With regards to ER-positive BC, which represents the most common type of BC, E2 promotes cancer cell growth by interacting with the estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ) [47]; moreover, drugs such as Tamoxifen, which antagonizes ER, are effective in blocking BC’s progression and increasing patients’ survival [48,49,50]. This evidence concerns the gene ESR2 and breast cancer.