WE‐EF‐BRA‐08: Cell Survival in Modulated Radiation Fields and Altered DNA‐Repair at Field Edges

Abstract

Purpose:Tissue damage prognoses in radiotherapy are based on clonogenic assays that provide dose dependent cell survival rates. However, recent work has shown that apart from dose, systemic reactions and cell‐cell communication crucially influence the radiation response. These effects are probably a key in understanding treatment approaches such as microbeam radiation therapy (MRT). In this study we tried to quantify the effects on a cellular level in spatially modulated radiation fields.Methods:Pancreas carcinoma cells were cultured, plated and irradiated by spatially modulated radiation fields with an X‐ray tube and at a synchrotron. During and after treatment cells were able to communicate via the intercellular medium. Afterwards we stained for DNA and DNA damage and imaged with a fluorescence microscope.Results:Intriguingly we found that DNA damage does not strictly increase with dose. Two cell entities appear that have either a high or a low amount of DNA lesions, indicating that DNA damage is also a cell stress reaction. Close to radiation boundaries damage‐levels became alike; they were higher than expected at low and lower than expected at high doses. Neighbouring cells reacted similarly. 6 hours after exposure around 40% of the cells resembled in their reactions neighbouring cells more than randomly chosen cells that received the same dose. We also observed that close to radiation boundaries the radiation induced cell‐cycle arrest disappeared and the size of DNA repair‐centres increased.Conclusion:Cell communication plays an important role in the radiation response of tissues and may be both, protective and destructive. These effects may not only have the potential to affect conventional radiotherapy but may also be exploited to spare organs at risk by intelligently designing irradiation geometries. To that end intensive work is required to shed light on the still obscure processes in cell‐signalling and radiation biology.