ID: 82: DISTINCT ACTIONS OF ERα AND ERβ IN HUMAN PROSTATE STEM AND PROGENITOR CELL SELF-RENEWAL AND DIFFERENTIATION

Estrogens are implicated in prostate development and cancer, while stem cells are essential in tissue homeostasis and carcinogenesis. We have previously demonstrated that estradiol-17β (E 2 ) treatment augments prostaspheres (PS) number and size, implicating them as direct estrogen targets. The present studies sought to elucidate specific roles for ERα and ERβ in prostate stem and progenitor cells. Prostate stem-progenitor cells were identified and isolated from normal primary prostate epithelial cells (PrEC) using long term BrdU retention in 3-D PS culture. FACS analyses (BrdU/ERα or ERβ) showed prostate stem and progenitor populations were both ERα + and ERβ + . BrdU-retaining stem cells expressed high levels of ERβ and lower ERα as compared to non-label-retaining progenitor cells, suggesting ERβ dominance in the prostate stem cell. Estradiol increased BrdU-retaining cell numbers by enhancing stem cell self-renewal through symmetric division. While ERα siRNA blocked the E 2 -stimulated BrdU-retaining cells, ERβ knockdown augmented the E 2 -induced increase of BrdU-retaining cells. Together these findings suggest that ERα stimulates whereas ERβ suppresses stem cell self-renew. This conclusion is supported by separate studies on 2-D cultured PrEC with FACS stem-like cell side-population analysis using selective ER antagonists and siRNA. Although ERβ siRNA did not influence ERα mRNA levels, ERα siRNA doubled ERβ expression suggesting a suppressive role of ERα on ERβ action. In total, the present findings identify distinct localization patterns and roles for ERα and ERβ in human prostate stem-like and daughter progenitor cells with ERα driving self-renewal and ERβ braking division. We propose that a delicate balance between ERα and ERβ contributes to prostate stem cell niche homeostasis and that their dysregulation may contribute to prostate carcinogenesis and progression.