Abstract 1189: MiR-145 inhibits cell proliferation of human lung adenocarcinoma by targeting EGFR and NUDT1

Abstract

Abstract OBJECTIVE: MicroRNAs (miRNAs) are emerging as important modulators in cellular pathways and appear to play a key role in tumorigenesis. MiR-145 is downregulated in several human malignancies, including lung cancer, but the responsible molecular mechanisms remain unclear. We previously reported that restoration of miR-145 inhibits cancer cell growth in lung adenocarcinoma patients with epidermal growth factor receptor (EGFR) mutation. The present study is undertaken to confirm and extend our previous findings through the identification of target genes for miR-145, and to analyze its biological functions in lung adenocarcinoma. METHODS: Systemic bioinformatic analysis was performed to investigate the potential targets of miR-145 in lung cancer, using publicly available algorithms. The associations of miR-145 and its targeted genes’ expressions were analyzed by mRNA and miRNA microarray profiling in tumor specimens from patients with lung adenocarcinoma. Expressions of miR-145 and its gene targets in human lung adenocarcinoma cells were determined using quantitative RT-PCR. Further validation was performed by Western blot analysis. RESULTS: This study showed that miR-145 targets EGFR and nucleoside diphosphate linked moiety X-type motif 1 (NUDT1 or MTH1) in lung adenocarinoma cells. A significant negative correlation was shown between expressions of miR-145 vs EGFR mRNA (r = -0.72; P = 6.3E-8) and NUDT1 mRNA (r = -0.78; P = 6.3E-8), indicating that miR-145 either directly or indirectly suppresses EGFR and NUDT1 transcriptions. The mRNA expressions of EGFR and NUDT1 were significantly downregulated by 60% and 50% after miR-145 transfection in human lung adenocarcinoma cells (P < 0.05). The enforced expression of miR-145 in three lung adenocarcinoma cell lines (NCI-H1975, HCC827, and NCI-H358) led to a decrease (2.5-, 5-, and 2-fold) of EGFR protein and the abolishing of NUDT1 protein expressions. Our results demonstrated miR-145 in the negative regulation of EGFR and NUDT1 expressions at both mRNA and protein levels. Further analysis showed that miR-145 has the ability to significantly inhibit cell proliferation on transfected lung adenocarcinoma cells over three time points (24, 48, and 72 hours). Proliferation of cells was elevated in a time-dependent fashion after transfection with pEP-miR-Null control (by 3%, 27%, and 58%). Conversely, transfection of miR-145 into the cells resulted in gradual reduction of cell viability (by 22%, 37%, and 34%). Upregulation of miR-145 appeared to be an important gene regulation mechanism for the proliferation of lung adenocarcinoma cells and it correlated strongly with the downregulation of EGFR and NUDT1. DISCUSSION: Our findings provided new insight into the complex regulating pathway comprising miR-145, EGFR, and NUDT1. Understanding miR-145's targets and its regulating pathways may lead to new therapeutic strategies for lung adenocarcinoma. 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 1189. doi:10.1158/1538-7445.AM2011-1189