ESR1 and breast carcinoma: Four breast cancer cell lines including MCF-7 (luminal A, ER+/PR+/HER2−), BT-474 (luminal B, ER+/PR+/HER2+), MDA-MB-231 (basal-like, ER−/PR−/HER2−), and SK-BR-3 (ER−/PR−/HER2+) were tested with CHCP at various dosages.