Abstract 2497: Inositol Polyphosphate 4-Phosphatase Type-II B protects mice from benign prostatic hyperplasia

Abstract

Abstract BPH is the most common tumor-like condition that afflicts more than 50% of men between the ages of 51-60 and over 90% in men older than 80. While connection between obesity and BPH is well established, the driving signaling pathways are not clear. BPH is a nonmalignant enlargement of prostate epithelium that requires androgen receptor (AR) signaling. INPP4B and EZH2 are highly expressed in prostate epithelium where they regulate AR signaling and play an important role in prostate cancer etiology. EZH2 is an epigenetic silencer that methylates histone H3 on K9 and K27 residues and INPP4B is a dual specificity phosphatase that dephosphorylates PI(3,4)P2 and PI(4,5)P2, membrane lipids that activate Akt and PKC signaling pathways respectively. We discovered that Inpp4b-/- male mice develop BPH at 3 months old of age and subsequently prostate intraepithelial neoplasia (PIN) when fed high fat diet. While expression of AR in the prostates of these mice is similar, AR activity is reduced. The loss of INPP4B caused reduction in EZH2 protein levels in prostate cancer cell lines and in mouse prostate. Inhibition of Akt and PKC signaling reduced EZH2 levels in ventral and dorsolateral prostate lobes of Inpp4b-/- males, suggesting that INPP4B upregulates EZH2 levels by suppressing Akt and PKC signaling pathways. Consistent with decline in EZH2 levels, Inpp4b-/- males have reduced levels of H3K27me3 and H3K9me2 in the ventral prostate, and high fat diet exacerbated this phenotype. Our data suggests that INPP4B modulates epigenetic profile of prostate epithelium by stabilizing EZH2 levels. Both loss of INPP4B and high fat diet treatment lead to decline in EZH2 levels and activity and contribute to development of BPH in mouse model. Citation Format: Yasemin Ceyhan, Manqi Zhang, Irina U. Agoulnik. Inositol Polyphosphate 4-Phosphatase Type-II B protects mice from benign prostatic hyperplasia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2497.