M.X., Wang, X.F., Lu, Q., and Zhang, J. (2009). Induced apoptosis with ultrasound-mediated microbubble destruction and shRNA targeting survivin in transplanted tumors. Advances in therapy 26, 99-106. 237
Cho, C.W., Poo, H., Cho, Y.S., Cho, M.C., Lee, K.A., Lee, S.J., Park, S.N., Kim, I.K., Jung, Y.K., Choe, Y.K., et al. (2002). HPV E6 antisense induces apoptosis in CaSki cells via suppression of E6 splicing. Experimental & molecular medicine 34, 159-166. Cho, S., Cinghu, S., Yu, J.R., and Park, W.Y. (2011). Helicase-like transcription factor confers radiation resistance in cervical cancer through enhancing the DNA damage repair capacity. Journal of cancer research and clinical oncology 137, 629-637. Choo, C.K., Ling, M.T., Suen, C.K., Chan, K.W., and Kwong, Y.L. (2000). Retrovirus-mediated delivery of HPV16 E7 antisense RNA inhibited tumorigenicity of CaSki cells. Gynecol Oncol 78, 293-301. Chung, J.K. (2002). Sodium iodide symporter: its role in nuclear medicine. J Nucl Med 43, 1188- 1200. Clifford, G.M., Smith, J.S., Aguado, T., and Franceschi, S. (2003). Comparison of HPV type distribution in high-grade cervical lesions and cervical cancer: a meta-analysis. Br J Cancer 89, 101-105. Contag, C.H., Jenkins, D., Contag, P.R., and Negrin, R.S. (2000). Use of reporter genes for optical measurements of neoplastic disease in vivo. Neoplasia 2, 41-52. Cortez, C., Tomaskovic-Crook, E., Johnston, A.P., Scott, A.M., Nice, E.C., Heath, J.K., and Caruso, F. (2007). Influence of size, surface, cell line, and kinetic properties on the specific binding of A33 antigen-targeted multilayered particles and capsules to colorectal cancer cells. ACS nano 1, 93-102. Crowe, D.L., Tsang, K.J., and Shemirani, B. (2001). Jun N-terminal kinase 1 mediates transcriptional induction of matrix metalloproteinase 9 expression. Neoplasia 3, 27-32. D'Orsi, C.J., Bruckman, J., Mauch, P., and Smith, E.H. (1979). Lung metastases in cervical and endometrial carcinoma. AJR American journal of roentgenology 133, 719-722. Dass, C.R., Galloway, S.J., Clark, J.C., Khachigian, L.M., and Choong, P.F. (2008a). Involvement of c-jun in human liposarcoma growth: supporting data from clinical immunohistochemistry and DNAzyme efficacy. Cancer Biol Ther 7, 1297-1301. Dass, C.R., Khachigian, L.M., and Choong, P.F.M. (2008b). c-Jun Is Critical for the Progression of Osteosarcoma: Proof in an Orthotopic spontaneously Metastasizing Model. Molecular Cancer Research 6, 1289–1292. Dass, C.R., Saravolac, E.G., Li, Y., and Sun, L.Q. (2002). Cellular uptake, distribution, and stability of 10-23 deoxyribozymes. Antisense & nucleic acid drug development 12, 289-299. Davidson, B., Goldberg, I., Liokumovich, P., Kopolovic, J., Gotlieb, W.H., Lerner-Geva, L., Reder, I., Ben-Baruch, G., and Reich, R. (1998). Expression of metalloproteinases and their inhibitors in adenocarcinoma of the uterine cervix. Int J Gynecol Pathol 17, 295-301. Davis, M.E., Chen, Z.G., and Shin, D.M. (2008). Nanoparticle therapeutics: an emerging treatment modality for cancer. Nature reviews Drug discovery 7, 771-782. Davy, M.L., Dodd, T.J., Luke, C.G., and Roder, D.M. (2003). Cervical cancer: effect of glandular cell type on prognosis, treatment, and survival. Obstet Gynecol 101. De-Castro Arce, J., Go¨ ckel-Krzikalla, E., and and Ro¨ sl, F. (2004a). Retinoic Acid Receptor Silences Human Papillomavirus-18 Oncogene Expression by Induction of de Novo Methylation and Heterochromatinization of the Viral Control Region. The Journal of Biological Chemistry 282, 28520–28529. De-Castro Arce, J., Gockel-Krzikalla, E., and Rosl, F. (2007). Retinoic acid receptor beta silences human papillomavirus-18 oncogene expression by induction of de novo methylation and heterochromatinization of the viral control region. J Biol Chem 282, 28520-28529. De-Castro Arce, J., Soto, U., van Riggelen, J., Schwarz, E., zur Hausen, H., and Rosl, F. (2004b). Ectopic expression of nonliganded retinoic acid receptor beta abrogates AP-1 activity by selective degradation of c-Jun in cervical carcinoma cells. J Biol Chem 279, 45408-45416. de Wilde, J., De-Castro Arce, J., Snijders, P.J., Meijer, C.J., Rosl, F., and Steenbergen, R.D. (2008). Alterations in AP-1 and AP-1 regulatory genes during HPV-induced carcinogenesis. 238
Cellular oncology : the official journal of the International Society for Cellular Oncology 30, 77- 87. de Wilde, J., Kooter, J.M., Overmeer, R.M., Claassen-Kramer, D., Meijer, C.J., Snijders, P.J., and Steenbergen, R.D. (2010). hTERT promoter activity and CpG methylation in HPV-induced carcinogenesis. BMC Cancer 10, 271. Deng, Z., Sui, G., Rosa, P.M., and Zhao, W. (2012). Radiation-induced c-Jun activation depends on MEK1-ERK1/2 signaling pathway in microglial cells. PLoS One 7, e36739. Dérijard, B., Hibi, M., Wu, I., Barrett, T., Su, B., Deng, T., Karin, M., and and Davls, R.J. (1994). JNKI: A Protein Kinase Stimulated by UV Light and Ha-Ras That Binds and Phosphorylates the c- Jun Activation Domain. Cell 76. Deshpande, A., Sicinski, P., and Hinds, P.W. (2005). Cyclins and cdks in development and cancer: a perspective. Oncogene 24, 2909-2915. DeYoung, M., Siwkowski, A.M., Lian, Y., and Hampel, A. (1995). Catalytic properties of hairpin ribozymes derived from Chicory yellow mottle virus and arabis mosaic virus satellite RNAs. Biochemistry 34, 15785-15791. Dianzani, C., Brucato, L., Gallicchio, M., Rosa, A.C., Collino, M., and Fantozzi, R. (2008). Celecoxib modulates adhesion of HT29 colon cancer cells to vascular endothelial cells by inhibiting ICAM-1 and VCAM-1 expression. British journal of pharmacology 153, 1153-1161. DiPaolo, J.A., and Alvarez-Salas, L.M. (2004). Advances in the development of therapeutic nucleic acids against cervical cancer. Expert opinion on biological therapy 4, 1251-1264. Doorbar, J. (2006). Molecular biology of human papillomavirus infection and cervical cancer. Clinical science 110, 525-541. Dubois, R.N., Abramson, S.B., Crofford, L., Gupta, R.A., Simon, L.S., Van De Putte, L.B., and Lipsky, P.E. (1998). Cyclooxygenase in biology and disease. FASEB J 12, 1063-1073. Dutta, T., Burgess, M., McMillan, N.A., and Parekh, H.S. (2010). Dendrosome-based delivery of siRNA against E6 and E7 oncogenes in cervical cancer. Nanomedicine : nanotechnology, biology, and medicine 6, 463-470. Edinger, M., Cao, Y.-a., and Hornig, Y.S.e.a. (2002). Advancing animal models of neoplasia through in vivo bioluminescence imaging. European Journal of Cancer 38, 2128–2136. Edinger, M., Sweeney, T.J., Tucker, A.A., Olomu, A.B., Negrin, R.S., and Contag, C.H. (1999). Noninvasive assessment of tumor cell proliferation in animal models. Neoplasia 1, 303-310. Eferl, R., Ricci, R., Kenner, L., Zenz, R., David, J.P., Rath, M., and Wagner, E.F. (2003). Liver tumor development. c-Jun antagonizes the proapoptotic activity of p53. Cell 112, 181-192. Eferl, R., Sibilia, M., Hilberg, F., Fuchsbichler, A., Kufferath, I., Guertl, B., Zenz, R., Wagner, E.F., and Zatloukal, K. (1999). Functions of c-Jun in liver and heart development. J Cell Biol 145, 1049-1061. Eferl, R., and Wagner, E.F. (2003). AP-1: a double-edged sword in tumorigenesis. Nat Rev Cancer 3, 859-868. Egeblad, M., and Werb, Z. (2002). New functions for the matrix metalloproteinases in cancer progression. Nat Rev Cancer 2, 161-174. Egerod, F.L., Bartels, A., and Fristrup, N.e.a. (2009). High frequency of tumor cells with nuclear Egr-1 protein expression in human bladder cancer is associated with disease progression. BMC Cancer 9. Eichele, K., Ramer, R., and Hinz, B. (2008). Decisive role of cyclooxygenase-2 and lipocalin-type prostaglandin D synthase in chemotherapeutics-induced apoptosis of human cervical carcinoma cells. Oncogene 27, 3032-3044. Elbakry, A., Zaky, A., Liebl, R., Rachel, R., Goepferich, A., and Breunig, M. (2009). Layer-by-layer assembled gold nanoparticles for siRNA delivery. Nano letters 9, 2059-2064. Ellington, A.D., and Szostak, J.W. (1990). In vitro selection of RNA molecules that bind specific ligands. Nature 346, 818. 239
Ercoli, A., Iannone, V., Legge, F., Fagotti, A., Fanfani, F., Carone, V., D'Asta, M., Scambia, G., and Ferrandina, G. (2009). Advances in surgical management of cervical cancer. Minerva Ginecol 61, 227-237. Etienne-Manneville, S., Chaverot, N., Strosberg, A.D., and Couraud, P.O. (1999). ICAM-1- Coupled Signaling Pathways in Astrocytes Converge to Cyclic AMP Response Element-Binding Protein Phosphorylation and TNF-a Secretion. The Journal of Immunology 163, 668-674. Fahmy, R.G., Dass, C.R., Sun, L.Q., Chesterman, C.N., and Khachigian, L.M. (2003). Transcription factor Egr-1 supports FGF-dependent angiogenesis during neovascularization and tumor growth. Nature medicine 9, 1026-1032. Fahmy, R.G., and Khachigian, L.M. (2004). Locked nucleic acid modified DNA enzymes targeting early growth response-1 inhibit human vascular smooth muscle cell growth. Nucleic Acids Res 32, 2281-2285. Faisal Khan, K.M., Kothari, P., Du, B., Dannenberg, A.J., and Falcone, D.J. (2012). Microsomal Prostaglandin E Synthase-1 Matrix Metalloproteinase-Dependent and the EP4 Prostanoid Receptor Expression in Macrophages: Role of TNF-α and the EP4 Prostanoid Receptor. Journal of immunology 188, 1970-1980. Faour, W.H., Alaaeddine, N., Mancini, A., He, Q.W., Jovanovic, D., and Di Battista, J.A. (2005). Early growth response factor-1 mediates prostaglandin E2-dependent transcriptional suppression of cytokine-induced tumor necrosis factor-alpha gene expression in human macrophages and rheumatoid arthritis-affected synovial fibroblasts. J Biol Chem 280, 9536- 9546. Farley, J., Sill, M.W., Birrer, M., Walker, J., Schilder, R.J., Thigpen, J.T., Coleman, R.L., Miller, B.E., Rose, P.G., and Lankes, H.A. (2011). Phase II study of cisplatin plus cetuximab in advanced, recurrent, and previously treated cancers of the cervix and evaluation of epidermal growth factor receptor immunohistochemical expression: a Gynecologic Oncology Group study. Gynecol Oncol 121, 303-308. Ferlay, J., Shin, H.R., Bray, F., Forman, D., Mathers, C., and Parkin, D.M. (2010). Estimates of worldwide burden of cancer in 2008: GLOBOCAN 2008. Int J Cancer 127, 2893-2917. Ferrandina, G., Lauriola, L., Zannoni, G.F., Distefano, M.G., Legge, F., Salutari, V., Gessi, M., Maggiano, N., Scambia, G., and Ranelletti, F.O. (2002). Expression of cyclooxygenase-2 (COX-2) in tumour and stroma compartments in cervical cancer: clinical implications. Br J Cancer 87, 1145-1152. Ferrandina, G., Legge, F., Fagotti, A., Fanfani, F., Distefano, M., Morganti, A., Cellini, N., and Scambia, G. (2007). Preoperative concomitant chemoradiotherapy in locally advanced cervical cancer: safety, outcome, and prognostic measures. Gynecol Oncol 107, S127-S132. Ferraro, B., Bepler, G., Sharma, S., Cantor, A., and Haura, E.B. (2005). EGR1 predicts PTEN and survival in patients with non-small-cell lung cancer. Journal of clinical oncology : official journal of the American Society of Clinical Oncology 23, 1921-1926. Fialka, I., Schwarz, H., Reichmann, E., Oft, M., Busslinger, M., and Beug, H. (1996). The estrogen-dependent c-JunER protein causes a reversible loss of mammary epithelial cell polarity involving a destabilization of adherens junctions. J Cell Biol 132, 1115-1132. Finkelstein, S.E., Rodriguez, F., Dunn, M., Farmello, M.J., Smilee, R., Janssen, W., Kang, L., Chuang, T., Seigne, J., Pow-Sang, J., et al. (2012). Serial assessment of lymphocytes and apoptosis in the prostate during coordinated intraprostatic dendritic cell injection and radiotherapy. Immunotherapy 4, 373-382. Fitzgerald, D.W., Bezak, K., and Ocheritina, O.e.a. (2011). The Effect of HIV and HPV Co- infection on Cervical COX-2 Expression and Systemic Prostaglandin E2 Levels. Cancer Prevention Research. Fluiter, K., Frieden, M., Vreijling, J., Koch, T., and Baas, F. (2005). Evaluation of LNA-modified DNAzymes targeting a single nucleotide polymorphism in the large subunit of RNA polymerase II. Oligonucleotides 15, 246-254. 240
