BMC Cancer (May 2018)

Cancer-derived exosomes from HER2-positive cancer cells carry trastuzumab-emtansine into cancer cells leading to growth inhibition and caspase activation

  • Mark Barok,
  • Maija Puhka,
  • Gyorgy Vereb,
  • Janos Szollosi,
  • Jorma Isola,
  • Heikki Joensuu

DOI
https://doi.org/10.1186/s12885-018-4418-2
Journal volume & issue
Vol. 18, no. 1
pp. 1 – 12

Abstract

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Abstract Background Trastuzumab emtansine (T-DM1) is an antibody-drug conjugate that carries a cytotoxic drug (DM1) to HER2-positive cancer. The target of T-DM1 (HER2) is present also on cancer-derived exosomes. We hypothesized that exosome-bound T-DM1 may contribute to the activity of T-DM1. Methods Exosomes were isolated from the cell culture medium of HER2-positive SKBR-3 and EFM-192A breast cancer cells, HER2-positive SNU-216 gastric cancer cells, and HER2-negative MCF-7 breast cancer cells by serial centrifugations including two ultracentrifugations, and treated with T-DM1. T-DM1 not bound to exosomes was removed using HER2-coated magnetic beads. Exosome samples were analyzed by electron microscopy, flow cytometry and Western blotting. Binding of T-DM1-containing exosomes to cancer cells and T-DM1 internalization were investigated with confocal microscopy. Effects of T-DM1-containg exosomes on cancer cells were investigated with the AlamarBlue cell proliferation assay and the Caspase-Glo 3/7 caspase activation assay. Results T-DM1 binds to exosomes derived from HER2-positive cancer cells, but not to exosomes derived from HER2-negative MCF-7 cells. HER2-positive SKBR-3 cells accumulated T-DM1 after being treated with T-DM1-containg exosomes, and treatment of SKBR-3 and EFM-192A cells with T-DM1-containing exosomes resulted in growth inhibition and activation of caspases 3 and/or 7. Conclusion T-DM1 binds to exosomes derived from HER2-positive cancer cells, and T-DM1 may be carried to other cancer cells via exosomes leading to reduced viability of the recipient cells. The results suggest a new mechanism of action for T-DM1, mediated by exosomes derived from HER2-positive cancer.

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