Abstract 122: MiR-9-3 and miR-193a are targets for DNA methylation in non-small cell lung cancers

Abstract

Abstract DNA methylation (referred to as methylation) is part of the epigenetic gene regulation complex which is relevant for the pathogenesis of different malignant diseases including non-small cell lung cancers (NSCLC). Recently, it has been reported that besides protein encoding genes also microRNA (miRNA) encoding genes may be targets for methylation in NSCLCs, however, the number of known methylated miRNA genes is still small. To investigate the role of methylation on miRNA gene silencing in NSCLCs, we performed microarray expression analyses of 856 miRNA genes in NSCLC A549 cells before and after treatment with the DNA methyltransferase inhibitor 5-aza-2′-deoxycytidine (Aza-dC) and with a combination of Aza-dC and the histone deacetylase inhibitor trichostatin A. Comparing microarray data of untreated and drug treated A549 cells, we identified 33 miRNA genes whose expression was upregulated after drug treatment and which are associated with a CpG island. Methylation of these miRNA genes was determined in 11 NSCLC cell lines by methylation-sensitive high resolution melting (MS-HRM) analysis and 30 of 33 (91%) miRNA genes were found to be methylated in at least 1 NSCLC cell line. In addition, methylation of the miRNA genes miR-9-3 and miR-193a was also analysed in primary tumors and corresponding non-malignant lung tissue samples of 101 stage I-III NSCLC patients and was found to be tumor-specific. Moreover, we compared miR-9-3 and miR-193a methylation results and clinico-pathological characteristics of NSCLC patients. We found a shorter disease-free survival of miR-9-3 methylated lung squamous cell carcinoma (LSCC) patients compared to miR-9-3 unmethylated LSCC patients by multivariate analysis (HR = 3.8, 95% CI = 1.3 to 11.2, p = 0.017) and a shorter overall survival of miR-9-3 methylated LSCC patients compared to miR-9-3 unmethylated LSCC patients by univariate analysis (p = 0.013). In conclusion, our results suggest that methylation is an important mechanism for silencing certain miRNA genes in NSCLCs and that miR-9-3 methylation may serve as a prognostic parameter in LSCC patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 122. doi:1538-7445.AM2012-122