Sensitivity to chemotherapeutics of NSCLC cells with acquired resistance to EGFR-TKIs is mediated by T790M mutation or epithelial-mesenchymal transition.

Chemotherapy is one of the methods to treat patients with non-small cell lung cancer (NSCLC) developing resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), such as gefitinib. Previous studies revealed that the sensitivity to chemotherapy may depend on different cellular mechanisms of acquired EGFR-TKIs resistance. Thus, the present study aimed to investigate the sensitivity of distinct gefitinib-resistant NSCLC cell lines to chemotherapy in order to help select effective treatment regimens for patients with EGFR-TKI resistance. In the present study, we established two gefitinib-resistant cell lines (PC-9/ZD and PC-9/GR) with the human lung adenocarcinoma cell line PC-9 (carrying the delE746-A750 mutation in the EGFR gene). PC-9/ZD cell line expressed the T790M mutation, while PC-9/GR presented the phenotypes of epithelial to mesenchymal transition (EMT). PC-9/ZD cells were more sensitive to paclitaxel and docetaxel than PC-9 cells and knockdown of T790M decreased this sensitivity. In addition, PC-9/GR cells were less sensitive to chemotherapeutic drugs tested, including cisplatin, gemcitabine, pemetrexed, paclitaxel and docetaxel, compared to PC-9 and PC-9/ZD cells. CDH1 transfection reversed the EMT and restored the sensitivity to chemotherapy in PC-9/GR cells. Furthermore, PC-9 cells became resistant to chemotherapy after TGF-β1-induced EMT. The EMT in NSCLC cells significantly increased cancer stem cell (CSC) properties and tumorgenicity. Collectively, the present study revealed that gefitinib-resistant NSCLC cells carrying the T790M mutation were sensitive to taxane chemotherapy, indicating that T790M is a useful biomarker for the selection of chemotherapy. EMT in NSCLC cells confers resistance to chemotherapy, which may be associated with enhanced CSC properties.