Original Article BCL7B, a Predictor of Poor Prognosis of Pancreatic Cancers, Promotes Cell Motility and Invasion by Influencing CREB Signaling
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Am J Cancer Res 2018;8(3):387-404 www.ajcr.us /ISSN:2156-6976/ajcr0070155 Original Article BCL7B, a predictor of poor prognosis of pancreatic cancers, promotes cell motility and invasion by influencing CREB signaling Keisuke Taniuchi1,2, Mutsuo Furihata3, Seiji Naganuma3, Ken Dabanaka4, Kazuhiro Hanazaki4, Toshiji Saibara1,2 Departments of 1Gastroenterology and Hepatology, 2Endoscopic Diagnostics and Therapeutics, 3Pathology, 4Sur- gery, Kochi Medical School, Kochi University, Nankoku, Kochi 783-8505, Japan Received December 1, 2017; Accepted December 12, 2017; Epub March 1, 2018; Published March 15, 2018 Abstract: The functions of B-cell CLL/lymphoma 7B (BCL7B) are unknown and the protein lacks any known func- tional domains. The aim of this study was to investigate the role of BCL7B in the motility and invasiveness of pan- creatic cancer cells. Immunohistochemistry was performed to determine whether high BCL7B expression in human pancreatic cancer tissues is correlated with poor prognosis. High BCL7B expression was an independent predictor of worse overall survival of pancreatic cancer patients. Immunocytochemistry showed that BCL7B was accumulated in cell protrusions of migrating pancreatic cancer cells. Knockdown of BCL7B inhibited the motility and invasiveness of pancreatic cancer cells through a decrease in cell protrusions. Phosphoprotein array analysis was performed to determine BCL7B-associated intracellular signaling pathways. Suppression of BCL7B increased phosphorylated CREB expression in pancreatic cancer cells, and knockdown of CREB promoted the motility and invasiveness by increasing cell protrusions. The combined data suggest that BCL7B promotes pancreatic cancer cell motility and invasion through a signaling pathway that involves dephosphorylation of CREB. Keywords: BCL7B, pancreatic cancer, cell invasion, CREB, actin-cytoskeleton Introduction tion syndrome [3]. Hemizygous loss of 7q11.23, and the concomitant reduced expression of The B-cell CLL/lymphoma 7 (BCL7) family in- BCL7B, has been reported in pilocytic astrocy- cludes three members, BCL7A, BCL7B, and tomas [4]. Despite these potentially important BCL7C. The family was discovered through the links to disease, the cellular roles of the BCL7 involvement of the BCL7A gene in a complex family are largely unknown, and the proteins translocation seen in a Burkitt lymphoma cell lack any known functional domains [5]. line [1]. The cloning of chromosomal translo- cations from haematologic malignancies has CREB belongs to the leucine zipper class of facilitated the identification of several gene transcription factors [6, 7]. Pathologically, CREB families of importance in the control of normal promotes hepatocellular carcinoma progres- cell differentiation, proliferation and cell death sion by promoting angiogenesis and resistance [2]. Although this phenomenon points to poten- to apoptosis [8]. Phosphorylated CREB inter- tially important roles of the BCL7 family, partic- acts with diverse transcriptional co-activators, ularly BCL7A, in the regulation of cell growth, including the histone acetyltransferases and chromosomal rearrangements affecting BCL7B CREB-binding protein (CBP/p300), thereby in- or BCL7C have not been detected in hemato- creasing CREB’s transcriptional activity [9, 10]. logic malignancies [3]. BCL7B belongs to a fam- CREB activates transcription in response to ily of highly conserved genes involved in early cAMP, intracellular Ca2+, various growth factors embryonic development; BCL7B is located in a (e.g. nerve growth factor, fibroblast growth fact- region at 7q11.23 which is consistently deleted or and the insulin growth factor 1), as well as in the Williams-Beuren contiguous gene dele- cytokines, including IL-4, IL-10, IL-13 and trans- BCL7B promotes cell motility and invasion forming growth factor-β [11, 12]. CREB activity review board of Kochi Medical School and might also be controlled by its subcellular local- Matsuyama Shimin Hospital prior to patient ization [13]. The underlying molecular mecha- recruitment. Written informed consent was nisms driving CREB overexpression and activa- acquired from each patient prior to initiation. tion in tumors have not yet been elucidated in detail [14]. In some cases, CREB is considered Immunohistochemical staining to be an oncogenic transcription factor because it is overexpressed and/or constitutively phos- Immunohistochemistry was carried out, as pub- phorylated in several human cancers, and in- lished previously [16]. Tissue sections from nor- duces a cell growth and antiapoptotic survival mal pancreas, brain, lung, liver and kidney were signal [15]. The functions of CREB in PDAC purchased