Some responses of cells and tumors to elevated temperatures.
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Animals↗
Biomedical subjects
G M Hahn
Publications and source records attributed to G M Hahn.
Thermal injury and thermotolerance in mesenchymal tissues.
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Adipose Tissue↗
Responses of RIF tumors to heat and drugs: dependence on tumor size.
The effects of hyperthermia and drugs on RIF tumors of three sizes were studied in C3H mice. The animals were treated with bleomycin, carmustine, or a combination of both drugs and with or without concomitant localized hyperthermia. The hyperthermia dose was 44 degrees C for 30 minutes for each treatment. Each animal was given two treatments, 7 days apart. The tumors were classified according to approximate size: 0.1, 0.3, or 0.7 cm3. Among the animals bearing the smaller tumors, no cures were observed. Growth delay measurements indicated that heat and drugs had approximately additive effects. Several cures were seen among the animals bearing medium- and large-sized tumors. Our results indicate that medium and large tumors may respond better to the combination treatment than small tumors.
Animals↗
Effect of hyperthermia on murine cell surface histocompatibility antigens.
The effect of heat on the density of cell surface histocompatibility antigens was examined. Antigen density and distribution were determined by radioimmunoassay and flow cytometry after the binding of radioiodinated or fluoresceinated monoclonal antibody (anti-H-2Kk and anti-H-2Kb) to murine lymphoma cells in suspension cultures. Antibody binding was unaffected by temperatures between 37 degrees and 41 degrees following a 30-min heat exposure. At 42 degrees, some inhibition of binding was measurable. However, at 43 degrees, antibody binding was reduced by 30 to 50%, and a further 15 to 20% reduction was observed at 45 degrees. Flow cytometry showed that all cells were equally affected. There was no indication of the selection of a specific cell population. The temperature-dependent decrease in antibody binding was due to a decrease in receptor number and not to changes in the affinity. Measurement of the diffusion coefficient of the lipid probe N,N-dioctadecyl indocarbocyanine iodide showed that heat did not affect significantly the fluidity of the membrane lipids. Hyperthermic temperatures, therefore, have a direct effect on these membrane proteins.
Animals↗
Hyperthermia as a clinical treatment modality.
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Body Temperature↗
Radiosensitivity and thermosensitization of thermotolerant Chinese hamster cells and RIF-1 tumors.
CHO cells subline HA-1 were made thermotolerant by a priming heat treatment (43 degrees C, 30 min). Later, 4, 16, or 24 hr, they were either irradiated or heated (43 degrees C, 30 min) and irradiated. Thermotolerance had no effect on the radiation sensitivity of the cells as measured by the D0 value of the clonogenic survival curve. However, the N value of the curve (width of shoulder) showed a significant increase at 24 hr, indicating an increased capacity to accumulate sublethal damage. This indicates that the fractionation schedule 43 degrees C, 30 min + 37 degrees C, 24 hr + 43 degrees C, 30 min + X ray required approximately 100 rad more radiation than 43 degrees C, 30 min + X ray to reduce survival to the same level. The same priming treatment was given to RIF-1 tumors growing in C3H mice. Later, 24 hr, when the tumors were either irradiated or heated (43 degrees C, 30 min) and irradiated, it was found that thermotolerance had no effect on the radiosensitivity of the cells as measured by in vitro assay. However, thermal radiosensitization was not apparent 24 hr after the priming treatment.
Acclimatization↗
Stable heat-resistant clones selected from wild-type and surface variants of B-16 melanoma.
Stable heat-resistant clones were selected from wild-type B-16 melanoma cells and from three of their surface variants resistant to the lectins wheat-germ agglutinin, ricin and concanavalin A. The selection procedure included three or four cycles of heating the cells in culture at 43 degrees C for 2-1/2 to 3-1/2 h interspersed with growth at 37 degrees C. The survivability of the heat-resistant (HR) variant cells at elevated temperatures of 43 degrees C for 160 min and 45 degrees C for 40 min was 2-4 logs greater than that of their respective parents. This acquired property of heat resistance appeared to be a stable phenomenon, persisting in these cell lines for more than 80 generations. One HR variant cell line carried in tissue culture for 250 generations showed no change in the heat-resistance characteristic. Acquisition of resistance appeared to be a gradual process with intermediate stages preceding the more pronounced degree of resistance. These newly selected HR variants join the existing surface variants of B-16 melanoma to result in a large family of variants from the same cell lineage to make this system a powerful tool for studying the relationship between heat sensitivity, metastasis and hyperthermia treatment of cancer.
Animals↗
Thermal sensitivity and resistance of insulin-receptor binding in thermotolerant cells.
