The ortho-quinone metabolite of the anticancer drug etoposide (VP-16) is a potent inhibitor of the topoisomerase II/DNA cleavable complex.
Mol Pharmacol
; 53(3): 422-8, 1998 Mar.
Article
em En
| MEDLINE
| ID: mdl-9495807
ABSTRACT
Epipodophyllotoxin derivatives, such as etoposide (VP-16), constitute an important class of anticancer agents, the major cytotoxic effects of which are associated with trapping of the topoisomerase II/DNA cleavable complex and formation of protein-DNA cross-links and nicked DNA. VP-16, however, can be metabolized to several highly reactive products, including an ortho-quinone (VPQ). The inhibitory activity of VPQ against purified human topoisomerase II processing of supercoiled DNA was studied and compared with that of the parent compound, VP-16. Our results show that VPQ is a powerful inhibitor of topoisomerase II, which prevents DNA strand passage in the presence of ATP. As with VP-16, trapping of the cleavable complex is highly reversible upon removal of divalent ions, which indicating that VPQ alters the cleavage-reunion equilibrium of topoisomerase II and DNA mainly by noncovalent interactions, as does the parent compound. However, we observed several differences between the effects induced by VP-16 and VPQ, including a strong inhibition of the second DNA strand religation, which implies the involvement of additional (asymmetric) mode(s) of interactions of the VPQ, possibly by interference with ATP binding by the homodimeric enzyme, and/or involving covalent interactions. Reduced or oxidized glutathione prevented trapping of the topoisomerase/DNA cleavable complex by VPQ, but not by VP-16, probably by forming covalent adducts with the former.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
DNA
/
Inibidores Enzimáticos
/
Etoposídeo
/
Inibidores da Topoisomerase II
/
Antineoplásicos Fitogênicos
Limite:
Humans
Idioma:
En
Revista:
Mol Pharmacol
Ano de publicação:
1998
Tipo de documento:
Article
País de afiliação:
Canadá