Abstract
Resistance to chemotherapy is a major problem facing breast cancer patients. Cisplatin, a highly effective DNA-damaging drug, has shown only little success in breast cancer treatment. We are reporting that low nanomolar doses of bisphenol A (BPA) or estradiol antagonize cisplatin cytotoxicity in breast cancer cells, with their effects not mediated via classical estrogen receptors. Although both compounds increase the expression of Bcl-2, a Bcl-2 inhibitor completely blocked the protective effects of BPA while only partially affecting those of estradiol. Blockade of BPA and E2 actions should sensitize ER-negative breast tumors to anti-cancer drugs and allow for the inclusion of cisplatin in treatment regimens.