Heat-enhanced radioresponse in HeLa cells.

The response of HeLa cells to X-irradiation increases when the cells are irradiated at elevated temperatures or when irradiation is followed by hyperthermia. The magnitude of this thermal effect increases with increasing temperature and varies inversely with dose rate during exposure of the cells to the combined treatment. Enhancement of the radioresponse by postirradiation incubation at elevated temperatures increases with increased incubation time. The results suggest that in HeLa cells the synergistic interaction between hyperthermia and irradiation is due to interference with the repair of potentially lethal damage and/or enhanced expression of lethal damage.