Of P53-Deficient Cells (Tumor Suppressor Gene/Adfovrs Ela/Adenovirus E1B) Scorr W

Total Page:16

File Type:pdf, Size:1020Kb

Of P53-Deficient Cells (Tumor Suppressor Gene/Adfovrs Ela/Adenovirus E1B) Scorr W Proc. Natl. Acad. Sci. USA Vol. 91, pp. 2026-2030, March 1994 Cell Biology Abrogation of oncogene-associated apoptosis allows transformation of p53-deficient cells (tumor suppressor gene/adfovrs ElA/adenovirus E1B) Scorr W. LoWE*, TYLER JACKS*, DAVID E. HOUSMAN*, AND H. EARL RULEYt* *Center for Cancer Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139; and *Department of Microbiology and Immunology, Room AA5206 MCN, Vanderbilt University School of Medicine, 1161 21st Avenue South, Nashville, TN 37232-2363 Communicated by Peter M. Howley, November 12, 1993 ABSTRACT p53-defiient mouse embryonic fibroblasts associated apoptosis (adenovirus pl9ElB and mutant p53) can were used to establish a direct canism oftumor suppression collaborate with ElA in oncogenic transformation (8, 14-16). by p53 involving the d on ofoncogene-expressing cells by The evidence that p53 directly suppresses oncogenic trans- apoptous. The absence of p53 enhan cell growth, appeared formation is circumstantial, since it has not been possible to sut iet for Immorlization, and allowed a single oncogene assess the physiological activities of endogenous p53. While [adenovirus early region 1A (E1A)] to transform cells to a forced overexpression of wild-type or mutant p53 can reveal tumorigenic state. p53 su transformation of E1A- potential p53 activities, the relevance of this approach to expressing cells by apoptouis. Apoptosis was associated with circumstances in which endogenous p53 suppresses trans- p53 stabilization and was triggered by environmental signals formation is unknown. Certainly, proteins not normally in- that normally suppress cell growth. Absence of even a single volved in proliferation might suppress growth or viability p53 allele s nty d cell growth and survival. when sufficiently overexpressed. Furthermore, mutant p53 Although abrogation of apoptosis allowed transformation by alleles can transform p53-deficient cells, indicating that they ElA alone, escape from apoptosis susceptibility was not a are not simply dominant-negative suppressors of wild-type prerequisite for tumor growth. Consequently, p53 mouton p53 (17). cMu enhance the survival of maiant cells expressing onco- In this study, transforming interactions between endoge- genes activated early in tumor progression. nous p53 and transfected oncogenes were analyzed by using embryonic fibroblasts derived from mice carrying disrupted The p53 tumor suppressor is the most frequently mutated p53 genes. Since the recipient cells differed only in their p53 gene in human tumors (1). Presently, the only model to status, differences between cellular responses could be un- account for the action ofp53 as a tumor suppressor views p53 ambiguously attributed to p53 function. Embryonic fibro- as a "'guardian of the genome" (2). According to this model, blasts also provide a well-characterized model of multistep p53 is an essential component of a DNA damage control carcinogenesis in which oncogenic transformation typically system that, when operating normally, reduces the likelihood requires two or more oncogenes acting in concert (12). These that cells will sustain oncogenic mutations. This view stems studies indicate that p53 can directly suppress oncogenic from the observations that p53 expression and stability are transformation by its involvement in apoptosis. Conse- induced in cells exposed to DNA-damaging agents (3), lead- quently, p53 loss allows transformation ofprimary cells by a ing to either cell cycle arrest [which may facilitate DNA single oncogene. repair (4)] or cell death by apoptosis (5, 6). Failure to