activation of ER by soy phytoestrogens
 

Stimulatory effect of genistein and apigenin on the growth of breast cancer cells correlates with their ability to activate ER alpha [Breast Cancer Research and Treatment]
Genistein and apigenin are phytoestrogens present in commercial preparations used for the treatment of postmenopausal symptoms. In this study, we assessed the influence of these compounds on mammary tumor growth. Both compounds stimulate the proliferation of MCF-7 and T47D cells [estrogen receptor alpha (ER?-positive)], but do not stimulate the proliferation of an ER?-negative cell line (MDA-MB-435 cells). Genistein appeared more efficient in this regard due to its higher binding affinity for ER?, a property explained by a structural analysis of the binding of these compounds to the ER?'s ligand binding domain. As previously described for estradiol (E2), genistein and apigenin down regulated ER? and enhanced estrogen response element (ERE)-dependent gene expression. The additional finding that genistein antagonizes the anti-proliferative effect of hydroxytamoxifen suggests phytoestrogens may be detrimental in women with breast cancer who are being treated with tamoxifen. In addition, because of their ability to stimulate breast cell growth, the widespread use of phytoestrogens in postmenopausal women could be detrimental.

Great Post !
 

Thanks for that data Lani. Mom is ER/PR negative, but I have always lost sleep thinking about the potential negative effects of naturally occuring estrogens in food and supplements for all of you that are ER+ and receiving Tamoxifen or other estrogen inhibitors. It would be a shame for women to take those drugs daily, and be shooting themselves in the foot at the same time by taking phytoestrogens in an attempt to improve their health.

It is also comforting to know that Mom's ER- BC won't be aggravated or provoked into jumping ship to an estrogen positive status. Thanks again for all of your hard work at providing the many informative posts every week.

Sincerely,
Tom