Thiol-dependent DNA damage produced by anthracycline-iron complexes. The structure-activity relationships and molecular mechanisms.

Doxorubicin (Adriamycin) and daunomycin analogs have been examined for their ability to chelate iron and catalyze the oxidative cleavage of DNA. The results show that the C-11-hydroxyl group is essential for iron binding and DNA damage. Thus, the iron complexes of doxorubicin, daunomycin, carminomycin, and 4-demethoxydaunomycin are potent redox catalysts capable of reducing molecular oxygen in the presence of physiologic concentrations of glutathione. They are also effective catalysts of hydroxyl radical formation from hydrogen peroxide. With the exception of daunomycin, generation of hydroxyl radical from hydrogen peroxide is stimulated by greater than 200% by DNA addition. Analogs that lack the C-11-hydroxyl group are relatively inefficient at oxygen reduction, hydroxyl radical formation, and DNA cleavage. The potencies of the anthracycline analogs tested in the H2O2-dependent DNA cleavage reaction correlated well with their relative cardiac toxicities.