ESR1 and breast cancer: The rat model of dimethylbenzanthracene or methylnitrosourea (MNU) induced breast cancer has been employed in the development of new chemopreventive agents, which is highly responsive to a number of regimens that are both hormone related (selective estrogen receptor modulators (SERM), aromatase inhibitors, ovariectomy) [1,2,3] and non-hormone related (agonists for the retinoid X receptor) [4,5].