Abstract 4354: Methylation-mediated silenced PYCARD plays a key role in human prostate cancer

Abstract

Abstract Epigenetic gene silencing by aberrant DNA methylation leads to loss of key cellular pathways in tumorigenesis. In order to analyze effects of DNA methylation in prostate cancer, we constructed LNCaP-derived human prostate cancer cells that can induce global reactivation of hypermethylated genes by the methyl-CpG targeted transcriptional activation (MeTA) method. In MeTA, a cassette construct of MBD2-derived methyl-CpG binding domain (MBD) with NFκB-derived transcriptional activation domain is transfected into cancer cells. Then expressed MBD domain specifically binds to the hypermethylated promoter regions, and NFκB transcriptional activation domain recruits p300/CREB-binding protein (CBP) and reactivates hypermethylation-mediated silenced genes. A cell proliferation assay indicated that MeTA suppressed the growth of LNCaP cells. Furthermore, both flow cytometry and TUNEL assays demonstrated that MeTA induced apoptosis. In order to search genes responsible for apoptosis, we performed gene expression microarray analysis of MeTA-uninduced and -induced LNCaP cells: Five genes encoding apoptosis-inducing factors upregulated two-fold or more in accordance with the induction of MeTA; PYCARD (PYD and CARD domain containing), TNFRSF25 (tumor necrosis factor receptor superfamily 25), HRK (harakiri, BCL2 interacting protein), BIK (BCL2 interacting killer), and CIDEA (cell death-inducing DFFA-like effector a). These genes also contained CpG islands (CGIs) within ± 1,000-bp of the transcription start site. We focused on PYCARD and TNFRSF25 because these two genes upregulated 10-fold or more in accordance with the induction of MeTA. We found that both genes were hypermethylated and showed low expression levels in LNCaP prostate cancer cells, whereas only PYCARD was unmethylated in RWPE-1 normal prostate epithelial cells. We further analyzed primary prostate cancer tissues and found tumor-specific promoter hypermethylation of PYCARD in 53.8% (7/13; P < 0.01). These results suggest that methylation-mediated silencing of PYCARD contributes to escape from apoptosis in human prostate cancer, and MeTA may provide important clues to analyze changes in cancer cell phenotypes by DNA methylation alterations. Citation Format: Shinichi Fukushige, Toshiya Miyauchi, Teppei Okubo, Koji Mitsuzuka, Yoichi Arai, Akira Horii. Methylation-mediated silenced PYCARD plays a key role in human prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4354. doi:10.1158/1538-7445.AM2017-4354