ESR1 and breast cancer: Biological evaluation showed promising anticancer activity across both tested breast cancer cell lines, with greater potency generally observed against ER-α-positive MCF-7 cells (average IC50 = 11.5 μM; average LE = 0.207) as compared to the triple-negative MDA-MB-231 line (average IC50 = 20 μM; average LE = 0.197).