Cyclooxygenase-2 (COX-2), known to be elevated in several human cancers, regulates angiogenesis by inducing production of angiogenic factors. These mechanisms require clarification in endometrial cancer. COX-2 expression was examined by immunohistochemistry and reverse-transcription polymerase chain reaction (RT-PCR) in endometrial cancer, endometrial hyperplasia, and normal endometrium in various phases. We investigated the relationship between COX-2 expression and clinicopathologic variables, microvessel count, and expression of vascular endothelial growth factor (VEGF) and thymidine phosphorylase (TP). Immunohistochemistry demonstrated COX-2 protein in cancerous epithelial cells but not in stromal cells. COX-2 expression in epithelial cells was significantly greater in endometrial cancer (n = 63) and endometrial hyperplasia (n = 6) than in normal endometrium in any phase (n = 53). Although COX-2 did not correlate with any conventional clinicopathologic factor in patients with endometrial cancer, COX-2 expression was associated with high microvessel count, VEGF expression, and TP expression. By combined analysis of COX-2, VEGF, and TP, tumors with high expression of at least one factor had a significantly higher microvessel count than tumors expressing little of the three factors. We confirmed upregulation of COX-2 mRNA expression by RT-PCR in endometrial cancer (n = 17) compared to normal endometrium (n = 12). COX-2 mRNA expression significantly correlated with VEGF mRNA expression in these tumors. COX-2 is upregulated in endometrial cancer and facilitates tumor growth via angiogenesis produced in associated with VEGF and TP. Specific inhibition of COX-2 may be a useful therapeutic intervention in endometrial cancer.

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