ESR1 and breast carcinoma: Various studies have reported that BAP1 acts as a tumor suppressor by binding BRCA1 in breast cancer13 and BAP1 cancer syndrome, in which metastatic breast cancer develops with loss of BAP1 protein expression.29 This results suggest that the overexpression of BAP1 in breast cancer is involved in the transcriptional regulation of ER by stabilizing the Med1 protein.