Interstrand cross-linking by adriamycin in nuclear and mitochondrial DNA of MCF-7 cells.
Activation of Adriamycin by formaldehyde leads to the formation of drug-DNA adducts in vitro and these adducts stabilise the DNA to such a degree that they function as virtual interstrand cross-links. The formation of these virtual interstrand cross-links by Adriamycin was investigated in MCF-7 cells using a gene-specific interstrand cross-linking assay. Cross-linking was measured in both the nuclear-encoded DHFR gene and in mitochondrial DNA (mtDNA). Cross-link formation increased linearly with Adriamycin concentration following a 4 h exposure to the drug. The rate of formation of Adriamycin cross-links in each of the genomes was similar, reaching maximal levels of 0.55 and 0.4 cross-links/10 kb in the DHFR gene and mtDNA respectively, following exposure to 20 micro M Adriamycin for 8 h. The interstrand cross-link was short lived in both DNA compartments, with a half-life of 4.5 and 3.3 h in the DHFR gene and mtDNA respectively. The kinetics of total Adriamycin adduct formation, detected using [(14)C]Adriamycin, was similar to that of cross-link formation. Maximal adduct levels (30 lesions/10 kb) were observed following incubation at 20 micro M drug for 8 h. The formation of such high levels of adducts and cross-links could therefore be expected to contribute to the mechanism of action of Adriamycin.
Cullinane
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Department of Biochemistry, La Trobe University, Bundoora, Victoria 3083, Australia.
Cutts
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SM
Panousis
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Phillips
D R
DR
D002250:Carbon Radioisotopes; D002467:Cell Nucleus / Q000737:chemistry*; D018736:DNA Adducts; D004272:DNA, Mitochondrial / Q000737:chemistry*; D004273:DNA, Neoplasm / Q000737:chemistry*; D004317:Doxorubicin / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics; D014407:Tumor Cells, Cultured
D002250:Carbon Radioisotopes; D018736:DNA Adducts; D004272:DNA, Mitochondrial; D004273:DNA, Neoplasm; D004317:Doxorubicin; D013762:Tetrahydrofolate Dehydrogenase