activate p53 expression after DNA damage may account for thb high cancer incidence in individuals with ataxia-telangiectasia (4) MATERIALS AND METHODS and in mice lacking p53 (5). Cells, Plasmids, and Gene Transfer. p53+/+, p53+/-, and Nevertheless, there are reasons to doubt that this indirect p53-/- mouse embryonic fibroblasts (MEFs) were cultured mechanism is the only means by which p53 mutation con- in Dulbecco's modified Eagle's medium containing 10% fetal tributes to cancer. First, loss of p53 typically occurs late in bovine serum (FBS) and used between passages 3 and 5. tumor progression, after oncogenic mutations have already plAHygro contains the adenovirus type 5 ElA gene (nucle- occurred (7). Second, mutant p53 alleles, which can inhibit otides 1-1834) inserted into pY3 [expressing hygromycin normal p53 function (8), enable ras oncogenes to transform phosphotransferase (18)]. pT24neo encodes a ras oncogene both primary and established cells (9, 10). Transformed foci (T24 H-ras; designated ras) (19) and pSXX encodes the E1B appear within days, and stable transformation requires con- gene. pLTRKH215 and pLTRcGala expressed a dominant- tinuous expression ofmutant p53 (11). Thus, p53 may directly transforming p53 allele (p53KH215) and mouse wild-type p53, influence both the initiation and maintenance of transformed respectively (9). Stable lines expressing ElA were generated phenotypes. This view is supported by the transforming by calcium phosphate precipitation (19) using 1 ,yg of interactions between the adenovirus early region 1A (E1A) plAHygro and a 10-fold molar excess of pT24neo, pSXX, gene and other oncogenes. ElA, while unable to transform pLTRKH215, or pLTRcGala. Alternatively, pY3 was used at alone, collaborates with either adenovirus E1B or activated a molar amount equivalent to 1 pg of plA~ygro. For each ras oncogenes to oncogenically transform primary cells (12). precipitation, the total mass ofDNA was adjusted to 20 pg by We recently demonstrated that p53 levels and stability in- using pBluescript. Transfected cells were subcultured into crease in response to ElA and suggested that stabilized p53 medium containing either 100 pg (pS3-/- MEFs) or 15 pg suppressed transformation by enhancing apoptosis (13). Con- (p53+/+ and p53+/- MEFs) ofhygromycin B per ml (Sigma), sequently, proteins that either block p53 transactivation concentrations that were determined empirically. After 2-3 (adenovirus p55E1B and mutant p53) or protect against E1A- Abbreviations: ElA, adenovirus early region 1A; E1B, adenovirus The publication costs ofthis article were defrayed in part by page charge early region 1B; MEF, mouse embryonic fibroblast; FBS, fetal payment. This article must therefore be hereby marked "advertisement" bovine serum; BrdU, 5-bromo-2'-deoxyuridine. in accordance with 18 U.S.C. §1734 solely to indicate this fact. tTo whom reprint requests should be addressed. 2026 Downloaded by guest on September 25, 2021 Cell Biology: Lowe et al. Proc. Natl. Acad. Sci. USA 91 (1994) 2027 weeks, several clones from each transfection were expanded and colony numbers were estimated. Viability Assays. ElA-expressing colonies (which are mor- phologically distinct) were marked and transferred to 0.1% FBS, photographed at various times, and scored for regres- 0 sion. Alternatively, cell lines were seeded at 1-2 x 106 cells 500- per 100-mm plate and subsequently transferred to 0.1% FBS. 05 Later, adherent and nonadherent cells were pooled for via- bility measurements using fluorescein isothiocyanate stain- ing and flow cytometry (5). For analyzing DNA fragmenta- E tion, low molecular weight DNA was purified from pools of 3 250- adherent and nonadherent cells 24 hr after transfer to 0.1% FBS and analyzed by agarose gel electrophoresis (20). p53 Expression and