Fig. 2

EGFR CNG or overexpression predicts a higher sensitivity to afatinib. a Western blotting showed the basal protein levels of EGFR expression in six ESCC cell lines. b The relative EGFR expression across six ESCC cell lines was calculated according to the above western blotting after normalized to β-actin using ImageJ software. The bar chart of IC50 was drawn using the data in Additional file 2: Table S1. EC109, KYSE450, and KYSE140 are drawn in red while KYSE510, TE-1, and TE-10 are drawn in gray according to their sensitivity to afatinib. c The EGFR copy number of the six ESCC cell lines was detected using copy number assays. A copy number ≥ 3 was defined as an EGFR copy number gain. Data are presented as means ± SDs of three independent assays. CN, copy number; Ref, normal human control DNA . d The expression of EGFR in seven ESCC PDXs was detected by IHC (× 200 magnification; scale bars = 100 μM). e This bar chart demonstrated ESCC PDXs with EGFR CNG were more sensitive to afatinib treatment.1-TGI% was calculated using the data in Additional file 3: Figure S1B and Fig. 1c. When 1-TGI% was close to 0 or a negative value, the xenografts showed growth cessation or shrinkage. When 1-TGI% was a positive value or far greater than 0, the xenografts exhibited tumor growth. Data are presented as means ± SDs of three independent assays. f The main genetic features of ESCC cell lines and PDX models were detected using next-generation panel sequencing. Only genes in EGFR-related pathways or important tumor suppressor genes are listed. Mutations containing single nucleotide variant (SNV) and InDel are depicted in blue whereas CNV (only copy number gain) is depicted in red