Mechanism research of miR‐34a regulates Axl in non‐small‐cell lung cancer with gefitinib‐acquired resistance

BACKGROUND: To investigate the regulatory mechanism behind miR-34a-altered Axl levels in non-small-cell lung cancer (NSCLC) with gefitinib-acquired resistance. METHODS: The expression of miR-34a, Axl, Gas6 and related downstream signaling proteins in the EGFR mutant NSCLC cell lines were determined by qRT-PCR and Western blot; PC9-Gef-miR-34a and HCC827-Gef-miR-34a cells were established by transfecting the parent cells with a miR-34a overexpressing virus, then the expression of Axl, Gas6 and the downstream channel-related proteins were also compared in PC9-Gef-miR-34a and HCC827-Gef-miR-34a and drug-resistant strains. The survival rate of the cells were measured by CCK8 assay. A luciferase reporter detected whether Axl was the target of miR-34a. Finally, a tumor-bearing nude mouse model was established to verify the relationship between the expression of miR-34a, Axl and Gas6 mRNA in vivo. RESULTS: The expression levels of Axl mRNA and protein, Gas6 mRNA and protein, and related downstream proteins in PC9-Gef and HCC827-Gef cell lines were higher than those in PC9 and HCC827 parental cell lines, while the expression of miR-34a was lower than it was in the parental cell lines (P < 0.05). The expression of Axl mRNA and protein, Gas6 mRNA and protein, and related downstream signaling proteins in PC9-Gef and HCC827-Gef cell lines was higher than the expression in PC9-Gef-miR-34a and HCC827-Gef-miR-34a cells, which overexpressed miR-34a (P < 0.05). CONCLUSION: The miR-34a regulation of Axl plays an important role in NSCLC-acquired gefitinib resistance, and their expression is inversely correlated, which suggests that they can be used as prognostic markers or potential therapeutic targets for NSCLC.