Induction of HL-60 cell differentiation by 3-deaza-(+/-)-aristeromycin, an inhibitor of S-adenosylhomocysteine hydrolase.

The metabolically stable inhibitor of S-adenosylhomocysteine hydrolase (AdoHcyase), 3-deaza-(+/-)-aristeromycin (dzAri) has recently been shown to induce differentiation in HL-60 cells. The present study was undertaken to characterize the cytostatic, cytotoxic, and differentiation inducing properties of dzAri in HL-60 cells and to investigate biochemical consequences of AdoHcyase inhibition. A dye exclusion test and a clonogenic assay were used to test cytotoxic and cytostatic properties. dzAri had reversible cytostatic effects on HL-60 cells at concentrations lower than 10 microM and partially reversible cytotoxic effects above 10 microM. The induction of differentiation was dependent upon concentration and time of exposure, with maximal effect after 6 days incubation with 5-10 microM dzAri. Washout experiments demonstrated that the cells were not committed to differentiation after 48 h of incubation with dzAri. The AdoHcyase of HL-60 cells was inhibited with a Ki of 20 nM. The concentration of S-adenosylhomocysteine increased dose dependently 48 h after incubation with 0.1-100 microM dzAri. The incorporation of [3H]methyl from [methyl-3H]methionine into 5-methylcytosine of DNA was reduced by 26% at 5 microM dzAri. The findings indicate that continuous presence of dzAri is necessary to induce differentiation and inhibit proliferation in HL-60 cells. The inhibition of AdoHcyase perturbs levels of transmethylation metabolites and the incorporation of [3H]methyl into 5-methyl-cytosine of DNA.