Effects of the new mitotic inhibitor pyrimidinsulfone NY 4137 on human cells in vitro and on colchicine binding to tubulin.

The effect of 2-(2-thenyl)sulfonyl-5-bromopyrimidine (NY 4137) on cells of the human line NHIK 3025 was investigated. It was shown that NY 4137 induces cell cycle specific inhibition in metaphase. A dose-dependent prolongation of metaphase was found and the fraction of cells able to escape metaphase arrest declined gradually as the concentration of NY 4137 increased. A total block in metaphase was achieved with 0.016 mM and higher concentrations of NY 4137. Interphase was also prolonged in cells treated with 0.016 mM. Inhibition of valine incorporation by NY 4137 was also found to be dose-dependent. Following a 2-h exposure to 0.2 mM NY 4137 valine incorporation was inhibited by 80-85%. Inhibition of colchicine and vincristine binding to purified tubulin was also investigated. Double reciprocal plot and gel filtration chromatography showed that NY 4137 competitively inhibited colchicine binding to DEAE-cellulose purified tubulin. NY 4137 had no effect on vincristine binding to tubulin. The binding of NY 4137 to tubulin at or near the colchicine binding site may be responsible for the metaphase arrest.