Differential expression of immune-associated cancer regulatory genes in low- versus high-dose-rate irradiated AKR/J mice.

AKR/J mice carrying leukemia viral inserts develop thymic lymphoma. Recently, we demonstrated that the incidence of thymic lymphoma was decreased when these mice were raised in a low-dose-rate γ-irradiation facility. In contrast, mice irradiated at a high-dose rate developed severe thymic lymphoma and died much earlier. To understand the genetic changes occurred by low- versus high-dose-rate γ-irradiation whole genome microarray was performed. Both groups of mice demonstrated up-regulation of Ifng, Igbp1, and IL7 in their thymuses, however, mice exposed to high-dose-rate γ-irradiation exhibited marked down-regulation of Sp3, Il15, Traf6, IL2ra, Pik3r1, and Hells. In contrast, low-dose-rate irradiated mice demonstrated up-regulation of Il15 and Jag2. These gene expression profiles imply the impaired immune signaling pathways by high-dose-rate γ-irradiation while the facilitation of anti-tumor immune responses by low-dose-rate γ-irradiation. Therefore, our data delineate common and distinct immune-associated pathways downstream of low- versus high-dose-rate irradiation in the process of cancer progression in AKR/J mice.