title: Efficient induction of chromosome-type aberrations by topoisomerase II inhibitors closely associated with stabilization of the cleavable complex in cultured fibroblastic cells.
abstract: Eukaryotic topoisomerase II (Topo-II) inhibitors such as etoposide, adriamycin and mitoxantrone, which commonly stabilize the cleavable complex of the enzyme and DNA, have been found to efficiently induce chromosome-type aberrations (mainly breaks and exchanges) in cultured Chinese hamster lung fibroblastic cells (CHL cells). To clarify whether the induction of chromosome-type aberrations is mediated by stabilization of the cleavable complex, the present study investigated (1) the correlation between the induction of chromosome-type aberrations and the amount of cleavable complex formed; and (2) the ATP dependence of the Topo-II inhibitor-induced chromosome-type aberrations due to the ATP requirement of cleavable complex formation by Topo-II. First, in cells treated with the Topo-II inhibitors, (etoposide, adriamycin) and aclarubicin, an antagonist of the inhibitor of cleavable complex formation, the frequency of chromosome-type aberrations decreased dose-dependently with aclarubicin, in contrast to an increase of chromatid-type aberrations. The formation of the cleavable complex was further established by a proteinase K/SDS precipitation assay for cleaved double-strand DNA in a cell-free system and in CHL cells. Results from both experiments showed that aclarubicin caused a dose-dependent suppression of the accumulation of the cleavable complex induced by etoposide, which corresponded particularly well to the reduction of chromosome-type aberrations in etoposide-treated cells. In ATP-depleted cells simultaneously treated with etoposide and dinitrophenol (DNP), chromosome-type aberrations were reduced as compared with DNP-untreated cells, in contrast to an increase of chromatid exchanges in the cells. This means that etoposide-induced chromosome-type aberrations in ATP-depleted cells may be attributable to incompleteness of Topo-II activities to form DNA double-strand breaks. The present findings indicate that the stabilization of the cleavable complex on Topo-II is closely associated with the induction of chromosome-type aberrations.
authors.affiliation: Taisho Pharmaceutical Co., Ltd., Ohmiya, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Suzuki
authors.forename: T
authors.initials: T
authors.lastname: Ikeda
authors.forename: T
authors.initials: T
authors.lastname: Yamagishi
authors.forename: S
authors.initials: S
authors.lastname: Nakaike
authors.forename: S
authors.initials: S
authors.lastname: Nakane
authors.forename: M
authors.initials: M
authors.lastname: Ohsawa
mesh_terms: D019297:2,4-Dinitrophenol; D015250:Aclarubicin / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002166:Camptothecin / Q000037:antagonists & inhibitors / Q000633:toxicity; D002478:Cells, Cultured; D002869:Chromosome Aberrations; D006224:Cricetinae; D004247:DNA / Q000187:drug effects*; D004249:DNA Damage; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004140:Dinitrophenols / Q000494:pharmacology; D004317:Doxorubicin / Q000037:antagonists & inhibitors / Q000633:toxicity; D005047:Etoposide / Q000037:antagonists & inhibitors / Q000633:toxicity; D005347:Fibroblasts / Q000187:drug effects; D059005:Topoisomerase II Inhibitors
chemical_list: D004140:Dinitrophenols; D059005:Topoisomerase II Inhibitors; D005047:Etoposide; D015250:Aclarubicin; D004317:Doxorubicin; D000255:Adenosine Triphosphate; D004247:DNA; D004250:DNA Topoisomerases, Type II; D019297:2,4-Dinitrophenol; D002166:Camptothecin