Fogel, S., and and Riou, G. (1998). The Early HPV16 Proteins Can Regulate mRNA Levels of Cell Cycle Genes in Human Cervical Carcinoma Cells by p53-Independent Mechanisms. Virology 244, 97–107. Fong, Y.C., Lin, C.Y., Su, Y.C., Chen, W.C., Tsai, F.J., Tsai, C.H., Huang, C.Y., and Tang, C.H. (2012). CCN6 enhances ICAM-1 expression and cell motility in human chondrosarcoma cells. Journal of cellular physiology 227, 223-232. Fontaine, V., van der Meijden, E., and ter Schegget, J. (2001). Inhibition of human papillomavirus-16 long control region activity by interferon-gamma overcome by p300 overexpression. Molecular carcinogenesis 31, 27-36. Frankowski, H., Gu, Y.H., Heo, J.H., Milner, R., and del Zoppo, G.J. (2012). Use of Gel Zymography to Examine Matrix Metalloproteinase (Gelatinase) Expression in Brain Tissue or in Primary Glial Cultures. Methods Mol Biol 814, 221–233. Franks, T.M., and Lykke-Andersen, J. (2007). TTP and BRF proteins nucleate processing body formation to silence mRNAs with AU-rich elements. Genes Dev 21, 719-735. Friedl, P., and Wolf, K. (2003). Tumour-cell invasion and migration: diversity and escape mechanisms. Nat Rev Cancer 3, 362-374. Gaffney, D.K., Winter, K., Dicker, A.P., Miller, B., Eifel, P.J., Ryu, J., Avizonis, V., Fromm, M., and Greven, K. (2007a). A Phase II study of acute toxicity for Celebrex (celecoxib) and chemoradiation in patients with locally advanced cervical cancer: primary endpoint analysis of RTOG 0128. International journal of radiation oncology, biology, physics 67, 104-109. Gaffney, D.K., Winter, K., Dicker, A.P., Miller, B., Eifel, P.J., Ryu, J., Avizonis, V., Fromm, M., Small, W., and Greven, K. (2007b). Efficacy and patterns of failure for locally advanced cancer of the cervix treated with celebrex (celecoxib) and chemoradiotherapy in RTOG 0128. International journal of radiation oncology, biology, physics 69, 111-117. Gao, Y., Shan, Z.Y., Wang, H., Zhang, H.M., and Teng, W.P. (2009). Inhibitory effect of shRNA targeting GPR48 on invasion and metastasis of human cervical carcinoma cell line HeLa. Ai zheng = Aizheng = Chinese journal of cancer 28, 104-107. Gey, G.O., Coffman, W.D., and Kubicek, M.T. (1952). Tissue culture studies of the proliferative capacity of cervical carcinoma and normal epithelium. Cancer Res 12, 264-265. Gilboa, E. (2007). DC-based cancer vaccines. J Clin Invest 117, 1195-1203. Gilhooly, E.M., and Rose, D.P. (1999). The association between a mutated ras gene and cyclooxygenase-2 expression in human breast cancer cell lines. International journal of oncology 15, 267-337. Greer, B.E., Koh, W.J., Abu-Rustum, N.R., Apte, S.M., Campos, S.M., Chan, J., Cho, K.R., Copeland, L., Crispens, M.A., Dupont, N., et al. (2010). Cervical cancer. Journal of the National Comprehensive Cancer Network : JNCCN 8, 1388-1416. Gregg, J., and Fraizer, G. (2011). Transcriptional Regulation of EGR1 by EGF and the ERK Signaling Pathway in Prostate Cancer Cells. Genes & cancer 2, 900-909. Grosch, S., Maier, T.J., Schiffmann, S., and Geisslinger, G. (2006). Cyclooxygenase-2 (COX-2)- independent anticarcinogenic effects of selective COX-2 inhibitors. J Natl Cancer Inst 98, 736- 747. Grothey, A., and Galanis, E. (2009). Targeting angiogenesis: progress with anti-VEGF treatment with large molecules. Nature reviews Clinical oncology 6, 507-518. Gu, W., Payne, E., Sun, S., Burgess, M., and McMillan, N.A. (2011). Inhibition of cervical cancer cell growth in vitro and in vivo with dual shRNAs. Cancer gene therapy 18, 219-227. Gu, W., Putral, L., Hengst, K., Minto, K., Saunders, N.A., Leggatt, G., and McMillan, N.A. (2006). Inhibition of cervical cancer cell growth in vitro and in vivo with lentiviral-vector delivered short hairpin RNA targeting human papillomavirus E6 and E7 oncogenes. Cancer gene therapy 13, 1023-1032. Gu, Z., and Matlashewski, G. (1995). Effect of human papillomavirus type 16 oncogenes on MAP kinase activity. J Virol 69, 8051-8056. 241
Gurzov, E.N., Bakiri, L., Alfaro, J.M., Wagner, E.F., and Izquierdo, M. (2008). Targeting c-Jun and JunB proteins as potential anticancer cell therapy. Oncogene 27, 641-652. Guvakova, M.A., Yakubov, L.A., Vlodavsky, I., Tonkinson, J.L., and Stein, C.A. (1995). Phosphorothioate oligodeoxynucleotides bind to basic fibroblast growth factor, inhibit its binding to cell surface receptors, and remove it from low affinity binding sites on extracellular matrix. J Biol Chem 270, 2620-2627. Hacia, J.G., Dervan, P.B., and Wold, B.J. (1994). Inhibition of Klenow fragment DNA polymerase on double-helical templates by oligonucleotide-directed triple-helix formation. Biochemistry 33, 6192-6200. Hallahan, D.E., Sukhatme, V.P., Sherman, M.L., Virudachalam, S., Kufe, D., and Weichselbaum, R.R. (1991). Protein kinase C mediates x-ray inducibility of nuclear signal transducers EGR1 and JUN. Proceedings of the National Academy of Sciences of the United States of America 88, 2156-2160. Hammond, P.T. (2004). Form and function of multilayer assembly: new applications at the nanoscale. Advanced Materials 16. Han, C., Michalopoulos, G.K., and Wu, T. (2006). Prostaglandin E2 receptor EP1 transactivates EGFR/MET receptor tyrosine kinases and enhances invasiveness in human hepatocellular carcinoma cells. Journal of cellular physiology 207, 261-270. Hargreaves, D.C., Horng, T., and Medzhitov, R. (2009). Control of inducible gene expression by signal-dependent transcriptional elongation. Cell 138, 129-145. Hass, R., Brach, M., and Gunji, H.e.a. (1992). INHIBITION OF EGR-I AND NF-ZCB GENE EXPRESSION BY DEXAMETHASONE DURING PHORBOL ESTER-INDUCED HUMAN MONOCYTIC DIFFERENTIATION. Biochemical Pharmacology 44, 1569-1576. Hayes, M.M., Matisic, J.P., Chen, C.J., Mohamed, A., Anderson, G.H., LeRiche, J.C., and Amy, R. (1997). Cytological aspects of uterine cervical adenocarcinoma, adenosquamous carcinoma and combined adenocarcinoma-squamous carcinoma: appraisal of diagnostic criteria for in situ versus invasive lesions. Cytopathology : official journal of the British Society for Clinical Cytology 8, 397-408. Hayes, S.H., and Seigel, G.M. (2009). Immunoreactivity of ICAM-1 in human tumors, metastases and normal tissues. International journal of clinical and experimental pathology 2, 553-560. Haynes, J., Srivastava, J., Madson, N., Wittmann, T., and Barber, D.L. (2011). Dynamic actin remodeling during epithelial-mesenchymal transition depends on increased moesin expression. Mol Biol Cell 22, 4750-4764. Hebner, C.M., and Laimins, L.A. (2006). Human papillomaviruses: basic mechanisms of pathogenesis and oncogenicity. Reviews in medical virology 16, 83-97. Heiska, L., Alfthan, K., Gronholm, M., Vilja, P., Vaheri, A., and Carpen, O. (1998). Association of ezrin with intercellular adhesion molecule-1 and -2 (ICAM-1 and ICAM-2). Regulation by phosphatidylinositol 4, 5-bisphosphate. J Biol Chem 273, 21893-21900. Helm, C.W., Shrestha, K., Thomas, S., Shingleton, H.M., and Miller, D.M. (1993). A unique c- myc-targeted triplex-forming oligonucleotide inhibits the growth of ovarian and cervical carcinomas in vitro. Gynecol Oncol 49, 339-343. Herschman, H.R. (1991). Primary response genes induced by growth factors and tumor promoters. Annual review of biochemistry 60, 281-319. Hilberg, F., and Wagner, E.F. (1992). Embryonic stem (ES) cells lacking functional c-jun: consequences for growth and differentiation, AP-1 activity and tumorigenicity. Oncogene 7, 2371-2380. Hill, C.S., Wynne, J., and Treisman, R. (1994). Serum-regulated transcription by serum response factor (SRF): a novel role for the DNA binding domain. EMBO J 13, 5421-5432. Hill, R., Li, Y., Tran, L.M., Dry, S., Calvopina, J.H., Garcia, A., Kim, C., Wang, Y., Donahue, T.R., Herschman, H.R., et al. (2012). Cell intrinsic role of COX-2 in pancreatic cancer development. Mol Cancer Ther 11, 2127-2137. 242
Hinz, B., Ro¨sch, S., Ramer, R., Tamm, E.R., and Brune, K. (2005). Latanoprost induces matrix metalloproteinase-1 expression in human nonpigmented ciliary epithelial cells through a cyclooxygenase-2-dependent mechanism. The FASEB Journal 19, 1929-1931. Hjoberg, J., Le, L., Imrich, A., Subramaniam, V., Mathew, S.I., Vallone, J., Haley, K.J., Green, F.H., Shore, S.A., and Silverman, E.S. (2004). Induction of early growth-response factor 1 by platelet- derived growth factor in human airway smooth muscle. American journal of physiology Lung cellular and molecular physiology 286, L817-825. Hodge, L.S., Downs, L.S., Jr., Chura, J.C., Thomas, S.G., Callery, P.S., Soisson, A.P., Kramer, P., Wolfe, S.S., and Tracy, T.S. (2012). Localized delivery of chemotherapy to the cervix for radiosensitization. Gynecol Oncol. Hoffmann, E., Ashouri, J., Wolter, S., Doerrie, A., Dittrich-Breiholz, O., Schneider, H., Wagner, E.F., Troppmair, J., Mackman, N., and Kracht, M. (2008). Transcriptional regulation of EGR-1 by the interleukin-1-JNK-MKK7-c-Jun pathway. J Biol Chem 283, 12120-12128. Hong, D., Lu, W., Ye, F., Hu, Y., and Xie, X. (2009). Gene silencing of HPV16 E6/E7 induced by promoter-targeting siRNA in SiHa cells. British journal of cancer 101, 1798-1804. Hong, X., Dong, T., Hu, J., Yi, T., Li, W., Zhang, Z., Lin, S., and Niu, W. (2012). Synergistical toll- like receptors activated dendritic cells induce antitumor effects against carcinoembryonic antigen-expressing colon cancer. Int J Colorectal Dis. Horinaka, M., Yoshida, T., Shiraishi, T., Nakata, S., Wakada, M., Nakanishi, R., Nishino, H., and Sakai, T. (2005). The combination