cPLA2, COX-2 and PPAR-gamma in Cholangiocarcinoma

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DESCRIPTION (provided by applicant): Cholangiocarcinomas are highly malignant epithelial neoplasms of the biliary tree with a high rate of mortality. The exact molecular mechanism of cholangiocarcinogenesis is not completely defined and currently there is no effective treatment or chemoprevention. On the basis of published data from our laboratory and new preliminary findings, we hypothesize that the cytosolic phospholipase A2 (cPLA2) and cyclooxygenase-2 (COX-2)-controlled prostaglandin (PG) promotes cholangiocarcinoma growth through activation of EP1 receptor and Akt. Thus, interruption of these growth-promoting PG signaling pathways may provide promising potential therapeutic targets for the chemoprevention and treatment of human cholangiocarcinoma. This application proposes three interrelated specific aims to examine the above hypotheses using cultured primary and neoplastic biliary epithelial cells, experimental animal models and evaluation of human tissues. Aim I will examine the hypothesis that the cPLA2 and COX-2 are two rate-limiting key enzymes that mediate PG production and biliary mitogen HGF and IL-6-induced cell proliferation and invasion. Aim II is proposed to evaluate the hypothesis that PG and PPARgamma coordinately modulate cholangiocarcinogenesis and simultaneous targeting of COX-2 and PPARgamma is a novel therapeutic strategy for the chemoprevention and treatment of human cholangiocarcinoma. The mechanisms for their actions will be examined in detail, with the expectation that the cPLA2 and COX-2-controlled PGE2 promotes cell growth via EP1 receptor-mediated Akt activation, whereas PPARgamma ligands prevent growth through induction of p53/p21/GADD45 and inhibition of COX-2/PGE2 signaling. Aim III will examine the expression and phosphorylation of cPLA2, COX-2, PPARgamma and their downstream signaling molecules in human cholangiocarcinoma and pre-cancerous tissues. The proposed studies will help understand the pathobiological functions and molecular mechanisms of cPLA2 and COX-2-controlled PG metabolism in cholangiocarcinoma growth and provide important therapeutic implications.