The effects of hyperthermia on the cell cycle of Ehrlich ascites cancer cells in vivo.

The effects of hyperthermia on the cell cycle of Ehrlich ascites cancer cells were studied, and these effects simultaneously evaluated in terms of prolonging the survival of test mice inoculated with tumor cells from heat-treated mice. DDY mice bearing Ehrlich ascites cancer cells were placed in a water bath at 37 degrees C, 39 degrees C, 41 degrees C, 42 degrees C. The heating of mice at 41 degrees C, 42 degrees C and 43 degrees C induced the accumulation of cancer cells at the G2M phase of the cell cycle with many cells exhibiting polyploidy (16 C). The extent of accumulation increased as the temperature of incubation was raised, however the interrupted cell cycle resumed 120 hours after heating. The retransplantation of cells from the heat-treated mice revealed that the mice which were inoculated with Ehrlich ascites cancer cells from mice heated at 43 degrees C survived longer, while the mice which were inoculated with Ehrlich ascites cancer cells from mice heated at 39 degrees C survived for only a slightly shorter time than those which were inoculated with cells from mice heated at 37 degrees C.