Abstract 3085: ERα phosphorylation on Ser167 in the development of endometrial cancer

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Abstract Endometrial carcinoma (EC) is the most common malignancy of the female genital tract. Type I (endometrioid) EC is associated with elevated estrogen signaling. One of the earliest genetic events in human type I EC is loss of the tumor suppressor gene PTEN. Loss of PTEN allows unrestrained activation of the AKT kinase, which, in turn, regulates such key processes as proliferation, survival, cell size, and mRNA translation. We have previously shown, using a Pten+/− mouse model, that the neoplastic lesions develop even in the absence of estrogen, suggesting that there might exist a functional and physiological link between loss of Pten and hormone-independent increased estrogen receptor activity. Previous studies have suggested that AKT can phosphorylate and activate estrogen receptor alpha (ERα) at Ser167, promoting the activation of this nuclear receptor both in vivo and in vitro, even in the absence of ligand. In order to define in vivo the role of ERα phosphorylation on Ser167 in normal endometrial physiology and during neoplastic transformation, we have designed a knock-in approach to introduce the S167A mutation in the mouse germline (ERαA/A). These mice are viable and fertile. We bred ERαA/A mice to Pten+/− mice to test whether ERα phosphorylation on Ser167 is required for the development of endometrial hyperplasia and carcinoma. We found that, at the age of 6 months, the uterus weight of ERαA/A/Pten+/− mice was significantly reduced compared to that of Pten+/− mice. To elucidate whether inhibition of ERα phosphorylation on Ser167 affects cell cycle progression, we analyzed BrdU incorporation in primary cultures of control and ERαA/A endometrial epithelial cells, and found that impairment of ERα phosphorylation on Ser167 leads to a significant reduction of the number of actively proliferating cells. In order to understand the molecular mechanisms responsible for this cell cycle impairment, we analyzed by real-time PCR the expression levels of cell cycle-related genes in the uterus of control and ERαA/A mice. Surprisingly, our results indicate that many genes related with the G2/M phase of the cell cycle, like Ccna2 or Ccnb1, and spindle formation, like Plk1 or Tpx2, are deregulated in ERαA/A uteri, compared to wild-type controls. In conclusion, our results indicate that ERα phosphorylation on Ser167 is an obligatory pathway for the development of endometrial lesions consequent to loss of Pten in endometrial cancer, at least in part by affecting the expression of cell cycle genes. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3085. doi:1538-7445.AM2012-3085