Effects of Isoflavones on Estrogen Receptor Mediated Estrogenicity and Aromatase Activity

Abstract

Phytoestrogens are plant derived estrogens that can have a estrogenic effect in humans. A number of women undergoing breast cancer treatment are taking phytoestrogens to relieve postmenopausal symptoms that are the result of breast cancer medication. In literature different effects of phytoestrogens on the Estrogen receptor and aromatase activity are described. These different effects could influence estrogen positive breast cancer, therefore it is important to make a risk assessment for these compounds. This thesis focuses on current literature surrounding a selection of isoflavone phytoestrogens and their relative potencies (REP) on the estrogen receptor (ant)agonism and aromatase interaction (inhibition/induction) in order to determine the most relevant mode of action with respect to estrogen-dependent breast cancer. Most information was available on the isoflavones genistein therefore, this was the main compound studied. Genistein exposure in vitro and in vivo results in ER mediated estrogenicity. Genistein is able to induce estrogen positive breast tumor proliferation in multiple in vivo and in vitro experiments. More research needs to be conducted on the effects of genistein on aromatase activity since results on the effect of genistein on aromatase are not conclusive.