EP3 receptor is a prognostic factor in TA-MUC1-negative ovarian cancer

Prostaglandin-mediated inflammatory reactions play a major role in different cancers. Recently, it has been observed that prostaglandin E2-receptor 3 (EP3) might be an independent prognostic factor for overall survival in cervical and endometrial cancer. The role of EP3 expression in ovarian cancer is currently unknown.

EP3 expression was analyzed by immunohistochemistry in 156 patient samples using the IR-scoring system. Expression levels were correlated with clinical and pathological parameters and with overall survival (OS) to assess for prognostic relevance. Data analysis was performed using Spearman's correlations, Kruskal-Wallis test and Kaplan-Meier estimates.

EP3 expression was significantly higher in clear-cell carcinoma (p < 0.001) compared to the other histological subtypes. No further correlations with clinical parameters could be found. EP3 expression correlated significantly with FSH-receptor expression (p < 0.001), galectin-1 expression in the tumor (p = 0.012) and with cytoplasmatic TA-MUC1 expression (p = 0.001). None of these parameters showed significant correlation with OS. In the TA-MUC1 negative subgroup, EP3 negative patients showed significantly longer OS (median OS: 102 months vs. 34 months in EP3 positive patients, p = 0.035), while EP3 did not appear to have prognostic relevance in the TA-MUC1-positive subgroup.

The potential prognostic relevance of EP3 expression for OS in TA-MUC1 negative patients might reflect an interplay between the COX and the MUC1 pathway, as it has been shown that MUC1 could induce COX2 expression. Our findings support the importance of the prostanoid signaling in TA-MUC1 negative ovarian cancer; however, future studies are necessary to characterize specific pathways and possible interactions.