Fig. 1.
Derivation and characterization of TKI-resistant cells. (A and B) PC-9 erlotinib-resistant cells (PC-9/ER) (panel A) and PC-9 BIBW-2992–resistant cells (PC-9/BR) (panel B) were derived after ~120 days of culture with increasing concentrations of drug. Growth inhibition assays show that these cells are resistant to respective TKIs compared to the parental cells. (C) Direct dideoxynucleotide sequencing chromatograms from EGFR exon 20 (ex20) show the presence of the T790M mutation (*ACG→ATG) in the PC-9/ER and PC-9/BR cells but not in parental cells. F, forward; R, reverse directions.