Cells may be made extremely resistant to elevated temperatures (thermotolerant) by a mild heat shock a few hours prior to more rigorous heating. In the present report, we show that a single cellular process - insulin binding to its receptor (in HA-1 Chinese hamster ovary cells) - may be made similarly heat-resistant. Heat resistance, whether expressed as cell survival or insulin binding, had similar dose-response characteristics, showing maximum resistance after 30 min at 43 degrees C. The processes had similar induction kinetics (2-6 h) and decayed over a similar time-course (100 h) after 43 degrees C, 30 min preheating. Thermal resistance of insulin binding was induced only when residual receptor loss (due to heating) occurred. Also, decay of resistance was closely correlated with recovery of insulin binding capacity. There thus appeared to be an inverse relationship between receptor number and the degree of heat resistance of both receptors and whole cells. (Scatchard analysis indicated that decreased insulin binding was due to receptor loss, not affinity decrease.) Whether the insulin receptor has a direct role in the mediation of cell killing or whether it passively reflects the state of the whole cell is not clear. However, identification of the receptor as an entity specifically protected in the thermotolerant cells may permit examination of the expression of thermotolerance at the molecular level.
Animals↗
Thermal sensitivity and resistance of insulin-receptor binding.
Membrane proteins may be key targets in thermal cell killing. In the present study, insulin binding to cellular receptors has been used as a probe for membrane protein behavior after heat shock (42-45 degrees C). Heating and binding studies were carried out on monolayers of HA-1 Chinese hamster ovary cells. Binding was unaffected by temperatures below 43 degrees C, but above this temperature (43-45 degrees C) it was inhibited in a time-temperature dependent manner. The kinetics of inhibition of insulin binding were similar to those for cell inactivation. Scatchard analysis indicated a decrease in receptor number rather than affinity for insulin in heated cells. In cells made resistant to further heat treatment (thermotolerant cells) by a mild pretreatment dose of hyperthermia (45 degrees C/10 min) insulin binding was also made heat resistant. Heating appeared to act directly on the insulin receptor rather than indirectly on subsequent energy dependent processes such as internalization. The data thus indicate that the fate of at least one membrane protein is closely tied up with the ultimate destiny of the cell per se after heating.
Animals↗
Concomitant up-regulation of insulin binding and elevated heat sensitivity in serum depleted CHO cells.
When HA-1 CHO cells were cultured in media with a range of fetal calf serum (FCS) concentrations, they became increasingly heat sensitive at low (5%) serum levels. Heat sensitization occurred concomitantly with increased insulin binding capacity. Insulin binding capacity also became more heat sensitive. Thermotolerance induced by a mild treatment (10 min/45 degrees C) 12 hr prior to assay, caused marked heat resistance expressed both as cell survival or insulin binding and abolished differences in sensitivity between the serum adapted cell lines.
Animals↗
Combined continuous ultra low dose rate irradiation and radiofrequency hyperthermia in the C3H mouse.
Intradermally inoculated RIF tumors and normal skin of male C3H mice were implanted with variable activities of Iodine 125 seeds or dummy seeds enclosed in Vicryl sutures, and subjected to 0, 1, 2 or 3 local radiofrequency heat treatments for 30 minutes. Each treatment raised the tumor volume to 44 degrees C. Gastrointestinal toxicity (assessed by weight change), skin reaction, tumor growth delay, and tumor cure were assessed. Neither radiofrequency treatment alone or continuous ultra low dose rate irradiation up to 16,000 rad over 180 days alone was successful in curing these tumors; however, combined modality treatments employing doses as low as 8,000 rad over 180 days plus two radiofrequency treatments did effect cures. Gastrointestinal toxicity was best correlated with hyperthermia treatments, while skin reactions secondary to hyperthermia were prolonged by continuous ultra low dose rate irradiation. Implications for clinical usage are discussed.
Animals↗
Effects of lonidamine alone or combined with hyperthermia in some experimental cell and tumour systems.
Lonidamine or 1-[(2, 4-dichlorophenyl) methyl]-1H-indazole-3-carboxylic acid, studied in a battery of in vitro and in vivo tests currently used for the screening of anti-tumour agents affecting cell division, has been shown to have a narrow spectrum of anti-tumour activity. The significance of this finding is discussed in the light of previous investigations suggesting that lonidamine affects mitochondrial function and not cell replication. Hyperthermia has been shown to sensitize tumour cells to lonidamine. This observation indicates that in combination with hyperthermia lonidamine has some potential for the treatment of cancer; moreover, it suggests that hyperthermia might reproduce a metabolic condition occurring in some stages of the disease. The blood levels corresponding to the anti-tumour action of lonidamine in animals are in the range of those detected in patients treated with the drug.
Animals↗
Effect of pH and elevated temperatures on the cytotoxicity of some chemotherapeutic agents on Chinese hamster cells in vitro.
The cytotoxicity of some drugs is a function of extracellular pH. We show that this dependence is greatly enhanced at 43 degrees. At this temperature, we have examined the cell-killing ability of four drugs in the pH range of 6.5 to 8.5. For 1,3-bis(2-chloroethyl)-1-nitrosourea, cytotoxicity is minimum at alkaline pH and increases in monotonic fashion as the milieu becomes more acidic. There is little or no effect of pH on the cytotoxicity of methotrexate. Bleomycin is most effective at acidic pH (less than 7.5). Above that pH, its cytotoxicity remains unchanged. Amphotericin B is least cytotoxic at the pH of normal tissue, 7.4. At higher or lower values, its cell-killing efficiency increases symmetrically. These results may have some relevance in designing thermo-chemotherapeutic treatment protocols.
