pyrimidinones and 1-propargyl-5-chloropyrimidin-2-one

Sulfhydryl-related reduction of the mitotic inhibition and cell inactivation induced by the pyrimidine analogs NY 3170, NY 4137 and NY 4138 was investigated. Human NHIK 3025 cells grown in culture were treated with the SH-compounds glutathione (GSH) and cysteine, and the S-S-compound cystine in combination with the above pyrimidine analogs. Simultaneous combination of GSH or cysteine with NY 4137 (a pyrimidine sulfone) abolished the ability of the drug to arrest cells in metaphase, while simultaneous combination of NY 4137 with cystine had no such effect. The mitigating effect of GSH and cysteine was dose-dependent and maximal at 1 mM GSH or 2.5 mM cysteine. In combination with NY 4138 (a pyrimidine sulfoxide) GSH and cysteine, but not cystine, reduced slightly the ability of NY 4138 to accumulate cells in mitosis. By contrast, neither GSH, cysteine nor cystine affected the mitotic inhibiting property of NY 3170 when in simultaneous combination with this pyrimidinone. With respect to cell inactivation, an increase in the fraction of cells surviving treatment with NY 4137 was found when GSH or cysteine, but not cystine, was simultaneously present. In order to evaluate the importance of endogenous SH-groups, we measured the effect of NY 4137 on NHIK 1922-C3 cells, a mouse-human hybrid, having a lower endogenous sulfhydryl content than NHIK 3025 cells. Treatment of these cells with NY 4137 resulted in a lower surviving fraction of cells than identical treatment of NHIK 3025 cells.

Topics: Cell Cycle; Cell Line; Cell Survival; Chemical Phenomena; Chemistry; Cysteine; Cystine; Glutathione; Humans; Mitosis; Mitotic Index; Pyrimidines; Pyrimidinones; Sulfhydryl Compounds

A synergistic effect with respect to inactivation of human NHIK 3025 cells cultured in vitro was displayed when treatment with cis-dichlorodiammineplatinum(II) (cis-DDP) and the mitotic inhibitor 1-propargyl-5-chloropyrimidin-2-one (NY 3170) were given in simultaneous combination. Cell inactivation was measured by loss of colony-forming ability. Treatment with NY 3170 alone produced no significant inactivation at concentrations up to 2 mM. However, treatment with NY 3170 in combination with cis-DDP induced increased cell inactivating effects equal to a doubling of either the concentration of cis-DDP or treatment time. Scheduling of NY 3170 treatment in relationship to a 1 h cis-DDP pulse revealed that synergism occurred only when the two drugs were present simultaneously. The inactivating effect of 10 microM cis-DDP in combination with 2 mM NY 3170 given to synchronized NHIK 3025 cells at various stages of the cell cycle was also determined. For cells treated in S or in G2 + M cell survival was reduced by a factor of 5 after a 1 h treatment with the drug combination as compared to similar treatment with cis-DDP alone. The cells appeared to be most sensitive at the time of initiation of DNA synthesis. Here cell survival was reduced by a factor of 100 following treatment with the drug combination than following treatment with cis-DDP alone. Measurement of cell-associated platinum by atomic absorption spectroscopy indicated that cellular uptake of cis-DDP was increased when NY 3170 was simultaneously present during drug treatment.

Topics: Cell Cycle; Cell Line; Cell Survival; Cisplatin; Dose-Response Relationship, Drug; Drug Synergism; Humans; Mitosis; Pyrimidinones; Time Factors

The mitotic inhibitor 1-propargyl-5-chloropyrimidin-2-one (a metahalone) was found to bind to DEAE-cellulose purified rat brain tubulin. A decrease in the fluorescence of 1-propargyl-5-chloropyrimidin-2-one was seen when the drug was incubated in the presence of increasing tubulin concentrations. The decrease in metahalone fluorescence was not affected by the addition of GTP, indicating drug interaction at other portions of the tubulin molecule than the nucleotide binding sites. Scatchard plot analysis following incubation of tubulin with 1-propargyl-5-chloro-[2-14C]pyrimidin-2-one revealed that 1 mol of metahalone bound to 1 mol of tubulin dimer with a measured association constant of 8.0 X 10(3) M-1. Double reciprocal plots of vincristine and colchicine binding to tubulin in the presence of 1-propargyl-5-chloropyrimidin-2-one showed that the metahalone competitively inhibited colchicine binding to tubulin but had no influence on vincristine binding. This conclusion was supported by gel filtration chromatography where an increase in unbound colchicine was measured when 1-propargyl-5-chloropyrimidin-2-one was present in an incubation mixture containing colchicine and tubulin. In the presence of 5 mM 1-propargyl-5-chloropyrimidin-2-one, tubulin self-aggregated into crystalline structures. The binding of 1-propargyl-5-chloropyrimidin-2-one to tubulin at or near the colchicine binding site may be responsible for the metaphase arresting characteristics of this drug.

