COX-2 inhibition by celecoxib in epithelial ovarian cancer attenuates E-cadherin suppression through reduced Snail nuclear translocation

Elevated cyclooxygenase-2 (COX-2) closely associates with tumor progression and distant metastasis in various human cancers. However, the role of COX-2 in epithelial ovarian cancer (EOC), and its mechanistic details, remain poorly understood. In the present study, we tested hypothesis that COX-2 induces loss of expression of E-cadherin, with resulting promotion of cancer cells' invasiveness in ovarian cancer. First, we observed an inverse relationship between COX-2 and E-cadherin expression as COX-2 was enhanced but E-cadherin was decreased in surgically-resected specimens of EOC. Depletion of COX-2, by celecoxib treatment, resulted in attenuated nuclear translocation of Snail, and, in turn, significantly increased E-cadherin in EOC cell line SKOV3, which was established to be due to the reduced binding of Snail onto E-cadherin promoter. Such COX-2 inhibition resulted in reduced invasion of EOC cells, similar to what was achieved through Snail silencing in SKOV as well as ES-2 EOC cells. These results suggest that COX-2-Snail signaling plays a critical role in regulation of E-cadherin and might provide insights into mechanisms for paracrine inflammation-mediated aggressiveness in EOC.