Cell Cycle Analysis. p53 half-life was estimated by p53 immunoprecipitation of 35S-labeled cell 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 lysates as described (13). Western blot analysis was per- formed with lysates derived from 106 cells (5). For cell cycle FIG. 1. Introduction ofgenes into MEFs. Transfection ofvarious analysis, cells were incubated with 5-bromo-2'-deoxyuridine plasmids into p53+/+ (A), p53+/F (B), and p53-/- (C) embryonic (BrdU) for 4 hr, beginning 14 hr after transfer to 0.5% FBS. fibroblasts (106 cells per transfection). The transfected plasmid(s) Subsequently, cultures were washed to remove dead cells, expressed the following: 1, hygromycin phosphotransferase; 2, ElA; and the adherent cells were prepared for flow cytometry (20). 3, ElA and E1B; 4, ElA and ras (T24 H-ras); 5, ElA and a mutant Proliferation was assessed by DNA content (propidium io- p53; 6, ElA and wild-type p53; 7, no DNA. The ElA expression vector (plAHygro) coexpressed the adenovirus type 5 ElA gene and dide staining) and DNA synthesis (BrdU immunostaining). hygromycin phosphotransferase, allowing isolation of E1A- Tumorigenicity Experiments. Male nude mice (Swiss nul expressing colonies in medium containing hygromycin B. Colony nu; Taconic) (4-6 weeks old) were injected with 2 x 106 cells numbers were estimated -2 weeks after transfection and represent and monitored for tumors at the injection sites for -10 the average ± SD determined from at least three transfections. months. Tumors were scored positive when they became clearly visible (diameter, m2 mm). To avoid selection for a that accompanies ElA expression may suppress clonal out- transformed phenotype, hygromycin-resistant clones were growth. expanded minimally before inoculation. Attempts to expand ElA-expressing colonies into stable cell lines revealed striking differences among fibroblast types. Most p53-/- colonies expressing ElA (12/15) or RESULTS hygromycin phosphotransferase (3/4) were established into Introduction of ElA into p53+/+, p53+/-, and p53-/- permanent lines. By contrast, ElA-expressing colonies de- MEFs. Both ElA and mutant
Recommended publications
  • Ret Oncogene and Thyroid Carcinoma
    ndrom Sy es tic & e G n e e n G e f T o Elisei et al., J Genet Syndr Gene Ther 2014, 5:1 Journal of Genetic Syndromes h l e a r n a DOI: 10.4172/2157-7412.1000214 r p u y o J & Gene Therapy ISSN: 2157-7412 Review Article Open Access Ret Oncogene and Thyroid Carcinoma Elisei R, Molinaro E, Agate L, Bottici V, Viola D, Biagini A, Matrone A, Tacito A, Ciampi R, Vivaldi A and Romei C* Endocrine Unit, Department of Clinical and Experimental Medicine, University of Pisa, Italy Abstract Thyroid cancer is a malignant neoplasm that originates from follicular or parafollicular thyroid cells and is categorized as papillary (PTC), follicular (FTC), anaplastic (ATC) or medullary thyroid carcinoma (MTC). The alteration of the Rearranged during trasfection (RET) (proto-oncogene, a gene coding for a tyrosine-kinase receptor involved in the control of cell differentiation and proliferation, has been found to cause PTC and MTC. In particular, RET/PTC rearrangements and RET point mutations are related to PTC and MTC, respectively. Although RET/PTC rearrangements have been identified in both spontaneous and radiation-induced PTC, they occur more frequently in radiation-associated tumors. RET/PTC rearrangements have also been reported in follicular adenomas. Although controversial, correlations between RET/PTC rearrangements, especially RET/PTC3, and a more aggressive phenotype and a more advanced stage have been identified. Germline point mutations in the RET proto-oncogene are associated with nearly all cases of hereditary MTC, and a strict correlation between genotype and phenotype has been demonstrated.
