Differential sensitivity of AKR murine leukemia and normal bone marrow cells to hyperthermia

To determine if there is a differential effect of hyperthermia on AKR murine leukemia and AKR normal bone marrow cells incubated in vitro, the fractional survival of leukemic and of normal cells with proliferative potential as a function of heating exposure was estimated by evaluating spleen colony formation. Normal bone marrow colony-forming units were assayed in lethally irradiated (750 centigrays) mice; leukemic colony-forming units were assayed in nonirradiated mice. Electron micrographic studies of leukemic cells treated with 41.8 degrees hyperthermia found that structural damage to the cell, i.e., changes in the Golgi apparatus, was associated with the lack of ability to form colonies. AKR leukemia cells were more sensitive than normal cells to hyperthermic killing at 41.8 degrees and at 42.5 degrees. This differential was found whether cells of each type were heated separately or when mixed together. This model system demonstrates an inherently greater sensitivity of neoplastic cells, as compared to normal syngeneic stem cells, to thermal killing. This finding may have relevance to autologous bone marrow transplantation in humans.