Combined treatment with N-acetylcysteine and gefitinib overcomes drug resistance to gefitinib in NSCLC cell line.

We aimed to explore the molecular substrate underlying EGFR-TKI resistance and investigate the effects of N-acetylcysteine (NAC) on reversing EGFR-TKI resistance. In the current research, the effects of NAC in combination with gefitinib on reversing gefitinib resistance were examined using CCK-8 assay, combination index (CI) method, matrigel invasion assay, wound-healing assay, flow cytometry, western blot, and quantitative real-time PCR (qRT-PCR). CCK8 assay showed that NAC plus gefitinib combination overcame EGFR-TKI resistance in non-small cell lung cancer (NSCLC) cells by lowering the value of half maximal inhibitory concentration (IC50). CI calculations demonstrated a synergistic effect between the two drugs (CI < 1). Matrigel invasion assay and wound healing assay demonstrated a decrease in migration and invasion ability of PC-9/GR cells after NAC and gefitinib treatment. Flow cytometry displayed enhanced apoptosis in the combination group. Western blot and qRT-PCR revealed that increased E-cadherin and decreased vimentin in the combination group. When PP2 was administered with gefitinib, the same effects were seen. Our findings suggest that NAC could restore the sensitivity of gefitinib-resistant NSCLC cells to gefitinib via suppressing Src activation and reversing epithelial-mesenchymal transition.