    [Show full text]
  • A Gain-Of-Function P53-Mutant Oncogene Promotes Cell Fate Plasticity and Myeloid Leukemia Through the Pluripotency Factor FOXH1
    Published OnlineFirst May 8, 2019; DOI: 10.1158/2159-8290.CD-18-1391 RESEARCH ARTICLE A Gain-of-Function p53-Mutant Oncogene Promotes Cell Fate Plasticity and Myeloid Leukemia through the Pluripotency Factor FOXH1 Evangelia Loizou1,2, Ana Banito1, Geulah Livshits1, Yu-Jui Ho1, Richard P. Koche3, Francisco J. Sánchez-Rivera1, Allison Mayle1, Chi-Chao Chen1, Savvas Kinalis4, Frederik O. Bagger4,5, Edward R. Kastenhuber1,6, Benjamin H. Durham7, and Scott W. Lowe1,8 Downloaded from cancerdiscovery.aacrjournals.org on September 27, 2021. © 2019 American Association for Cancer Research. Published OnlineFirst May 8, 2019; DOI: 10.1158/2159-8290.CD-18-1391 ABSTRACT Mutations in the TP53 tumor suppressor gene are common in many cancer types, including the acute myeloid leukemia (AML) subtype known as complex karyotype AML (CK-AML). Here, we identify a gain-of-function (GOF) Trp53 mutation that accelerates CK-AML initiation beyond p53 loss and, surprisingly, is required for disease maintenance. The Trp53 R172H muta- tion (TP53 R175H in humans) exhibits a neomorphic function by promoting aberrant self-renewal in leu- kemic cells, a phenotype that is present in hematopoietic stem and progenitor cells (HSPC) even prior to their transformation. We identify FOXH1 as a critical mediator of mutant p53 function that binds to and regulates stem cell–associated genes and transcriptional programs. Our results identify a context where mutant p53 acts as a bona fi de oncogene that contributes to the pathogenesis of CK-AML and suggests a common biological theme for TP53 GOF in cancer. SIGNIFICANCE: Our study demonstrates how a GOF p53 mutant can hijack an embryonic transcrip- tion factor to promote aberrant self-renewal.
    [Show full text]
  • Wnt-Independent and Wnt-Dependent Effects of APC Loss on the Chemotherapeutic Response
    International Journal of Molecular Sciences Review Wnt-Independent and Wnt-Dependent Effects of APC Loss on the Chemotherapeutic Response Casey D. Stefanski 1,2 and Jenifer R. Prosperi 1,2,3,* 1 Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46617, USA; [email protected] 2 Mike and Josie Harper Cancer Research Institute, South Bend, IN 46617, USA 3 Department of Biochemistry and Molecular Biology, Indiana University School of Medicine-South Bend, South Bend, IN 46617, USA * Correspondence: [email protected]; Tel.: +1-574-631-4002 Received: 30 September 2020; Accepted: 20 October 2020; Published: 22 October 2020 Abstract: Resistance to chemotherapy occurs through mechanisms within the epithelial tumor cells or through interactions with components of the tumor microenvironment (TME). Chemoresistance and the development of recurrent tumors are two of the leading factors of cancer-related deaths. The Adenomatous Polyposis Coli (APC) tumor suppressor is lost in many different cancers, including colorectal, breast, and prostate cancer, and its loss correlates with a decreased overall survival in cancer patients. While APC is commonly known for its role as a negative regulator of the WNT pathway, APC has numerous binding partners and functional roles. Through APC’s interactions with DNA repair proteins, DNA replication proteins, tubulin, and other components, recent evidence has shown that APC regulates the chemotherapy response in cancer cells. In this review article, we provide an overview of some of the cellular processes in which APC participates and how they impact chemoresistance through both epithelial- and TME-derived mechanisms. Keywords: adenomatous polyposis coli; chemoresistance; WNT signaling 1.
