ESR1 and breast cancer: Because we previously demonstrated that OU induces ERα degradation in cell lines modeling LumA primary (i.e., MCF-7 and ZR-75-1) and metastatic BC (i.e., MCF-7 Tam Res and expressing the Y537S receptor mutant) [4], the effect of OU on the regulation of the receptor in BT-474 cells was next evaluated.