Expression of cyclooxygenase-2 in uterine endometrial cancer and anti-tumor effects of a selective COX-2 inhibitor

A role for cyclooxygenase-2 (COX-2) in the development and progression of various tumors has been identified. Selective COX-2 inhibitors produce anti-proliferative effects in various cancer cell lines that express COX-2. However, the mechanisms underlying anti-tumor effects are unclear. Furthermore, few studies have studied COX-2 expression in gynecological cancers, especially endometrial cancer. The current study had two goals. We investigated the correlation between COX-2 expression and clinicopathological factors of uterine endometrial cancer. We also investigated effects of treatment with etodolac, a selective COX-2 inhibitor, on the uterine endometrial cancer cell line TMG-L, which expresses COX-2. We conclusively confirmed expression of COX-2 mRNA and protein in endometrial cancer that exceeded levels of COX-2 seen in normal endometrium. However, no significant correlations were observed between COX-2 expression in endometrial cancer tumor samples and clinicopathological factors or disease-free survival rate of patients with endometrial cancer. Study of COX-2 inhibition of TMG-L cells showed that etodolac produced dose-dependent inhibition of cell proliferation through G1 phase cell-cycle arrest. Etodolac-induced cell-cycle arrest might be caused by increases in p53 and P21WAF1 protein expression. Production of basic-fibroblast growth factor (bFGF, a pro-angiogenesis factor) was inhibited by etodolac in a dose-dependent manner. Furthermore, telomerase activity was inhibited and expression of hTERT mRNA was significantly inhibited with etodolac, leading to the conclusion that anti-tumor effects of etodolac on TMG-L cells are due to inhibition of both angiogenesis and telomerase activity. These results strongly suggest that COX-2 inhibitors have potential as therapeutic (and possibly, chemopreventive) agents for endometrial cancers that overexpress COX-2.