    [Show full text]
  • Targeting the Function of the HER2 Oncogene in Human Cancer Therapeutics
    Oncogene (2007) 26, 6577–6592 & 2007 Nature Publishing Group All rights reserved 0950-9232/07 $30.00 www.nature.com/onc REVIEW Targeting the function of the HER2 oncogene in human cancer therapeutics MM Moasser Department of Medicine, Comprehensive Cancer Center, University of California, San Francisco, CA, USA The year 2007 marks exactly two decades since human HER3 (erbB3) and HER4 (erbB4). The importance of epidermal growth factor receptor-2 (HER2) was func- HER2 in cancer was realized in the early 1980s when a tionally implicated in the pathogenesis of human breast mutationally activated form of its rodent homolog neu cancer (Slamon et al., 1987). This finding established the was identified in a search for oncogenes in a carcinogen- HER2 oncogene hypothesis for the development of some induced rat tumorigenesis model(Shih et al., 1981). Its human cancers. An abundance of experimental evidence human homologue, HER2 was simultaneously cloned compiled over the past two decades now solidly supports and found to be amplified in a breast cancer cell line the HER2 oncogene hypothesis. A direct consequence (King et al., 1985). The relevance of HER2 to human of this hypothesis was the promise that inhibitors of cancer was established when it was discovered that oncogenic HER2 would be highly effective treatments for approximately 25–30% of breast cancers have amplifi- HER2-driven cancers. This treatment hypothesis has led cation and overexpression of HER2 and these cancers to the development and widespread use of anti-HER2 have worse biologic behavior and prognosis (Slamon antibodies (trastuzumab) in clinical management resulting et al., 1989).
    [Show full text]
  • Extensive Analysis of the Retinoblastoma Gene in Adult T Cell Leukemia/Lymphoma (ATL) Y Hatta1, Y Yamada2, M Tomonaga2 and HP Koeffler1
    Leukemia (1997) 11, 984–989 1997 Stockton Press All rights reserved 0887-6924/97 $12.00 Extensive analysis of the retinoblastoma gene in adult T cell leukemia/lymphoma (ATL) Y Hatta1, Y Yamada2, M Tomonaga2 and HP Koeffler1 1Division of Hematology/Oncology, Department of Medicine, Cedars-Sinai Research Institute, UCLA School of Medicine, Los Angeles, CA, USA; and 2Department of Hematology, Atomic Disease Institute, Nagasaki University, School of Medicine, Nagasaki, Japan The retinoblastoma susceptibility gene (Rb) plays a key role in Tax;38 a long period of clinical latency (20–30 years) precedes regulating the cell cycle in association with cyclins and cyclin- the development of ATL;39,40 only a small percentage of dependent kinases (CDKs). Alteration of the Rb gene as well 40 as CDK inhibitors (CDKIs) leads to deregulated cellular growth HTLV-I-infected individuals develop this malignancy; and which promotes cancer formation. We examined the genomic ATL cells are monoclonal. configuration of the entire Rb gene in 40 primary adult T cell The missense inactivating mutations of the p53 gene have leukemias/lymphomas (ATL) and two ATL cell lines by South- been observed in ATL.41–44 We tested for the inactivation of ern blotting and also by polymerase chain reaction-single several CDK inhibitors (CDKIs) including p15INK4B, p16INK4A, strand conformation polymorphism (PCR-SSCP) analyses. p18INK4C, p19INK4D and p27KIP1, and have found deletions of Homozygous loss of exon 1 was identified in one of 21 acute the p16INK4A gene in 10 of 37 cases (27%); deletions of the ATL, one of 15 chronic ATL, and none of four lymphomatous INK4B 45 ATL samples.
    [Show full text]
  • Physical Interaction of the Retinoblastoma Protein with Human D Cyclins
    Cell, Vol. 73, 499-511, May 7, 1993, Copyright 0 1993 by Cell Press Physical Interaction of the Retinoblastoma Protein with Human D Cyclins Steven F. Dowdy,* Philip W. Hinds,’ Kenway Louie,’ into Rb- tumor cells by microinjection, viral infection, or Steven I. Reed,t Andrew Arnold,* transfection can lead to the growth arrest of these recipient and Robert A. Weinberg” cells (Huang et al., 1988; Goodrich et al., 1991; Templeton *The Whitehead Institute for Biomedical Research et al., 1991; Hinds et al., 1992). and Department of Biology Oncoproteins specified by the SV40, adenovirus, and Massachusetts Institute of Technology papilloma DNA tumor viruses have been shown to associ- Cambridge, Massachusetts 02142 ate with pRb in virus-transformed cells (Whyte et al., 1988; tThe Scripps Research Institute DeCaprio et al., 1988; Dyson et al., 1989). Oncoprotein Department of Molecular Biology binding of pRb is presumed to lead to its sequestration 10666 North Torrey Pines Road and functional inactivation. Conserved region II mutants La Jolla, California 92037 of adenovirus ElA, SV40 large T antigen, human papil- *Endocrine Unit loma E7 viral oncoproteins that have lost their ability to and Massachusetts General Hospital Cancer Center bind pflb, and other pRb-related proteins exhibit signifi- Massachusetts General Hospital cantly reduced transforming potential (Moran et al., 1986; and Harvard Medical School Lillie et al., 1987; Cherington et al., 1988; DeCaprio et al., Boston, Massachusetts 02114 1988; Moran, 1988; Smith and Ziff, 1988; Whyte et al., 1989). This suggests that binding of pRb and related pro- teins by these oncoproteins is critical to their transforming abilities.
