Abstract 2092: Pathway specific gene profiling analysis reveals potential target genes of the stress oncoprotein LEDGF/p75 in prostate cancer cells

Abstract

Chronic inflammation in the prostate microenvironment, with its associated increase in oxidative stress, is critical for prostate carcinogenesis since it leads to DNA mutations and epigenetic changes, as well as deregulation of stress and antioxidant proteins that protect prostate cells against oxidative damage and cell death. The lens epithelium-derived growth factor p75 (LEDGF/p75), an oxidative stress-induced transcription coactivator, is overexpressed in prostate tumors and other tumor types. LEDGF/p75 is emerging as a stress oncoprotein that protects cancer cells against lysosomal cell death and promotes resistance to chemotherapeutic drugs. We hypothesize that the pro-survival function of LEDGF/p75 is associated with its ability to promote the transcriptional activation of protective stress genes. To date, only very few candidate target genes of LEDGF/p75 have been identified in cancer cells. Towards this goal we initiated a stress focused gene profiling analysis of PC3 prostate cancer cells overexpressing or lacking LEDGF/p75, using the Real Time PCR Array System (SABiosciences). We selected an array that contained 80 genes involved in the cellular stress response and antioxidant defense. siRNA oligos targeting the C-terminus of the LEDGF/p75 mRNA sequence were used to induce transient LEDGF/p75 knockdown in PC3 cell. LEDGF/p75 was also stably overexpressed in PC3 cells by transduction with a lentiliviral vector. Both transient siRNA-mediated knockdown and overexpression of LEDGF/p75 were associated with significant changes in the expression of several stress/antioxidant genes, using a cutoff fold change value of 1.5 (P<0.001). We selected for further analysis common genes that were significantly downregulated when LEDGF/p75 was knocked down and upregulated when this protein was overexpressed. These genes are phosphoinositide-binding protein E, cytoglobulin, superoxide dismutase 3, thyroid peroxidase, titin, glutathione transferase zeta1 and albumin. The expression of these genes in response to LEDGF/p75 expression was further validated using real-time RT-PCR. This study identifies candidate stress genes potentially regulated by LEDGF/p75 in PC3 cells, and provides a rationale for investigating the mechanisms by which this emerging stress oncoprotein promotes resistance to lysosomal cell death and chemotherapy in prostate tumor cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2092. doi:10.1158/1538-7445.AM2011-2092