Dose-response Relationship of Thymic Lymphoma Induction by Gamma Radiation and Induction of Non-thymic Lymphomas at Very Low Doses in SCID Mice

Abstract

SCID mice which have the defect of DNA-dependent protein kinase catalytic subunit, exhibit the limited activities of repair from DNA double strand breaks and are sensitive to ionizing radiation. In order to study the relationship between repair capacity for DNA double strand breaks and carcinogenesis, and the responsibitily at the low dose of gamma rays, the effects of ionizing radiation on tumor induction were studied using scid homozygote (scid/scid), and C.B-17(+/+)mice. Carcinogenesis experiments showed the significant increase of the incidence of thymic lymphomas at 25cGy to sublethal dose. At very low dose(5 and 10cGy), non-thymic B or T cell lymphomas were incuced in SCID mice, whereas there was no induction of these lymphomas in wild-type mice. No tumors other than lymphomas were observed, because of the life shortning effect by the induction of thymic lymphomas. Thus SCID mice is highly sensitive to the induction of non-thymic lymphomas at very low doses. [J Radiat Res 44:395 (2003)]