Inhibition of osteopontin overcomes acquired resistance to afatinib in EGFR-mutant non-small-cell lung cancer

Background: We aimed to explore a novel therapeutic strategy to conquer acquired resistance to second generation EGFR-TKI afatinib in EGFR-mutant NSCLC. Methods: Firstly, we established afatinib-resistant cell lines using increasing concentrations of afatinib. Secondly, we over-expressed or silenced the expression of osteopontin (OPN) using in-vitro transfection. Further, western blot analysis was used to detect the expressions of OPN and epithelial-mesenchymal transition (EMT) biomarkers. Finally, cell proliferation was evaluated by MTT assay. Results: Afatinib (<= 5.0 mu mol/L)-resistant H1650 (H1650-AR) and H1975 (H1975-AR) cells were successfully established, and grew faster compared with both parental cells at the same time interval. Western blot analysis revealed that afatinib significantly promoted the expressions of OPN and EMT biomarkers in H1975-AR and H1650-AR cells. Gain and loss assays validated that OPN over-expression promoted acquired resistance to afatinib, and induced the expressions of EMT biomarkers in H1650-AR and H1975-AR cells. Conversely, silencing of OPN not only significantly sensitized resistant cells to afatinib, but also suppressed EMT progression in H1650-AR and H1975-AR cells. Conclusions: These results demonstrated that OPN was required for acquired resistance of EGFR-mutant NSCLC cells to afatinib.