Selective lethal effect of supranormal temperatures on mouse sarcoma cells.

characteristic studied (aneuploidy, length of time in culture, and rate of growth) could be correlated significantly with thermosensitivity. All the cultures of tumor-derived and tumor-producing cells exhibited the same high degree of thermosensitivity, i.e., death of 95% of the cells after 2 hr exposure at 42.5°. All the cultured normal, nontumor-producing cells exhib ited a lower degree of heat sensitivity, i.e., death of 43% of the cells after 2 hr exposure to 42.5°.When a cell subline having a high tumor-producing ability was derived from a nontumor-producing line, it acquired a greater thermosensi tivity, although its rate of growth was the same asthat of the original line. These results indicate that the acquisition of biological malignant potential, both in vitro and in vivo, is accompanied by increased thermosensitivity in mouse mesenchymal cells.