ESR1 and breast cancer: Here we have shown that the estrogen receptor agonist E2, which is the most prevalent estrogen in premenopausal women, functions as a potent stimulator of the expression of the PUFA elongases Elovl2 and Elovl5 but not the desaturases Fads1 and Fads2 in the human breast cancer cell line MCF7 and that the elevated expression was sustained for more than 24 hours.