Mechanism of action of the synthetic imidazole compound YM 534 on human promyelocytic leukemia line HL-60 cells

The effects of a novel anti-cancer drug, YM 534 on human promyelocytic leukemia line HL-60 cells were investigated. The growth of the cells was completely inhibited with an IC50 of 2.5 X 10(-6) M. The incorporation of 3H-thymidine or 3H-uridine into acid insoluble fraction of the cells was completely inhibited at a 10(-4) M concentration of the drug. However, that of 3H-leucine was suppressed by only 32% at this drug concentration. The single strand scission of DNA of the cells as revealed by alkali sucrose density gradient centrifugation was induced by YM 534 at a 10(-4)M concentration for 60 min. When PM2 DNA in a cell-free system was examined in the presence or absence of reducing agent, no damage to DNA was observed at a 10(-4)M YM 534. The processing of preribosomal to ribosomal RNA of HL-60 cells was retarded at a 10(-5) M level of the drug.