title: Activated Ki-Ras suppresses 12-O-tetradecanoylphorbol-13-acetate-induced activation of the c-Jun NH2-terminal kinase pathway in human colon cancer cells.
abstract: Although the frequency of activated Ki-ras genes is high in human colorectal tumors, much less is known of activated Ki-ras-mediated signaling pathways. Using gene targeting, we examined HCT116 cells that contain the Gly-13-->Asp mutation of Ki-ras and activated Ki-ras-disrupted clones derived from HCT116. 12-O-Tetradecanoylphorbol-13-acetate (TPA) induced immediate early genes, such as c-Jun, c-Fos, and Egr-1 in activated Ki-ras-disrupted clones, whereas c-Jun induction was rare in HCT116. TPA induced both phosphorylation of stress-activated protein kinase kinase 1 (SEK1) and c-Jun NH2-terminal kinase (JNK) in the activated Ki-ras-disrupted clones but not in HCT116. On the other hand, TPA-induced mitogen-activated protein kinase kinase 1/2 (MEK1/2)-extracellular signal-regulated kinase (ERK) activation was equally induced between HCT116 and the Ki-ras-disrupted clones. Furthermore, TPA-induced SEK1-JNK activation was observed in a DLD-1-derived activated Ki-ras-disrupted clone but not in DLD-1. The TPA-induced SEK1-JNK activation in these disrupted clones was completely inhibited by the protein kinase C (PKC) inhibitor, GF109203X (1 microM), but not by another PKC inhibitor, H7 (50 microM), whereas TPA-induced MEK1/2-ERK activation was partially and completely inhibited by GF109203X (1 microM) and H7 (50 microM), respectively. A phosphoinositol 3-kinase inhibitor, LY294002, did not inhibit the TPA-induced SEK1-JNK activation. Taken together, these results suggest that activated Ki-Ras-mediated signals are involved in the SEK1-JNK pathway through a PKC isotype that is distinct from that involved in MEK1/2-ERK activation in human colon cancer cells and independent of phosphoinositol 3-kinase activation, and the imbalance between ERK and JNK activity caused by activated Ki-Ras may play critical roles in human colorectal tumorigenesis.
authors.affiliation: Department of Genetics, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Okumura
authors.forename: S
authors.initials: S
authors.lastname: Shirasawa
authors.forename: M
authors.initials: M
authors.lastname: Nishioka
authors.forename: T
authors.initials: T
authors.lastname: Sasazuki
mesh_terms: D000483:Alleles; D019943:Amino Acid Substitution; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002867:Chromones / Q000494:pharmacology; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D003864:Depression, Chemical; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D017781:Genes, Immediate-Early; D011905:Genes, ras; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000502:physiology; D048031:JNK Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D048670:MAP Kinase Kinase 4; D048728:MAP Kinase Kinase Kinase 1; D008301:Maleimides / Q000494:pharmacology; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D009025:Morpholines / Q000494:pharmacology; D020125:Mutation, Missense; D009363:Neoplasm Proteins / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D020033:Protein Isoforms / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D011494:Protein Kinases / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002867:Chromones; D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D007211:Indoles; D007527:Isoenzymes; D048031:JNK Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D048670:MAP Kinase Kinase 4; D048728:MAP Kinase Kinase Kinase 1; D008301:Maleimides; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D009025:Morpholines; D009363:Neoplasm Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D020033:Protein Isoforms; D011493:Protein Kinase C; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D016283:Proto-Oncogene Proteins p21(ras); D013755:Tetradecanoylphorbol Acetate; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C482128:MAP2K2 protein, human; C482576:MAP3K1 protein, human; C482125:MAP2K1 protein, human; C482559:MAP2K4 protein, human; C501009:HRAS protein, human; C070515:bisindolylmaleimide I