Thermotolerance and Thermosensitization in CHO and R1H Cells: A Comparative Study

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Abstract
In CHO [chinese hamster ovary] and R1H [rhabdomyosarcoma] cells thermotolerance was induced by a pre-incubation at 40.degree. C, by an acute heat shock at 43.degree. C followed by a time interval at 37.degree. C, and during continuous heating at 42.degree. C. Thermotolerance, which was tested at 43.degree. C, primarily causes an increase in D0 [mean lethal dose] of the heat-response curve. The degree of maximum thermotolerance was generally more pronounced in CHO than in R1H cells, but the time interval at 37.degree. C, as well as at 40.degree. C, to reach this maximum level was the same in both cell lines. CHO and R1H cells could be sensitized to 40.degree. C by a pre-treatment at 43.degree. C. When compared for the same survival rate after pre-treatment at 43.degree. C alone the degree of thermosensitization was about the same in both cell lines. In either cell line thermosensitization was suppressed when cells were made thermotolerant by a previous incubation at 40.degree. C for 16 h. [The potential application of hyperthermia in tumor therapy has stimulated much work to undetstand the biology of heat.].