Dependence of nucleic acid degradation on in situ free-radical production by adriamycin.
Adriamycin (Adr) is one of the most powerful antitumor drugs. Its therapeutic effect may be due to its cyclic reduction-oxidation and, thus, generation of oxygen radicals. Using the spin-trap 5,5'-dimethyl-1-pyrroline N-oxide (DMPO) and EPR we have demonstrated that in an enzymatic system consisting of NADPH, NADPH-cytochrome P-450 reductase, and Fe(EDTA)2 Adr stimulates formation of .OH radicals in the presence of DNA or RNA with equal efficiency. Incubation of nucleic acids in the Adr-dependent reaction generating .OH radicals resulted in extensive degradation of double- and single-stranded DNA, but did not effect RNA. In contrast, both DNA and RNA were effectively destroyed in a footprinting system, ascorbate-Fe(EDTA)2-H2O2, which generates .OH radicals in massive quantities. Fluorescence assays indicated that Adr forms stable complexes with ds- and ss-DNA but reacts only slightly with RNA. We conclude that the formation of Adr-nucleic acid complex is necessary for .OH radical-mediated cleavage of the latter, and thus, Adr may be regarded as a chemical nuclease acting in situ.
Feinstein
E
E
Department of Chemical Immunology, Weizmann Institute of Science, Rehovot, Israel.
Canaani
E
E
Weiner
L M
LM
D004247:DNA / Q000737:chemistry*; D004249:DNA Damage; D004317:Doxorubicin / Q000737:chemistry*; D005609:Free Radicals; D006878:Hydroxides / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D012313:RNA / Q000737:chemistry*
D005609:Free Radicals; D006878:Hydroxides; D012313:RNA; D004317:Doxorubicin; D004247:DNA; D010100:Oxygen