Repair of Potentially Lethal Radiation Damage in Acute and Chronically Hypoxic Tumor Cells in Vivo

The ability of animal tumor cells to repair potentially lethat damage was studied in vivo. Fifth-generation isotransplants of a spontaneous mouse squamous-cell carcinoma were irradiated under tourniquet-induced hypoxia or in air. Tumors were removed either immediately or 6 hours after irradiation and dose-response curves were determined by TD50 assays. Repair was attributed to cells in the hypoxic cell component for animals irradiated in air. Extensive repair was also noted for those irradiated under typoxic conditions. Implications of these results are discussed.