Differential effect of hyperthermia on murine bone marrow normal colony-forming units and AKR and L1210 leukemia stem cells.

Thermal dose-survival curves for normal hematopoietic and leukemia cells were assessed by spleen colony assays after in vitro heat exposure ranging from 41 degrees to 45 degrees. No effect of 43 degrees heat treatment on the fraction of cells lodging in the spleen was observed. Marked differences in heat sensitivity were observed between normal, L1210, and AKR leukemia cells, the first being les sensitive than were the malignant cells. Furthermore, a greater relative difference between normal stem cells and leukemia cells was observed at lower temperatures. Normal bone marrow cells forced into regenerative activity prior to heat treatment were more heat sensitive than was their undisturbed counterpart, suggesting that noncycling hematopoietic cells are less heat sensitive than are proliferating cells.