Two human melanoma cell lines, one radioresistant (SK-MEL-3) and one radiosensitive (HT-144), and a normal human fibroblast line (AG1522) were evaluated for thermoradiosensitization of low-dose-rate irradiation by concurrent mild hyperthermia (39-41°C). None of the cell lines expressed chronic thermotolerance during heating at 39-41°C. The SK-MEL-3 cells were the most heat sensitive, while AG1522 and HT-144 cells had the same sensitivity at 39 and 40°C but HT-144 cells were more sensitive at 41°C. All cell lines expressed thermal enhancement of radiosensitivity with heating during irradiation which increased with heating temperature. The SK-MEL-3 cells, which were the most resistant to radiation and demonstrated the greatest repair of sublethal damage (SLD) during low-dose-rate irradiation, had the greatest thermal enhancement of radiosensitivity, while the HT144 cells, which were the most sensitive and expressed little repair of SLD during low-dose-rate irradiation, had the smallest thermal enhancement of radiosensitivity. These data show that concurrent mild hyperthermia during low-dose-rate irradiation may be most efficacious in radiation-resistant tumor cells which express resistance through an enhanced capacity for repair of SLD.
Comparison of Thermoradiosensitization in Two Human Melanoma Cell Lines and One Fibroblast Cell Line by Concurrent Mild Hyperthermia and Low-Dose-Rate Irradiation
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G. P. Raaphorst, A. Bussey, D. P. Heller, C. E. Ng; Comparison of Thermoradiosensitization in Two Human Melanoma Cell Lines and One Fibroblast Cell Line by Concurrent Mild Hyperthermia and Low-Dose-Rate Irradiation. Radiat Res 1 March 1994; 137 (3): 338–345. doi: https://doi.org/10.2307/3578708
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