Expression, localization, and signaling of prostaglandin F2 alpha receptor in human endometrial adenocarcinoma: regulation of proliferation by activation of the epidermal growth factor receptor and mitogen-activated protein kinase signaling pathways.

Prostaglandin F(2 alpha)(PGF(2 alpha)) is a bioactive lipid biosynthesized by cyclooxygenase (COX) enzymes and mediates its biological activity via the heptahelical G(q)-coupled PGF(2 alpha)receptor (FP receptor). This study investigated the expression and molecular signaling of the FP receptor in human endometrial adenocarcinomas. Real-time RT-PCR and Western blot analysis confirmed FP receptor expression in endometrial adenocarcinoma of all grades and differentiation. The expression of FP receptor was up-regulated in all endometrial adenocarcinomas compared with normal endometrium. The site of FP receptor expression was localized by in situ hybridization and immunohistochemistry to the neoplastic epithelial cells in all adenocarcinomas. Treatment of endometrial adenocarcinoma explants with PGF(2 alpha) resulted in mobilization of inositol phosphate signaling, indicating functional FP receptor expression. We investigated whether PGF(2 alpha) could trans-activate the epidermal growth factor receptor (EGFR) and trigger the MAPK signaling pathway. Treatment of adenocarcinoma explants and endometrial adenocarcinoma cells (Ishikawa) with PGF(2 alpha)-phosphorylated EGFR, triggered MAPK signaling and enhanced the proliferation of Ishikawa cells. Inactivation of phospholipase C, EGFR kinase, and MAPK kinase with specific inhibitors abolished PGF(2 alpha)-induced trans-activation of EGFR, MAPK signaling, and Ishikawa cell proliferation. These data suggest that PGF(2 alpha)-FP receptor promote endometrial tumorigenesis via a phospholipase C-mediated phosphorylation of the EGFR and MAPK signaling pathways.