    [Show full text]
  • Updated November 2019 KIT Mutation the KIT Gene Is Associated With
    Updated November 2019 KIT Mutation The KIT gene is associated with autosomal dominant piebaldism, gastrointestinal stromal tumors (GISTs), and familial mastocytosis.1-3 The type of mutation identified in the KIT gene determines the symptoms/cancer risks that the individual may have. Pathogenic loss-of-function (LOF) mutations in the KIT gene are generally only associated with Piebaldism. However, pathogenic gain of function mutations in the KIT gene are associated with systemic mastocytosis and gastrointestinal stromal tumors.4,5 Piebaldism: This is a rare condition characterized by the patchy absence of melanocytes in certain areas of the skin and hair. Melanocytes produce the pigment melanin, which contributes to hair, eye, and skin color. The absence of melanocytes leads to patches of skin and hair that are lighter than normal. These unpigmented areas are typically present at birth and do not increase in size or number.6-8 Gastrointestinal stromal tumors (GIST): GISTs are tumors that occur in the gastrointestinal tract, most commonly in the stomach or small intestine. Small tumors may cause no signs or symptoms. However, some people with GISTs may experience pain or swelling in the abdomen, nausea, vomiting, loss of appetite, or weight loss. These tumors can be cancerous (malignant) or noncancerous (benign). Mastocytosis: This is a blood disorder that occurs when white blood cells called mast cells accumulate in one or more tissues (most commonly in the bone marrow). Mast cells normally trigger inflammation during an allergic reaction. When an environmental trigger activates mast cells, they release proteins that signal an immune response. In systemic mastocytosis, excess mast cells mean more proteins are being released in the tissues where the cells accumulate, leading to an increased immune response.
    [Show full text]
  • Genetic Testing for Germline Mutations of the RET Proto-Oncogene AHS - M2078
    Corporate Medical Policy Genetic Testing for Germline Mutations of the RET Proto-Oncogene AHS - M2078 File Name: genetic_testing_for_germline_mutations_of_the_ret_proto-oncogene Origination: 1/2019 Last CAP Review 3/2021 Next CAP Review: 3/2022 Last Review: 3/2021 Description of Procedure or Service The RET (rearranged during transfection) proto-oncogene encodes a transmembrane receptor tyrosine kinase (Takahashi, Ritz, & Cooper, 1985) that regulates a complex network of signal transduction pathways during development, survival, proliferation, differentiation, and migration of the enteric nervous system progenitor cells (Hedayati, Zarif Yeganeh, Sheikholeslami, & Afsari, 2016). Disruption of RET signaling by mutation, gene rearrangement, overexpression or transcriptional up-regulation of the RET gene is implicated in several human cancers (Plaza-Menacho, Mologni, & McDonald, 2014), most commonly thyroid, but also chronic myelomonocytic leukemia, acute myeloid leukemia, and lung, breast, pancreatic, and colon cancers (Gordon et al., 2018). Mutation of the RET gene in a germline cell results in an autosomal dominant hereditary cancer syndrome, multiple endocrine neoplasia type 2 (MEN2) characterized by medullary thyroid carcinoma (MTC), pheochromocytoma (PHEO), and primary parathyroid hyperplasia (PPTH). (Figlioli, Landi, Romei, Elisei, & Gemignani, 2013). This policy covers genetic testing for germline variants in the RET gene. For information on testing of tumors for RET variants to guide chemotherapy. Related Policies M2109 Molecular Panel Testing of Cancers to Identify Targeted Therapy M2030 Testing for Targeted Therapy of Non-Small-Cell Lung Cancer M2108 Molecular Markers in Fine Needle Aspirates of the Thyroid. ***Note: This Medical Policy is complex and technical. For questions concerning the technical language and/or specific clinical indications for its use, please consult your physician.
