title: Cyclooxygenase-2-derived prostaglandin E2 activates beta-catenin in human cholangiocarcinoma cells: evidence for inhibition of these signaling pathways by omega 3 polyunsaturated fatty acids.
abstract: Cholangiocarcinoma is a highly malignant neoplasm of the biliary tree. It has a high rate of mortality, and currently, there is no effective chemoprevention and treatment. This study was designed to investigate the potential effect of omega 3 polyunsaturated fatty acids (omega 3-PUFA) on human cholangiocarcinoma cell growth and to determine their mechanisms of actions. Treatment of three human cholangiocarcinoma cells (CCLP1, HuCCT1, SG231) with two omega 3-PUFAs, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), for 12 to 72 h resulted in a dose- and time-dependent inhibition of cell growth; in contrast, arachidonic acid, a omega 6-PUFA, had no significant effect. The omega 3-PUFA effect is due to the induction of apoptosis, given that DHA induced the cleaved form of PARP, caspase-3, and caspase-9. DHA and EPA treatment caused dephosphorylation (and hence, the activation) of glycogen synthase kinase-3beta (GSK-3beta) with a decline of beta-catenin protein. Accordingly, DHA treatment also decreased the beta-catenin-mediated T cell factor/lymphoid enhancer factor (TCF/LEF) reporter activity, and inhibited the expression of c-Met, a beta-catenin-controlled downstream gene implicated in cholangiocarcinogenesis. The GSK-3beta inhibitor, SB216763, partially prevented DHA-induced reduction of beta-catenin protein and TCF/LEF reporter activity, and restored cell growth, suggesting the involvement of GSK-3beta dephosphorylation in omega 3-PUFA-induced beta-catenin degradation. In parallel, DHA treatment also induced the formation of the beta-catenin/Axin/GSK-3beta binding complex, further leading to beta-catenin degradation. Moreover, DHA inhibited the expression of cyclooxygenase-2 (COX-2) and enhanced the expression of 15-hydroxyprostaglandin dehydrogenase, a physiologic COX-2 antagonist, in human cholangiocarcinoma cells. These findings suggest that omega 3-PUFAs block cholangiocarcinoma cell growth at least in part through inhibition of Wnt/beta-catenin and COX-2 signaling pathways. Thus, utilization of omega 3-PUFAs may represent an effective and safe therapeutic approach for the chemoprevention and treatment of human cholangiocarcinoma.
authors.affiliation: Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Kyu
authors.initials: K
authors.lastname: Lim
authors.forename: Chang
authors.initials: C
authors.lastname: Han
authors.forename: Lihong
authors.initials: L
authors.lastname: Xu
authors.forename: Kumiko
authors.initials: K
authors.lastname: Isse
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Demetris
authors.forename: Tong
authors.initials: T
authors.lastname: Wu
mesh_terms: D000818:Animals; D001650:Bile Duct Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D001653:Bile Ducts, Intrahepatic / Q000378:metabolism* / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D018281:Cholangiocarcinoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D015232:Dinoprostone / Q000378:metabolism / Q000502:physiology*; D004281:Docosahexaenoic Acids / Q000494:pharmacology; D015525:Fatty Acids, Omega-3 / Q000494:pharmacology*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D015525:Fatty Acids, Omega-3; D051176:beta Catenin; D004281:Docosahexaenoic Acids; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011065:Poly(ADP-ribose) Polymerases; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3; D020169:Caspases; D015232:Dinoprostone