Importantly, the ER-negative MDA-MB-231, MDA-MB-453, and MDA-MB-468 breast cancer cell lines are sensitive to the cytotoxic effects of tamoxifen [29], and a previous study demonstrated that miR-17/20 enhanced tamoxifen-induced, ERα-mediated apoptosis [30]. The gene discussed is ESR1; the disease is breast carcinoma.