    [Show full text]
  • P53 Regulates the Transcription of Its &Delta
    Oncogene (2010) 29, 2691–2700 & 2010 Macmillan Publishers Limited All rights reserved 0950-9232/10 $32.00 www.nature.com/onc ORIGINAL ARTICLE p53 regulates the transcription of its D133p53 isoform through specific response elements contained within the TP53 P2 internal promoter V Marcel, V Vijayakumar, L Ferna´ndez-Cuesta, H Hafsi, C Sagne, A Hautefeuille, M Olivier and P Hainaut Molecular Carcinogenesis Group, International Agency for Research on Cancer, Lyon, Cedex, France The tumor suppressor p53 protein is activated by genotoxic Kubbutat et al., 1997). Under stress, p53 is post- stress and regulates genes involved in senescence, apoptosis translationally modified, escapes to Hdm2-mediated and cell-cycle arrest. Nine p53 isoforms have been degradation, accumulates in the nucleus and regulates described that may modulate suppressive functions of the the transcription of several target genes involved in canonical p53 protein. Among them, D133p53 lacks the 132 growth suppressive responses including cell-cycle arrest, proximal residues and has been shown to modulate p53- senescence and apoptosis. Among cell-cycle arrest genes, induced apoptosis and cell-cycle arrest. D133p53 is p21WAF1/CIP1 encodes a cyclin-dependent kinase inhibiting expressed from a specific mRNA, p53I4, driven by an cyclin:CDK complexes at both G1/S and G2/M alternative promoter P2 located between intron 1 and exon (el-Deiry et al., 1993; Waldman et al., 1995). p53- 5ofTP53 gene. Here, we report that the P2 promoter is dependent apoptosis is mediated through several distinct regulated in a p53-dependent manner. D133p53 expression pathways involving genes, such as BAX or PUMA, that is increased in response to DNA damage by doxorubicin in induce mitochondrial apoptosis through caspase activa- p53 wild-type cell lines, but not in p53-mutated cells.
    [Show full text]
  • The Adenomatous Polyposis Coli Tumour Suppressor Gene Regulates C-MYC Transcription in Colon Cancer Cells
    596 Gut 1999;44:596 SCIENCE @LERT Gut: first published as 10.1136/gut.44.5.596 on 1 May 1999. Downloaded from The adenomatous polyposis coli tumour suppressor gene regulates c-MYC transcription in colon cancer cells the mRNA and protein levels by northern and western He TC, Sparks AB, Rago C, et al. Identification of blotting analysis. Further evidence of this rather unex- c-MYC as a target of the APC pathway. Science pected finding came from a series of experiments where a 1998;281:1509–12. DNA sequence containing the c-MYC promoter region was inserted upstream of a luciferase reporter gene and the Abstract construct was tested for responsiveness to APC.As The adenomatous polyposis coli gene (APC) is a predicted, the c-MYC promoter conferred significant tran- tumor suppressor gene that is inactivated in scriptional activity that was inhibited by APC when it was most colorectal cancers. Mutations of APC cause introduced into colon carcinoma cells. Once again, the aberrant accumulation of â-catenin, which then APC–â-catenin–Tcf pathway seemed to play an important binds T cell factor-4 (Tcf-4), causing increased role in this novel interaction. The researchers demon- transcriptional activation of unknown genes. strated that c-MYC was significantly activated by a Here, the c-MYC oncogene is identified as a tar- mutated â-catenin construct which was previously shown get gene in this signaling pathway. Expression of to render cells insensitive to downregulation by endo- c-MYC was shown to be repressed by wild type genous wild type APC.
