title: Ras mutation promotes p53 activation and apoptosis of skin keratinocytes.
abstract: Previous studies in our laboratory demonstrated that 7,12-dimethylbenz[a]anthracene/12-O-tetradecanoylphorbol-13-acetate (DMBA/TPA) treatment induced apoptosis and mitochondrial translocation of the tumor suppressor p53 in a mouse skin carcinogenesis model, suggesting that oncogenic versus cell death signaling involve a common mediator. Mutational activation of oncogenic Ras is an early event and has been demonstrated to play a critical role in skin carcinogenesis. A malignant skin keratinocyte cell line (308), which carries a H-ras mutation at codon 61, showed elevated p53 levels, increased caspase 3 activity and enhanced apoptosis after TPA treatment. In contrast, the non-malignant counterpart (C50) showed undetectable levels of p53 and less apoptosis than 308 cells similarly treated. Inhibition of NADPH-oxidase (NOX) by diphenyleneiodonium suppressed p53 activation and apoptosis in 308 cells, linking Ras mutation to NOX-induced p53 activation, which was further supported by the finding that siRNA to Rac1 inhibited p53 activation after TPA treatment. Application of DPI to DMBA-initiated skin tissue significantly blocked TPA-mediated increased p53 levels and reduced apoptosis in skin epidermal tissues. Taken together, our results suggest that NOX bridges oncogenic activation and p53 mitochondrial translocation to apoptosis in the multistage chemical-induced skin carcinogenesis model.
authors.affiliation: Graduate Center for Toxicology, University of Kentucky, Lexington, KY 40536, USA.
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Zhao
authors.forename: Luksana
authors.initials: L
authors.lastname: Chaiswing
authors.forename: Vasudevan
authors.initials: V
authors.lastname: Bakthavatchalu
authors.forename: Terry D
authors.initials: TD
authors.lastname: Oberley
authors.forename: Daret K
authors.initials: DK
authors.lastname: St Clair
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity; D000818:Animals; D017209:Apoptosis; D002273:Carcinogens / Q000633:toxicity; D002471:Cell Transformation, Neoplastic; D004791:Enzyme Inhibitors / Q000494:pharmacology; D011905:Genes, ras / Q000502:physiology*; D015603:Keratinocytes / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors; D009861:Onium Compounds / Q000494:pharmacology; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D012867:Skin / Q000378:metabolism*; D012878:Skin Neoplasms / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D013755:Tetradecanoylphorbol Acetate / Q000633:toxicity; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
chemical_list: D002273:Carcinogens; D004791:Enzyme Inhibitors; D009861:Onium Compounds; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; D015127:9,10-Dimethyl-1,2-benzanthracene; C007517:diphenyleneiodonium; D019255:NADPH Oxidases; D020830:rac1 GTP-Binding Protein; D013755:Tetradecanoylphorbol Acetate