ESR1 and breast cancer: Combining our computational and experimental analysis, together with previous studies in the literature, we suggest TACSTD2 could be an attractive candidate for drug therapy against both ER+ and ER- subtypes, including possibly the triple negative (ER-, PR- (progesterone receptor) and HER2-) subtype of breast cancer, and finally with potential implications for treating drug-resistant cases that are non-responsive to ER/HER2-targeted therapies.