Abstract 5047: Role of estrogen receptors alpha and beta in the balance between proliferation and surveillance

Abstract

Abstract Estrogens have paradoxical effects in both promoting and preventing breast cancer. The proliferative actions of estrogens promote the expansion of both normal mammary epithelium and breast cancer. But estrogen also activates p53-mediated surveillance and apoptotic pathways to eliminate cells with potential oncogenic mutations. This is exemplified by tumor regression in response to high dose estrogen-treatment in postmenopausal breast cancer. Estrogens mediate their effects through the activation of two estrogen receptor subtypes: Estrogen Receptor alpha (ERα)and Estrogen Receptor beta (ERβ). Our objective is to examine the contribution of these receptors in mediating surveillance as opposed to proliferation by comparing selective estrogen receptor agonists with 17β-estradiol (E2) for induction of proliferation and surveillance in three model systems: (1) in vivo mouse model, (2) in vitro MCF7-tet-off-ERβ model, and (3) an ex-vivo human mammary explant model. Selective activation of ERβ with the agonist diarylpropionitrile (DPN) in vivo enhances p53-mediated apoptosis in the mouse mammary epithelium without stimulating proliferation. In addition, radiation-induced apoptosis is significantly reduced in mice lacking ERβ (βERKO). E2 or the ERα selective agonist pyrazole triol (PPT) induced the expression of estrogen response genes including progesterone receptor and amphiregulin in all three models. DPN-mediated activation of ERβ failed to induce the expression of these genes. The ERβ agonist DPN selectively induced the expression of genes that repress proliferation including TGFβ and inhibitors of canonical WNT signaling, WNT5a and AXIN2. DPN was also more potent in stimulating EGR1, a modulator of p53 activity, and CEBPd, a pro-apoptotic gene. Conclusions: The ability of DPN and ERβ to potentiate surveillance pathways while limiting proliferation suggests that ERβ agonists may provide a new approach for chemoprevention of breast cancer. Citation Format: D. Joseph Jerry, Karen A. Dunphy, Amy L. Roberts, Margarita Brown. Role of estrogen receptors alpha and beta in the balance between proliferation and surveillance. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5047. doi:10.1158/1538-7445.AM2015-5047