Expression of Enhancer of zeste homolog 2 and Flotillin-1 in Serous Ovarian Carcinomas and their clinicopathological significance

Background: Ovarian cancer (OC) is the 7th most prevalent among women globally. High grade serous carcinoma (HGSC) is the commonest type accounting for 70% of cases. Low grade serous carcinoma (LGSC) represents 5-7% of OC. Enhancer of zeste homolog 2 (EZH2) is a regulator of tumorogenesis and metastasis. EZH2 inhibitors were tested in clinical trials. Flotillins are proteins in lipid rafts within plasma membranes. Flotillin-1 (FLOT-1) is often low in normal cells, however it is up-regulated in tumors. Methods: Immunohistochemical expression of EZH2 and FLOT-1 was examined in 105 cases of serous OC samples divided into 85 HGSC and 20 LGSC. Association between immunoreactivity and clinicopathological data was measured. Also, correlation between both markers in HGSC and LGSC was examined. Results: Positive EZH2 and FLOT-1immunoexpressio detected in (67.05% and 62% respectively) of HGS and in (60% and 55% respectively) of LGSC. In HGSC, a significant association was detected between EZH2 and age, FIGO stage, and LNM. Regarding FLOT-1, a significant association was found with laterality, tumor size, FIGO stage, LNM, and LVI. A significant positive correlation was detected between both markers in HGSC. Concerning LGSC cases a significant association between EZH2 immunoreactivity and laterality and FLOT-1 immunostaining with tumor size and LVI was observed. No significant correlation was found between markers immunoexpression in LGSC. Conclusions: The current study could highlight the molecular importance of EZH2 and FLOT-1 and their link to prognostic factors of HGSC. Also, it recommends the possible utility of EZH2 inhibitors as novel therapeutic strategies in OC.