Repair of potentially lethal damage in FSa-II tumor irradiated under clamped hypoxia, in air or under HPO

Repair of potentially lethal damage (PLD) had been studied in animal tumors. Contradictory results were observed in the PLD repair capability of clamped hypoxic cells and chronically (and acute) hypoxic cells. One study reported that clamped hypoxic cells can repair PLD more substantially than chronically hypoxic tumor cells. In another study, more PLD repair was observed in chronically (and acute) hypoxic than clamped hypoxic cells. Therefore, the authors further studied the PLD repair in our FSa-II tumors (early generation tumors of a spontaneous fibrosarcoma) in C3Hf/Sed mice. Clamped hypoxia indicates that tumor cells were made hypoxic by applying a brass clamp only at the time of irradiation. Chronically hypoxic cells implies hypoxic tumor cells which were not reoxygenated under HPO. Tumor cells which were hypoxic when tumors were irradiated in air include acute and chronically hypoxic cells. Cell survival was assayed immediately or 6 hours after irradiation by the lung colony assay. Insignificant size of PLD repair was observed when the FSa-II tumor was irradiated under clamped hypoxia as well as under HPO