The effect of hypothermia on cell survival and on subsequent response to hyperthermia was studied in asynchronous and synchronized Neuro-2A cells. Cell cycle progression was blocked at temperatures below 27°C. Immediately after shift to hypothermic temperatures, cells became more sensitive to hyperthermia. Development of thermosensitization was time and temperature dependent. Thermosensitization of cells by hypothermia was high at 0°C and 15°-30°C and less at 5°-10°C. Sensitization started to occur before hypothermic cell death became manifest and developed gradually. Hypothermic cell death was observed when the cells were incubated for more than 1 day at temperatures of 0°-24°C with a minimal cell death during incubation at 6°C. Thermosensitization of cells by hypothermia depended on the position of the cell in the cell cycle at the time of shift to hypothermic temperatures. Cells in late G1 and early S phase became more thermosensitive than did cells in G1 or late S-G2 phase. Furthermore G1-S cells were more sensitive to prolonged hypothermia alone than were G1 or late S-G2 cells. In contrast, late S-G2 cells were most sensitive to hyperthermia alone. It is concluded that the temperature- and cell cycle-dependent way of hypothermic induced cell death was similar to the thermosensitization of cells by hypothermia. But thermosensitization became manifest prior to the actual cell death, following hypothermic treatment.
|Number of pages||6|
|Publication status||Published - 1 Sept 1985|