Platinated DNA adducts enhance poisoning of DNA topoisomerase I by camptothecin.
Camptothecins constitute a novel class of chemotherapeutics that selectively target DNA topoisomerase I (Top1) by reversibly stabilizing a covalent enzyme-DNA intermediate. This cytotoxic mechanism contrasts with that of platinum drugs, such as cisplatin, which induce inter- and intrastrand DNA adducts. In vitro combination studies using platinum drugs combined with Top1 poisons, such as topotecan, showed a schedule-dependent synergistic activity, with promising results in the clinic. However, whereas the molecular mechanism of these single agents may be relatively well understood, the mode of action of these chemotherapeutic agents in combination necessitates a more complete understanding. Indeed, we recently reported that a functional homologous recombination pathway is required for cisplatin and topotecan synergy yet represses the synergistic toxicity of 1-beta-D-arabinofuranosyl cytidine in combination with topotecan (van Waardenburg, R. C., de Jong, L. A., van Delft, F., van Eijndhoven, M. A., Bohlander, M., Bjornsti, M. A., Brouwer, J., and Schellens, J. H. (2004) Mol. Cancer Ther. 3, 393-402). Here we provide direct evidence for Pt-1,3-d(GTG) poisoning of Top1 in vitro and demonstrate that persistent Pt-DNA adducts correlate with increased covalent Top1-DNA complexes in vivo. This contrasts with a lack of persistent lesions induced by the alkylating agent bis[chloroethyl]nitrosourea, which exhibits only additive activity with topotecan in a range of cell lines. In human IGROV-1 ovarian cancer cells, the synergistic activity of cisplatin with topotecan requires processive DNA polymerization, whereas overexpression of Top1 enhances yeast cell sensitivity to cisplatin. These results indicate that the cytotoxic activity of cisplatin is due, in part, to poisoning of Top1, which is exacerbated in the presence of topotecan.
Department of Experimental Therapy, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
Robert C A M
RC
van Waardenburg
Laurina A
LA
de Jong
Maria A J
MA
van Eijndhoven
Caroline
C
Verseyden
Dick
D
Pluim
Lars E T
LE
Jansen
Mary-Ann
MA
Bjornsti
Jan H M
JH
Schellens
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D001943:Breast Neoplasms; D002166:Camptothecin / Q000494:pharmacology*; D002945:Cisplatin / Q000494:pharmacology; D003110:Colonic Neoplasms; D003561:Cytarabine / Q000494:pharmacology; D004247:DNA / Q000737:chemistry; D018736:DNA Adducts / Q000737:chemistry / Q000494:pharmacology*; D004264:DNA Topoisomerases, Type I / Q000737:chemistry; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008958:Models, Molecular; D010051:Ovarian Neoplasms; D017671:Platinum Compounds / Q000494:pharmacology*; D059004:Topoisomerase I Inhibitors; D019772:Topotecan / Q000737:chemistry / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000972:Antineoplastic Agents, Phytogenic; D018736:DNA Adducts; D004791:Enzyme Inhibitors; D017671:Platinum Compounds; D059004:Topoisomerase I Inhibitors; D003561:Cytarabine; D019772:Topotecan; D004247:DNA; D004264:DNA Topoisomerases, Type I; D002945:Cisplatin; D002166:Camptothecin