@article{oai:repo.qst.go.jp:00044833,
 author = {Ishii-Ohba, Hiroko and Kobayashi, Shigeru and Nishimura, Mayumi and Shimada, Yoshiya and Sado, Toshihiko and Ogiu, Toshiaki and Tsuji, Hideo and 石井 洋子 and 西村 まゆみ and 島田 義也 and 佐渡 敏彦 and 荻生 俊昭 and 辻 秀雄},
 issue = {1/2},
 journal = {Fundamental and Molecular Mechanisms of Mutagenesis : A Section of Mutation Research},
 month = {Mar},
 note = {Severe combined immune deficiency (SCID) mice exhibit limited repair of DNA double-strand breaks and are sensitive to ionizing radiation due to a mutation of the DNA-dependent protein kinase catalytic subunit gene. To elucidate the effects of deficient DNA double-strand break repair on radiation-induced carcinogenesis, the dose-response relationship for the induction of all tumor types was examined in wild-type and SCID mice. In wild-type mice, the incidence of thymic lymphomas at gamma-ray doses up to 1 Gy was almost equal to the background level, increased gradually above 1 Gy, and reached a maximum of 12.5% at 5 Gy, which is indicative of a threshold dose of less than 1 Gy. SCID mice were extremely susceptible to the induction of spontaneous and radiation-induced thymic lymphomas. The incidence of thymic lymphomas in SCID mice irradiated with 0.1 Gy or less was similar to the background level; that is, it increased markedly from 31.7% at 0.1 Gy to 51.4% at 0.25 Gy, and reached a maximum of 80.6% at 2 Gy, suggesting the presence of a threshold-like dose at low gamma-ray doses, even in radiosensitive SCID mice. As the average latency for the induction of thymic lymphomas at 0.1 Gy was significantly shortened, the effect of 0.1 Gy gamma-rays on thymic lymphoma induction was marginal. The high susceptibility of SCID mice to develop thymic lymphomas indicates that thymic lymphomas are induced by a defect in DNA double-strand break repair or V(D)J recombination. Excessive development of tumors other than thymic and nonthymic lymphomas was not observed in SCID mice. Furthermore, our data suggest that the defective double-strand break repair in SCID mice is not a major determinant for the induction of nonlymphoid tumors.},
 pages = {124--133},
 title = {Existence of a threshold-like dose for gamma-ray induction of thymic lymphomas and no susceptibility to radiation-induced solid tumors in SCID mice},
 volume = {619},
 year = {2007}
}