Impact of lower concentrations of phytoestrogens on the effects of estradiol in breast cancer cells

Objective To explore the impact of lower concentrations of phytoestrogens on 17 beta-estradiol (E2) in the growth of MCF-7 breast cells. Methods MCF-7 cells were treated with E2 (10(-8) mol/l), one of three phytoestrogens (genistein, resveratrol, and quercetin) (10(-7) to 10(-5) mol/l), and with a combination of both E2 and one of these phytoestrogens for 48 h. These cells were then extracted for MTT and TUNEL assay. Western blot was utilized to evaluate the proteins involved in the proliferative and apoptotic pathways, as well as the differential effects on ER alpha and beta. Results MCF-7 cell proliferations were induced by both E2 alone and E2 plus one of the three phytoestrogens (at concentrations >= 10(-6) mol/l). Apoptotic cells were significantly increased in the phytoestrogen-treated MCF-7 cells and, conversely, suppressed in the cells treated with both E2 and phytoestrogens. Proliferating cell nuclear antigen, PI3K and p-Akt were increased in the cultures with E2 and substantially more in the cultures with E2 plus a phytoestrogen. The combination of E2 and phytoestrogen significantly inhibited the increase in FADD, cytochrome C, truncated Bid, caspase-9, caspase-3 and ER beta that was induced by phytoestrogens in the MCF-7. ER alpha expression was significantly induced by E2 regardless of the presence of these phytoestrogens. Conclusions This study demonstrates that, in the presence of E2, genistein, resveratrol, and quercetin may stimulate breast cancer cells, even at low physiological concentrations. Therefore, the conflicting results regarding the effects of phytoestrogens on breast cells may be attributed to the endogenous estrogen present in breast tissue.