RESUMO
OBJECTIVE: The aim of this study was to investigate the role of micro-ribonucleic acid (miR)-145 in acquired resistance of non-small cell lung cancer (NSCLC) to gefitinib, and to explore its potential mechanism. MATERIALS AND METHODS: PC-9 cells were continuously stimulated with low-concentration of gefitinib to induce the formation of acquired gefitinib-resistant PC-9/G cells. The sensitivity of PC-9 and PC-9/G cells to gefitinib was detected via Cell Counting Kit-8 (CCK-8) assay. The expressions of miR-145 and adamalysin-19 (ADAM19) in PC-9 and PC-9/G cells were detected via quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) and Western blotting. Subsequently, PC-9 and PC-9/G cells were transfected with miR-145 mimics and miR-145 NC, respectively. The changes in ADAM19 expression were detected via qRT-PCR and Western blotting. The changes in the sensitivity of cells to gefitinib after transfection were explored via CCK-8 assay. Moreover, the influences of miR-145 transfection on cell apoptosis, invasion and migration were detected via flow cytometry, wound healing assay and transwell assay, respectively. Target gene and acting site of miR-145 were verified via Dual-Luciferase reporter gene assay. Furthermore, targeted regulation of miR-145 on ADAM19 was verified by in vitro cellular experiments. RESULTS: The sensitivity of PC-9/G cells to gefitinib was significantly lower than that of PC-9 cells, with nearly 15-fold difference in half maximal inhibitory concentration (IC-50) (p<0.05). QRT-PCR results indicated that miR-145 expression in PC-9/G cells was significantly decreased (p<0.01). The results of Western blotting showed that the expression level of ADAM19 in PC-9/G cells was markedly higher than that of PC-9 cells. The overexpression of miR-145 could remarkably reduce the expression level of ADAM19 in PC-9/G cells, increase the sensitivity of PC-9/G cells to gefitinib, and inhibit cell invasion and metastasis. The detection of Luciferase activity revealed that miR-145 could bind to the 3'-untranslated region (UTR) of ADAM19 gene and negatively regulate the protein expression. CONCLUSIONS: MiR-145 improves the sensitivity of acquired gefitinib-resistant cells to gefitinib. Meanwhile, it inhibits cell invasion and metastasis through negative regulation on ADAM19. Furthermore, the low-expression of miR-145 may become a biomarker and therapeutic target for acquired resistance to gefitinib.
