In the treatment of breast cancer, Tamoxifen, which is a selective estrogen-receptor modulator (SERM),56 is currently used for the treatment of both early and advanced estrogen receptor-positive breast cancer in pre- and post-menopausal women.57 Unfortunately, up to half of ERα-positive tumors have intrinsic or acquired endocrine therapy resistance.58 Here, ESR1 is linked to breast carcinoma.