of TRAIL and luteolin enhances apoptosis in human cervical cancer HeLa cells. Biochem Biophys Res Commun 333, 833-838. Hou, Z., Falcone, D.J., Subbaramaiah, K., and Dannenberg, A.J. (2011). Macrophages induce COX-2 expression in breast cancer cells: role of IL-1b autoamplification. Carcinogenesis 32. Howie, H.L., Katzenellenbogen, R.A., and Galloway, D.A. (2009). Papillomavirus E6 proteins. Virology 384, 324-334. Huang, C., Wang, J., and Kikkawa, U.e.a. (2008). Calcineurin-mediated dephophorylation of c- Jun Ser-243 is required for c-Jun stability and cell transformation. Oncogene 27, 2422-2429. Huang, R.P., and and Adamson, E.D. (1994). The Phosphorylated Forms of the Transcription Factor, Egr-1, Bind to DNA More Efficiently than Non-phosphorylated. Biochem Biophys Res Commun 200, 1271-1276. Huang, R.P., Fan, Y., de Belle, I., Niemeyer, C., Gottardis, M.M., Mercola, D., and Adamson, E.D. (1997). Decreased Egr-1 expression in human, mouse and rat mammary cells and tissues correlates with tumor formation. International journal of cancer Journal international du cancer 72, 102-109. Huang, W.C., Chan, S.T., and Yang, T.L.e.a. (2004a). Inhibition of ICAM-1 gene expression, monocyte adhesion and cancer cell invasion by targeting IKK complex: molecular and functional study of novel a-methylene-g-butyrolactone derivatives. Carcinogenesis 25, 1925- 1934. Huang, Y., Keen, J.C., Hager, E., Smith, R., Hacker, A., Frydman, B., Valasinas, A.L., Reddy, V.K., Marton, L.J., Casero, R.A., Jr., et al. (2004b). Regulation of polyamine analogue cytotoxicity by c-Jun in human MDA-MB-435 cancer cells. Mol Cancer Res 2, 81-88. Ilmonen, S., Vaheri, A., Asko-Seljavaara, S., and Carpen, O. (2005). Ezrin in primary cutaneous melanoma. Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc 18, 503-510. International Collaboration of Epidemiological Studies of Cervical, C. (2007). Comparison of risk factors for invasive squamous cell carcinoma and adenocarcinoma of the cervix: collaborative reanalysis of individual data on 8,097 women with squamous cell carcinoma and 1,374 women with adenocarcinoma from 12 epidemiological studies. International journal of cancer Journal international du cancer 120, 885-891. Irie T., Kigawa J., and Minagawa Y., e.a. (2000). Prognosis and clinicopathological characteristics of Ib–IIb adenocarcinoma of the uterine cervix in patients who have had radical hysterectomy. Eur J Surg Oncol 26, 464-467. 243
Ishibashi, T., and Lippard, S.J. (1998). Telomere loss in cells treated with cisplatin. Proceedings of the National Academy of Sciences of the United States of America 95, 4219-4223. Jacobson, D.L., Peralta, L., Farmer, M., Graham, N.M., Wright, T.C., and Zenilman, J. (1999). Cervical ectopy and the transformation zone measured by computerized planimetry in adolescents. International journal of gynaecology and obstetrics: the official organ of the International Federation of Gynaecology and Obstetrics 66, 7-17. Jeon, S., Allen-Hoffmann, B.L., and Lambert, P.F. (1995). Integration of Human Papillomavirus Type 16 into the Human Genome Correlates with a Selective Growth Advantage of Cells. Journal of Virology 69, 2989–2997. Jeon, S., and Lambert, P.F. (1995). Integration of human papillomavirus type 16 DNA into the human genome leads to increased stability of E6 and E7 mRNAs: Implications for cervical carcinogenesis. Proc Natl Acad Sci USA 92, 1654-1658. Jeon, Y.H., Lee, H.W., Lee, Y.L., Kim, J.E., Hwang, M.H., Jeong, S.Y., Lee, S.W., Ahn, B.C., Ha, J.H., and Lee, J. (2011). Combined E7-dendritic cell-based immunotherapy and human sodium/iodide symporter radioiodine gene therapy with monitoring of antitumor effects by bioluminescent imaging in a mouse model of uterine cervical cancer. Cancer Biother Radiopharm 26, 671-679. Jiang, L., Zeng, X., Wang, Z., Ji, N., Zhou, Y., Liu, X., and Chen, Q. (2010). Oral cancer overexpressed 1 (ORAOV1) regulates cell cycle and apoptosis in cervical cancer HeLa cells. Molecular cancer 9, 20. Jiao, X., Katiyar, S., and Liu, M.e.a. (2008). Disruption of c-Jun Reduces Cellular Migration and Invasion through Inhibition of c-Src and hyperactivation of ROCK II Kinase. Molecular Biology of the Cell 19, 1378-1390. Jiao, X., Katiyar, S., Willmarth, N.E., Liu, M., Ma, X., Flomenberg, N., Lisanti, M.P., and Pestell, R.G. (2010). c-Jun induces mammary epithelial cellular invasion and breast cancer stem cell expansion. J Biol Chem 285, 8218-8226. Jochum, W., Passegue, E., and Wagner, E.F. (2001). AP-1 in mouse development and tumorigenesis. Oncogene 20, 2401-2412. Johnson, R.S., van Lingen, B., Papaioannou, V.E., and and Spiegelman, B.M. (1993). A null mutation at the c-jun locus causes embryonic lethality and retarded cell growth in culture. Genes and Development 7, 1309-1317. Jones, D.L., Alani, R.M., and Münger, K. (1997). The human papillomavirus E7 oncoprotein can uncouple cellular differentiation and proliferation in human keratinocytes by abrogating p21Cip1-mediated inhibition of cdk2. Genes and Development 11, 2101-2111. Judge, A.D., Sood, V., Shaw, J.R., Fang, D., McClintock, K., and MacLachlan, I. (2005). Sequence- dependent stimulation of the mammalian innate immune response by synthetic siRNA. Nat Biotechnol 23, 457-462. Jung, H.S., Erkin, O.C., Kwon, M.J., Kim, S.H., Jung, J.I., Oh, Y.K., Her, S.W., Ju, W., Choi, Y.L., Song, S.Y., et al. (2012). The synergistic therapeutic effect of cisplatin with Human papillomavirus E6/E7 short interfering RNA on cervical cancer cell lines in vitro and in vivo. Int J Cancer 130, 1925-1936. Kang, J.H., Chung, J.K., Lee, Y.J., Shin, J.H., Jeong, J.M., Lee, D.S., and Lee, M.C. (2004). Establishment of a human hepatocellular carcinoma cell line highly expressing sodium iodide symporter for radionuclide gene therapy. J Nucl Med 45, 1571-1576. Keller, W., and Crouch, R. (1972). Degradation of DNA RNA hybrids by ribonuclease H and DNA polymerases of cellular and viral origin. Proceedings of the National Academy of Sciences of the United States of America 69, 3360-3364. Keys, H.M., Bundy, B.N., Stehman, F.B., Muderspach, L.I., Chafe, W.E., Suggs, C.L., 3rd, Walker, J.L., and Gersell, D. (1999). Cisplatin, radiation, and adjuvant hysterectomy compared with radiation and adjuvant hysterectomy for bulky stage IB cervical carcinoma. N Engl J Med 340, 1154-1161. 244
Khalil, A.A., Jameson, M.J., and Broaddus, W.C. (2013). The Influence of Hypoxia and pH on Bioluminescence Imaging of Luciferase-transfected Tumor Cells and Xenografts. International Journal of Molecular Imaging 2013. Khunamornpong, S., Settakorn, J., Sukpan, K., Srisomboon, J., Ruangvejvorachai, P., Thorner, P.S., and Siriaunkgul, S. (2009). Cyclooxygenase-2 expression in squamous cell carcinoma of the uterine cervix is associated with lymph node metastasis. Gynecologic oncology 112, 241-247. Kim, D.H., Longo, M., Han, Y., Lundberg, P., Cantin, E., and Rossi, J.J. (2004). Interferon induction by siRNAs and ssRNAs synthesized by phage polymerase. Nat Biotechnol 22, 321- 325. Kim, H.J., Wu, H.G., Park, I.A., and Ha, S.W. (2003). HIGH CYCLOOXYGENASE-2 EXPRESSION IS RELATED WITH DISTANT METASTASIS IN CERVICAL CANCER TREATED WITH RADIOTHERAPY. Int J Radiation Oncology Biol Phys 55, 16-20. Kim, M.J., Lee, K.H., and Lee, S.J. (2008). Ionizing radiation utilizes c-Jun N-terminal kinase for amplification of mitochondrial apoptotic cell death in human cervical cancer cells. The FEBS journal 275, 2096-2108. Kleine, W., Rau K., Schwoeorer, D., Pfleiderer, A. (1989). Prognosis of the adenocarcinoma of the cervix uteri: a comparative study. Gynecol Oncol 35. Koivusalo, R., Mialon, A., Pitkanen, H., Westermarck, J., and Hietanen, S. (2006). Activation of p53 in cervical cancer cells by human papillomavirus E6 RNA interference is transient, but can be sustained by inhibiting endogenous nuclear export-dependent p53 antagonists. Cancer Res 66, 11817-11824. Konstantinopoulos, P.A., and Papavassiliou, A.G. (2011). Seeing the future of cancer-associated transcription factor drug targets. JAMA : the journal of the American Medical Association 305, 2349-2350. Kore, A.R., Vaish, N.K., Kutzke, U., and Eckstein, F. (1998). Sequence specificity of the hammerhead ribozyme revisited; the NHH rule. Nucleic Acids Res 26, 4116-4120. Koshkin, A.A., and Wengel, J. (1998). Synthesis of Novel 2',3'-Linked Bicyclic Thymine Ribonucleosides. The Journal of organic chemistry 63, 2778-2781. Kovary, K., and Bravo, R. (1991). The Jun and Fos Protein Families Are Both Required for Cell Cycle Progression in Fibroblasts. Molecular and Cellular Biology 11, 4466-4472. Krones-Herzig, A., Mittal, S., Yule, K., Liang, H., English, C., Urcis, R., Soni, T., Adamson, E.D., and Mercola, D. (2005). Early Growth Response 1 Acts as a Tumor Suppressor In vivo and In vitro via Regulation of p53. Cancer Research 65, 5133-5143. Kruse, M.L., Arlt, A., and Sieke, A.e.a. (2005). Immediate Early Gene X1 (IEX-1) Is Organized in Subnuclear Structures and Partially Co-localizes with Promyelocytic Leukemia Protein in HeLa Cells. Journal of Biological Chemistry 280, 24849 –24856. Kubota, H., Suzuki, T., Lu, J., and Takahashi, S. (2005). Increased expression of GRP94 protein is associated with decreased sensitivity to X-rays in cervical cancer cell lines. Int J Radiat Biol 81, 701 – 709. Kulkarni, S., Rader, J.S., Zhang, F., Liapis, H., Koki, A.T., Masferrer, J.L., Subbaramaiah, K., and Dannenberg, A.J. (2001). Cyclooxygenase-2 Is Overexpressed in Human Cervical Cancer. Clinical Cancer Research 7, 429-434. Kumbrink, J., Kirsch, K.H., and and Johnson, J.P. (2010). EGR1, EGR2, and EGR3 activate the expression of their coregulator NAB2 establishing a negative feedback loop in cells of neuroectodermal and epithelial origin. J Cell Biochem 111, 207-217. Kuroda, M., Kiyono, T., Oikawa, K., Yoshida, K., and Mukai, K. (2005). The human papillomavirus E6 and E7 inducible oncogene, hWAPL, exhibits potential as a therapeutic target. British journal of cancer 92, 290-293. Kwona, O., Sounga, N.K., and Thimmegowdaa, N.R.e.a. (2012). Patulin induces colorectal cancer cells apoptosis through EGR-1 dependent ATF3 up-regulation. Cell Signal 24, 943-950. 245
