MiR-23c Regulates the Resistance to Gefitinib in EGFR Mutant Non-Small-Cell Lung Cancer Cells

Mechanisms of primary and acquired resistance are responsible for treatment failure with the Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors (EGFR-TKIs) in the majority of patients with advanced Non-Small-Cell Lung Cancer (NSCLC) carrying EGFR-activating mutations. MicroRNAs (miRNAs) are important modulators of EGFR signaling in lung cancer. Recent studies suggested the role of miR-23c as a tumor suppressor or oncogenic miRNA in different tumor types. However, the role of miR-23c in NSCLC carrying EGFR mutations and its involvement in resistance to EGFR-TKIs has not been explored yet. We found that miR-23c was strongly downregulated in H1975 and HCC827-Gefitinib-Resistant (GR) NSCLC cell lines with intrinsic and acquired resistance to gefitinib, respectively, as compared to gefitinib-sensitive cell lines. Moreover, we demonstrated that miR-23c mimic inhibited proliferation, migration, invasion, and epithelial-mesenchymal transition of resistant cells and that Interleukin-6 Receptor (IL-6R) is a direct target of miR-23c in H1975 and HCC827-GR cell lines. Importantly, miR-23c mimic re-sensitized NSCLC-resistant cells to gefitinib, whereas the combination of miR-23c mimic with a neutralizing IL-6R antibody potentiated the sensitivity to the drug. Collectively, our data demonstrated that miR-23c acts as a tumor suppressor in NSCLC cell lines carrying EGFR mutations and that the axis miR-23c/IL-6R might represent a potential target for the development of therapeutic approaches to overcome resistance to gefitinib.