Abstract 5698: MicroRNA-31 acts as an oncomir in lung cancer by repressing specific tumor suppressors

MicroRNAs (miRNAs) encode small RNAs that regulate gene expression. The expression profiles of miRNAs have proven useful to improve classification, diagnostic and prognostic information for human cancers. We sought to uncover miRNAs preferentially over-expressed in lung cancers versus adjacent normal lung tissues. We comprehensively interrogated miRNA array expression profiles conducted on lung cancers versus adjacent normal lung tissues isolated from murine transgenic cyclin E models that were engineered. Notably, miR-136, miR-376a and miR-31 were each significantly over-expressed in murine lung cancers as compared to adjacent normal lung tissues. Real-time RT-PCR and in situ hybridization assays independently confirmed these miRNA expression profiles in paired normal-malignant lung tissues from transgenic mice as well as from a well characterized panel of paired human normal-malignant lung tissues. Knock-down of miR-31, but not other highlighted miRNAs, using a synthetic antagonist significantly repressed lung cancer cell growth and in vivo tumorigenicity. Bioinformatically predicted miR-31 target genes were identified and studied. These included two tumor suppressors: large tumor suppressor 2 (LATS2) and PP2A regulatory subunit B alpha isoform (PPP2R2A) that were each substantially increased by miR-31 knock-down and repressed by miR-31 over-expression. Engineered repression of either LATS2 or PPP2R2A significantly antagonized miR-31-mediated growth inhibition. Luciferase binding assays confirmed that miR-31 directly suppressed LATS2 and PPP2R2A through binding to their respective 3′-untranslated regions (UTRs). Interestingly, miR-31 was inversely expressed relative to these identified target genes in both murine and human lung cancers. Clinical relevance was uncovered using miR-31 in situ hybridization and cyclin E immunohistochemistry assays performed on tissue arrays from the population-based New Hampshire Lung Cancer Registry. As expected, cyclin E expression was significantly associated with miR-31 levels. Real-time RT-PCR assays validated LATS2 and PPP2R2A repression in lung cancers versus adjacent normal lung tissues. Thus, these findings implicate miR-31 as an oncogenic miRNA (oncomir) that exerts its effects by repressing specific tumor suppressors. Taken together, miR-31 is proposed as a novel molecular target for lung cancer therapy and chemoprevention. 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 5698.