Effect of Hyperthermia on the Cell Cycle and Cyclin B Expression in Human Glioblastoma Cell Line

Cell kinetic effects of hyperthermia on glioblastoma cells were investigated using flow cytometry. Pulse-labeling with 5-bromodeoxyuridine (BUdR) and chasing of the labeled cells showed a temporary accumulation of the labeled cells in the G2M phase and a reduction of DNA synthesis.Cyclin B protein rises rapidly in G2 phase and falls at the end of mitosis in normal sysling cells. Cyclin Bprotein binds to p34cdc2, resulting in histone kinase activity which is necessary for the initiation of mitosis. The amount of p34cdc2 is constant throughout the cell cycle. The level of cyclin B was measured by an anti-cyclin B antibody and flow cytometry in order to investigate the couseof the G2 accumulation induced by hyperthermia. The low level of cyclin B after hyperthermia, in comparison with that of normal cycling cells, persisted for more than 3 hours. These results indicate that the temporary accumulation of cells in the G2M phase after hyperthermia may be coused at least in part by an insufficient level of cyclin B.

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