Oxygen effect of cell survival, initial DNA-DSB and unrejoined DNA-DSB induced by carbon ion

Abstract

The oxygen effects that are prominent for low LET radiations become small with increase of the LET. Radio-chemical reactions are generally believed as the fundamental mechanisms underlying oxygen effects. In this research, we studied here significance of cell survival, initial DNA-DSB and unrejoined DNA-DSB in CHO cells after low- and high-LET radiation. The CHO cells were exposed to 200 kVp X-ray or HIMAC carbon ions (80 keV/μm) under oxic or hypoxic conditions. Amounts of DNA-DSB in the cells were analyzed by a static field gel electrophoresis. The oxygen enhancement ratio (OER) of cell killing after irradiation of carbon ion was 1.9, and that after X-ray was 2.8. The OER of DNA-DSB by carbon ion was 2.1, and was not affected by rejoining treatment. On the other hand, the OERs of initial DNA-DSB (3.7) and unrejoined DNA-DSB (5.8) after X-ray were affected by rejoining treatment. The quantity of initial DNA-DSB after carbon ions under oxic condition was larger than hypoxic condition. However, oxygen did not affect on the quality of DNA-DSB.