Studies on the mechanism of action of anthramycin methyl ether, a new antitumor antibiotic.

Abstract

Summary Anthramycin methyl ether (AME), an antibiotic with antitumor activity, inhibits the in vivo and in vitro synthesis of RNA and DNA by Ehrlich ascites carcinoma cells. AME is a competitive inhibitor (with respect to DNA) of the cell-free synthesis of RNA and DNA by the DNA-dependent polymerase enzymes, as well as the enzymatic hydrolysis of DNA by DNase I. The interaction of AME with DNA was demonstrated by the isolation of an AME-DNA complex by gel filtration chromatography on Sephadex G-50 columns, by equilibrium dialysis studies, by ultraviolet absorption spectroscopy, by an increase in the melting temperature (Tm) of DNA when AME was added, and by the displacement of methyl green from a DNA-methyl green complex by AME. The DNA helix must be intact for AME to bind to DNA and for AME to inhibit the DNA-dependent enzymic reactions. These results are compatible with the proposition that AME exerts its actions as a growth inhibitor by interacting with helical, double-stranded DNA to form an AME-DNA complex, which in turn prevents DNA from participating as a template in the biosynthesis of RNA and DNA.