Kyo, S., Klumpp, D.J., Inoue, M., Kanaya, T., and Laimins, L.A. (1997). Expression of AP1 during cellular differentiation determines human papillomavirus E6/E7 expression in stratified epithelial cells. The Journal of general virology 78 ( Pt 2), 401-411. Lacey, J.V.J., Swanson, C.A., and Brinton, L.A., et al. (2003). Obesity As a Potential Risk Factor for Adenocarcinomas and Squamous Cell Carcinomas of the uterine Cervix. Cancer 98, 814- 821. Lamb, R.F., Hennigan, R.F., Turnbull, K., Katsanakis, K.D., MacKenzie, E.D., Birnie, G.D., and Ozanne, B.W. (1997). AP-1-mediated invasion requires increased expression of the hyaluronan receptor CD44. Mol Cell Biol 17, 963-976. Landoni, F., Maneo, A., Colombo, A., Placa, F., Milani, R., Perego, P., Favini, G., Ferri, L., and Mangioni, C. (1997). Randomised study of radical surgery versus radiotherapy for stage Ib-IIa cervical cancer. Lancet 350, 535-540. Lau, L.F., and Nathans, D. (1987). Expression of a set of growth-related immediate early genes in BALB/c 3T3 cells: coordinate regulation with c-fos or c-myc. Proceedings of the National Academy of Sciences of the United States of America 84, 1182-1186. Lea, J.S., Sunaga, N., Sato, M., Kalahasti, G., Miller, D.S., Minna, J.D., and Muller, C.Y. (2007). Silencing of HPV 18 oncoproteins With RNA interference causes growth inhibition of cervical cancer cells. Reproductive sciences 14, 20-28. Lee, E.J., Choi, E.M., Kim, S.R., Park, J.H., Kim, H., Ha, K.S., Kim, Y.M., Kim, S.S., Choe, M., Kim, J.I., et al. (2007). Cyclooxygenase-2 promotes cell proliferation, migration and invasion in U2OS human osteosarcoma cells. Experimental & molecular medicine 39, 469-476. Lee, J.S., Choi, Y.D., Lee, J.H., Nam, J.H., Choi, C., Lee, M.C., Park, C.S., Juhng, S.W., Kim, H.S., and Min, K.W. (2004). Expression of cyclooxygenase-2 in adenocarcinomas of the uterine cervix and its relation to angiogenesis and tumor growth. Gynecologic oncology 95, 523-529. Lee, S.L., Wang, Y., and Milbrandt, J. (1996). Unimpaired Macrophage Differentiation and Activation in Mice Lacking the Zinc Finger Transcription Factor NGFI-A (EGR1). Molecular and Cellular Biology 16, 4566–4572. Leechanachai, P., Banks, L., Moreau, F., and Matlashewski, G. (1992). The E5 gene from human papillomavirus type 16 is an oncogene which enhances growth factor-mediated signal transduction to the nucleus. Oncogene 7, 19-25. Legge, F., Fuoco, G., Lorusso, D., Lucidi, A., Borriello, M., Pisconti, S., Scambia, G., and Ferrandina, G. (2010). Pharmacotherapy of cervical cancer. Expert opinion on pharmacotherapy 11, 2059-2075. Lehmann, S., Stiehl, D.P., Honer, M., Dominietto, M., Keist, R., Kotevic, I., Wollenick, K., Ametamey, S., Wenger, R.H., and Rudin, M. (2009). Longitudinal and multimodal in vivo imaging of tumor hypoxia and its downstream molecular events. Proceedings of the National Academy of Sciences of the United States of America 106, 14004-14009. Leppä, S., and Bohmann, D. (1999). Diverse functions of JNK signaling and c-Jun in stress response and apoptosis. Oncogene 18, 6158-6162. Levi, J.A., Aroney, R.S., and Dalley, D.N. (1981). Haemolytic anaemia after cisplatin treatment. British medical journal 282, 2003-2004. Levkovitz, Y., and Baraban, J.M. (2002). A dominant negative Egr inhibitor blocks nerve growth factor-induced neurite outgrowth by suppressing c-Jun activation: role of an Egr/c-Jun complex. The Journal of neuroscience : the official journal of the Society for Neuroscience 22, 3845-3854. Lewis, M.A., Richer, E., and Slavine, N.V.e.a. (2013). A Multi-Camera System for Bioluminescence Tomography in Preclinical Oncology Research. Diagnostics 3, 325-343. Li, Q.X., Zhao, J., Liu, J.Y., Jia, L.T., Huang, H.Y., Xu, Y.M., Zhang, Y., Zhang, R., Wang, C.J., Yao, L.B., et al. (2006). Survivin stable knockdown by siRNA inhibits tumor cell growth and angiogenesis in breast and cervical cancers. Cancer Biol Ther 5, 860-866. Li, Y., Li, H., Yao, G., Li, W., Wang, F., Jiang, Z., and Li, M. (2007). Inhibition of telomerase RNA (hTR) in cervical cancer by adenovirus-delivered siRNA. Cancer gene therapy 14, 748-755. 246
Lin, Y.M., Chang, Z.L., Liao, Y.Y., Chou, M.C., and Tang, C.H. (2013). IL-6 promotes ICAM-1 expression and cell motility in human osteosarcoma. Cancer Lett 328, 135-143. Lin, Z., Bazzaro, M., Wang, M.C., Chan, K.C., Peng, S., and Roden, R.B. (2009). Combination of proteasome and HDAC inhibitors for uterine cervical cancer treatment. Clin Cancer Res 15, 570-577. Liu, C., Yao, J., de Belle, I., Huangi, R.P., Adamson, E., and Mercola, D. (1999). The Transcription Factor EGR-1 Suppresses Transformation of Human Fibrosarcoma HT1080 Cells by Coordinated Induction of Transforming Growth Factor-b1, Fibronectin, and Plasminogen Activator Inhibitor- 1. The Journal of Biological Chemistry 274, 4400–4411. Liu, H., Guo, S., Roll, R., Li, J., Diao, Z., Shao, N., Riley, M.R., Cole, A.M., Robinson, J.P., Snead, N.M., et al. (2007). Phi29 pRNA vector for efficient escort of hammerhead ribozyme targeting survivin in multiple cancer cells. Cancer Biol Ther 6, 697-704. Liu, W.L., Green, N., Seymour, L.W., and Stevenson, M. (2009). Paclitaxel combined with siRNA targeting HPV16 oncogenes improves cytotoxicity for cervical carcinoma. Cancer gene therapy 16, 764-775. Liu, X.H., Kirschenbaum, A., Yao, S., and Levine, A.C. (2005a). Cross-Talk between the Interleukin-6 and Prostaglandin E2 Signaling Systems Results in Enhancement of Osteoclastogenesis through Effects on the Osteoprotegerin/Receptor Activator of Nuclear Factor-κB (RANK) ligand/RANK System. Endocrinology 146, 1991-1998. Liu, Y., Xing, H., and Han, X. (2005b). The Mechanism of Cisplatin-induced Apoptosis in HeLa Cells. Chinese Journal of Clinical Oncology 2, 866-869. Loehrer, P.J., and Einhorn, L.H. (1984). Drugs five years later. Cisplatin. Annals of internal medicine 100, 704-713. Long, H.J., 3rd, Bundy, B.N., Grendys, E.C., Jr., Benda, J.A., McMeekin, D.S., Sorosky, J., Miller, D.S., Eaton, L.A., Fiorica, J.V., and Gynecologic Oncology Group, S. (2005). Randomized phase III trial of cisplatin with or without topotecan in carcinoma of the uterine cervix: a Gynecologic Oncology Group Study. J Clin Oncol 23, 4626-4633. Long, H.J., 3rd, Monk, B.J., Huang, H.Q., Grendys, E.C., Jr., McMeekin, D.S., Sorosky, J., Miller, D.S., Eaton, L.A., Fiorica, J.V., and Gynecologic Oncology, G. (2006). Clinical results and quality of life analysis for the MVAC combination (methotrexate, vinblastine, doxorubicin, and cisplatin) in carcinoma of the uterine cervix: A Gynecologic Oncology Group study. Gynecol Oncol 100, 537-543. Longworth, M.S., and Laimins, L.A. (2004). Pathogenesis of human papillomaviruses in differentiating epithelia. Microbiology and molecular biology reviews : MMBR 68, 362-372. Lopez-Bergami, P., Huang, C., Goydos, J.S., Yip, D., Bar-Eli, M., Herlyn, M., Smalley, K.S.M., Mahale, A., Eroshkin, A., Aaronson, S., et al. (2007). Re-wired ERK-JNK signaling pathways in melanoma. Cancer Cell 11, 447–460. Lu, Z.X., Ye, M., Yan, G.R., Li, Q., Tang, M., Lee, L.M., Sun, L.Q., and Cao, Y. (2005). Effect of EBV LMP1 targeted DNAzymes on cell proliferation and apoptosis. Cancer gene therapy 12, 647- 654. Lucerna, M., Pomyje, J., Mechtcheriakova, D., Kadl, A., Gruber, F., Bilban, M., Sobanov, Y., Schabbauer, G., Breuss, J., Wagner, O., et al. (2006). Sustained expression of early growth response protein-1 blocks angiogenesis and tumor growth. Cancer Res 66, 6708-6713. Luo, A., Wang, W., Sima, N., Lu, Y., Zhou, J., Xu, G., Yu, H., Wang, S., and Ma, D. (2008). Short hairpin RNA targeting c-FLIP sensitizes human cervical adenocarcinoma Hela cells to chemotherapy and radiotherapy. Cancer letters 271, 323-332. Mack, D.H., and Laimins, L.A. (1991). A keratinocyte-specific transcription factor, KRF-1, interacts with AP-1 to activate expression of human papillomavirus type 18 in squamous epithelial cells. Proceedings of the National Academy of Sciences of the United States of America 88, 9102-9106. Maduro, J.H., de Vries, E.G., Meersma, G.J., Hougardy, B.M., van der Zee, A.G., and de Jong, S. (2008). Targeting pro-apoptotic trail receptors sensitizes HeLa cervical cancer cells to 247
irradiation-induced apoptosis. International journal of radiation oncology, biology, physics 72, 543-552. Maihofner, C., Charalambous, M.P., Bhambra, U., Lightfoot, T., Geisslinger, G., Gooderham, N.J., and Colorectal Cancer, G. (2003). Expression of cyclooxygenase-2 parallels expression of interleukin-1beta, interleukin-6 and NF-kappaB in human colorectal cancer. Carcinogenesis 24, 665-671. Mariani, O., Brennetot, C., Coindre, J.M., Gruel, N., Ganem, C., Delattre, O., Stern, M.H., and Aurias, A. (2007). JUN oncogene amplification and overexpression block adipocytic differentiation in highly aggressive sarcomas. Cancer Cell 11, 361-374. Maritz, M.F., van der Watt, P.J., Holderness, N., Birrer, M.J., and Leaner, V.D. (2011). Inhibition of AP-1 suppresses cervical cancer cell proliferation and is associated with p21 expression. Biol Chem 39, 439–448. Marks, P.A., Rifkind, R.A., Richon, V.M., Breslow, R., Miller, T., and Kelly, W.K. (2001). Histone deacytylases and cancer: causes and therapies. Nature Reviews 1, 195-202. Marquez-Gutierrez, M.A., Benitez-Hess, M.L., DiPaolo, J.A., and Alvarez-Salas, L.M. (2007). Effect of combined antisense oligodeoxynucleotides directed against the human papillomavirus type 16 on cervical carcinoma cells. Archives of medical research 38, 730-738. McCaffrey, T.A., Fu, C., Du, B., Eksinar, S., Kent, K.C., Bush, H., Jr., Kreiger, K., Rosengart, T., Cybulsky, M.I., Silverman, E.S., et al. (2000). High-level expression of Egr-1 and Egr-1-inducible genes in mouse and human atherosclerosis. The Journal of clinical investigation 105, 653-662. McDaid, H.M., and Horwitz, S.B. (2001). Selective potentiation of paclitaxel (taxol)-induced cell death by mitogen-activated protein kinase kinase inhibition in human cancer cell lines. Molecular pharmacology 60, 290-301. Meister, G., Landthaler, M., Dorsett, Y., and Tuschl, T. (2004). Sequence-specific inhibition of microRNA- and siRNA-induced RNA silencing. Rna 10, 544-550. Mialon, A., Sankinen, M., Söderström, H., and Junttila, T.T.e.a. (2005). DNA Topoisomerase I Is a Cofactor for c-Jun in the Regulation of Epidermal Growth Factor Receptor Expression and Cancer Cell Proliferation. Molecular and Cellular Biology 25, 5040-5051. Miano, J.M., and Berk, B.C. (1999). NAB2: a transcriptional brake for activated gene expression in the vessel wall? Am J Pathol 155, 1009-1012. Milde-Langosch, K., Roder, H., Andritzky, B., Aslan, B., Hemminger, G., Brinkmann, A., Bamberger, C.M., Loning, T., and Bamberger, A.M. (2004). The role of the AP-1 transcription factors c-Fos, FosB, Fra-1 and Fra-2 in the invasion process of mammary carcinomas. Breast Cancer Res Treat 86, 139-152. Milosavljevic, N., Duranton, C., and Djerbi, N.e.a. (2010). Nongenomic Effects of Cisplatin: Acute Inhibition of Mechanosensitive Transporters and Channels without Actin Remodeling. Cancer Reseach 70, 7514–7522. Mitchell, A., Dass, C.R., Sun, L.Q., and Khachigian, L.M. (2004). Inhibition of human breast carcinoma proliferation, migration, chemoinvasion and solid tumour growth by DNAzymes targeting the zinc finger transcription factor EGR-1. Nucleic acids research 32, 3065-3069. Moellering, R.E., Cornejo, M., Davis, T.N., Del Bianco, C., Aster, J.C., Blacklow, S.C., Kung, A.L., Gilliland, D.G., Verdine, G.L., and Bradner, J.E. (2009). Direct inhibition of the NOTCH transcription factor complex. Nature 462, 182-188. Monk, B.J., Sill, M.W., Burger, R.A., Gray, H.J., Buekers, T.E., and Roman, L.D. (2009). Phase II trial of bevacizumab in the treatment of persistent or recurrent squamous cell carcinoma of the cervix: a gynecologic oncology group study. J Clin Oncol 27, 1069-1074. Monk, B.J., Willmott, L.J., and Sumner, D.A. (2010). Anti-angiogenesis agents in metastatic or recurrent cervical cancer. Gynecologic Oncology 116, 181–186. Moon, Y., Bottone, F.G., and McEntee, J.M.F.e.a. (2005). Suppression of tumor cell invasion by cyclooxygenase inhibitors is mediated by thrombospondin-1 via the early growth response gene Egr-1. Molecular Cancer Therapy 4, 1551-1558. 248
