A low microRNA-630 expression confers resistance to tyrosine kinase inhibitors in EGFR-mutated lung adenocarcinomas via miR-630/YAP1/ERK feedback loop

Purpose: MicroRNA-630 plays dual roles in apoptosis and drug resistance in human cancers. However, the role of miR-630 in resistance to tyrosine kinase inhibitors (TKIs) in lung adenocarcinoma remains to be elucidated. Methods: Manipulation of miR-630 and its targeted gene YAP1 and/or combination of inhibitor treatments was performed to explore whether low miR-630 could confer TKI resistance due to de-targeting YAP1, and this could decrease proapoptotic protein Bad expression through the miR-630/YAP1/ERK feedback loop. A retrospective study was conducted to examine whether the expression of miR-630 and YAP1 could be associated with TKI therapeutic response in patients with lung adenocarcinoma. Results: Low miR-630 expression may confer TKI resistance via decreased SP1 binding to the miR-630 promoter due to ERK activation by YAP1 de-targeting. Persistent activation of ERK signaling via the miR-630/YAP1/ERK feedback loop may be responsible for TKI resistance in EGFR-mutated cells. Moreover, a decrease in Bad expression by its phosphorylation at Serine 75 through ERK activation conferred low miR-630-mediated TKI resistance by modulating the apoptotic pathway. Xenographic tumors induced by miR-630-knockdown PC9 and PC9GR cells in nude mice were nearly suppressed by the combination of gefitinib with the YAP1 inhibitor verteporfin or an MEK/ERK inhibitor AZD6244. Patients with low miR-630 and high YAP1 expressing tumors had a higher prevalence of unfavorable responses to TKI therapy and poorer outcomes when compared with their counterparts. Conclusion: MiR-630 may be a potential biomarker for the prediction of TKI therapeutic response and outcome in patients with lung adenocarcinoma.