PROSTAGLANDIN EP2 RECEPTOR PROMOTES VEGF EXPRESSION VIA THE EGFR AND ERK1/2 SIGNALLING PATHWAYS
KJ Sales, R Gallagher, S Maudsley & HN Jabbour
Prostaglandin (PG) E2 has been implicated in benign and neoplastic endometrial pathologies. PGE2 exerts its function by coupling to 4 subtypes of G protein coupled receptors (EP1-EP4). Recently a role for the EP2 receptor in angiogenesis has been established. This study investigated signal transduction and vascular endothelial growth factor (VEGF) expression by the EP2 receptor in Ishikawa endometrial epithelial cells. Ishikawa cells were stably transfected with EP2 cDNA in the sense or antisense directions. Stable transfectants were selected by quantitative RT-PCR and Western blot analysis and screened for functionality by measuring cAMP accumulation in response to 100nM PGE2. Intracellular signalling of the EP2 receptor was determined by measuring activation of extracellular regulated kinase (ERK1/2). Cells were treated with 100nM PGE2 in the presence or absence of inhibitors of epidermal growth factor receptor (EGFR) activation (AG1478) or ERK1/2 activation (PD98059). Finally the effect of EP2-PGE2 ligand-receptor interaction on expression of VEGF was determined by quantitative RT-PCR analysis and ELISA following treatment with 100nM PGE2, in the presence or absence of AG1478 and PD98059. Treatment of wild-type, sense and antisense cells with PGE2 caused a rapid activation of ERK1/2 signalling, which was elevated in sense cells compared with wild-type and antisense cells (P less than 0.05). Co-treatment of cells with AG1478 and PD98059 abolished ERK1/2 activation (P less than 0.01). VEGF expression was significantly elevated (P less than 0.01) in EP2 sense cells following treatment with 100nM PGE2 compared with wild-type and antisense cells. The elevation of expression of VEGF by PGE2 was significantly reduced following co-treatment of cells with AG1478 (P less than 0.01) and PD98059 (P less than 0.001). These data suggest that EP2 receptor may modulate endometrial angiogenesis by promoting the expression of pro-angiogenic factors such as VEGF, via activation of the EGFR and ERK1/2 signalling pathways.