Abstract 2168: Detections of olfactomedin 4 gene expression by qRT-PCR in human prostatic samples and cell lines

Abstract

Abstract The human olfactomedin 4 gene (OLFM4) encodes an olfactomedin-related glycoprotein. OLFM4 gene is normally expressed in a limited number of tissues, including the prostate, but the regulation of OLFM4 gene expression in prostate are largely unknown. We have previously reported that reduced or lost expression of OLFM4 protein is correlated with higher Gleason scores in prostate cancer and loss of gene expression is due to deletions within the OLFM4 gene in about 36.7% (11/30) of prostate cancer patient samples studied. In this study, we investigated the regulation of OLFM4 gene expression in human prostate cancer pathogenesis. We have investigated the mRNA expression levels using quantitative RT-PCR analysis in 144 human prostate cDNA samples (OriGene). We found that the average expression level of OLFM4 gene is significantly reduced in cancer tissues compared with normal tissues. The expression level of OLFM4 mRNA is inversely corrected with higher Gleason Score in prostate cancer. Interestingly, we also found higher expression of OLFM4 gene within small subset of samples with inflammation including prostatitis, hyperplasia and well differentiated tumor tissue. We have also screened the expression of OLFM4 mRNA level using qRT-PCR in primary cultured human normal prostate epithelial cells (PREC), benign immortalized prostate epithelial cell (RWPE1), androgen-responsible cancer cells (LNCaP and VCaP), androgen-independent cancer cells (PC-3 and DU145). We found lower expression of OLFM4 in RWPE1 cells. We also confirmed our previous results that OLFM4 mRNA was not expressed in cancer cell lines, LNCaP, VCaP, PC-3 and DU145. We have reported previously that deletions within the OLFM4 gene were present in about 40% in human prostate cancer samples studied. To test whether methylation is also involved in the loss of OLFM4 gene expression in human prostate cancer, the methylation status of CpG sites in OLFM4 promoter region has been analyzed in primary prostate tissues obtained by Laser Capture Microdissection. Hypermethylation of CpG sites at -91, -486 and -681 were detected in higher Gleason score of cancer samples. We further treated PC-3 cells (in which the OLFM4 gene is intact) using the demethylation reagent, 5-aza-2’-deoxycytidine and found restoration of OLFM4 mRNA expression. The results suggest that methylation status of OLFM4 gene promoter region may affect OLFM4 gene expression in prostate cancer 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 2168. doi:10.1158/1538-7445.AM2011-2168