A COMPARISON OF THE MODES AND KINETICS OF HEAT-INDUCED CELL-KILLING IN HELA AND L5178Y CELLS

The mode and kinetics of cell killing in HeLa and L5178Y cells were in vestigated to elucidate possible relationships between the mechanisms and modes of heat-induced cell death. L5178Y cells were heat-shocked f or either 24 min at 43 degrees C or 30 min at 45 degrees C, while HeLa cells were given only the latter treatment. The degree of heat-induce d excess nuclear protein correlated with cell death in HeLa cells but not in L5178Y cells. This difference suggests that the mechanism of ce ll death differs between these cell lines. With L5178Y cells the main mode of death after treatment at 43 degrees C was apoptosis with littl e progression of cells through the cell cycle. However, after treatmen t at 45 degrees C these cells died by necrosis without progressing thr ough the cell cycle. HeLa cells were found to die by a mechanism other than apoptosis after significant progression of cells through the cel l cycle and perturbation of the normal distribution of cells in the ph ases of the cell cycle (specifically, the fraction of cells in S and G (2) phase increased 50% and 30%, respectively, prior to the occurrence of measurable cell death). These results are consistent with the hypo thesis that the response to injury which has the potential to be letha l varies between different cell types, and results in the induction of different pathways leading to cell death. (C) 1997 by Radiation Resea rch Society.