miRNA Expression Profiling of Lung Adenocarcinomas: Correlation with Mutational Status
S Dacic, S Chiosea, L Aspden, MN Nikiforova. University of Pittsburgh, Pittsburgh, PA
Background: MicroRNA (miRNA) expression is deregulated in many types of human cancers and expression of some miRNAs is associated with prognosis and survival. In this study we investigated the miRNA expression patterns in lung adenocarcinomas with different oncogenic mutations.
Design: 2 KRAS+, 2 EGFR + and 2 KRAS-/EGFR- stage matched primary lung adenocarcinomas and corresponding normal lung tissues were analyzed for expression levels of 328 human mature miRNAs. Total RNA was extracted from frozen tissue using Trizol reagent (Invitrogen). Quality of RNA was evaluated on 2100 Bioanalyzer (Agilent). Expression profiling was performed using Flexmir MicroRNA Human Panel (Exiqon) and analyzed on Luminex 200. Analysis of miRNA expression was performed using Luminex IS software v.2.3 (Luminex) relatively to normal lung tissue.
Results: Overall, all tumor groups revealed similar miRNA expression profiles, with most highly overexpressed miRNAs being miR-18b, miR-20a, and miR-328. Similarly, miR-32, miR-137 and miR-342 were most downregulated in all tumors. However, a number of miRNAs were differentially expressed between the groups: miR-25 and miR-30a-3p were significantly more overexpressed in EGFR + tumors (>12 folds) and miR-495 in KRAS + tumors (>10 folds). In KRAS-/EGFR- tumors, miR-155 and miR-154 were upregulated more than 12 folds whereas found at normal levels in KRAS and EGFR positive tumors. Expression of miR-155 and let-7 is of particular interest since it has been shown to correlate with poor prognosis in lung cancer. In our study, EGFR+ tumors demonstrated normal levels of miRNA-155 and down regulation of let-7g; KRAS-/EGFR- tumors showed severe upregulation of miR-155 and down regulation of let-7g and KRAS + positive didn't demonstrate deregulation of these miRNAs.
Conclusions: Our results indicate that number of miRNAs was differentially expressed in lung adenocarcinomas. Correlation between expression of several miRNAs and somatic mutations was found. miR-155 and let-7g (negative prognostic factors in lung cancer) were differentially expressed in tumors positive and negative for EGFR mutations, but remained at normal levels in KRAS positive tumors. Larger number of cases should be analyzed to validate potential role of miRNAs expression in prediction of lung adenocarcinomas mutational profile.
Tuesday, March 10, 2009 1:00 PM
Poster Session IV # 224, Tuesday Afternoon