Nuclear receptor co-repressor NCOR2 and its relation to GPER with prognostic impact in ovarian cancer

Purpose: The significance of the non-classical G-protein coupled estrogen receptor (GPER) as positive or negative prognostic factor for ovarian cancer patients remains still controversial. Recent results indicate that an imbalance of both co-factors and co-repressors of nuclear receptors regulate ovarian carcinogenesis by altering the transcriptional activity through chromatin remodeling. The present study aims to investigate whether the expression of the nuclear co-repressor NCOR2 plays a role in GPER signaling which thereby could positively impact overall survival rates of ovarian cancer patients. Methods NCOR2 expression was evaluated by immunohistochemistry in a cohort of 156 epithelial ovarian cancer (EOC) tumor samples and correlated to GPER expression. The correlation and differences in clinical and histopathological variables as well as their effect on prognosis was analyzed by Spearman´s correlation, Kruskal-Wallis-test and Kaplan-Meier-estimates. Results Histologic subtypes were associated with different NCOR2 expression patterns. More specifically, serous and mucinous EOC demonstrated a higher NCOR2 expression ( P  = 0.008). In addition, high nuclear NCOR2 expression correlated significantly with high GPER expression (cc = 0.245, P  = 0.008). A combined evaluation of both, high NCOR2 (IRS > 6) and high GPER (IRS > 8) expression revealed an association of a significantly improved overall survival (median OS 50.9 versus 105.1 months, P  = 0.048). Conclusion Our results support the hypothesis that nuclear co-repressors such as NCOR2 may influence the transcription of target genes in EOC such as GPER. Understanding the role of nuclear co-repressors on signaling pathways will allow a better understanding of the factors involved in prognosis and clinical outcome of EOC patients.