Abstract 129: miR-145 reduces tumor growth by regulating EGFR in human lung adenocarcinoma but not in Erlotinib-resistant cells
Authors: Cho William C. S. , Au Joseph S. K. 
Published: August 2012

Abstract
OBJECTIVE: Recent studies suggested that lung adenocarcinomas in never-smokers have characteristics distinct from those in smokers. miRNAs are important modulators in cellular pathways. In this study, we investigate the expression profile of miRNAs in lung adenocarcinomas from nonsmokers and identify their target genes. Our in vitro analyses also assess the miRNA expression associated with erlotinib therapy. METHODS: Lung adenocarcinoma and adjacent normal lung parenchyma were obtained from nonsmokers. Microarray analysis was preformed and the profiling results were validated by qRT-PCR. Transfected cell viability assays were applied to determine the effects of candidate miRNAs on lung cancer cells. Systemic bioinformatic analysis was performed to investigate the potential targets of miRNA in lung cancer. The associations of miRNA and its targeted genes’ expressions were analyzed by miRNA and mRNA microarray profiling in tumor specimens from patients with lung adenocarcinoma. Expressions of miRNA and its gene targets in lung cancer cells were determined by qRT-PCR and validated by Western blot analysis. RESULTS: Comparing paired lung adenocarcinoma tissue with corresponding noncancerous tissues, miR-126*, -145, -21, -182, -183, and -210 were found to be the most differentially expressed miRNAs. An obvious inhibition of cell growth was observed in the EGFR mutant lung adenocarcinoma cells after transfection of pre-miR-145. Our study further identified EGFR and NUTD1 as potential targets of miR-145. The mRNA expressions of EGFR and NUDT1 were significantly downregulated by 60% and 50% respectively after miR-145 transfection. The enforced expression of miR-145 in three lung adenocarcinoma cell lines led to a decrease (2.5-, 5-, and 2-fold) of EGFR protein and the abolishing of NUDT1 protein expressions. In vitro analysis showed that miR-145 can gradually inhibit cell proliferation on transfected lung adenocarcinoma cells over three time points (24, 48, and 72 hours). It was also noteworthy that miR-145 expression and EGFR status correlated with sensitivity to erlotinib. The 3 cell lines treated with erlotinib showing increased expression levels of miR-145 were all mutant EGFR, but not in the 4 lung cancer cell lines with wild-type EGFR or T790M point mutation. DISCUSSION: This study has identified several miRNAs that may play a role in carcinogenesis of lung adenocarcinomas in nonsmokers. Our results also show that restoration of miR-145 inhibits cancer cell growth in EGFR mutant lung adenocarcinoma by targeting EGFR and NUDT1. We further reveal that miR-145 may reduce tumor growth by regulating EGFR in human lung adenocarcinoma but not in erlotinib-resistant cells. Our findings provide new insight into the complex regulating pathway comprising miR-145 and EGFR. Understanding this important pathway may lead to new therapeutic strategies for lung adenocarcinoma in nonsmokers.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 129. doi:1538-7445.AM2012-129