Figure 1. Variable sensitivity of resistant T790M PC9 cell lines to EGFR inhibition.
(a) PC9 parental cells were cultured in escalating concentrations of gefitinib as tolerated until fully resistant, which was defined as lack of inhibitory effect of drug on cell proliferation.
(b) PC9-GR3, PC9-GR2 and parental PC9 cells were cultured with 1 μM gefitinib (G), WZ4002 (W) or vehicle (V) for 72 hours and apoptosis was determined by annexin staining (mean and s.e.m. of four independent experiments*P < 0.05, two-tailed t-test.).
(c) PC9-GR3, PC9-GR2 and parental PC9 cells were treated with 1 μM gefitinib (GEF), WZ4002 (WZ) or vehicle (VEH) and cell proliferation was determined by CellTiter-Glo assay at indicated time points (mean and s.e.m. of 4 independent experiments). The dotted line indicates relative cell number at time of drug addition.
(d) Mice bearing PC9-GR2 or PC9-GR3 subcutaneous xenograft tumors were treated with 50 mg/kg/day WZ4002. (PC9-GR2 - control (N=8), WZ (N=8); PC9-GR3 - control (N=8), WZ (N=8)). Tumors were measured with electronic calipers and % tumor response was calculated as the percentage change in tumor volume (V = 0.52 × L × W2) relative to the start of drug treatment (mean and s.e.m.). P < 0.01 (*) comparing WZ treatment arms at indicated time points by multiple t-tests with Sidak-Bonferroni multiple comparison.