Prostaglandin E 2 receptor EP1 phosphorylate CREB and mediates MMP2 expression in human cholangiocarcinoma cells

Cyclooxygenase-2 (COX-2) and COX-2-induced prostaglandin E 2 (PGE 2 ) have been implicated in all stages of malignant tumorigenesis. Although many aspects of matrix metalloproteinase (MMP2) on tumor invasion have been studied, the exact mechanism of PGE 2 -induced MMP2 overproduction has not been clearly defined. We have previously demonstrated that PGE 2 -enhanced extracellular signal-regulated kinase (Erk) phosphorylation via EP1 signaling pathway involved in PGE 2 -induced cell proliferation. Based on the identification of the transcription factor cyclic AMP response element-binding protein (CREB) as an important regulator of MMP2 and Erk phosphorylate CREB at ser133, we hypothesize that CREB may be implicated in the signaling of PGE 2 stimulation to MMP2 overproduction via EP1 receptor. In the study, we investigated the role of EP1 receptor on PGE 2 -induced MMP2 expression and delineated the signaling pathway that contributes to EP1 receptor modulation of MMP2 in human cholangiocarcinoma cells. We found PGE 2 or selective EP1 receptor agonist 17-P-T-PGE 2 -stimulated MMP2 expression and selective EP1 receptor antagonist SC-51322 or EP1 receptor siRNA abrogated PGE 2 -induced MMP2 expression. Intracellular calcium chelator BAPTA-AM, the selective inhibitor of EGFR AG1478 and the selective inhibitor of Erk PD98059 blocked EP1 receptor activation-induced CREB phosphorylation and MMP2 expression. A novel dominant-negative (D-N) inhibitor protein of the CREB, termed A-CREB, attenuated EP1 receptor activation-induced MMP2 expression. Our findings suggest that PGE2-enhanced MMP2 expression is, at least in part, mediated through EP1 receptors and calcium signaling pathway-induced CREB phosphorylation in human cholangiocarcinoma cells.