CYP1B1 and breast carcinoma: Although we did not find any significant changes in CYP11A1 and CYP1B1 expression in the breast tissue of the metformin-treated group, it has been reported that metformin is able to directly reduce the protein levels of CYP11A1 in the ovary granulosa cells83 and CYP1B1 in breast cancer cells84.