Topics: Animals; Binding Sites; Brain; Kinetics; Macromolecular Substances; Protein Binding; Pyrimidinones; Rats; Spectrometry, Fluorescence; Tubulin; Vincristine

Mutant CHO cells have been isolated which are resistant to NY 3170, a member of the metahalone group of antimitotic drugs. One NY 3170 resistant mutant is hypersensitive to the microtubule-stabilising drug, taxol, but there is not a reciprocal relationship between levels of resistance to these drugs in CHO cells, since it was found that sixteen other mutants isolated on the basis of taxol resistance had wild type levels of NY 3170 resistance. Our NY 3170 resistant mutants are cross-resistant to vincristine and other mutants, selected on the basis of vincristine resistance, are cross-resistant to NY 3170.

Topics: Animals; Cell Line; Cell Survival; Cricetinae; Cricetulus; Drug Resistance; Female; Kinetics; Mitosis; Mutation; Ovary; Pyrimidinones; Structure-Activity Relationship

Topics: Carcinoma in Situ; Cell Line; Cell Survival; Cells, Cultured; Dose-Response Relationship, Drug; Drug Resistance; Female; Humans; Mitotic Index; Pyrimidinones; Uterine Cervical Neoplasms; Vincristine

Inactivating effects caused by vincristine alone or in combination with another mitotic inhibitor, 1-propargyl-5-chloropyrimidin-2-one, were studied as loss of colony-forming ability in exponentially growing or synchronized populations of the human cell line NHIK 3025. Treatment with 4 ng vincristine per ml(4.3 nM) in G2 led to irreversible mitotic arrest. Both mitotic arrest and lethal damage due to vincristine were primarily induced when cells were exposed in late S and G2, suggesting a correlation between the cell cycle-inhibitory and inactivating effect of this drug at clinically relevant concentrations. No repair of sublethal damage after vincristine treatment could be detected within 5 hr. A common feature in the age response of NHIK 3025 cells to the two mitotic inhibitors is drug resistance in G1. However, while mitosis is the most sensitive stage in the cycle with respect to inactivation by 1-propargyl-5-chloropyrimidin-2-one, mitotic cells are relatively resistant to treatment with vincristine. The combined inactivating effect of vincristine and 1-propargyl-5-chloropyrimidin-2-one was purely additive during interphase. In mitosis, the two drugs demonstrated a striking synergistic effect.

Topics: Cell Survival; Cells, Cultured; Drug Resistance; Drug Synergism; Female; Humans; Interphase; Mitosis; Pyrimidinones; Vincristine

Inactivation of NHIK 3025 cells ny the mitotic inhibitor NY 3170 (1-propargyl-5-chloropyrimidin-2-one) was measured as loss of colony-forming ability. NY 3170 at a concentration of 0.15 nM allowed no formation of colonies after 12 days of continuous exposure to the drug. Metaphase arrest after treatment with NY 3170 was reversible if the drug was removed immediately after the onset of the arrest. When the cells were kept in mitosis by the presence of NY 3170, inactivation was complete after 8h incubation of mitotic cells with 0.4 nM NY 3170. Using synchronized cell populations, it was shown that mitosis is by far the most sensitive stage of the cell cycle to inactivation by NY 3170. This leads to the suggestion that there is a connection between the inactivating and the metaphase-arresting effect of this drug. The age response curves show that after mitosis the stages in order of decreasing sensitivity to NY3170 are: G2, late S, early S and G1. This is a similar age response to that reported for proliferating cells treated with bleomycin, whereas the mitotic inhibitors vincristine and vinblastine have shown qhite different age response curves.

Topics: Cell Cycle; Cell Survival; Cells, Cultured; Humans; Metaphase; Mitosis; Pyrimidinones; Time Factors