Exosomes from breast cancer cells stimulate proliferation and inhibit apoptosis of CD133+ cancer cells in vitro

Exosomes are a family of bioactive vesicles that are secreted from various types of cell, including tumor cells. Exosomes derived from breast cancer cells have been demonstrated to perform important functions in tumor progression in vitro and in vivo. However, few studies exist regarding the function of exosomes in CD133(+) breast cancer cells. In the present study, exosomes from 4T1 mouse breast cancer cells and mouse mammary gland epithelial cells were purified. The exosome-associated markers CD63, CD9 and CD81 were detected, and the size distribution and potential of the exosomes were determined. Exosome uptake by CD133(+) and CD133(-) 4T1 cells was confirmed by confocal microscopy. An ATPlite assay indicated that the proliferation of CD133(+) cells was increased and the apoptosis was suppressed by exosomes from 4T1 cells. Collectively, the findings of the present study demonstrate a novel mechanism by which the action of exosomes on CD133(+) 4T1 cells may contribute to breast cancer progression.