量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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Radiation carcinogenesis in human is considered as a result of the combined exposure with other environment factors. The aim of this study is to examine the mechanism of thymic lymphomagenesis induced by combined exposure of radiation and chemical carcinogen. We investigated frequency and spectrum of the mutation, and an expression of repair genes after combined exposure of X-rays with N-ethyl-N-nitrosourea (ENU).
B6C3F1gpt-delta transgenic mice were exposed to X irradiation at 0.2 or 1.0 Gy for consecutive 4 weeks, followed by ENU at 200ppm for 4 weeks. Four weeks after the end of ENU treatment, genome DNA was prepared from thymus and determined the mutation frequency and spectrum in gpt gene. The expression of Mgmt and other repair genes during ENU treatment was examined by Real Time PCR or RT-PCR array.
We previously reported that irradiation with 0.2 Gy suppressed ENU-induced thymic lymphomagenesis while that with 1.0 Gy enhanced. This study showed that exposure to 0.2Gy dramatically suppressed mutation induction by ENU, especially G to A transition. When combined with 1.0 Gy, mutant frequency was enhanced by 30-folds and accelerated clonal expansion of mutated cells. The expression of Mgmt after exposure of 0.2Gy resulted in a higher expression than that after ENU alone at the initial one week, but increase was smaller thereafter. Other candidate repair genes are now investigated by Real Time PCR Array.
会議概要（会議名, 開催地, 会期, 主催者等）
1st Asian Conference on Environmental Mutagens, 36th Annual Meeting of the Japanese Environmental Mutagen Society
Mutation induction and expression of repair genes in thymus lymphomagenesis by combined exposure of X-rays and ENU
