Analysis of ionizing radiation induced effects in radioresistant tumours and bystander normal cells

International audienceChondrosarcoma is a chemo and radioresistant tumour for which the main treatment remains surgery. Hadron therapy has shown better specificity and lower toxicity for the surrounding normal tissue when compared to conventional photon therapy. This study focuses on analysing cellular mechanisms involved in stress and response to DNA damage induced by ionizing radiation in radioresistant tumour cells and bystander normal cells. Two different chondrosarcoma cell lines (SW1353 and L835) were irradiated with X-ray and low energy 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 irradiated chondrosarcoma cells, was transferred to non-irradiated normal chondrocyte (T/C-28a2) and endothelial (EA.hy926) cells. In order to investigate the oxidative stress induced by irradiation we used flow cytometry to quantify the mitochondrial and cellular reactive oxygen species at 3h and 24h following exposure to X-ray. Similar, for the bystander cells, we investigated the oxidative stress induced by the irradiated cells at 3 and 24h after media transfer. Chondrosarcoma cells present an increase in mitochondrial stress 3h after irradiation in contrast with the bystander cells that present modifications 24h after media transfer. To understand the mechanisms behind the cellular response in bystander cells we used a proteomic assay for the chondrocyte cells receiving medium from the irradiated chondrosarcoma SW1353 cells at the dose of 0.1 Gy. The proteomic assay of the bystander chondrocytes receiving media from either X-ray and proton irradiated cells highlighted a series of modified proteins involved in several cellular mechanisms such as oxidative stress responses, cellular motility, cell death, cancer pathways and exosomes pathways. Our results showed the potential for these proteins to be good biomarker-candidates involved in cellular response in bystander cells