EGFR and non-small cell lung carcinoma: Initial growth curves (MTT assays) showed that H1975 NSCLC cells [TKI-resistant, harbors EGFR exon 20 (T790M) and exon 21 (L858R) mutations] was more resistant to gefitinib than PC14 cells [TKI-sensitive, EGFR exon 19 (delE746-A750)] (Fig. 1A).