Cell-cycle inhibition by misonidazole of human cells cultivated in vitro under aerobic conditions.

By means of flow cytometric recording of DNA histograms and counting of cells in synchronized populations, we have found that misonidazole (MIS) in clinically relevant concentrations induces cell-kinetic changes in human cells (NHIK 3025) cultivated in vitro under aerobic conditions. The effect seems to be a general lengthening of the cell cycle, affecting all phases. However, induction of this effect is phase-dependent, since only cells exposed to MIS during mitosis and/or early G1 will suffer significant cell-cycle prolongation. In exponentially growing populations this effect of MIS leads to a transient increase in the fraction of G1 cells and a corresponding decrease in the fraction of S cells. The possible significance of this effect for the clinical use of MIS is discussed.