Fig. 1
Resistance of TNBC cells to EGFR-TKIs. a RNA-Seq-based log2 EGFR expression levels in oestrogen receptor-positive (ER+) breast cancer (991 cases) and TNBC tumours (116 cases) derived from 1107 cases in The Cancer Genome Atlas (TCGA) database. Graphs show data distribution, the mean and the lower and upper quartiles. Error bars represent standard deviation. b RNA-Seq-based log2 EGFR expression in basal-like and luminal-like BC cell line subtypes (total 50 BC cell lines, in-house). Graphs show data distribution, the mean and the lower and upper quartiles. Error bars represent standard deviation c EGFR expression in 20 TNBC cell lines. d Resistance of TNBC cells to EGFR inhibitors (EGFRi). Cells were treated with 1 μM inhibitor for 4 days. Proliferation was assessed using sulphorhodamine B (SRB) assay. Z-score was represented by normalising raw values to those of DMSO control. e Dose response of EGFRi-resistant TNBC cell lines (Hs578T, BT549 and SKBR7) and an EGFRi-sensitive cell line (HCC1806) to lapatinib. Percentage of proliferation was normalised to DMSO control. Data shown as mean ± standard deviation for two independent experiments performed in triplicate. f EGFR pathway functionality in TNBC cell lines Hs578T, BT549 and SKBR7 and HCC1806. Cells were starved for 24 h in serum-free medium, treated with drug solutions prepared in serum-free medium for 4 h then stimulated with 100 ng/ml EGF for 5 min