ESR1 and breast carcinoma: Clinically, breast cancer hormone replacement therapy (HRT) is based on ER as a treatment index (Larionov and Miller, 2009), such as tamoxifen and fulvestrant which are ER-targeted drugs for the treatment of breast cancer (William and Kilian, 2016; Li et al., 2018), but there are problems such as large adverse reactions and insignificant therapeutic effects (Zhou et al., 2021).