報告書番号

G03009

タイトル（和文）

培養細胞における小核形成を指標とした放射線適応応答

タイトル（英文）

Radiation Adaptive Response in Terms of Micronuclei Formation in Cultured Cells

概要 （図表や脚注は「報告書全文」に掲載しております）

修復されなかったＤＮＡ損傷を反映する「小核」の形成率を指標として、遺伝的背景の異なる培養細胞における放射線適応応答の有無を解析した。マウスあるいはチャイニーズハムスター由来の線維芽細胞株4種では、低線量のＸ線を予め照射することにより、高線量照射による小核形成の低減が認められ、放射線適応応答が示された。ヒト悪性腫瘍由来細胞株2種では同様の条件では適応応答は認められなかった。放射線適応応答の有無と各細胞の遺伝子型とを検討した結果、放射線感受性の決定に深く関わっているｐ53遺伝子やATM遺伝子の遺伝子型と放射線適応応答の有無が直接は相関せず、これら以外の遺伝的背景の関与が示された。

概要 （英文）

The radiation adaptive responses have been typically demonstrated as an acquired resistance induced by a low dose of radiation. The frequency of micronuclei induced by a test dose of 3Gy of X-rays in Chinese hamster V79 cells was reduced by a pre-irradiation at 0.1 or 0.2 Gy which was given 4 hr before the test dose; the adaptive response was observed in this cell line. On the other hand, in human glioma A7 cells and cervix carcinoma HeLa cells the adaptive response was not observed. As the three cell lines contain p53 of mutation type, the presence or absence of the adaptive response was not ascribed to the p53 status. To examine the involvement of ATM gene in the adaptive response, the frequency of radiation-induced micronuclei was examined in ATM 2-1, ATM 14-1, and ATM 15-1, which are mouse skin fibroblast cell lines with genotype of ATM (+/+), ATM (+/-), and ATM (-/-), respectively. These three cell lines all showed the adaptive response; ATM gene is not involved in the adaptive response. These results indicated that some other mechanisms other than those involving p53 or ATM should be responsible for the radiation adaptive responses.

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