Exosomes Promote Survival in Squamous Head and Neck Cancer Cells after Ionizing Radiation

Exosomes were isolated from conditioned medium of irradiated as well as non-irradiated head and neck cancer cells (BHY and FaDu) by serial ultracentrifugation. Quantification by NanoSight technology indicates an increased exosome release from irradiated compared to non-irradiated cells 24 hours after treatment. To test whether the released exosomes influence the radiation response, exosomes isolated from non-irradiated and irradiated donor cells were transferred on non-irradiated and irradiated recipient cells. We find an enhanced uptake of exosomes, when transferred to irradiated recipient cells compared to the transfer to non-irradiated cells. Functional analyses after exosome transfer indicate that exosomes increase not only the proliferation but also the survival after irradiation in recipient cells. These findings mesh with an increased DNA double strand break repair after the transfer of exosomes isolated from irradiated cells.
Our results demonstrate that radiation increases exosome abundance and influences their effects on recipient cells. This study indicates a functional role for exosomes in the response of tumor cells to therapeutic radiation exposure, suggests that radiotherapy modified exosomes influence the cancer progression and encourages that exosomes might be a useful tool to improve therapy strategies.