Modification of X-Ray-Induced Oncogenic Transformation and Cell Killing by Hyperthermia and 5-Bromdeoxyuridine in Cultured C3H-10T1/2 Cells

摘要

The thermal sensitivity, radiosensitivity and sensitivity to combinations of heat and X-rays of C3H-10T1/2 cells have been examined. At 42.0 exp 0 C the cells displayed thermal tolerance, while at 45.0 exp 0 C no thermal tolerance was observed. Radiosensitivity was enhanced by heat treatment before, during, or after irradiation, while the greatest sensitization occurred for simultaneous treatments. Recovery occurred when the treatments were separated by incubation times at 37 exp 0 C. Thermal radiosensitization increased as a function of heating time at 42.0 exp 0 C before irradiation. Even when cells attained a thermal tolerant state and no further cell killing occurred at prolonged heating intervals, thermal radiosensitization still increased as a function of heating time. When cells were subjected to heat plus radiation no significant increase in the transformation frequency per viable cell (TF/VC) was observed after simultaneous treatment or treatments immediately following each other, but an increase was seen when the heat and radiation treatments were separated by incubation intervals at 37 exp 0 C. No significant increase in the TF/VC was observed when cells were exposed to heat alone. The incorporation of 5-bromodeoxyuridine (BUdR) for 30 h resulted in enhanced X-ray sensitivity while incorporation for 52.5 h increased the degree of cell killing from radiation by a factor about the same as the increase in toxicity for the prolonged exposure to BUdR. The TF/VC for the 30-h BUdR exposure was not significantly increased while the 52.5-h exposure to BUdR resulted in a six-fold increase. The dose response of TF/VC induction for X-radiation alone was linear between 1.0 and 4.0 Gy, while the dose response for BUdR incorporation and X-radiation was non-linear and curved upwards. (Atomindex citation 12:609938)