Moore, D.H., Blessing, J.A., McQuellon, R.P., and Thaler, H.T.e.a. (2004). Phase III Study of Cisplatin With or Without Paclitaxel in Stage IVB, Recurrent, or Persistent Squamous Cell Carcinoma of the Cervix: A Gynecologic Oncology Group Study. J Clin Oncol 22, 3113-3119. Morris, M., Eifel, P.J., Lu, J., Grigsby, P.W., Levenback, C., Stevens, R.E., Rotman, M., Gershenson, D.M., and Mutch, D.G. (1999). Pelvic radiation with concurrent chemotherapy compared with pelvic and para-aortic radiation for high-risk cervical cancer. N Engl J Med 340, 1137-1143. Morrison, W.B. (2012). Inflammation and cancer: a comparative view. Journal of veterinary internal medicine / American College of Veterinary Internal Medicine 26, 18-31. Morton, S.W., Poon, Z., and Hammond, P.T. (2013). The architecture and biological performance of drug-loaded LbL nanoparticles. Biomaterials 34, 5328-5335. Moser, H.E., and Dervan, P.B. (1987). Sequence-specific cleavage of double helical DNA by triple helix formation. Science 238, 645-650. Munger, K., Baldwin, A., Edwards, K.M., Hayakawa, H., Nguyen, C.L., Owens, M., Grace, M., and Huh, K. (2004). Mechanisms of human papillomavirus-induced oncogenesis. J Virol 78, 11451- 11460. Munoz, N., Castellsague, X., de Gonzalez, A.B., and Gissmann, L. (2006). Chapter 1: HPV in the etiology of human cancer. Vaccine 24 Suppl 3, S3/1-10. Muscolini, M., Cianfrocca, R., Sajeva, A., Mozzetti, S., Ferrandina, G., Costanzo, A., and Tuosto, L. (2008). Trichostatin A up-regulates p73 and induces Bax-dependent apoptosis in cisplatin- resistant ovarian cancer cells. Mol Cancer Ther 7, 1410-1419. Nagao, S., Fujiwara, K., Oda, T., Ishikawa, H., Koike, H., Tanaka, H., and Kohno, I. (2005). Combination chemotherapy of docetaxel and carboplatin in advanced or recurrent cervix cancer. A pilot study. Gynecol Oncol 96, 805-809. Nair, P., Muthukkumar, S., and Sells, S.F. (1997). Early Growth Response-1-dependent Apoptosis Is Mediated by p53. The Journal of Biological Chemistry 272, 20131–20138. Nakamura, K., Hongo, A., Kodama, J., Miyagi, Y., Yoshinouchi, M., and Kudo, T. (2000). Down- regulation of the insulin-like growth factor I receptor by antisense RNA can reverse the transformed phenotype of human cervical cancer cell lines. Cancer Res 60, 760-765. Nakanishi, Y., Kamijo, R., Takizawa, K., Hatori, M., and Nagumo, M. (2001). Inhibitors of cyclooxygenase-2 (COX-2) suppressed the proliferation and differentiation of human leukaemia cell lines. Eur J Cancer 37, 1570-1578. Ndlovu, M.N., Lint, C.V., and Wesemael, K.V. (2009). Hyperactivated NF-B and AP-1 Transcription Factors Promote Highly Accessible Chromatin and Constitutive Transcription across the Interleukin-6 Gene Promoter in Metastatic Breast Cancer Cells. Molecular and Cellular Biology 29, 5488–5504. Neeb, A., Wallbaum, S., Novac, N., Dukovic-Schulze, S., Scholl, I., Schreiber, C., Schlag, P., Moll, J., Stein, U., and Sleeman, J.P. (2012). The immediate early gene Ier2 promotes tumor cell motility and metastasis, and predicts poor survival of colorectal cancer patients. Oncogene 31, 3796-3806. Nguyen, M.L., Nguyen, M.M., Lee, D., Griep, A.E., and Lambert, P.F. (2003). The PDZ Ligand Domain of the Human Papillomavirus Type 16 E6 Protein Is Required for E6's Induction of Epithelial Hyperplasia In Vivo. Journal of Virology 77, 6957-6964. Nishioka, Y., Sagae, S., Nishikawa, A., Ishioka, S., and Kudo, R. (2003). A relationship between Matrix metalloproteinase-1 (MMP-1) promoter polymorphism and cervical cancer progression. Cancer Letters 200, 49-55. Noguera, R., Fredlund, E., Piqueras, M., Pietras, A., Beckman, S., Navarro, S., and Pahlman, S. (2009). HIF-1alpha and HIF-2alpha are differentially regulated in vivo in neuroblastoma: high HIF-1alpha correlates negatively to advanced clinical stage and tumor vascularization. Clin Cancer Res 15, 7130-7136. Noordhuis, M.G., Eijsink, J.J., Ten Hoor, K.A., Roossink, F., Hollema, H., Arts, H.J., Pras, E., Maduro, J.H., Reyners, A.K., de Bock, G.H., et al. (2009). Expression of epidermal growth factor 249
receptor (EGFR) and activated EGFR predict poor response to (chemo)radiation and survival in cervical cancer. Clin Cancer Res 15, 7389-7397. Nrnberg, W., Artuc, M., and Vorbrueggen, G.e.a. (1995). Nuclear proto-oncogene products transactivate the human papiliomavirus type 16 promoter. British Journal of Cancer 71, 1018- 1024. Nykanen, A., Haley, B., and Zamore, P.D. (2001). ATP requirements and small interfering RNA structure in the RNA interference pathway. Cell 107, 309-321. Offord, E.A., and Beard, P. (1990). A Member of the Activator Protein 1 Family Found in Keratinocytes but Not in Fibroblasts Required for Transcription from a Human Papillomavirus Type 18 Promoter. JOURNAL OF VIROLOGY 64, 4792-4798. Oh, J.M., Kim, S.H., Lee, Y.I., Seo, M., Kim, S.Y., Song, Y.S., Kim, W.H., and Juhnn, Y.S. (2009). Human papillomavirus E5 protein induces expression of the EP4 subtype of prostaglandin E2 receptor in cyclic AMP response element-dependent pathways in cervical cancer cells. Carcinogenesis 30, 141-149. Okamoto, Y., Tsurunaga, T., and Ueki, M. (1999). Serum soluble ICAM-1 levels in the patients with cervical cancer. Acta obstetricia et gynecologica Scandinavica 78, 60-65. Ouyang, X., Jessen, W.J., Al-Ahmadie, H., Serio, A.M., Lin, Y., Shih, W.J., Reuter, V.E., Scardino, P.T., Shen, M.M., Aronow, B.J., et al. (2008). Activator protein-1 transcription factors are associated with progression and recurrence of prostate cancer. Cancer Res 68, 2132-2144. Ozcelik, B., Turkyilmaz, C., Ozgun, M.T., Serin, I.S., Batukan, C., Ozdamar, S., and Ozturk, A. (2010). Prevention of paclitaxel and cisplatin induced ovarian damage in rats by a gonadotropin-releasing hormone agonist. Fertility and sterility 93, 1609-1614. Parashari, A., Singh, V., Gupta, M.M., Satyanarayana, L., Chattopadhya, D., Sodhani, P., and Sehgal, A. (1995). Significance of inflammatory cervical smears. APMIS : acta pathologica, microbiologica, et immunologica Scandinavica 103, 273-278. Park, D.C., Yeo, S.G., Shin, E.Y., Mok, S.C., and Kim, D.H. (2006). Clusterin confers paclitaxel resistance in cervical cancer. Gynecol Oncol 103, 996-1000. Parra, E., Ortega, A., and Saenz, L. (2009). Down-regulation of Egr-1 by siRNA inhibits growth of human prostate carcinoma cell line PC-3. Oncology reports 22, 1513-1518. Paulmurugan, R., Umezawa, Y., and Gambhir, S.S. (2002). Noninvasive imaging of protein– protein interactions in living subjects by using reporter protein complementation and reconstitution strategies. PNAS 99, 15608-15613. Pawlinski, R., Pedersen, B., Kehrle, B., Aird, W.C., Frank, R.D., Guha, M., and Mackman, N. (2003). Regulation of tissue factor and inflammatory mediators by Egr-1 in a mouse endotoxemia model. Blood 101, 3940-3947. Perez-Plasencia, C., Duenas-Gonzalez, A., and Alatorre-Tavera, B. (2008). Second hit in cervical carcinogenesis process: involvement of wnt/beta catenin pathway. International archives of medicine 1, 10. Pérez-Plasencia, C., Vázquez-Ortiz, G., López-Romero, R., Piña-Sanchez, P., and M., M.J.a.S. (2007). Genome wide expression analysis in HPV16 Cervical Cancer: identification of altered metabolic pathways. Infectious Agents and Cancer 2. Peters, W.A.I.L., P.Y.; Barrett, R. J. II; Stock, R. J.; Monk, B. J.; Berek, J. S.; Souhami, L.; Grigsby, P.; Gordon, W. Jr.; Alberts, D. S. (2000). Concurrent Chemotherapy and Pelvic Radiation Therapy Compared With Pelvic Radiation Therapy Alone as Adjuvant Therapy After Radical Surgery in High-Risk Early-Stage Cancer of the Cervix. J Clin Oncol 18, 1606-1613. Pett, M., and Coleman, N. (2007). Integration of high-risk human papillomavirus: a key event in cervical carcinogenesis? The Journal of pathology 212, 356-367. Pillinger, M.H., Rosenthal, P.B., Tolani, S.N., Apsel, B., Dinsell, V., Greenberg, J., Chan, E.S., Gomez, P.F., and Abramson, S.B. (2003). Cyclooxygenase-2-derived E prostaglandins down- regulate matrix metalloproteinase-1 expression in fibroblast-like synoviocytes via inhibition of extracellular signal-regulated kinase activation. Journal of immunology 171, 6080-6089. 250
Piques, M., Schulze, W.X., Hohne, M., Usadel, B., Gibon, Y., Rohwer, J., and Stitt, M. (2009). Ribosome and transcript copy numbers, polysome occupancy and enzyme dynamics in Arabidopsis. Mol Syst Biol 5, 314. Poon, Z., Chang, D., Zhao, X., and Hammond, P.T. (2011). Layer-by-layer nanoparticles with a pH-sheddable layer for in vivo targeting of tumor hypoxia. ACS nano 5, 4284-4292. Potapova, O., Basu, S., Mercola, D., and Holbrook, N.J. (2001). Protective role for c-Jun in the cellular response to DNA damage. J Biol Chem 276, 28546-28553. Potapova, O., Haghighi, A., Bost, F., Liu, C., Birrer, M.J., Gjerset, R., and Mercola, D. (1997). The Jun kinase/stress-activated protein kinase pathway functions to regulate DNA repair and inhibition of the pathway sensitizes tumor cells to cisplatin. J Biol Chem 272, 14041-14044. Prusty, B.K., and Das, B.C. (2005). Constitutive activation of transcription factor AP-1 in cervical cancer and suppression of human papillomavirus (HPV) transcription and AP-1 activity in HeLa cells by curcumin. International journal of cancer Journal international du cancer 113, 951-960. Przybyszewski, J., Yaktine, A.L., and al., D.E.e. (2001). Inhibition of phorborl ester-induced AP- 1-DNA binding, c-Jun protein and c-Jun mRNA by dietary energy restriction is reversed by adrenalectomy in SENCAR mouse epidermis. Carcinogenesis 22, 1421-1427. Puerta-Fernandez, E., Romero-Lopez, C., Barroso-delJesus, A., and Berzal-Herranz, A. (2003). Ribozymes: recent advances in the development of RNA tools. FEMS microbiology reviews 27, 75-97. Pulukuri, S.M., and Rao, J.S. (2008). Matrix metalloproteinase-1 