Estrogen receptor alpha drives proliferation in PTEN-deficient prostate carcinoma by stimulating survival signaling, MYC expression and altering glucose sensitivity

While high doses of estrogen, in combination with androgens, can initiate prostate cancer (PCa) via activation of the estrogen receptor alpha (ER alpha), the role of ER alpha in PCa cells within established tumors is largely unknown. Here we show that expression of ER alpha is increased in high grade human PCa. Similarly, ER alpha is elevated in mouse models of aggressive PCa driven by MYC overexpression or deletion of PTEN. Within the prostate of PTEN-deficient mice, there is a progressive pattern of ER alpha expression: low in benign glands, moderate in tumors within the dorsal, lateral and ventral lobes, and high in tumors within the anterior prostate. This expression significantly correlates with the proliferation marker Ki67. Furthermore, in vitro knockdown of ER alpha in cells derived from PTEN-deficient tumors causes a significant and sustained decrease in proliferation. Depletion of ER alpha also reduces the activity of the PI3K and MAPK pathways, both downstream targets of non-genomic ER alpha action. Finally, ER alpha knockdown reduces the levels of the MYC protein and lowers the sensitivity of cellular proliferation to glucose withdrawal, which correlates with decreased expression of the glucose transporter GLUT1. Collectively, these results demonstrate that ER alpha orchestrates proliferation and metabolism to promote the neoplastic growth of PCa cells.