While blocking ERα, such as with tamoxifen, as a general strategy has been proved to be effective in treatment of roughly 50% of the breast cancers for a period of time (26, 54), we wonder whether the opposite may also work, i.e. shifting the ERα expression from some harmful, probably some smaller, isoforms to a salubrious one (probably the canonical uterine wt form or the lactating specific wt form). This evidence concerns the gene ESR1 and breast cancer.