promotes prostate tumor growth and metastasis. International journal of oncology 32, 757-765. Putral, L.N., Bywater, M.J., Gu, W., Saunders, N.A., Gabrielli, B.G., Leggatt, G.R., and McMillan, N.A. (2005). RNA interference against human papillomavirus oncogenes in cervical cancer cells results in increased sensitivity to cisplatin. Molecular pharmacology 68, 1311-1319. Qi, Z., Xu, X., Zhang, B., Li, Y., Liu, J., Chen, S., Chen, G., and Huo, X. (2010). Effect of simultaneous silencing of HPV-18 E6 and E7 on inducing apoptosis in HeLa cells. Biochemistry and cell biology = Biochimie et biologie cellulaire 88, 697-704. Reddy, S.T., Wadleigh, D.J., and Herschman, H.R. (2000). Transcriptional regulation of the cyclooxygenase-2 gene in activated mast cells. J Biol Chem 275, 3107-3113. Regan, J.A., and Laimins, L.A. (2008). Bap31 Is a Novel Target of the Human Papillomavirus E5 Protein. Journal of Virology 82, 10042–10051. Reyes-Gutierrez, P., and Alvarez-Salas, L.M. (2009). Cleavage of HPV-16 E6/E7 mRNA mediated by modified 10-23 deoxyribozymes. Oligonucleotides 19, 233-242. Reynolds, A., Anderson, E.M., and Vermeulen, A.e.a. (2006). Induction of the interferon response by siRNA is cell type– and duplex length–dependent. RNA 12, 988-993. Rockwell, P., O'Connor, W.J., King, K., Goldstein, N.I., Zhang, L.M., and Stein, C.A. (1997). Cell- surface perturbations of the epidermal growth factor and vascular endothelial growth factor receptors by phosphorothioate oligodeoxynucleotides. Proceedings of the National Academy of Sciences of the United States of America 94, 6523-6528. Rockwell, S., Dobrucki, I.T., Kim, E.Y., Marrison, S.T., and Vu, V.T. (2009). Hypoxia and radiation therapy: past history, ongoing research, and future promise. Current molecular medicine 9, 442-458. Rose, P.G., Bundy, B.N., Watkins, E.B., Thigpen, J.T., Deppe, G., Maiman, M.A., Clarke-Pearson, D.L., and Insalaco, S. (1999). Concurrent cisplatin-based radiotherapy and chemotherapy for locally advanced cervical cancer. N Engl J Med 340, 1144-1153. Rosette, C., Roth, R.B., Oeth, P., Braun, A., Kammerer, S., Ekblom, J., and Denissenko, M.F. (2005). Role of ICAM1 in invasion of human breast cancer cells. Carcinogenesis 26, 943-950. Rösl, F., Das, B.C., Lengert, M., Geletneky, K., and Hausen, H.Z. (1997). Antioxidant-Induced Changes of the AP-1 Transcription Complex Are Paralleled by a Selective Suppression of Human Papillomavirus Transcription. JOURNAL OF VIROLOGY, 362–370. 251
Rossi, A., Ciafre, S., Balsamo, M., Pierimarchi, P., and Santoro, M.G. (2006). Targeting the heat shock factor 1 by RNA interference: a potent tool to enhance hyperthermochemotherapy efficacy in cervical cancer. Cancer Res 66, 7678-7685. Rubin, E., Kharbanda, S., Gunji, H., Weichselbaum, R., and Kufe, D. (1992). cis- Diamminedichloroplatinum(II) induces c-jun expression in human myeloid leukemia cells: potential involvement of a protein kinase C-dependent signaling pathway. Cancer Res 52, 878- 882. Russo, M.W., Sevetson, B.R., and Milbrandt, J. (1995). Identification of NAB1, a repressor of NGFI-A- and Krox20-mediated transcription. Proceedings of the National Academy of Sciences of the United States of America 92, 6873-6877. Ryu, H.S., Chang, K.H., Yang, H.W., Kim, M.S., Kwon, H.C., and Oh, K.S. (2000). High cyclooxygenase-2 expression in stage IB cervical cancer with lymph node metastasis or parametrial invasion. Gynecologic oncology 76, 320-325. Ryzhakova, O.S., Zavalishina, L.É., Andreeva, I., and Solov'eva, N.I. (2013). Interstitial collagenase, gelatinases A and B and their endogenous inhibitors in squamous cell cervical carcinomas. Biomed Khim 59, 55-64. Saito, S., Yamamoto, H., Mukaisho, K., Sato, S., Higo, T., Hattori, T., Yamamoto, G., and Sugihara, H. (2013). Mechanisms underlying cancer progression caused by ezrin overexpression in tongue squamous cell carcinoma. PLoS One 8, e54881. Sakaue, M., Adachi, H., Dawson, M., and Jetten, A.M. (2001). Induction of Egr-1 expression by the retinoid AHPN in human lung carcinoma cells is dependent on activated ERK1/2. Cell Death and Differentiation 8, 411 - 424. Sanchez-Perez, I., and Perona, R. (1999). Lack of c-Jun activity increases survival to cisplatin. FEBS letters 453, 151-158. Sankpal, N.V., Mayfield, J.D., Willman, M.W., Fleming, T.P., and Gillanders, W.E. (2011). Activator protein 1 (AP-1) contributes to EpCAM-dependent breast cancer invasion. Breast Cancer Res 13, R124. Santin, A.D., Sill, M.W., McMeekin, D.S., Leitao, M.M., Jr., Brown, J., Sutton, G.P., Van Le, L., Griffin, P., and Boardman, C.H. (2011). Phase II trial of cetuximab in the treatment of persistent or recurrent squamous or non-squamous cell carcinoma of the cervix: a Gynecologic Oncology Group study. Gynecol Oncol 122, 495-500. Santoro, S.W., and Joyce, G.F. (1997). A general purpose RNA-cleaving DNA enzyme. Proceedings of the National Academy of Sciences of the United States of America 94, 4262- 4266. Sarver, A.L., Li, L., and Subramanian, S. (2010). MicroRNA miR-183 Functions as an Oncogene by Targeting the transcription Factor EGR1 and Promoting Tumor Cell Migration. Cancer Res 70, 9570-9580. Sas-Chen, A., Avraham, R., and Yarden, Y. (2012). A crossroad of microRNAs and immediate early genes (IEGs) encoding oncogenic transcription factors in breast cancer. J Mammary Gland Biol Neoplasia 17, 3-14. Schafer, K.A. (1998). The cell cycle: a review. Veterinary pathology 35, 461-478. Scharnhorst, V., Menke, A.L., Attema, J., Haneveld, J.K., Riteco, N., van Steenbrugge, G.J., van der Eb, A.J., and Jochemsen, A.G. (2000). EGR-1 enhances tumor growth and modulates the effect of the Wilms' tumor 1 gene products on tumorigenicity. Oncogene 19, 791-800. Schiffman, M., Castle, P.E., Jeronimo, J., Rodriguez, A.C., and Wacholder, S. (2007). Human papillomavirus and cervical cancer. Lancet 370, 890-907. Schiffman, M., Herrero, R., Desalle, R., Hildesheim, A., Wacholder, S., Rodriguez, A.C., Bratti, M.C., Sherman, M.E., Morales, J., Guillen, D., et al. (2005). The carcinogenicity of human papillomavirus types reflects viral evolution. Virology 337, 76-84. Schilder, R.J., Sill, M.W., Lee, Y.C., and Mannel, R. (2009). A phase II trial of erlotinib in recurrent squamous cell carcinoma of the cervix: a Gynecologic Oncology Group Study. 252
International journal of gynecological cancer : official journal of the International Gynecological Cancer Society 19, 929-933. Schmidt, J., Stoffels, B., Moore, B.A., Chanthaphavong, R.S., Mazie, A.R., Buchholz, B.M., and Bauer, A.J. (2008). Proinflammatory role of leukocyte-derived Egr-1 in the development of murine postoperative ileus. Gastroenterology 135, 926-936, 936 e921-922. Schropfer, A., Kammerer, U., Kapp, M., Dietl, J., Feix, S., and Anacker, J. (2010). Expression pattern of matrix metalloproteinases in human gynecological cancer cell lines. BMC Cancer 10, 553. Schuringa, J.J., Timmer, H., Luttickhuizen, D., Vellenga, E., and Kruijer, W. (2001). c-Jun AND c- Fos COOPERATE WITH STAT3 IN IL-6-INDUCED TRANSACTIVATION OF THE IL-6 RESPONSE ELEMENT (IRE). Ctyokine 14, 78-87. Seoud, M., Tjalma, W.A., and Ronsse, V. (2011). Cervical adenocarcinoma: moving towards better prevention. Vaccine 29, 9148-9158. Settakorn, J., Khunamornpong, S., Sukpan, K., Srisomboon, J., and Siriaungkul, S. (2009). Cyclooxygenase-2 Expression in Cervical Squamous Cell Carcinoma: the Significance of Expression in Neoplastic Cells within the Lymphovascular Space. Asian Pacific Journal of Cancer Prevention 10, 1011-1014. Shaulian, E., and Karin, M. (2002). AP-1 as a regulator of cell life and death. Nature Cell Biology 4, 131-136. Sheets, E.E., Urban, R.G., Crum, C.P., Hedley, M.L., Politch, J.A., Gold, M.A., Muderspach, L.I., Cole, G.A., and Crowley-Nowick, P.A. (2003). Immunotherapy of human cervical high-grade cervical intraepithelial neoplasia with microparticle-delivered human papillomavirus 16 E7 plasmid DNA. Am J Obstet Gynecol 188, 916-926. Shen, L., Shui, Y., Wang, X., Sheng, L., Yang, Z., Xue, D., and Wei, Q. (2008). EGFR and HER2 expression in primary cervical cancers and corresponding lymph node metastases: implications for targeted radiotherapy. BMC Cancer 8, 232. Shi, X., Chen, G., Xing, H., Weng, D., Bai, X., and Ma, D. (2007). VEGF-C, VEGFR-3, and COX-2 enhances growth and metastasis of human cervical carcinoma cell lines in vitro. Oncology reports 18, 241-247. Shiau, M.Y., Fan, L.C., Yang, S.C., Tsao, C.H., Lee, H., Cheng, Y.W., Lai, L.C., and Chang, Y.H. (2013). Human papillomavirus up-regulates MMP-2 and MMP-9 expression and activity by inducing interleukin-8 in lung adenocarcinomas. PLoS One 8, e54423. Shimada, M., Kigawa, J., Nishimura, R., Yamaguchi, S., Kuzuya, K., Nakanishi, T., Suzuki, M., Kita, T., Iwasaka, T., and Terakawa, N. (2006). Ovarian metastasis in carcinoma of the uterine cervix. Gynecologic oncology 101, 234-237. Shimoyamada, H., Yazawa, T., Sato, H., Okudela, K., Ishii, J., Sakaeda, M., Kashiwagi, K., Suzuki, T., Mitsui, H., Woo, T., et al. (2010). Early growth response-1 induces and enhances vascular endothelial growth factor-A expression in lung cancer cells. Am J Pathol 177, 70-83. Shin, S.Y., Kim, J.H., Baker, A., Lim, Y., and Lee, Y.H. (2010). Transcription Factor Egr-1 Is Essential for Maximal Matrix Metalloproteinase-9 Transcription by Tumor Necrosis Factor α. Molecular Cancer Research 8, 507-519. Shozu, M., Murakami, K., Segawa, T., Kasai, T., Ishikawa, H., Shinohara, K., Okada, M., and Inoue, M. (2004). Decreased expression of early growth response-1 and its role in uterine leiomyoma growth. Cancer Res 64, 4677-4684. Silverman, S.K. (2005). In vitro selection, characterization, and application of deoxyribozymes that cleave RNA. Nucleic Acids Res 33, 6151-6163. Sima, N., Wang, S., Wang, W., Kong, D., Xu, Q., Tian, X., Luo, A., Zhou, J., Xu, G., Meng, L., et al. (2007). Antisense targeting human papillomavirus type 16 E6 and E7 genes contributes to apoptosis and senescence in SiHa cervical carcinoma cells. Gynecol Oncol 106, 299-304. Smith, L.M., Wise, S.C., Hendricks, D.T., Sabichi, A.L., Bos, T., Reddy, P., Brown, P.H., and Birrer, M.J. (1999). cJun overexpression in MCF-7 breast cancer cells produces a tumorigenic, invasive and hormone resistant phenotype. Oncogene 18, 6063-6070. 253
