ESR1 and breast cancer: Then, we examined the half maximal inhibitory concentrations (IC50) of FZU-0025-065 in five TNBC cell lines (HCC1806, HCC1937, MDA-MB-468, MDA-MB-231 and SUM-149PT), two ERα positive breast cancer cell lines (MCF-7 and T47D), two HER2 positive breast cancer cell lines (BT474 and SK-BR-3), and the human immortalized breast epithelial cell line 184B5.