Study On The Mechanism Of Celecoxib Induces Epithelial-mesenchymal Transition In Epithelial Ovarian Cancer Cells

Background Ovarian cancer (OC) has the highest mortality rate among all gynecological malignancies. Epithelial ovarian cancer (EOC) accounts for 90% of all ovarian cancers [1]. Despite advances in surgery and chemotherapy, the 5-year survival rate has remained approximately only 30%, which is due to diagnosis at the advanced stage [2]. It has been considered that the leading cause of relapse and death from patients with ovarian cancer is metastasis. Metastasisrelevant events, such as the omentum, peritoneum, diaphragm, and small bowel mesentery, have been confirmed that they are poor prognostic factors for EOC patients [3]. Hence, it is crucial for clarifying the relevant mechanism which prompts ovarian cancer metastasis.Compelling evidence suggested that inflammation has been implicated in cancer initiation and progression [4]. Cyclooxygenase-2 (COX-2), generated in inflammatory processes, is an inducible enzyme necessary for converting arachidonic acid into prostaglandin [5]. Studies indicated that COX-2 plays crucial roles in invasion, metastasis and epithelial-mesenchymal transition (EMT) in human epithelial tumors [6-8]. These findings supported the appealing strategy of applying Celecoxib, a selective inhibitor of COX-2, as an attractive compound for anticancer treatment. Several studies suggested that Celecoxib could evoke cell cycle arrest, apoptosis, and anti-angiogenesis [9]. Therefore, a number of clinical trials have been performed to inspect the effect of Celecoxib on the adjuvant therapy of cancers such as non-small cell lung cancer (NSCLC), colorectal cancer (CRC), and oral premalignant lesions, as well as in the treatment of EOC [10-13]. However, these trials demonstrated that using Celecoxib as adjuvant therapy failed to improve the prognosis of patients. Although a study on 45 recurrent patients with ovarian cancer treated with Celecoxib and carboplatin showed promising activity, another clinical trial on 151 patients with ovarian cancer who were treated with Celecoxib and docetaxel plus carboplatin showed no improvement in progression-free survival and overall survival [13,14]. The mechanisms of these controversial therapeutic effects of Celecoxib in ovarian cancer remain to be investigated.Purpose The purpose of our study was to investigate the therapeutic potential of Celecoxib for epithelial ovarian cancer (EOC), especially on cellular morphological changes, proliferation, invasion and epithelial-mesenchymal transition (EMT).Method The MTT and transwell assays were performed to evaluate the effect of Celecoxib on proliferation and invasion ability of ovarian cancer cell lines, respectively. Western blot was carried out to detect protein the expression of epithelial phenotypes, E-cadherin and Keratin, and mesenchymal phenotypes, N-cadherin and Vimentin, as well as p-AKT, p-ERK and ZEB1. ZEB1 small-interfering RNA (siRNA) was used to downregulation the expression of ZEB1 to further inquiring into the downstream of Celecoxib-induced EMT.Results Cellular morphological assessment revealed that both A2780 and SKOV3 cells gradually appeared the fibroblast-like morphology of mesenchymal cells after Celecoxib treatment. The MTT assay demonstrated that celecoxib had no effect on cell proliferation. Tranwell assay showed that Celecoxib significantly increased the cell invasion ability. Western blot data proved that the expression of E-cadherin and keratin was elevated, whereas the expression of N-cadherin and Vimentin was decreased in a dose-dependent manner compared with the untreated cells, the expression of p-AKT, p-ERK and ZEB1 were also obviously elevated. However, ZEB1 siRNA inhibited Celecoxib-induced E-cadherin expression and N-cadherin expression, as well as cellular invasiveness.Conclusion Celecoxib induced EMT and upregulated an EMT-related transcription factor, ZEB1. Downregulation of ZEB1 reversed Celecoxib-induced EMT and cellular invasiveness. Our experiments suggested that Celecoxib could act in part through a mechanism involving ZEB1 upregulation in ovarian cancer cells, which also implied that it needed a comprehensive evaluation in preclinical researches before introducing Celecoxib into the clinical regimen.