from Biochain (Hayward, CA). remain unknown. Evaluation of BCL7B staining Here, we show that the overexpression of Staining was evaluated by two independent BCL7B in pancreatic cancer tissue is signifi- cantly correlated with overall survival, and observers (SN and MF) who were blinded to BCL7B contributes to the formation of addition- clinical and outcome data. BCL7B expression al membrane protrusions by decreasing CREB levels were classified semi-quantitatively based phosphorylation, resulting in increased motility on the total combined scores of positive-stain- and invasiveness of PDAC cells. ing tumor cell percentage (1, < 50% reacting cells; 2, 50-80% reacting cells; 3, > 80%) and Material and methods staining intensity (1, weaker than the intensity of surface staining in the islet of Langerhans; 2, Antibodies equal to the intensity of the islet of Langerhans; 3, stronger than the intensity of the islet of Anti-BCL7B antibody (H00009275) was pur- Langerhans). A total immunohistochemical sc- chased from Abnova (Taipei City, Taiwan). The ore was calculated by summing the percentage JLA20 anti-actin antibody (MABT219) was pur- score and the intensity score. BCL7B expres- chased from Merck Millipore (Temecula, CA). sion was classified into two groups based on Anti-myc (sc-789) antibody was purchased from total score (low group, 2-3; high group, 4-6) with Santa Cruz Biotechnology (Santa Cruz, CA). reference to a previous report [16, 19]. Anti-BCL7A antibody (C20948) was purchased from Assay Biotechnology Company (Sunnyvale, Cell culture CA). Anti-CREB antibody (A301-669A) was pur- chased from Bethyl Laboratories (Montgomery, The human PDAC cell line S2-013, a subline TX). of SUIT-2, was obtained from Dr. T. Iwamura (Miyazaki Medical College, Miyazaki, Japan) Primary human PDAC samples [20]. The human PDAC cell line, PANC-1 [21] was purchased from the American Type Culture Tumor tissues were obtained from 102 patients Collection (Manassas, VA). HPNE immortalized who underwent surgical treatment for PDAC normal pancreatic epithelial cells were a kind and received surgical resection during 1999- gift from Dr. Michel Ouellette (University of 2014 at the Departments of Surgery, Kochi Nebraska Medical Center, NE) [22]. All cells Medical School Hospital (Nankoku, Japan) and were grown in Dulbecco’s modified Eagle’s Matsuyama Shimin Hospital (Matsuyama, Ja- medium (DMEM; Gibco-BRL, Carlsbad, CA) sup- pan), as published previously [16]. All patients plemented with 10% heat-inactivated fetal calf had clinical records and none of them received serum (FCS) at 37°C in a humidified atmo- chemotherapy or radiation therapy before sur- sphere saturated with 5% CO . gery. Of these patients, 83 received adjuvant 2 chemotherapy with gemcitabine or S-1, or ch- Confocal immunofluorescence microscopy emoradiation therapy after resection of PDAC. Tumors were classified according to the classi- Immunocytochemistry was carried out, as pub- fication of pancreatic carcinoma of the Japan lished previously [23]. Briefly, coverslips were Pancreas Society [17] and UICC TNM classifica- coated with 10 μg/mL fibronectin (Sigma- tion [18]. The study was approved by the ethical Aldrich, St. Louis, MO) for 1 h at room tempera- 388 Am J Cancer Res 2018;8(3):387-404 BCL7B promotes cell motility and invasion ture. S2-013 cells were seeded on fibronectin- antibodies were diluted according to the manu- coated glass coverslips, incubated for 5 h; facturer’s instructions and incubated overnight and then fixed with 4% paraformaldehyde at 4°C. Subsequently, horseradish peroxidase- and permeabilized with 0.1% Triton X-100. linked secondary antibodies were added at a Blocking solution (3% BSA/PBS) was added, dilution of 1:5,000 and incubated at room tem- followed by incubation with the primary an- perature for 1 h. The membranes were washed tibody for 1 h. After washing, Alexa488-, with PBS and the immunoreactive bands were Alexa594-, or Alexa647-conjugated secondary visualized using the ECL Plus kit according to antibody (Molecular Probes, Carlsbad, CA) was the manufacturer’s instructions. applied. In some experiments, a commercial antibody-labeling technology (Zenon; Life Te- In vitro growth rate by MTT assay chnologies, Carlsbad, CA) was used according Cells were each seeded at a concentration of 5 to the manufacturer’s instructions to conjugate × 104 cells per well using 12-well plates. The green or red fluorophores to primary antibod- viability of cells was evaluated by 3-(4,5-dimeth- ies. Each specimen was visualized using a ylthiazol-2-yl)-2,5-diphenyltetrazolium bromide Zeiss LSM 510 META microscope (Carl Zeiss, (MTT) assay according to the manufacturer’s Gottingen, Germany). instructions. Briefly, cell counting kit-8 solution PDAC cells that formed cell protrusions, in (Dojindo, Kumamoto, Japan) was added to each which peripheral actin structures