Snoek-van Beurden, P.A.M., and Von den Hoff, J.W. (2005). Zymographic techniques for the analysis of matrix metalloproteinases and their inhibitors. BioTechniques 38, 78-83. Song, H., Xin, X.Y., Xiao, F., Wang, D.T., Yue, Q.H., and Han, X. (2008). Survivin gene RNA interference inhibits proliferation, induces apoptosis, and enhances radiosensitivity in HeLa cells. European journal of obstetrics, gynecology, and reproductive biology 136, 83-89. Soto, U., Das, B.C., and Lengert, M.e.a. (1999). Conversion of HPV 18 positive non-tumorigenic HeLa-fibroblast hybrids to invasive growth involves loss of TNF-a mediated repression of viral transcription and modi®cation of the AP-1 transcription complex. Oncogene, 3187-3198. Soto, U., Denk, C., Finzer, P., Hutter, K.J., zur Hausen, H., and Rosl, F. (2000). Genetic complementation to non-tumorigenicity in cervical-carcinoma cells correlates with alterations in AP-1 composition. International journal of cancer Journal international du cancer 86, 811- 817. Soutschek, J., Akinc, A., Bramlage, B., Charisse, K., Constien, R., Donoghue, M., Elbashir, S., Geick, A., Hadwiger, P., Harborth, J., et al. (2004). Therapeutic silencing of an endogenous gene by systemic administration of modified siRNAs. Nature 432, 173-178. Spitzweg, C., Dietz, A.B., O'Connor, M.K., Bergert, E.R., Tindall, D.J., Young, C.Y., and Morris, J.C. (2001). In vivo sodium iodide symporter gene therapy of prostate cancer. Gene Ther 8, 1524- 1531. Splettstoesser, F., Florea, A.-M., and Bu¨sselberg, D. (2007). IP3 receptor antagonist, 2-APB, attenuates cisplatin induced Ca2þ-influx in HeLa-S3 cells and prevents activation of calpain and induction of apoptosis. British Journal of Pharmacology 151, 1176–1186. Staber, P.B., Vesely, P., Haq, N., Ott, R.G., Funato, K., Bambach, I., Fuchs, C., Schauer, S., Linkesch, W., Hrzenjak, A., et al. (2007). The oncoprotein NPM-ALK of anaplastic large-cell lymphoma induces JUNB transcription via ERK1/2 and JunB translation via mTOR signaling. Blood 110, 3374-3383. Stacey, S., Jordan, D., Williamson, A.J.K., Brown, M., Coote, J.H., and Arrand, J.R. (2000). Leaky Scanning Is the Predominant Mechanism for Translation of Human Papillomavirus Type 16 E7 Oncoprotein from E6/E7 Bicistronic mRNA. Journal of Virology 74, 7284–7297. Steenport, M., Khan, K.M., Du, B., Barnhard, S.E., Dannenberg, A.J., and Falcone, D.J. (2009). Matrix metalloproteinase (MMP)-1 and MMP-3 induce macrophage MMP-9: evidence for the role of TNF-alpha and cyclooxygenase-2. Journal of immunology 183, 8119-8127. Stewart B.W., and P., K. (2003). World Cancer Report. IARC Press. Stoltenburg, R., Reinemann, C., and Strehlitz, B. (2007). SELEX--a (r)evolutionary method to generate high-affinity nucleic acid ligands. Biomolecular engineering 24, 381-403. Su, J.H., Wu, A., Scotney, E., Ma, B., Monie, A., Hung, C.F., and Wu, T.C. (2010). Immunotherapy for cervical cancer: Research status and clinical potential. BioDrugs 24, 109- 129. Subbaramaiah, K., Chung, W.J., and Dannenberg, A.J. (1998). Ceramide regulates the transcription of cyclooxygenase-2. Evidence for involvement of extracellular signal-regulated kinase/c-Jun N-terminal kinase and p38 mitogen-activated protein kinase pathways. J Biol Chem 273, 32943-32949. Subbaramaiah, K., and Dannenberg, A.J. (2007a). Cyclooxygenase-2 Transcription Is Regulated by Human Papillomavirus 16 E6 and E7 Oncoproteins: Evidence of a Corepressor/Coactivator Exchange. Cancer Res 67, 3976-3985. Subbaramaiah, K., and Dannenberg, A.J. (2007b). Cyclooxygenase-2 Transcription Is Regulated by Human Papillomavirus 16 E6 and E7 Oncoproteins: Evidence of a Corepressor/Coactivator Exchange. Cancer Res 67, 3976–3985. Sun, T., Tian, H., Feng, Y.G., Zhu, Y.Q., and Zhang, W.Q. (2013). Egr-1 Promotes Cell Proliferation and Invasion by Increasing ß-Catenin Expression in Gastric Cancer. Dig Dis Sci 58, 423-430. 254
Tan, M.L., Choong, P.F., and Dass, C.R. (2010). Direct anti-metastatic efficacy by the DNA enzyme Dz13 and downregulated MMP-2, MMP-9 and MT1-MMP in tumours. Cancer Cell Int 10, 9. Tan, S., Hougardy, B.M., Meersma, G.J., Schaap, B., de Vries, E.G., van der Zee, A.G., and de Jong, S. (2012). Human papilloma virus 16 E6 RNA interference enhances cisplatin and death receptor-mediated apoptosis in human cervical carcinoma cells. Molecular pharmacology 81, 701-709. Tartour, E., Gey, A., Sastre-Garau, X., Pannetier, C., Mosseri, V., Kourilsky, P., and Fridman, W.H. (1994). Analysis of Interleukin 6 Gene Expression in Cervical Neoplasia Using a Quantitative Polymerase Chain Reaction Assay: Evidence for Enhanced Interleukin 6 Gene Expression in Invasive Carcinoma. Cancer Res 54, 6243-6248. Tell, G., Pines, A., Arturi, F., Cesaratto, L., Adamson, E., Puppin, C., Presta, I., Russo, D., Filetti, S., and Damante, G. (2004). Control of phosphatase and tensin homolog (PTEN) gene expression in normal and neoplastic thyroid cells. Endocrinology 145, 4660-4666. Tewari, K.S., and Monk, B.J. (2009). Recent achievements and future developments in advanced and recurrent cervical cancer: trials of the Gynecologic Oncology Group. Seminars in oncology 36, 170-180. Thierry, F., Spyrou, G., Yaniv, M., and Howley, P.e.a. (1992). Two API Sites Binding JunB Are Essential for Human Papillomavirus Type 18 Transcription in Keratinocytes. JOURNAL OF VIROLOGY, 3740-3748. Thierry, F., and Yaniv, M. (1987). The BPV1-E2 trans-acting protein can be either an activator or a repressor of the HPV18 regulatory region. The EMBO Journal 6, 3391 -3397. Thigpen, T., Shingleton, H., Homesley, H., Lagasse, L., and Blessing, J. (1981). Cis-platinum in treatment of advanced or recurrent squamous cell carcinoma of the cervix: a phase II study of the Gynecologic Oncology Group. Cancer 48, 899-903. Thomas, M., and Banks, L. (1998). Inhibition of Bak-induced apoptosis by HPV-18 E6. Oncogene 17, 2943-2954. Thomas, M., Pim, D., and Banks, L. (1999). The role of the E6-p53 interaction in the molecular pathogenesis of HPV. Oncogene 18, 7690-7700. Thompson, E.W., Newgreen, D.F., and Tarin, D. (2005). Carcinoma invasion and metastasis: a role for epithelial-mesenchymal transition? Cancer Res 65, 5991-5995; discussion 5995. Thun, M.J., DeLancey, J.O., Center, M.M., Jemal, A., and Ward, E.M. (2010). The global burden of cancer: priorities for prevention. Carcinogenesis 31, 100-110. Tierney, J.F., Vale, C., and Symonds, P. (2008). Concomitant and neoadjuvant chemotherapy for cervical cancer. Clin Oncol (R Coll Radiol) 20, 401-416. Toscano-Garibay, J.D., Benitez-Hess, M.L., and Alvarez-Salas, L.M. (2011). Isolation and characterization of an RNA aptamer for the HPV-16 E7 oncoprotein. Archives of medical research 42, 88-96. Toyoshima, M., Tanaka, N., and Aoki, J.e.a. (2007). Inhibition of Tumor Growth and Metastasis by Depletion of Vesicular Sorting Protein Hrs: Its Regulatory Role on E-Cadherin and ß-Catenin. Cancer Research 67, 5162-5171. Treinies, I., Paterson, H.F., Hooper, S., Wilson, R., and Marshall, C.J. (1999). Activated MEK stimulates expression of AP-1 components independently of phosphatidylinositol 3-kinase (PI3-kinase) but requires a PI3-kinase signal To stimulate DNA synthesis. Mol Cell Biol 19, 321- 329. Trigg, M.E., and Flanigan-Minnick, A. (2011). Mechanisms of action of commonly used drugs to treat cancer Community Oncology 8, 357-369. Trimble, C.L., Peng, S., Kos, F., Gravitt, P., Viscidi, R., Sugar, E., Pardoll, D., and Wu, T.C. (2009). A phase I trial of a human papillomavirus DNA vaccine for HPV16+ cervical intraepithelial neoplasia 2/3. Clin Cancer Res 15, 361-367. Tseng, C.W., Monie, A., Trimble, C., Alvarez, R.D., Huh, W.K., Buchsbaum, D.J., Straughn, J.M., Jr., Wang, M.C., Yagita, H., Hung, C.F., et al. (2008). Combination of treatment with death 255
receptor 5-specific antibody with therapeutic HPV DNA vaccination generates enhanced therapeutic anti-tumor effects. Vaccine 26, 4314-4319. Tseng, C.W., Trimble, C., Zeng, Q., Monie, A., Alvarez, R.D., Huh, W.K., Hoory, T., Wang, M.C., Hung, C.F., and Wu, T.C. (2009). Low-dose radiation enhances therapeutic HPV DNA vaccination in tumor-bearing hosts. Cancer Immunol Immunother 58, 737-748. Turturro, F., Von Burton, G., and Friday, E. (2007). Hyperglycemia-induced thioredoxin- interacting protein expression differs in breast cancer-derived cells and regulates paclitaxel IC50. Clin Cancer Res 13, 3724-3730. Urban-Klein, B., Werth, S., and Abuharbeid, S.e.a. (2005). RNAi-mediated gene-targeting through systemic application of polyethylenimine (PEI)-complexed siRNA in vivo. Gene Ther 12, 461-466. Vasquez, K.M., Wensel, T.G., Hogan, M.E., and Wilson, J.H. (1996). High-efficiency triple-helix- mediated photo-cross-linking at a targeted site within a selectable mammalian gene. Biochemistry 35, 10712-10719. Vincenti, M.P., and Brinckerhoff, C.E. (2001). Early response genes induced in chondrocytes stimulated with the inflammatory cytokine interleukin-1beta. Arthritis research 3, 381-388. Vincenti, M.P., White, L.A., ., Schroen, D.J., ., Benbow U, and CE., B. (1996). Regulating expression of the gene for matrix metalloproteinase-1 (collagenase): mechanisms that control enzyme activity, transcription, and mRNA stability. Crit
Rev Eukaryot Gene Exp 6, 391–411. Vinokurova, S., Wentzensen, N., and Kraus, I.e.a. (2008). Type-Dependent Integration Frequency of Human Papillomavirus Genomes in Cervical Lesions. Cancer Res 68, 307-313. Virolle, T., Adamson, E.D., Baron, V., Birle, D., Mercola, D., Mustelin, T., and de Belle, I. (2001). The Egr-1 transcription factor directly activates PTEN during irradiation-induced signalling. Nat Cell Biol 3, 1124-1128. Vleugel, M.M., Greijer, A.E., Bos, R., van der Wall, E., and van Diest, P.J. (2006). c-Jun activation is associated with proliferation and angiogenesis in invasive breast cancer. Human Pathology 37, 668– 674. Vogt, P.K. (2001). Jun, the oncoprotein. Oncogene 20, 2365-2377. von Knebel Doeberitz, M. (2002). New markers for cervical dysplasia to visualise the genomic chaos created by aberrant oncogenic papillomavirus infections. Eur J Cancer 38, 2229-2242. Wahlestedt, C., Salmi, P., Good, L., Kela, J., Johnsson, T., Hokfelt, T., Broberger, C., Porreca, F., Lai, J., Ren, K., et al. (2000). Potent and nontoxic antisense oligonucleotides containing locked nucleic acids. Proceedings of the National Academy of Sciences of the United States of America 97, 5633-5638. Wang, D., and Lippard, S.J. (2004). Cisplatin-induced post-translational modification of histones H3 and H4. J Biol Chem 279, 20622-20625. Wang, N., Verna, L., Hardy, S., Forsayeth, J., Zhu, Y., and Stemerman, M.B. (1999a). Adenovirus-mediated overexpression of c-Jun and c-Fos induces intercellular adhesion molecule-1 and monocyte chemoattractant protein-1 in human endothelial cells. Arteriosclerosis, thrombosis, and vascular biology 19, 2078-2084. Wang, Q., Li, M., Wang, Y., Zhang, Y., Jin, S., Xie, G., Liu, Z., Wang, S., Zhang, H., Shen, L., et al. (2008a). RNA interference targeting CML66, a novel tumor antigen, inhibits proliferation, invasion and metastasis of HeLa cells. Cancer Lett 269, 127-138. Wang, R., Wang, X., Lin, F., Gao, P., Dong, K., and Zhang, H.Z. (2008b). shRNA-targeted cyclooxygenase (COX)-2 inhibits proliferation, reduces invasion and enhances chemosensitivity in laryngeal carcinoma cells. Mol Cell Biochem 317, 179-188. Wang, S., Li, W., Xue, Z., Lu, Y., Narsinh, K., Fan, W., Li, X., Bu, Q., Wang, F., Liang, J., et al. (2012). Molecular imaging of p53 signal pathway in lung cancer cell cycle arrest induced by cisplatin. Molecular carcinogenesis. 256
