Recent outcome on age and tissue dependence of radiation carcinogenesis in mice and rats

Radiation is a useful tool for disease diagnosis and therapy. On the other hand, a risk of subsequent malignant neoplasms several decades after receiving radiation is a serious public concern. In this study, we introduce our current program on the carcinogenic effect of early-life exposure to radiation using mouse and rat models. We here show that there exist susceptible age windows for radiation carcinogenesis in a tissue dependent manner. Perinatal period is the most susceptible for radiation-induction of both medulloblastomas and renal cell carcinomas. Irradiation at neonatal and infant age efficiently induces intestinal and liver tumors. Mammary cancers develop frequently at around pubertal exposure. Conversely, the incidence of lung cancers rather increases as a function of age-at-exposure. Underlying mechanisms include age dependent changes in the rate of clonal expansion and susceptibility to radiation-induced cell killing of the progenitor cells.The 3rd Asian Congress of Radiation Researc