title: Critical role of Smad2 in tumor suppression and transforming growth factor-beta-induced apoptosis of prostate epithelial cells.
abstract: Transforming growth factor-beta (TGF-beta) functions as a tumor suppressor of the prostate through mechanisms that remain unresolved. Although TGF-beta receptors directly activate both Smads 2 and 3, to date, Smad3 has been shown to be the essential mediator of most Smad-dependent TGF-beta responses, including control of gene expression, cell growth, apoptosis, and tumor suppression. Using a robust lentiviral short hairpin RNA system to silence Smads 2 and/or 3 in the NRP-152 nontumorigenic rat prostate basal epithelial cell line, we provide the first evidence for Smad2 as a critical mediator of TGF-beta-induced apoptosis and gene expression. Parallel analyses revealed that Smad3 is the major mediator of TGF-beta-induced transcriptional and apoptotic responses in the NRP-154 rat prostate carcinoma cell line. Remarkably, silencing Smad2 alone caused malignant transformation of NRP-152 cells, as assayed by s.c. tumor growth in athymic mice, whereas silencing Smad3 alone did not induce tumors. Nevertheless, tumors induced by silencing both Smads 2 and 3 were larger than those from silencing Smad2 alone. Given previous reports that NRP-152 cells have a stem cell phenotype, we speculate a critical role for Smad2 as a tumor suppressor in the basal epithelial or stem cell compartment of the prostate.
authors.affiliation: The Case Comprehensive Cancer Center, Departments of Pharmacology and Biochemistry, Case School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Jiayi
authors.initials: J
authors.lastname: Yang
authors.forename: Reema
authors.initials: R
authors.lastname: Wahdan-Alaswad
authors.forename: David
authors.initials: D
authors.lastname: Danielpour
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D045744:Cell Line, Tumor; D020868:Gene Silencing; D016086:Lentivirus / Q000235:genetics; D008297:Male; D051379:Mice; D008819:Mice, Nude; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D051899:Smad2 Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D014161:Transduction, Genetic; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*
chemical_list: D034741:RNA, Small Interfering; D051899:Smad2 Protein; C497784:Smad2 protein, rat; D051900:Smad3 Protein; C497787:Smad3 protein, rat; D016212:Transforming Growth Factor beta