Fig. 6. Effects of ectopic overexpression of mutant EGFR in DFCI81 and DFCI161 cell lines.

(A) Quantification of drug sensitivities in the presence of doxycycline-inducible expression of EGFR Del19 and EGFR L858R in DFCI81 and DFCI161 cells, respectively. Drug sensitivity in the presence of a doxycycline-inducible control RFP vector is shown for comparison. IC₅₀ values were derived from cell viability readout after a 96-hour drug treatment with a nine-point dose curve (n = 6 replicates per dose). Data shown are representative of three replicate studies. Significance of P < 0.0001 was determined by one-way ANOVA of technical replicates, followed by Tukey’s posttest for multiple comparisons. (B) Assessment of downstream ERK1/2 and Akt activation in the presence of doxycycline after treatment with single-agent and combined gefitinib and crizotinib. EGFR* denotes corresponding mutant-specific EGFR antibody (Del19 for DFCI81 and L858R for DFCI161). (C) Quantification of ERBB3-p85 dimerization after induction of ectopic mutant EGFR overexpression and crizotinib treatment. Bars on graphs represent means and SD of normalized quantification for three independent studies. Statistical significance for each treatment pair was assessed by t test.