title: p38 MAPK activation selectively induces cell death in K-ras-mutated human colon cancer cells through regulation of vitamin D receptor.
abstract: Ras is the most characterized oncogene in human cancer, and yet there are no effective therapeutics to selectively target this oncogene. Our previous work demonstrated the inhibitory activity of the p38 pathway in Ras proliferative signaling in experimental NIH 3T3 cells (Chen, G., Hitomi, M., Han, J., and Stacey, D. W. (2000) J. Biol. Chem. 275, 38973-38980). Here we explore the therapeutic potential of p38 kinase activation in human colon cancer cells with and without endogenous K-ras activation. p38 activation by both adenovirus-mediated gene delivery of constitutively active p38 activator MKK6 and by arsenite selectively induces cell death in K-ras-activated human colon cancer HCT116 cells but not in the K-ras-disrupted HCT116-derived sublines. The cell death-inducing effect of MKK6 is not because of its selective activation of p38 kinase or its downstream transcription factor substrates, ATF-2 or c-Jun, in K-ras-activated cells. Rather, cell death in K-ras-activated cells is linked to the down-regulation of vitamin D receptor (VDR) by an AP-1-dependent mechanism. Forced VDR expression in K-ras-activated cells inhibits p38 activation-induced cell death, and inhibition of endogenous VDR protein expression in K-ras-disrupted cells increased the arsenite-induced toxicity. Analysis of an additional two human colon cancer cell lines with and without K-ras mutation also showed a K-ras- and VDR-dependent toxicity of MKK6. Hence, p38 pathway activation selectively induces cell death in K-ras-mutated human colon cancer cells by mechanisms involving the suppression of VDR activity.
authors.affiliation: Department of Radiation Oncology, Loyola University of Chicago, Maywood, IL 60153, USA.
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Qi
authors.forename: Jun
authors.initials: J
authors.lastname: Tang
authors.forename: Rocky
authors.initials: R
authors.lastname: Pramanik
authors.forename: Richard M
authors.initials: RM
authors.lastname: Schultz
authors.forename: Senji
authors.initials: S
authors.lastname: Shirasawa
authors.forename: Takehiko
authors.initials: T
authors.lastname: Sasazuki
authors.forename: Jiahuai
authors.initials: J
authors.lastname: Han
authors.forename: Guan
authors.initials: G
authors.lastname: Chen
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D018053:Arsenites / Q000378:metabolism; D015153:Blotting, Western; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D016923:Cell Death; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000235:genetics*; D018076:DNA, Complementary / Q000378:metabolism; D015536:Down-Regulation; D004789:Enzyme Activation; D015972:Gene Expression Regulation, Neoplastic; D011905:Genes, ras; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D048669:MAP Kinase Kinase 6; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000378:metabolism*; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D018053:Arsenites; D018076:DNA, Complementary; D034741:RNA, Small Interfering; D018167:Receptors, Calcitriol; D018808:Transcription Factor AP-1; D008156:Luciferases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048669:MAP Kinase Kinase 6; C482566:MAP2K6 protein, human; C015001:arsenite