title: Insulin-like growth factor-I induces cyclooxygenase-2 expression via PI3K, MAPK and PKC signaling pathways in human ovarian cancer cells.
abstract: Elevated levels of insulin-like growth factor-I (IGF-I) are associated with ovarian carcinogenesis and progression. However, the molecular mechanisms by which IGF-I contributes to ovarian cancer development remain to be elucidated. Cyclooxygenase-2 (COX-2) is a crucial player in the pathogenesis of human malignancies. Herein we showed that IGF-I efficiently induced COX-2 expression and PGE(2) biosynthesis at physiologically relevant concentrations in human ovarian cancer cells. IGF-I treatment significantly increased COX-2 transcriptional activation. IGF-I also stabilized COX-2 mRNA through the COX-2 3'-untranslated region (3'-UTR), which appeared independent of the conserved AU-rich elements. We next investigated the signaling pathways involved in IGF-I-induced COX-2 expression. We found that PI3K inhibitor wortmannin or LY294002 blocked COX-2 expression induced by IGF-I. Wortmannin treatment or a dominant negative PI3K mutant significantly inhibited IGF-I-induced COX-2 mRNA stabilization, but only slightly decreased COX-2 transcriptional activation. We showed that ERK1/2 and p38 MAPKs were required for IGF-I-induced COX-2 expression and that activation of both pathways by IGF-I increased COX-2 transcriptional activation and its mRNA stability. IGF-I stimulated PKC activation in the cells and pretreatment with PKC inhibitor bisindolylmaleimide prevented IGF-I-induced COX-2 transcriptional activation and mRNA stabilization, and inhibited COX-2 mRNA and protein expression. Taken together, our data demonstrate that IGF-I induces COX-2 expression in human ovarian cancer cells, which is mediated by three parallel signaling cascades--PI3K, MAPK, and PKC pathways that differentially regulate COX-2 expression at transcriptional and post-transcriptional levels.
authors.affiliation: Mary Babb Randolph Cancer Center, Department of Microbiology, Immunology and Cell Biology, West Virginia University, Morgantown, WV 26506-9300, USA.
authors.forename: Zongxian
authors.initials: Z
authors.lastname: Cao
authors.forename: Ling-Zhi
authors.initials: LZ
authors.lastname: Liu
authors.forename: Dan A
authors.initials: DA
authors.lastname: Dixon
authors.forename: Jenny Z
authors.initials: JZ
authors.lastname: Zheng
authors.forename: Bala
authors.initials: B
authors.lastname: Chandran
authors.forename: Bing-Hua
authors.initials: BH
authors.lastname: Jiang
mesh_terms: D051546:Cyclooxygenase 2 / Q000096:biosynthesis* / Q000235:genetics; D015232:Dinoprostone / Q000096:biosynthesis; D004789:Enzyme Activation / Q000187:drug effects; D004790:Enzyme Induction / Q000187:drug effects; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D008954:Models, Biological; D010051:Ovarian Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D020871:RNA Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D015533:Transcriptional Activation / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D051546:Cyclooxygenase 2; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D015232:Dinoprostone