ABCC4 and ovarian endometriosis: Western blotting for MRP4 and β-catenin in ectopic endometrial lesions collected from total 19 women diagnosed of ovarian endometriosis (clinical data shown in Table 1) revealed a significant correlation of protein levels between MRP4 and total β-catenin (r = 0.7173, p = 0.0005) or active β-catenin (r = 0.5528, p = 0.0141) (Figure 6A).