Abstract 2035: The levels of miR-145 are regulated by DNA methylation and p53 gene status in prostate cancer

Abstract

Abstract MiR-145 is down-regulated in various cancers. However, the regulation of miR-145 and its role in the prostate cancer is not known. We analyzed the expression of miR-145 in microdissected prostate cancers and adjacent normal prostate tissues. In 17 of 21 (81%) prostate cancers, the levels of miR-145 (measured by qRT-PCR) were significantly lower than those in the adjacent normal tissues. Down-regulated miR-145 levels correlated with DNA methylation (identified by methylation-specific PCR and sequencing) in the upstream region of miR-145, indicating that methylation may be involved in its regulation. The levels of miR-145 were also measured in 49 cancer cell lines, including 4 prostate cancer, 3 kidney cancer, 11 breast cancer, 23 colorectal cancer and 8 pancreatic cancer cell lines. In cancer cell lines, the down-regulation of miR-145 was also significantly correlated with its methylation. In seven cancer cell lines (3 prostate cancer, 2 kidney cancer and 2 colorectal cancer cell lines) with methylated miR-145, treatment with the demethylation agent, 5-aza-deoxycytidine significantly induced miR-145 expression. We also found a significant correlation between miR-145 expression and the status of the p53 gene in 49 cancer cell lines. In 31 cell lines with a p53 gene mutation, miR-145 levels were low in 30 cell lines (97%) while in 18 cell lines with wild type p53, miR-145 levels were low in only 6 cell lines (33%, p<0.001). There is a potential p53 protein binding site upstream of miR-145 flanked by methylated CpG sites. The binding ability of wild type and mutant p53 to this site with or without methylation, and the effects on the expression of miR-145 were tested by electrophoretic mobility shift assay (EMSA) and luciferase assay. In summary, this is the first report on miR-145 regulation by p53 mutation and DNA hypermathylation in prostate cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2035.