Fig. 5

Resistance to EGFR inhibitors in mesenchymal T-Epi cells. T-Epi cells were treated with recombinant TGF-β1 (5 ng/mL) for 14 days to establish mesenchymal T-Epi cells. Mesenchymal T-Epi cells were cultured with normal KSFM medium (TGF-β1 free) for 24 h, and then parental T-Epi and mesenchymal T-Epi cells were treated with erlotinib or cetuximab. a Phase-contrast images of parental T-Epi cells and mesenchymal T-Epi cells. Note that T-Epi cells treated with TGF-β1 changed to spindle-shaped cells. b Protein levels of E-cadherin and vimentin in parental T-Epi and mesenchymal T-Epi cells, determined by western blotting. c Phosphorylated- and total-EGFR protein levels in parental T-Epi and mesenchymal T-Epi cells treated with erlotinib or cetuximab, determined by western blotting. The inhibitory effect of EGFR phosphorylation due to EGFR inhibitors was lower in mesenchymal T-Epi cells compared with parental T-Epi cells. d Cell growth of mesenchymal T-Epi cells treated with or without erlotinib or cetuximab. The results are presented as means ± SD (bars). (n.s., not significant, vs vehicle control; n = 3) Inhibition of cell growth was not observed in mesenchymal T-Epi cells. e Involucrin protein levels in parental T-Epi and mesenchymal T-Epi cells treated with or without erlotinib or cetuximab, determined by western blotting. The promotion of involucrin expression due to treatment with EGFR inhibitors was more suppressed in mesenchymal T-Epi cells compared with parental T-Epi cells