Objective: To clarify the function of miRNA-153-3p in gefitinib-sensitive non-small cell lung cancer (NSCLC) and the underlying mechanism.
Patients and methods: The expressions of miRNA-153-3p, LC3B and ATG5 in gefitinib-resistant and gefitinib-sensitive NSCLC tissues were determined by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The correlation between miRNA-153-3p to LC3B or ATG5 was analyzed. We evaluated autophagy level in gefitinib-resistant NSCLC cells by calculating the percentage of PC-9/GR and HCC827/GR cells with positive GFP-LC3, as well as determining autophagy-related gene levels. The potential binding between ATG5 and miRNA-153-3p were verified by Dual-Luciferase reporter gene assay. The regulatory effects of miRNA-153-3p/ATG5 on gefitinib-sensitivity and apoptosis were finally examined by cytotoxicity assay and Annexin V-fluorescein isothiocyanate (FITC)/Propidium Iodide (PI) staining, respectively.
Results: MiRNA-153-3p was lowly expressed in gefitinib-resistant NSCLC relative to the gefitinib-sensitive ones. MiRNA-153-3p was negatively correlated with autophagy activity marker LC3B in gefitinib-resistant NSCLC patients. Compared with parental cells, gefitinib-resistant NSCLC cell lines PC-9/GR and HCC827/GR presented a lower level of miRNA-153-3p and a higher level of autophagy. The overexpression of miRNA-153-3p greatly inhibited autophagy level. ATG5 could directly bind to miRNA-153-3p, and ATG5 was highly expressed in gefitinib-resistant NSCLC. The correlation analysis found a negative correlation between ATG5 and miRNA-153-3p and a positive correlation between ATG5 and LC3B in gefitinib-resistant NSCLC. More importantly, ATG5 reversed the regulatory effects of miRNA-153-3p on autophagy, gefitinib-sensitivity and apoptosis of PC-9/GR and HCC827/GR cells.
Conclusions: MiRNA-153-3p is lowly expressed in gefitinib-resistant NSCLC patients. The overexpression of miRNA-153-3p enhances gefitinib-sensitivity in NSCLC by inhibiting autophagy via downregulating ATG5.