Fig. 3.

T-DM1 carried on Type A exosomes may bind to cells and internalize. Confocal microscopy images of HER2-positive SKBR-3 breast cancer cells treated with Type A exosomes or unbound T-DM1. T-DM1 was stained with Alexa 488-goat anti-human-IgG (A488-GAHIG) and the nuclei with DAPI. No T-DM1 is detected in SKBR-3 cells when treated with MCF-7 exosomes treated with T-DM1 (a–c) or when treated with SKBR-3 exosomes treated with PBS (d–f) (negative controls). Treatment of SKBR-3 cells with unbound T-DM1 (positive control) resulted in strong cell membrane staining (g–i) and internalization of T-DM1 (insert j). Treatment of SKBR-3 cells with SNU-216 exosomes treated with T-DM1 (k–m) or with SKBR-3 exosomes treated with T-DM1 (o–q) resulted in cell membrane staining, and internalization of some T-DM1 (inserts n and r, respectively). The images were taken with identical microscope settings