Consistent with previous reports, H3255 (EGFR L858R) and HCC827 (EGFR E746_A750del) were sensitive to erlotinib treatment ( 15, 16), with IC50 values of 0.031 and 0.003 μmol/L, respectively ( Fig. 1A). Both cell lines were also extremely sensitive to HKI-272 treatment with IC50 values of 0.0049 and 0.039 μmol/L, respectively.