Abstract 2972: Pharmacological reactivation of epigenetically regulated genes in prostate cancer.

Abstract

Abstract Transcriptional silencing caused by promoter hypermethylation is a widespread mechanism for inactivation of known and putative tumor suppressor genes in many types of cancers. GSTP1, CDKN2A, CDH1, APC, and RASSF1A among others are known to be downregulated in prostate cancer. The aim of this study was to search for hitherto unknown genes that are upregulated after treatment by demethylating agents (i.e. DMNT inhibitors) thereby marking them as potential new therapeutic targets and putative biomarkers in prostate carcinogenesis. Prostate cancer cell lines DU-145 and LNCaP were treated in three independent biological experiments with 100μM zebularine for ten days and monitored for cytotoxic and apoptotic side effects. Efficacy of the treatment was verified on the RNA expression level of known epigenetically regulated genes. Expression changes of total RNA from treated and untreated cells were compared using whole genome expression microarrays (Affymetrix Human Gene 1.0 ST). A number of conspicuously upregulated genes (>15.0-fold, presence of CpG islands, higher expression in normal prostate) were further evaluated by Q-PCR in 50 cases of paired normal and tumor tissue samples of prostate cancer patients who underwent radical prostatectomy in our clinic between 2002 and 2004. The seryl-tRNA synthetase gene SARS was discovered by us for the first time to be downregulated in 34/50 cases (66%; p = 0,04) in prostate cancer. The DNA-damage-inducible transcript 1 (DDIT1), also known as GADD45A and was downregulated in 42/50 cases (84%; p = 0,0004). The discovery of a downregulated GADD45A in our independent experiments supports the already known fact of a methylation-mediated repression of GADD45A in prostate cancer (Ramachandran et al., 2009) and its suitability as a potential therapeutic target. In addition, we found a statistically significant inverse correlation of SARS expression and raising patient Gleason scores. Based on our estimated “upregulation-rate” of the promoter hypermethylation gold standard gene for prostate cancer GSTP1 in 98% of our patient samples (48/50; p = 0,0001) we present a robust workflow for the discovery of methylation-mediated transcriptionally inactivated genes. Citation Format: Hans Krause, Odiljon Ikromov, Imad Al Kamal, Ahmed Magheli, Carsten Kempkensteffen, Kurt Miller. Pharmacological reactivation of epigenetically regulated genes in prostate cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2972. doi:10.1158/1538-7445.AM2013-2972