Author of

• 17398

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  P2.01 - Poster Session with Presenters Present (ID 461)

  • Event: WCLC 2016
  • Type: Poster Presenters Present
  • Track: Biology/Pathology
  • Presentations: 1
  • Moderators:
  • Coordinates: 12/06/2016, 14:30 - 15:45, Hall B (Poster Area)

  • 17422

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    P2.01-024 - Expression of miR-106 Paralogs Improves Prognostic Value of Mesenchymal Signatures but Only miR-106b Promotes Invasiveness (ID 6250)

    14:30 - 14:30  |  Author(s): S.H.Y. Kung
    • Abstract

    Background:
    Improved understanding of the molecular mechanisms driving lung cancer progression can lead to novel therapeutic strategies to improve the currently poor patient treatment outcome. Deregulation of microRNA (miRNA) expression in malignant cells activates molecular pathways that drive tumor progression such as epithelial-mesenchymal transition (EMT). We identify miRNA paralogs, miR-106a and miR-106b, to be elevated in metastatic lung adenocarcinoma (LUAD). We assess whether these two highly similar miRNAs share the same functions in vitro, and measure how their elevated expression increases invasiveness or induces EMT in LUAD tumor.
    
    Methods:
    MiRNA expression was obtained from small RNA sequencing data derived from clinical primary LUAD specimens and paired non-malignant tissues (60 localized, 27 with lymph node invasion). Non-invasive, epithelial LUAD cell lines with low endogenous miR-106a/b levels were transfected and co-transfected with overexpression vectors for miR-106a and miR-106b. Invasiveness of experimentally-modulated tumor cells was assessed in vitro by Boyden chamber assay and in vivo using a zebrafish model, and expression of EMT markers was determined by Western Blot. Predicted miRNA targets were identified using mirDIP portal. To identify putative genetic mechanisms of mir-106a/b overexpression, DNA copy number, methylation, and Gene Set Enrichment Analysis (GSEA) were performed. Clinical associations were computed in an independent cohort of TCGA LUAD samples.
    
    Results:
    Both miR-106 paralogs were significantly overexpressed in LUAD samples with lymph node invasion. However, increased expression of miR-106b alone or together with miR-106a, but not miR-106a alone, enhanced metastatic phenotypes, and correlated with increased mesenchymal and decreased epithelial marker expression. Predicted targets include EP300, a transcriptional activator of E-cadherin, and members of the TGFβ signaling pathway. Copy number and methylation status did not correlate with miRNA expression; however, GSEA analysis revealed enrichment of E2F transcription factor targets in LUAD with high expression of either miR-106 paralogs. Furthermore, expression of miR-106 paralogs was significantly positively correlated with E2F1 and E2F2, suggesting that upstream regulation by E2F is a potential mechanism. Interestingly, miR-106a and miR-106b expression was associated with poor survival and advanced stage when stratified by mesenchymal marker vimentin.
    
    Conclusion:
    Although both miR-106a and miR-106b are overexpressed in metastatic LUAD, the strongest prognostic association was found in LUAD with a mesenchymal expression signature and high expression of both miRNAs. Our cell models suggest that miR-106b may play a direct role in EMT, with miR-106a influencing tumor progression via alternative mechanisms. Inhibition of one or both of these miRNAs may provide a strategy for treating advanced stage disease.