A study of combined therapy of X-ray and hyperthemia inducded by RF heating system on cultured cells.

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The combined effects of the radiation and hyperthermia on cultured tumor cells were estimated in vitro, and the mechanism of the radiosensitization of hyperthermia was studied in this research. The radiation response of the 4 tumor cell line (HeLa, HMV1, M10, HL60) were greatly sensitized by the hyperthermia treated at 43^0Cfor 1 h immediately after irradiation to X-rays, but have no effect on survival curve below 41^0Ctraatment. The combined treatment of radiation and hyperthermia induced apoptotic cell death of HL60 cells which was detected by DNA ladder formation To demonstrate the mechanism (s) of radiosensitization by hyperthermia, the activities of transcriptional factor NF-kappaB was examined using gel shift assay. X-ray irradiation stimulated the activities of NF-kappaB at dose of 10-20 Gy, which was inhibited by hyperthermia to the control level when treated with 43^0Cfor 2h. Although the mechanism is unclear, it was suggested that down regulation of NF-kappaB activation might be an important rule to the cell survival or apoptic cell death.The difference of heating system on the biological effect of hyperthermia was also examined. The RF heating system had the radiosensitizing effect at the temperature of 41^0C,which showed no effect at the water bath system. These results suggested the posssible effects of electro-magnetic wave including radio-frequency wave to the living cells may exist.