[Screening of metastasis-related microRNAs in the large-cell lung cancer cell lines with different metastastic potentials]

Up-Regulation of MiRNA-125a-5p Inhibits Cell Proliferation and Increases EGFR-TKI Induced Apoptosis in Lung Cancer Cells

BACKGROUND

Despite the dramatic efficacy of erlotinib, an EGFR tyrosine kinase inhibitor (TKI), most of non-small cell lung cancer (NSCLC) patients ultimately acquire resistance to this agent. Different studies indicated that miRNA-125a-5p is down-regulated in human lung cancer cells and may function as a tumor suppressor by targeting EGFR. However, the biological function of miRNA-125a-5p in NSCLC resistance to EGFR-TKIs is not fully understood. In this study the effect of miRNA-125a-5p on cell proliferation, apoptosis and sensitivity of the A549 lung cancer cells to erlotinib was investigated.

METHODS

After miRNA-125a-5p transfection, the expression levels of EGFR mRNA were measured by QRT-PCR. Trypan blue assays were performed to evaluate the proliferation of the A549 lung cancer cells. The cytotoxic effects of miRNA-125a-5p and erlotinib, alone and in combination, were determined using MTT assay. Combination index study was performed using the method of Chou-Talalay. Apoptosis was assessed using an ELISA cell death assay kit.

RESULTS

MiRNA-125a-5p clearly reduced the expression of EGFR mRNA in a time dependent manner, causing marked cell proliferation inhibition and spontaneous apoptosis (p<0.05, relative to control). Pretreatment with miRNA-125a-5p synergistically increased the cytotoxic effect of erlotinib and decreased its IC50. Furthermore, miRNA-125a-5p significantly enhanced the apoptotic effect of erlotinib. Negative control miRNA had no significant effect on biological parameter of the tumor cells.

CONCLUSIONS

Our data suggest that suppression of EGFR by miRNA-125a-5p can effectively trigger apoptosis and overcome EGFR-TKs resistance of lung cancer cells. Therefore, miRNA-125a-5p may be a potential therapeutic adjuvant in patients with lung cancer.
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MicroRNAs and lung cancers: from pathogenesis to clinical implications

Lung cancer is the leading cause of cancer-related deaths in the US and worldwide. Better understanding of the disease is warranted for improvement in clinical management. Here we summarize the functions of small-RNA-based, posttranscriptional gene regulators, i.e. microRNAs, in the pathogenesis of lung cancers. We discuss the microRNAs that play oncogenic as well as tumor suppressive roles. We also touch on the value of microRNAs as markers for diagnosis, prognosis and the promising field of microRNA-based novel therapies for lung cancers.