To determine which specific protein contributes to acquired EGFR-TKI resistance in NSCLC, two EGFR mutant NSCLC cell lines, PC9 and HCC827 [25], were exposed to gefitinib at gradually increasing concentrations for more than 6 months to establish gefitinib-resistant (GR) cell lines (PC9GR and HCC827GR), as previously reported [24]. This evidence concerns the gene EGFR and non-small cell lung carcinoma.