Abstract
The sensitivity of V79 cells and normal or morphologically transformed C3H-10T 1/2 cells to X-rays, heat or heat plus X-rays was examined. The normal and transformed C3H-10T 1/2 cell lines were equally sensitive to heat at 42.0 degrees C and radiation. The V79 cells were more heat sensitive. Thermal radiosensitization occurred for all 3 cell lines for the combined heat and radiation treatments and was greatest for simultaneous treatment. Recovery occurred when the treatments were separated by an incubation interval at 37 degrees C. For the V79 cells, recovery was much greater for X-rays preceding heat compared to X-rays following heat. This difference was not as great in the C3H-10T 1/2 cell lines. The transformed C3H-10T 1/2 cells were more sensitive compared to the normal for the simultaneous treatment or for heating followed by irradiation. For prolonged heating at 42.0 degrees C, after which thermotolerance occurred in all 3 cell lines, the radiosensitivity still increased as a function of heating time even though no additional cell killing occurred from the heat treatment alone. For heating V79 cells at 41.0 degrees C no further increase in radiosensitivity occurred, as cells became thermotolerant during prolonged heating. Also for the development of thermotolerance during incubation at 37 degrees C between two heat treatments, thermal radiosensitization decreased demonstrating that thermotolerance can affect radiosensitization by hyperthermia.
Highlights
A Chinese hamster lung fibroblast cell line designated V79-S171-Wi was used in these experiments
The thermal enhancement ratios (TER's) were calculated for the 10% survival level by taking the X-ray dose required to reduce survival to 10% and dividing by the X-ray dose required to reduce the survival of the cell population receiving hyperthermia to 10% of the survival level after heat treatment alone
The normal and transformed C3H cells were sensitive at 42.0°C and both these cell lines were more resistant than the V79 cells
Summary
A Chinese hamster lung fibroblast cell line designated V79-S171-Wi was used in these experiments. The medium used was Basal Medium Eagle (BME) containing 13% heat-inactivated foetal calf serum and 1% penicillin and streptomycin from a stock solution 104Uml and 104 g ml -1, respectively. The cells had a population doubling time of h. During the course of these experiments, V79 culture medium was changed to 1: 1 Dulbecco's modified BME and F12 medium containing 5% foetal calf serum (DF5). Under these conditions the cells had the same doubling time as in BME but would grow at a much lower serum concentration.
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