Abstract 3954: Identification of microRNAs epigenetically silenced in bladder cancer

Purpose: Bladder cancer is the one of the most common malignancies in the urothelial tract. MicroRNAs (miRNAs) are small, non-coding RNAs that control gene expression post-transcriptionally, either by degradation of target mRNAs or by inhibition of protein translation. MiRNAs are involved in cancer development and progression, acting as tumor suppressors or oncogenes. Recent studies have demonstrated a role of DNA methylation in silencing miRNAs in bladder cancer. The aim of current study is to identify bladder cancer-related miRNAs by screening epigenetically silenced miRNAs in bladder cancer. Materials & Methods: Two bladder cancer cell lines (T-24, UM-UC3) were treated with or without 5-aza-2’deoxycytidine (5-aza-dC) and 4-phenylbutyric acid (4-PBA), and expression of mature miRNAs was examined using a TaqMan Low Density Array System. We used UCSC genome browser to examine if CpG islands are located in the proximal upstream of the miRNAs upregulated after drug treatment. Methylation-specific PCR (MSP) and bisulfite pyrosequencing were carried out to analyze methylation status of the miRNA genes in bladder cancer cell lines and primary bladder cancer specimens. Results: Of 664 miRNAs examined, 208 miRNAs were up-regulated (>5-fold) in T24 cells, and 200 miRNAs were up-regulated in UM-UC3 cells, respectively. Among the miRNAs, 146 were commonly up-regulated in both T-24 and UM-UC3 cells. Among those 146 miRNAs, 36 miRNAs contain CpG islands in their 5’ end of the genes, and further analyzed. Methylation-specific PCR (MSP) was carried out, and 12 miRNAs showed aberrant methylation in bladder cancer cell lines. Bisulfite pyrosequencing of these 12 miRNAs was carried out, and we identified hypermethylation of 12 miRNAs in cultured and primary bladder cancer specimens. Conclusions: Our results suggest that DNA methylation is associated with miRNAs silencing in bladder cancer, and that these miRNAs may have a role in the development and progression of bladder cancer. 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 3954. doi:10.1158/1538-7445.AM2011-3954