Background: Despite effective activity of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), such as erlotinib, all non-small cell lung cancer (NSCLC) patients eventually acquire resistance to these agents. Studies have demonstrated that down-regulation of miRNA-145 leads to enhancement of EGFR expression, cell proliferation and metastasis. The aim of this study was to investigate the effect of miRNA-145 on sensitivity of the A549 NSCLC cells to erlotinib. Methods: Quantitative real-time PCR was used to examine the effect of miRNA-145 on EGFR expression. The effect of miRNA-145 on cell growth and sensitivity the lung cancer cells to erlotinib was examined by trypan blue and MTT assays, respectively. The combination index was calculated using the non-constant method of Chou-Talalay. Apoptosis was determined by ELISA cell death assay. Results: We found that miRNA-145 was markedly suppressed the expression of EGFR and inhibited the cancer cell growth, relative to blank control and negative control miRNA (p<0.05). Pretreatment with miRNA-145 synergistically enhanced the sensitivity of the lung cancer cells to erlotinib. Results of apoptosis assay revealed that miRNA-145 can induce apoptosis and increase the erlotinib-mediated apoptosis. Conclusions: Our data demonstrate that miRNA-145 play a critical role in the lung cancer cell growth, survival and EGFR-TKIs resistance possibly by regulation of EGFR. Therefore, miRNA-145 replacement therapy can become a new therapeutic strategy in lung cancer.
Keywords: Apoptosis; Lung cancer; MiRNA-145; growth; tyrosine kinase inhibitor.