Amphotericin B↗
Heat-induced protection of mice against thermal death.
The possibility that the exposure of organisms to whole-body hyperthermia may provide protection against subsequent thermal exposures is intriguing and may play an important role in the clinical scheduling of fractionated hyperthermia. We used C3H mice to investigate whether whole-body heating can be used as a conditioning treatment to induce protection of mice against thermal death from a subsequent heat treatment. Our data clearly show that a conditioning whole-body heat dose (41 degrees for 40 min), by itself nonlethal, can give substantial protection to animals against a later heat treatment. The heat-induced protection is transient in nature: it reaches a maximum by 6 to 24 hr following the 41 degrees conditioning dose and decays by approximately 60% by 72 hr. The data presented do not shed any light on the cause of death following whole-body hyperthermia. Our results show clearly that the response of a complex organism to heat can be altered by previous heat exposure.
Animals↗
The effects of hyperthermia on normal mesenchymal tissues. Application of a histologic grading system.
The alterations produced by radiofrequency-induced hyperthermia of 42 to 48 degrees C for 30 minutes were studied in the subcutaneous adipose tissue and skeletal muscle of swine. Acute lesions (18 to 24 hours) included edema, hemorrhage, necrosis (predominantly of myocytes) and granulocytic exudate in fat or muscle. The most important chronic lesion (28 to 31 days) was fibrosis replacing either tissue. There was a histiolymphocytic exudate with foreign-body giant cells around large lipid vacuoles. Muscle necrosis persisted and there was variable myocyte regeneration. Several specimens showed deep necrosis and abscesses. A grading system was developed to quantitate independently acute and chronic damage in each tissue. Acute lesions were usually less severe and extensive than chronic ones, without obvious dose response. Chronic lesions showed clearly a dose response, which began at 43 degrees C and increased with temperature. The latter appear to be reliable indicators of hyperthermic damage in deep soft tissues.
Adipose Tissue↗
Thermal sensitivity and thermotolerance in normal porcine tissues.
We have previously presented a histopathological grading scheme for thermal damage in normal porcine adipose and skeletal muscle tissues. Here we have used this scheme to assess the heat sensitivity of these tissues, and evaluate the protective benefit of thermotolerance as induced by a prior thermal exposure. Tissues were exposed to temperatures ranging from 40-50 degrees for 30 min. Half of all sites also received a thermal exposure of 41.0-43.0 degrees 4 hr earlier. Biopsies for histological evaluation were obtained at 18 to 24 hr ("acute") and at 28 to 31 days ("chronic") following treatment. Only mild acute injury was seen in the early samples, following either single or double heat exposures, at all temperature levels. Minimal chronic damage was also seen in the late samples following single exposures of 45 degrees or less. Higher single exposures caused important chronic lesions, the severity of which was dose dependent. Regions that had received the earlier conditioning thermal exposure showed a significant protection against the subsequent thermal exposure. In such regions, mean (chronic) pathology scores were reduced by 76 to 86% over the temperature range 45-48 degrees. The degree of acute damage failed to predict the degree of chronic damage. Overall, induction of thermotolerance provided an advantage of 2 degrees or more in normal tissue protection.
Adipose Tissue↗
Influence of heat on the intracellular uptake and radiosensitization of 2-nitroimidazole hypoxic cell sensitizers in vitro.
The effect of elevated temperature (44 degrees) on the intracellular uptake of the 2-nitroimidazole hypoxic cell radiosensitizer, misonidazole (MIS), and analogues more hydrophilic than MIS was studied in Chinese hamster ovary cells. It was found that the intracellular uptake of these compounds which enter cells by restricted passive diffusion can be enhanced approximately 4-fold when incubated at 44 degrees compared to the uptake at 37 degrees. Peak intracellular uptake (expressed as the ratio of intracellular concentration to extracellular concentration) following incubation of cells in 2 mM MIS was 100% at 44 degrees but only 25% at 37 degrees. Furthermore, a short-term nonlethal heat pulse (44 degrees for 15 min) with MIS present caused a 2-fold enhancement in uptake which was sustained for an additional 45 min at 37 degrees. This same nonlethal heat pulse was found to induce a similar enhancement in uptake even when MIS was added at subsequent time intervals at 37 degrees. The heat pulse induced a time-related enhancement of uptake at 37 degrees which increased for 1 hr and persisted for at least 6 hr. Finally, in vitro radiosensitization studies of hypoxic Chinese hamster ovary cells showed that the nonlethal heat pulse of 44 degrees for 15 min could greatly enhance the sensitization by low concentrations (0.5 mM) of MIS added after heating due to increased intracellular concentrations of the drug. MIS (0.5 mM) alone achieved a radiosensitization enhancement ratio of 1.29 (compared to irradiated hypoxic cells alone), while the addition of the short-term heat pulse, which had only a minor effect itself, achieved an enhancement ratio of 1.78.
Animals↗
Lack of correlation between membrane lipid composition and thermotolerance in Chinese hamster ovary cells.
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Adaptation, Physiological↗