Effects of prospidine on survival and growth of mammalian cells in culture.

The effects of prospidine, chemically known as 3, 12-diaza-6,9 diazoniadispiro[5.2.5.2]hexadecane,3,12-bis(3-chloro-2-hydroxypropyl)-dichloride (NSC-166100), on cell viability, growth, and colony formation were investigated in several mammalian cell lines. Cell cycle progression and the terminal point of action of the drug were monitored by flow cytometry. Prospidine was cytostatic for two suspension cultures (Friend leukemia and L1210 cells) at a concentration of 10 mg/ml during the first cell cycle after exposure to the drug. Cells were blocked in G2 at lower concentrations of prospidine (e.g., 1.0 mg/ml) but only after 12--24 hours of continuous exposure, i.e., during the second cell cycle in the presence of drug. Cells could be observed to accumulate in G2 by 24 hours even if prospidine (0.1 mg/ml) was removed after 12 hours. A short incubation with a liver cytosol fraction (30 min) or with cultured cells (12 hr) failed to enhance the potency of the drug. Formation of colonies of the adherent Chinese hamster ovary cell line was inhibited by 50% following 24-hour exposure to 1.1 mg prospidine/ml. Under culture conditions in which cells were blocked in G2, their RNA content increased only slightly, but the incorporation of [5-(3)H]uridine into RNA was suppressed by 15--20%. Incubation of cells with prospidine increased the stability of DNA in situ to acid-induced denaturation, which thus suggested that the drug may interact with cellular DNA.