Abstract
Oxaliplatin is a clinical anticancer drug with a pharmacological profile distinct from that of cisplatin. Our studies compared site- and region-specificity of lesions induced by oxaliplatin and cisplatin in naked and intracellular DNA, respectively. Oxaliplatin adducts in naked Simian virus 40 (SV40 DNA) were mapped by repetitive primer extension. The sites of oxaliplatin adducts were nearly identical to the sites of cisplatin adducts and were focused in G clusters and GNG motifs probably reflecting intrastrand cross-links. Although alkaline agarose electrophoresis of specific SV40 fragments showed that oxaliplatin formed interstrand cross-links, the levels of this lesion type were low. Drug-induced lesions in discrete loci of cellular DNA were assessed by the polymerase chain reaction stop assay in human tumor A2780 cells. Oxaliplatin at 200 μm induced ∼1300, ∼1500, ∼800, and ∼300 lesions/106 bp in the human β-globin, c-myc, andHPRT genes and in mitochondrial DNA, respectively. Cisplatin formed two to six times more lesions in the same regions. For both drugs, lesion frequencies seem to parallel the density of drug-binding motifs in the nuclear regions, whereas mitochondrial DNA was disproportionately less affected. Despite less potent induction of DNA lesions, oxaliplatin was more cytotoxic than cisplatin against A2780 cells. Because our findings clearly demonstrate that oxaliplatin forms covalent adducts with a similar sequence- and region-specificity to that of cisplatin, other properties of oxaliplatin adducts, factors other than DNA binding, or both determine the unique features of the mechanism of action of oxaliplatin.
Footnotes
- Received May 28, 1998.
- Accepted August 3, 1998.
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Send reprint requests to: Jan M. Woynarowski, Ph.D., Cancer Therapy and Research Center, Institute for Drug Development, 14960 Omicron Drive, San Antonio, TX 78245-3217. E-mail: jmw1{at}saci.org
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This study was supported in part by a grant from Sanofi-Research, a Division of Sanofi Pharmaceuticals, Inc., and by Cancer Therapy and Research Center Research Foundation. A preliminary account of this study was presented in part at the 88th Annual Meeting of the American Association for Cancer Research [Proc Am Assoc Cancer Res 38:311 (1097)].
- The American Society for Pharmacology and Experimental Therapeutics
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