Thermal radiosensitization in Chinese hamster (V79) and mouse C3H 10T 1/2 cells. The thermotolerance effect

Abstract

Summary The sensitivity of V79 cells and normal or morphologically transformed C3H-1OT 1/2 cells to Xrays, heat or heat plus X-rays was examined. The normal and transformed C3H-1OT 1/2 cell lines were equally sensitive to heat at 42.0°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°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-1OT 1/2 cell lines. The transformed C3H-1OT 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°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°C no further increase in radiosensitivity occurred, as cells became thermotolerant during prolonged heating. Also for the development of thermotolerance during incubation at 37°C between two heat treatments, thermal radiosensitization decreased demonstrating that thermotolerance can affect radiosensitization by hyperthermia.

Differences in Heat-induced Cell Killing as Determined in Three Mammalian Cell Lines Do Not Correspond with the Extent of Heat Radiosensitization

“…Many data, based on different heat treatments in one cell line, using altered pH, heat modifying agents or development of thermotolerance have suggested a causal relationship between heat killing and heat radiosensitization (Konings and van der Meer-Kalverkamp 1980, Freeman et al 1981, Djordjevic 1983, Haveman 1983, Raaphorst and Azzam 1983, Dewey 1983, Holahan et al 1984, van Rijn et al 1984 although other data do not show this relationship (Lunec and Parker 1980, Mivechi and Hofer 1983, Nielsen 1983, Hartson-Eaton et al 1984. The different results of these investigations may possibly be explained by the differences in cell lines used and in the different heat schedules employed.…”

“…Also, effects of heat modifying agents such as procaine or glycerol increased or decreased, respectively, heat killing and heat radiosensitization (Konings and van der Meer-Kalverkamp 1980, Djordjevic 1983, Dewey 1984. Furthermore, several studies involving the effect of thermotolerance on the slope and/or the shoulder region of radiation survival curves (Haveman 1983, Raaphorst and Azzam 1983, Holahan etal. 1984, Van Rijn et al 1984 led Leeper (1985) to conclude that in general greater thermoradiosensitization is observed when greater thermal damage is achieved.…”

Long duration mild temperature hyperthermia and brachytherapy

“…While, the Chinese hamster cells (V79) showed a thermotolerance plateau the three human tumour cell lines showed no evidence of thermotolerance for up to 40 h of heating while such cells were still able to express thermotolerance to acute hyperthermia. Thus, while LDMH produced chronic thermotolerance in rodent cells which could reduce the effectiveness of LDMH in thermoradiosensitization 66 , studies with human cells indicated that protracted mild hyperthermia could have continually increasing effectiveness as a radiosensitizer as was observed in human glioma cells heated chronically at 40, 41 and 42 C 67 . This could be especially effective when combined with LDR or PDR where extensive SLDR occurs, which could be inhibited by LDMH.…”

Recent Advances in Upconversion Nanoparticles‐Based Multifunctional Nanocomposites for Combined Cancer Therapy

“…Encouraged by the exciting outcomes from combined radio‐/chemotherapy and radio‐photodynamic therapy, Shi's group extended their research field by combining UCNP‐based enhanced radiotherapy with photothermal therapy in consideration that: i) S‐phase cancer cells are extremely radioresistant but very sensitive to hyperthermia; ii) an appropriate level of hyperthermia can increase intratumoral blood flow and subsequently improve oxygenation status in the tumor, consequently considerably improving cell sensitivity to radiation therapy . They constructed a novel core/satellite nanotheranostic (CSNT) by decorating ultrasmall CuS NPs onto the surface of the silica‐coated NaYbF 4 :Er/Gd UCNPs to integrate photothermal ablation (PTA, also called PTT) with radiotherapy for improved cancer therapy ( Figure a).…”