Effects of thermotherapy on the morphology and cell cycle of a transplanted ascites hepatoma in rats.

The effects of heating on the morphology and cell cycle of ascites hepatoma AH-100B cells were investigated. Five rats with AH-100B ascites cells were warmed in a water bath at 39 degrees C, 41 degrees C, or 43 degrees C, respectively. After heating, changes in the morphology of tumor cells were observed every day over a 3-day period under a light microscope and changes in the nuclear DNA content were measured by microspectrophotometry. Morphologic changes in AH-100B cells, which included swelling and vacuolization of the cytoplasm and constriction, vacuolization and destruction of nuclei, were observed. Multinucleated giant cells were characteristically observed in the cells from rats heated to 43 degrees C. In the case of rats heated to 43 degrees C, an increase was seen in the number of cells with a DNA content of 8C to 10C, and some of the cells exhibited polyploidy with a DNA content greater than 10C. It appears that one of the mechanisms of the antitumor effect of hyperthermia in vivo involves changes in the cell cycle of cancer cells and the accumulation of polyploid cells.