MiR-142-5p reverses the resistance to gefitinib through targeting HOXD8 in lung cancer cells.

OBJECTIVE: To investigate the role and potential mechanism of micro ribonucleic acid (miR)-142-5p in the acquired resistance to gefitinib in lung cancer cells. MATERIALS AND METHODS: The drug resistance of PC9/G cells was detected via methyl thiazolyl tetrazolium (MTT) assay. Expression levels of miR-142-5p and HOXD8 in PC9 and PC9/G cells were detected via quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) and Western blotting. PC9/G cells were transfected with miR-142-5p mimic, while PC9 cells were transfected with miR-142-5p inhibitor. Subsequently, expression changes of HOXD8 were determined using qRT-PCR and Western blotting, cell sensitivity to gefitinib was detected through MTT assay, and the apoptosis was detected via flow cytometry. Moreover, Dual-Luciferase reporter assay was conducted to determine the relationship between HOXD8 and miR-142-5p. Finally, potential involvement of HOXD8 in miR-142-5p-regulated gefitinib sensitivity was confirmed via rescue tests. RESULTS: PC9/G cells were more significantly resistant to gefitinib compared with its parental PC9 cells. MiR-142-5p was down-regulated in PC9/G cells, while that of HOXD8 was up-regulated in PC9/G cells. Transfection of miR-142-5p mimic could inhibit the expression level of HOXD8 in PC9/G cells and reverse its resistance to gefitinib. Conversely, transfection of miR-142-5p inhibitor could upregulate HOXD8 in PC9 cells and promote its resistance to gefitinib. According to the Dual-Luciferase reporter assay, miR-142-5p could suppress the expression of HOXD8 through the targeted binding to the HOXD8 3'UTR. Moreover, miR-142-5p could regulate mitochondrial apoptosis pathway by targeting HOXD8. Finally, rescue tests confirmed that miR-142-5p regulated the sensitivity of PC9 cells to gefitinib by acting on the target gene HOXD8. CONCLUSIONS: Down-regulation of miR-142-5p induces the resistance of lung cancer PC9 cells to gefitinib by upregulating HOXD8.