Fig. 5

T-DM1 is excreted from SKBR-3 cells on Type B exosomes. a, b Immuno-electron microscopy images of the exosomes obtained from the cell culture medium of SKBR-3 cells treated with either PBS or T-DM1. Immuno-gold labelled T-DM1 (small arrows) is detectable on exosomes isolated from cells exposed to T-DM1 (a), but not when the cells were treated with PBS (b). Large arrows point at exosomes, small arrows at T-DM1. c In flow cytometry, a higher fluorescent intensity (FI) was detected in exosome samples isolated from the cell culture medium of SKBR-3 cells treated with A488-T-DM1 (red) as compared to samples isolated from the medium of cells treated with PBS (black). d T-DM1 reduced markedly the growth of SKBR-3 breast cancer cells (positive control), whereas Type B exosomes secreted into the exosome-depleted growth medium from T-DM1-treated or PBS-treated SKBR-3 cells did not. **, P < 0.01