Direct and bystander effects of human chondrosarcoma cell line irradiated with protons
Résumé
Ionizing radiation induces complex cellular effects in targeted cells as well as neighbouring “bystander” cells which have received signals produced by irradiated cells. Characterising both direct and non-targeted bystander effects might improve the overall outcome of radiation exposure which could have implications in radiotherapy and radioprotection. In this study, we focused on analysing direct and bystander cellular effects of proton irradiation of chondrosarcoma cells. Chondrosarcoma is resistant towards conventional chemo-/radiotherapy and can be un-operable. Charged particle radiotherapy is now a good alternative for chondrosarcoma. The advantages of this method include higher specificity (given by its specific Bragg pick) and increased biological efficacy (due to the high LET). Two different chondrosarcoma cell lines (SW1353 and L835) were irradiated with protons at doses in the range 0.1-2 Gy. To study the bystander phenomena we used a medium transfer protocol. The bystander supernatant containing signals emitted by proton irradiated chondrosarcoma cells, was transferred to non-irradiated bystander normal chondrocyte (T/C-28a2) and endothelial (EA.hy) cells. Cell survival and DNA damage were assessed in directly irradiated chondrosarcoma cells and in bystander chondrocytes and endothelial cells. A dose dependent direct effect was observed in chondrosarcoma cells while the bystander cells showed a less pronounced effect then directly irradiated cells. Our results showed that proton-irradiated chondrosarcoma cells have the ability to release stress factors inducing bystander responses in the non-irradiated surrounding chondrocyte or endothelial cells.