Fig. 1

Identification of trastuzumab-resistant cells and the resistance-induced EMT. a Schematic presentation of the establishment of trastuzumab-resistant cell lines. b The cell viability of both trastuzumab-resistant and sensitive cells were determined by MTT assay. ^*P < 0.05 compared to parental cell group. c The IC₅₀ value of trastuzumab was detected for both sensitive and resistant cells by MTT assay. ^*P < 0.05 compared to parental cell group. d Trastuzumab-resistant cell lines, SKBR-3TR and BT474TR, were presented with specific morphologic changes, including increased intercellular separation and formation of pseudopodia. e Cell nuclear apoptosis was assessed by performing TUNEL assay (Images were magnified at 10×). f Wound-healing assay was performed to investigate the migratory ability of trastuzumab-resistant cells and parental cells. ^**P < 0.01 compared to parental cell group. g Matrigel-based transwell assay was performed to investigate the invasive ability of trastuzumab-resistant cells and parental cells. ^**P < 0.01 compared to parental cell group. h Western blot was done to identify the expression of epithelial proteins, E-cadherin and β-catenin, or mesenchymal proteins, vimentin and N-cadherin