title: BMI1 polycomb group protein acts as a master switch for growth and death of tumor cells: regulates TCF4-transcriptional factor-induced BCL2 signaling.
abstract: For advanced prostate cancer (CaP), the progression of tumors to the state of chemoresistance and paucity of knowledge about the mechanism of chemoresistance are major stumbling blocks in the management of this disease. Here, we provide compelling evidence that BMI1 polycomb group protein and a stem cell factor plays a crucial role in determining the fate of tumors vis-à-vis chemotherapy. We show that progressive increase in the levels of BMI1 occurs during the progression of CaP disease in humans. We show that BMI1-rich tumor cells are non-responsive to chemotherapy whereas BMI1-silenced tumor cells are responsive to therapy. By employing microarray, ChIP, immunoblot and Luciferase reporter assays, we identified a unique mechanism through which BMI1 rescues tumor cells from chemotherapy. We found that BMI1 regulates (i) activity of TCF4 transcriptional factor and (ii) binding of TCF4 to the promoter region of anti-apoptotic BCL2 gene. Notably, an increased TCF4 occupancy on BCL2 gene was observed in prostatic tissues exhibiting high BMI1 levels. Using tumor cells other than CaP, we also showed that regulation of TCF4-mediated BCL2 by BMI1 is universal. It is noteworthy that forced expression of BMI1 was observed to drive normal cells to hyperproliferative mode. We show that targeting BMI1 improves the outcome of docetaxel therapy in animal models bearing chemoresistant prostatic tumors. We suggest that BMI1 could be exploited as a potential molecular target for therapeutics to treat chemoresistant tumors.
authors.affiliation: Department of Molecular Chemoprevention and Therapeutics, The Hormel Institute, University of Minnesota, Austin, Minnesota, United States of America.
authors.forename: Hifzur Rahman
authors.initials: HR
authors.lastname: Siddique
authors.forename: Aijaz
authors.initials: A
authors.lastname: Parray
authors.forename: Rohinton S
authors.initials: RS
authors.lastname: Tarapore
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Hasan
authors.initials: H
authors.lastname: Mukhtar
authors.forename: R Jeffery
authors.initials: RJ
authors.lastname: Karnes
authors.forename: Yibin
authors.initials: Y
authors.lastname: Deng
authors.forename: Badrinath R
authors.initials: BR
authors.lastname: Konety
authors.forename: Mohammad
authors.initials: M
authors.lastname: Saleem
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D016922:Cellular Senescence; D002945:Cisplatin / Q000494:pharmacology; D000077143:Docetaxel; D019008:Drug Resistance, Neoplasm; D015972:Gene Expression Regulation, Neoplastic; D019073:HT29 Cells; D006801:Humans; D008297:Male; D015741:Metribolone / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D063150:Polycomb Repressive Complex 1 / Q000502:physiology*; D011401:Promoter Regions, Genetic; D011467:Prostate / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D011485:Protein Binding; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D043823:Taxoids / Q000494:pharmacology; D045165:Testosterone Congeners / Q000494:pharmacology; D000073940:Transcription Factor 4; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; C069077:BMI1 protein, human; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D019253:Proto-Oncogene Proteins c-bcl-2; C532096:TCF4 protein, human; D043823:Taxoids; D045165:Testosterone Congeners; D000073940:Transcription Factor 4; D014157:Transcription Factors; D000077143:Docetaxel; D015741:Metribolone; D063150:Polycomb Repressive Complex 1; D002945:Cisplatin