Abstract
Osimertinib, a third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), has overcome the acquired resistance of first- and second-generation EGFR-TKIs due to the EGFR T790M mutation in non-small cell lung cancer (NSCLC). However, acquired resistance to osimertinib remains a significant clinical challenge. Luteolin, a natural flavonoid from traditional Chinese medicine, has exerted antitumor effects in various tumors. In this study, we investigated whether the natural flavonoid luteolin can enhance the antitumor effects of osimertinib in NSCLC cells. We established an acquired osimertinib-resistant cell line, H1975/OR, and evaluated the effects of luteolin and osimertinib alone and in combination on proliferation, migration, invasion, and apoptosis of H1975/OR cells. The potential mechanisms by which the combination of luteolin and osimertinib exert their effects were investigated by PCR, western blot, gene silencing, molecular docking, SPR and kinase activity analysis. The combination of luteolin and osimertinib inhibited the proliferation, migration, and invasion of H1975/OR cells and promoted apoptosis. We identified mesenchymal-epithelial transition factor (MET) amplification and overactivation as important resistance mechanisms of H1975/OR cells. The combination downregulated the gene and protein expression of MET and inhibited its protein phosphorylation, thereby blocking the activation of the downstream Akt pathway. Additionally, the mediated effects of MET on the synergistic effect of luteolin and osimertinib were confirmed by silencing of MET. Luteolin strongly bound with nonphosphorylated MET by occupying the active pocket of MET and inhibiting its activation. Notably, the combination also downregulated the expression of autocrine hepatocyte growth factor (HGF), the sole ligand of MET. In conclusion, luteolin can synergize with osimertinib to overcome MET amplification and overactivation-induced acquired resistance to osimertinib by suppressing the HGF-MET-Akt pathway, suggesting the clinical potential of combining luteolin with osimertinib in NSCLC patients with acquired resistance.