Abstract LB-337: Post-transcriptional regulators of microRNA biogenesis drive glioblastoma-specific expression

Abstract

Abstract MicroRNAs have emerged as key regulators of both normal and pathologic phenotypes, including cancer. Fine grain regulation of their biogenesis, however, is still a poorly understood process and only a relatively small repertoire of proteins controlling its key steps has been characterized. In order to understand the extent and specificity of microRNA biogenesis control, as well as its role in glioblastoma tumorigenesis and progression, we developed and experimentally validated miRage, an algorithm for genome-wide inference of microRNA biogenesis regulators. MiRage identifies biogenesis-regulator candidates using the conditional mutual information between the candidates, mature microRNAs precursors, and abundance to identify those proteins that are required for the maturation of microRNAs. miRage predicted hundreds of potential biogenesis regulators that are either specific to individual microRNAs or to microRNA families. Several of the inferred regulators that are differentially expressed across glioblastoma prognosis were validated in the SNB19 cell line. Differential expression of mature microRNAs, their host genes, and their precursors were measured before and after ectopic expression or RNAi mediated silencing of predicted regulators. ACSM3, which is predicted to regulate 70% of the differentially expressed microRNAs in glioblastoma, was shown to post-transcriptionally inhibit miR-155. This microRNA is an experimentally validated regulator of CEBPβ, a master regulator of the mesenchymal signature of GBM; indeed siRNA-mediated silencing of ACSM3 dramatically activated miR-155 and down-regulated CEBPβ. In addition, several members of the DDX RNA-binding protein family were inferred as specific regulators of microRNA biogenesis. For instance, we show that DDX10 activates miR-218 and inhibits miR-9; up regulation of DDX10 may account for miR-218 overexpression in poor-prognosis tumors. We showed that RBBP4 inhibits miR-23b, WDR8 inhibits miR-18b, ACTA2 inhibits miR-218, and PRIC285 inhibits miR-196a and miR-25. Taken together, these results suggest that microRNA biogenesis is a much more complex and finely regulated process than previously thought, and that microRNA biogenesis regulators may play a key role in tumor initiation and progression. 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 LB-337. doi:10.1158/1538-7445.AM2011-LB-337