Proliferative Potential and Apoptosis in Rat Glioma Cell Lines after Hyperthermia

The proliferative potential of cultured rat glioma cells (C6 and 9L) was evaluated after hyperthermia using immunohistochemical staining with bromodeoxyuridine (BrdU) and Ki-67 monoclonal antibodies. Apoptosis was assessed by in situ end-labeling of deoxyribonucleic acid breaks. Both BrdU and Ki-67 labeling indexes decreased with increasing hyperthermia time. The decrease of the Ki-67 labeling index was not as great as that of the BrdU labeling index. The number of apoptotic cells increased with time after hyperthermia. These results indicate that the antitumor effect of hyperthermia may reflect the induction of apoptosis in the cells within the cell cycle, and the resultant reduction of the proliferative potential of surviving cells, especially in the S phase.