Role of iron in adriamycin biochemistry

Adriamycin forms a chelate with Fe(III) that exhibits complex redox chemistry. The drug ligand is able to directly reduce the bound Fe(III) with the concomitant production of a one-electron oxidized drug radical. This Fe(II) can reduce oxygen to hydrogen peroxide and cleave the peroxide to yield the hydroxyl radical. In addition, the drug-Fe complex can catalyze the transfer of electrons from reduced glutathione to molecular oxygen to yield superoxide, hydrogen peroxide, and hydroxyl radicals. The adriamycin · Fe complex binds to DNA to form a ternary drug · Fe · DNA complex, which is also able to catalyze the thiol-dependent reduction of oxygen and the formation of hydroxyl radical from hydrogen peroxide. As a consequence of this chemistry, the adriamycin·Fe complex can cleave DNA on the addition of glutathione or hydrogen peroxide. Although less well defined, the adriamycin·Fe complex can bind to cell membranes and cause oxidative destruction of these membranes in the presence of thiols or hydrogen peroxide.