EGFR and lung cancer: The results showed that the three lung cancer cell lines with wild-type EGFR exons 19–21 (A549, 95D, CALU-1) and the NCI-H1975 cell line with the T790M/L858R double mutation exhibited relative resistance to gefitinib, with IC50 values of 20.80 nM, 13.51 nM, 26.36 nM, and 14.26 nM, respectively.