    [Show full text]
  • Cancer Biology Introduction Proto-Oncogenes Tumor
    Introduction • Tissue homeostasis depends on the regulated cell division and self-elimination (programmed cell Cancer Biology death) of each of its constituent members except its stem cells • A tumor arises as a result of uncontrolled cell division and failure for self-elimination Chapter 18 • Alterations in three groups of genes are responsible Eric J. Hall., Amato Giaccia, for the deregulated control mechanisms that are the hallmarks of cancer cells: proto-oncogenes, tumor- Radiobiology for the Radiologist supressor genes, and DNA stability genes Proto-oncogenes Tumor-suppressor genes • Proto-oncogenes are components of signaling • Tumor-suppressor genes are also components of networks that act as positive growth the same signaling networks as proto-oncogenes, except that they act as negative growth regulators regulators in response to mitogens, cytokines, • They modulate proliferation and survival by and cell-to-cell contact antagonizing the biochemical functions of proto- • A gain-of-function mutation in only one copy oncogenes or responding to unchecked growth signals of a protooncogene results in a dominantly • In contrast to oncogenes, inactivation of both acting oncogene that often fails to respond to copies of tumor-suppressor genes is required for extracellular signals loss of function in most cases DNA stability genes Mechanisms of carcinogenesis • DNA stability genes form a class of genes • A single genetic alteration that leads to the involved in both monitoring and activation of an oncogene or loss of a tumor maintaining
    [Show full text]
  • Defective Human Retinoblastoma Protein Identified by Lack of Interaction with the E1A Oncoprotein I
    [CANCER RESEARCH 54, 1098-111~4. Fcbru:lrv 15. It~941 Defective Human Retinoblastoma Protein Identified by Lack of Interaction with the E1A Oncoprotein I Marco G. Paggi, z Fabio MarteUi, Maurizio Fanciulli, Armando Felsani, Salvatore Sciacchitano, Marco Varmi, Tiziana Bruno, Carmine M. Carapella, and Aristide Floridi Laboratori di Metabolismo Celhdare e Farmacocinetica [M. G. P., M. E, M. V, T. B., A. FI.]; Biologia Moh'cohu'e [F. M., A. Fe.], Centtv Ricerca Sperimentah', Istituto Regina Elena per lo Studio e la Cura dei Tumori, Via delle Messi d'Oro, 156, O0158 Rome; Istituto Tecnologie Biomediche, C. N. R., Via Morgagni 30/E, 00161 Rome [A. Fe.]; Dipartimento Medicina Sperimentale, Universith "La Sapienza, '" Viale Regina Elena, 361, 00161 Rome [S. S.]: and Divisione di Neurochirurgia, lstituto Regina Elena per lo Studio e la Cura dei Tumori, Viale Regina Elena, 291, 00161 Rome,/C. M. C.], Italy ABSTRACT The retinoblastoma gene product, pRb, is a nuclear phosphoprotein with DNA-binding property (21, 22). Normal pRb shows a certain Inactivating mutations of the retinoblastoma susceptibility gene (Rb) microheterogeneity in SDS-PAGE, due to different degrees of phos- are involved in the pathogenesis of hereditary and sporadic retinoblas- phorylation, so that the protein is usually found between 105 and 114 toma. Alterations in the Rb gene have also been found in several other human tumors occurring with epidemiological incidence higher than that kDa of apparent molecular mass. The phosphorylation status of pRb of retinoblastoma. Four human malignant glioma cell lines were examined oscillates between an unphosphorylated or an underphosphorylated for abnormalities in the retinoblastoma gene product (pRb), using a pro- form (fast-migrating), during the Go-G~ phases of the cell cycle, and cedure based on the interaction of pRb with an in vitro-translated adeno- a fully phosphorylated form (slow-migrating), when the cell reaches virus E1A oncoprotein.
    [Show full text]