Heat-resistant mutants of B-16 melanoma cells. I. Stepwise heating in vitro induces progressive increase in resistance to heat.
Cloned lines from 4 different families of B-16 melanoma cells were heated repeatedly in tissue culture at 45 degrees C with step-up time intervals. These lines included the partially heat-resistant lines previously selected at 43 degrees C(HR 43 degrees) from wheat-germ-agglutinin-resistant mutant (WGAR, HR43 degrees), concanavalin-resistant mutant (conR-HR 43 degrees), ricin-resistant mutant (ricinR, HR 43 degrees), and parental B-16 (B-16, HR 43 degrees) cells. The heating cycles were repeated 7 to 11 times at 45 degrees C increasing from 45 min to 150 min with 3 weeks of culturing at 37 degrees C between cycles. Heat resistance in most cases increased progressively with each heating step. An extensive library of mutants was thus generated, varying in the degree of heat resistance and the apparent stability. HR variants from the WGAR family appeared to be the most resistant and the most stable. The heat-resistant phenotype was expressed not only by increased survival after a normally lethal heat dose, but also by protection against heat-mediated suppression of proteins and DNA syntheses. Protein synthesis in the heat-resistant cells was not only less suppressed by heat shock, but also recovered more rapidly after removal of shock. Clinical implications of these results and the potential usefulness of the mutant lines for genetic studies are discussed.
D000222:Adaptation, Physiological; D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D003208:Concanavalin A / Q000494:pharmacology; D004351:Drug Resistance; D006358:Hot Temperature; D008545:Melanoma / Q000235:genetics*; D051379:Mice; D009154:Mutation; D010641:Phenotype; D012276:Ricin / Q000494:pharmacology; D013997:Time Factors
D003208:Concanavalin A; D012276:Ricin