Interestingly, recent in vitro studies indicate that carotenoids and retinol also exert a beneficial role in the prevention of estrogen receptor (ER)-positive cancers, such as mammary and endometrial [5,6,7,8,9,10,11], through the inhibition of either the activity of 17 β-estradiol (E2 or aromatase enzyme. The gene discussed is ESR1; the disease is cancer.