Wang, T.H., Popp, D.M., Wang, H.S., Saitohi, M., Mural, J.G., Henley, D.C., Ichijoi, H., and Wimalasena, J. (1999b). Microtubule Dysfunction Induced by Paclitaxel Initiates Apoptosis through Both c-Jun N-terminal Kinase (JNK)-dependent and -Independent Pathways in Ovarian Cancer Cells. THE JOURNAL OF BIOLOGICAL CHEMISTRY 274, 8208–8216. Wang, X., Ren, J., Lin, F., and Wei, J.e.a. (2010). Stathmin is involved in arsenic trioxide-induced apoptosis in human cervical cancer cell lines via PI3K linked signal pathway. Cancer Biology & Therapy 10, 632-643. Wang, X., Yu, B., Wu, Y., Lee, R.J., and Lee, L.J. (2011). Efficient down-regulation of CDK4 by novel lipid nanoparticle-mediated siRNA delivery. Anticancer Res 31, 1619-1626. Watt, F.M. (1998). Epidermal stem cells: markers, patterning and the control of stem cell fate. Philosophical transactions of the Royal Society of London Series B, Biological sciences 353, 831- 837. Wei, L.H., Kuo, M.L., Chen, C.A., Cheng, W.F., Cheng, S.P., Hsieh, F.J., and Hsieh, C.Y. (2001). Interleukin-6 in cervical cancer: the relationship with vascular endothelial growth factor. Gynecologic oncology 82, 49-56. Weiss, C., and Bohmann, D. (2004). Deregulated repression of c-Jun provides a potential link to its role in tumorigenesis. Cell Cycle 3, 111-113. Weiss, C., Schneider, S., Wagner, E.F., Zhang, X., Seto, E., and Bohmann, D. (2003). JNK phosphorylation relieves HDAC3-dependent suppression of the transcriptional activity of c-Jun. EMBO J 22, 3686-3695. Westermarck, J., and Kahari, V.M. (1999). Regulation of matrix metalloproteinase expression in tumor invasion. FASEB J 13, 781-792. Westwick, J.K., Cox, A.D., Der, C.J., Cobb, M.H., Hibi, M., Karin, M., and Brenner, D.A. (1994). Oncogenic Ras activates c-Jun via a separate pathway from the activation of extracellular signal-regulated kinases. Proceedings of the National Academy of Sciences of the United States of America 91, 6030-6034. Whitney CW, Sause W, and Bundy BN, e.a. (1999). Randomised comparison of fluorouracil plus cisplatin versus hydroxyurea as an adjunct to radiation therapy in stage IIB–IVA carcinoma of the cervix with negative para-aortic lymph nodes: a Gynecologic Oncology Group and Southwest Oncology Group study. J Clin Oncol 17, 1339-1348. Windsor, R.E., Strauss, S.J., Kallis, C., Wood, N.E., and Whelan, J.S. (2012). Germline Genetic Polymorphisms May Influence Chemotherapy Response and Disease Outcome in Osteosarcoma. Cancer 118, 1856-1867. Wisdom, R., Johnson, R.S., and Moore, C. (1999). c-Jun regulates cell cycle progression and apoptosis by distinct mechanisms. EMBO J 18, 188-197. Wu, M.X., Ustyugova, I.V., Han, L., and Akilov, O.E. (2013). Immediate early response gene X-1, a potential prognostic biomarker in cancers. Expert Opin Ther Targets. Wu, S., Meng, L., Wang, S., Wang, W., Xi, L., Tian, X., Chen, G., Wu, Y., Zhou, J., Xu, G., et al. (2006). Reversal of the malignant phenotype of cervical cancer CaSki cells through adeno- associated virus-mediated delivery of HPV16 E7 antisense RNA. Clin Cancer Res 12, 2032-2037. Wu, S.Y., Singhania, A., Burgess, M., Putral, L.N., Kirkpatrick, C., Davies, N.M., and McMillan, N.A. (2011). Systemic delivery of E6/7 siRNA using novel lipidic particles and its application with cisplatin in cervical cancer mouse models. Gene Ther 18, 14-22. Xiao, W., Hodge, D.R., and Wang, L.e.a. (2004). NF-kB activates IL-6 expression through cooperation with c-Jun and IL6-AP-1 site, but is independent of its IL6-NFkB regulatory site in autocrine human multiple myeloma cells. Cancer Biology and Therapy 3, 1007-1017. Yalcin, A., Clem, B., Makoni, S., Clem, A., Nelson, K., Thornburg, J., Siow, D., Lane, A.N., Brock, S.E., Goswami, U., et al. (2010). Selective inhibition of choline kinase simultaneously attenuates MAPK and PI3K/AKT signaling. Oncogene 29, 139-149. Yamato, K., Fen, J., Kobuchi, H., Nasu, Y., Yamada, T., Nishihara, T., Ikeda, Y., Kizaki, M., and Yoshinouchi, M. (2006). Induction of cell death in human papillomavirus 18-positive cervical cancer cells by E6 siRNA. Cancer gene therapy 13, 234-241. 257
Yamato, K., Yamada, T., Kizaki, M., Ui-Tei, K., Natori, Y., Fujino, M., Nishihara, T., Ikeda, Y., Nasu, Y., Saigo, K., et al. (2008). New highly potent and specific E6 and E7 siRNAs for treatment of HPV16 positive cervical cancer. Cancer gene therapy 15, 140-153. Yamayoshi, A., Kato, K., Iwase, R., Yamaoka, T., Wake, N., and Murakami, A. (2003). Photodynamic antisense therapy: regulation of cervical carcinoma cells by psoralen-conjugated oligonucleotides. Nucleic acids research Supplement, 75-76. Yang, S.F., Chen, M.K., Hsieh, Y.S., Chung, T.T., Hsieh, Y.H., Lin, C.W., Su, J.L., Tsai, M.H., and Tang, C.H. (2010). Prostaglandin E2/EP1 signaling pathway enhances intercellular adhesion molecule 1 (ICAM-1) expression and cell motility in oral cancer cells. J Biol Chem 285, 29808- 29816. Yang, S.Z., and Abdulkadir, S.A. (2003). Early growth response gene 1 modulates androgen receptor signaling in prostate carcinoma cells. J Biol Chem 278, 39906-39911. Yang, S.Z., Eltoum, I.A., and Abdulkadir, S.A. (2006). Enhanced EGR1 activity promotes the growth of prostate cancer cells in an androgen-depleted environment. J Cell Biochem 97, 1292-1299. Yao, M., Lam, E.C., Kelly, C.R., Zhou, W., and Wolfe, M.M. (2004). Cyclooxygenase-2 selective inhibition with NS-398 suppresses proliferation and invasiveness and delays liver metastasis in colorectal cancer. Br J Cancer 90, 712-719. Yatabe, N., Kyo, S., Kondo, S., Kanaya, T., Wang, Z., Maida, Y., Takakura, M., Nakamura, M., Tanaka, M., and Inoue, M. (2002). 2-5A antisense therapy directed against human telomerase RNA inhibits telomerase activity and induces apoptosis without telomere impairment in cervical cancer cells. Cancer gene therapy 9, 624-630. Yiu, G.K., and Toker, A. (2006). NFAT induces breast cancer cell invasion by promoting the induction of cyclooxygenase-2. J Biol Chem 281, 12210-12217. You, L., and Jakowlew, S.B. (1997). Identification of Early Growth Response Gene-1 (Egr-1) as a Phorbol Myristate Acetate-induced Gene in Lung Cancer Cells by Differential mRNA Display. Am J Respir Cell Mol Biol 17, 617-624. Young, M.R., Farrell, L., Lambert, P., Awasthi, P., and and Colburn, N.H. (2002a). Protection Against Human Papillomavirus Type 16-E7 Oncogene-Induced Tumorigenesis by In Vivo Expression of Dominant-Negative c-jun Molecular carcinogenesis 34, 72-77. Young, M.R., Farrell, L., Lambert, P., Awasthi, P., and Colburn, N.H. (2002b). Protection against human papillomavirus type 16-E7 oncogene-induced tumorigenesis by in vivo expression of dominant-negative c-jun. Molecular carcinogenesis 34, 72-77. Young, R.J., and Möller, A. (2009). Immunohistochemical Detection of Tumour Hypoxia. Methods in Molecular BIology 611, 151-159. Yu, L., and Wang, Z. (2009). Effects of Livin gene RNA interference on apoptosis of cervical cancer HeLa cells and enhanced sensitivity to cisplatin. Journal of Huazhong University of Science and Technology Medical sciences = Hua zhong ke ji da xue xue bao Yi xue Ying De wen ban = Huazhong keji daxue xuebao Yixue Yingdewen ban 29, 625-630. Yuan, H., Ito, S., Senga, T., Hyodo, T., Kiyono, T., Kikkawa, F., and Hamaguchi, M. (2009). Human papillomavirus type 16 oncoprotein E7 suppresses cadherin-mediated cell adhesion via ERK and AP-1 signaling. International journal of oncology 35, 309-314. Zeisel, A., Kostler, W.J., Molotski, N., Tsai, J.M., Krauthgamer, R., Jacob-Hirsch, J., Rechavi, G., Soen, Y., Jung, S., Yarden, Y., et al. (2011). Coupled pre-mRNA and mRNA dynamics unveil operational strategies underlying transcriptional responses to stimuli. Mol Syst Biol 7, 529. Zeng, Q., Peng, S., Monie, A., Yang, M., Pang, X., Hung, C.F., and Wu, T.C. (2011). Control of cervicovaginal HPV-16 E7-expressing tumors by the combination of therapeutic HPV vaccination and vascular disrupting agents. Hum Gene Ther 22, 809-819. Zenz, R., Scheuch, H., Martin, P., Frank, C., Eferl, R., Kenner, L., Sibilia, M., and Wagner, E.F. (2003). c-Jun Regulates Eyelid Closure and Skin Tumor Development through EGFR Signaling. Developmental Cell 4, 879–889. 258
Zhang, G., Dass, C.R., Sumithran, E., Di Girolamo, N., Sun, L.Q., and Khachigian, L.M. (2004). Effect of deoxyribozymes targeting c-Jun on solid tumor growth and angiogenesis in rodents. J Natl Cancer Inst 96, 683-696. Zhang, G., Fahmy, R.G., diGirolamo, N., and Khachigian, L.M. (2006a). JUN siRNA regulates matrix metalloproteinase-2 expression, microvascular endothelial growth and retinal neovascularisation. J Cell Sci 119, 3219-3226. Zhang, G., Luo, X., Sumithran, E., Pua, V.S.C., Barnetson, R.S.C., Halliday, G.M., and Khachigian, L.M. (2006b). Squamous cell carcinoma growth in mice and in culture is regulated by c-Jun and its control of matrix metalloproteinase-2 and -9 expression. Oncogene 25, 7260–7266. Zheng, Y., Zhang, J., and Rao, Z. (2004). Ribozyme targeting HPV16 E6E7 transcripts in cervical cancer cells suppresses cell growth and sensitizes cells to chemotherapy and radiotherapy. Cancer Biol Ther 3, 1129-1134; discussion 1135-1126. Zhou, J., Peng, C., Li, B., Wang, F., Zhou, C., Hong, D., Ye, F., Cheng, X., Lu, W., and Xie, X. (2012). Transcriptional gene silencing of HPV16 E6/E7 induces growth inhibition via apoptosis in vitro and in vivo. Gynecol Oncol 124, 296-302. Zhu, F., Choi, B.Y., Ma, W., Zhao, Z., Zhang, Y., Cho, Y.Y., Choi, H.S., Imamoto, A., Bode, A.M., and Dong, Z. (2006). CSK-Mediated c-Jun Phosphorylation Promotes c-Jun Degradation and Inhibits Cell Transformation. Cancer Reseach 6, 5729–5736. Zielinski, G.D., Snijders, P.J.F., and Rozendaal, L.e.a. (2003). The presence of high-risk HPV combined with specific p53 and p16INK4a expression patterns points to high-risk HPV as the main causative agent for adenocarcinoma in situ and adenocarcinoma of the cervix. Journal of Pathology 201, 535-543. Zoumpourlis, V., Papassava, P., Linardopoulos, S., Gillespie, D., Balmain, A., and Pintzas, A. (2000). High levels of phosphorylated c-Jun, Fra-1, Fra-2 and ATF-2 proteins correlate with malignant phenotypes in the multistage mouse skin carcinogenesis model. Oncogene 19, 4011- 4021. zur Hausen, H. (1996). Papillomavirus infections--a major cause of human cancers. Biochim Biophys Acta 1288, F55-78.
259
Appendix