ESR1 and breast cancer: To assess the relevance of these findings in breastcancer cells, we conducted in vitro experiments using TNBC cells.We used MDA-MB-231 (human TNBC cells), 4T1 (murine TNBC cells), andMCF-7 (human ER+, PR+, and HER2-breast cancer cells) cells to determinethe effects of Dox and ActD alone on cell viability and compared themto other commonly used chemotherapy drugs.