Presentation Radio-sensitivity Modifying Factors

根井, 充  ,  王, 冰  ,  中島, 徹夫  ,  藤森, 亮  ,  Vares, Guillaume  ,  勝部, 孝則  ,  二宮, 康晴  ,  田中, 薫  ,  劉, 翠華

Cancer susceptibility after exposure to ionizing radiation (IR) differs depending on individuals. Age and gender are known factors causing individual differences in IR sensitivity. In order to develop an individualized approach to radiation protection, it is vital to identify modifying factors in radiation sensitivity, and specify hypersensitive individuals to whom a particular radiation protective attention should be directed. Several potential factors have been suggested to modulate individual IR sensitivity. Variable efficiency of DNA repair resulting from single nucleotide polymorphisms (SNPs) located in DNA repair-related genes is one of such factors. For example, DNA damage frequency in lymphocytes from individuals bearing SNPs in the XRCC3 gene (a key player in DNA double strand break repair by homologous recombination) was reported to be significantly high among industrial radiographers. Lifestyle may also affect the risk of IR-induced cancers. Most lifestyle-related factors are believed not to have synergistic effects with IR at low dose on cancer risk (except for tobacco smoke which was shown to elevate the sensitivity to α–particle-induced lung cancer -UNSCEAR 2000); however some people may experience particular conditions of IR exposure combined with lifestyle conditions resulting in higher level of risk, such as residents of long-term-contaminated areas after a nuclear accident or astronauts during a prolonged cosmic space journey. We have tested genetic and epigenetic factors, which may cause individual differences in radiation sensitivity: high calorie intake, excessive alcohol consumption, mental stresses, SNPs in DNA repair-related genes and hormonal levels. Here we review our recent results, together with data reported from other laboratories, and we discuss the significance of this issue for radiation protection.

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