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内容記述 |
Radiation cancer therapy with ultra-high dose rate (UHDR) exposure, so called FLASH radiotherapy, appears to reduce normal tissue damage without compromising tumor response. The aim of this study was to clarify whether 59.5 MeV proton beam at UHDR of 40 Gy/s would be effective in reducing the DNA damage of pBR322 plasmid DNA in solution compared to that of conventional dose rate (CONV) of 0.08 Gy/s. Firstly, we applied a simple system, pBR322 plasmid DNA in 1×Tris-EDTA buffer, which were exposed to protons and using formamidopyrimidine-DNA glycosylase (FPG) enzymes that convert oxidative base damages of oxidized purines to DNA strand breaks, where DNA single strand breaks (SSBs) and double strand breaks (DSBs) can be precisely quantified by agarose gel electrophoresis. As result, the SSB induction rate (SSB per molecule/Gy) at UHDR and induction of FPG enzyme sensitive sites (ESS) were significantly reduced in UHDR compared to that of CONV. However, there was no significant difference in DSB induction and non-DSB cluster damages. Altogether, UHDR of 59.5 MeV proton beam were effective in reducing non-clustered, non-DSB damages, such as SSB and sparsely distributed ESS, thus it may not be significant in reducing lethal DNA damage that become apparent in acute radiation effect of mammalian cells and in vivo studies |
