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A general mechanism for microsomal activation of quinone anticancer agents to free radicals.

1978; National Institutes of Health; Volume: 38; Issue: 6 Linguagem: Inglês

Nicholas R. Bachur, Sandra Gordon, Malcolm V. Gee,

Synthesis and biological activity

Abstract The highly active, quinone-containing anticancer drugs, Adriamycin, daunorubicin, carminomycin, rubidazone, nogalamycin, aclacinomycin A, and steffimycin (benzanthraquinones); mitomycin C and streptonigrin (N-heterocyclic quinones); and lapachol (naphthoquinone) interact with mammalian microsomes and function as free radical carriers. These quinone drugs augment the flow of electrons from reduced nicotinamide adenine dinucleotide phosphate to molecular oxygen as measured by enhanced reduced nicotinamide adenine dinucleotide phosphate oxidation and oxygen consumption. This reaction is catalyzed by microsomal protein and produces a free radical intermediate form of the drugs as determined by electron paramagnetic resonance spectroscopy. Microsomes from mouse and rat liver, heart, lung, and spleen and mouse L1210 and P388 tumors all catalyze the augmented oxygen consumption. Apparent Km values determined with normal rat liver microsomes range from 0.49 × 10-4m for steffimycin to 13.4 × 10-4m for lapachol. Since SKF 525A and carbon monoxide have little effect on this reaction, cytochrome P-450 is probably not involved. Several nonquinone anticancer agents were tested and were found inactive in the system. Since quinone anticancer drugs are associated with chromosomal damage that appears to be dependent on metabolic activation of these drugs, we propose that the intracellular activation of these drugs to a free radical state may be primary to their cytotoxic activity. As free radicals, these drugs, because of their high affinity and selective binding to nucleic acids, have the potential to be “site-specific free radicals” that bind to DNA or RNA and either react directly or generate oxygen-dependent free radicals such as superoxide radical or hydroxyl radical to cause the damage associated with their cytotoxic actions.