Figure 1. Cytotoxicity of EGFR-TKIs and molecular profiles in parental HCC827 and resistant cell line HCC827/ER.

Cells were treated with the indicated concentrations of erlotinib (A) and gefitinib (B) for 72 h in medium containing 1% FBS. Cell viability was determined using an MTT assay, and IC₅₀ values were calculated using Graphpad Prism software 5.0. Results were expressed as the percentage of living cells compared to the control, error bars indicate SD of three independent measurements. *p <0.05, *p <0.01 vs control group. (C) The Met gene copy number of HCC827 and HCC827/ER cells was measured by real-time PCR using Taqman probes. (D) Basal expression of EGFR downstream signaling molecules in HCC827 and HCC827/ER cells was evaluated by Western blotting. (E) Protein expression of EGFR, bypass signal molecules c-Met and Axl, and epithelial-to-mesenchymal transition (EMT) markers in HCC827 and HCC827/ER cells. Protein (20 μg) from cell lysates was subjected to Western blot analysis. The results are representative of at least three independent experiments.