Indoloquinone EO9: DNA interstrand cross-linking upon reduction by DT-diaphorase or xanthine oxidase.
We report DNA interstrand cross-linking caused by the anti-tumour indoloquinone EO9 following reductive activation with purified rat liver DT-diaphorase or xanthine oxidase. Reduction was a necessary event for cross-linking to occur. DNA cross-link formation by EO9 following DT-diaphorase reduction was completely inhibited by addition 10 microM dicoumarol, whereas only a minor effect of dicoumarol on xanthine oxidase-mediated DNA cross-linking by EO9 was observed. DNA cross-linking was pH dependent, with increasing cross-link formation from pH 5.5 to 7.0 for both DT-diaphorase and xanthine oxidase mediated reactions. Also, conversion of EO9 upon reduction was pH dependent. However, in contrast to DNA cross-linking, conversion rates of EO9 decreased at higher pH. EO9 was shown to be more efficient in DNA cross-linking than mitomycin C under identical conditions, using both DT-diaphorase and xanthine oxidase reductive activation at pH 5.5 and 7.0. This study indicates that the anti-tumour activity of EO9 may be at least partly mediated by interstrand DNA cross-link formation, and that various reducing enzymes may be important for activation of EO9 in vitro and in vivo.
Maliepaard
M
M
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Utrecht University, The Netherlands.
Wolfs
A
A
Groot
S E
SE
de Mol
N J
NJ
Janssen
L H
LH
D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D001388:Aziridines / Q000378:metabolism* / Q000494:pharmacology*; D001711:Biotransformation; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004247:DNA / Q000187:drug effects* / Q000378:metabolism; D001728:Dicumarol / Q000494:pharmacology; D045563:Indolequinones; D007211:Indoles / Q000378:metabolism* / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology; D008297:Male; D016685:Mitomycin / Q000494:pharmacology; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar; D014969:Xanthine Oxidase / Q000378:metabolism*
D000970:Antineoplastic Agents; D001388:Aziridines; D003432:Cross-Linking Reagents; D045563:Indolequinones; D007211:Indoles; D016685:Mitomycin; D001728:Dicumarol; D004247:DNA; D014969:Xanthine Oxidase; D016660:NAD(P)H Dehydrogenase (Quinone); C060817:apaziquone