Elevated prostaglandin EP2 receptor in endometrial adenocarcinoma cells promotes vascular endothelial growth factor expression via cyclic 3',5'-adenosine monophosphate-mediated transactivation of the epidermal growth factor receptor and extracellular signal-regulated kinase 1/2 signaling pathways.

Prostaglandin (PG) E(2) E-series prostanoid-2 (EP2) receptor is elevated in numerous carcinomas including the endometrium and has been implicated in mediating the effects of PGE(2) on vascular function. In this study, we investigated the intracellular signaling pathways that are activated by the EP2 receptor and their role in regulation of the expression of vascular endothelial growth factor in endometrial adenocarcinoma (Ishikawa) cells. Ishikawa cells were stably transfected with EP2 receptor cDNA in the sense or antisense directions. Treatment of Ishikawa cells with PGE(2) rapidly induced transactivation of the epidermal growth factor receptor (EGFR) and activation of ERK1/2 via the EP2 receptor. Preincubation of cells with chemical inhibitors of protein kinase A, c-Src, and EGFR kinase abolished the EP2-induced activation of EGFR and ERK1/2. PGE(2) signaling via the EP2 receptor also promoted the mRNA expression and secretion of vascular endothelial growth factor protein in Ishikawa cells. This effect was inhibited by preincubation with chemical inhibitors of EGFR kinase, ERK1/2 signaling, and small inhibitory RNA molecules targeted against the EGFR. Therefore, we have demonstrated that elevated EP2 receptor expression may facilitate the PGE(2)-induced release of proangiogenic factors in reproductive tumor cells via intracellular cAMP-mediated transactivation of the EGFR and ERK1/2 pathways.