title: Postincubation with aclarubicin reverses topoisomerase II mediated DNA cleavage, strand breaks, and cytotoxicity induced by VP-16.
abstract: In previous studies, we found that VP-16 (etoposide) induced cytotoxicity and protein-concealed strand break formation was prevented in a small cell lung cancer (SCLC) cell line, when the cells were incubated with aclarubicin prior to treatment with VP-16. In the present work, we studied the effect of adding aclarubicin to the cell suspension after VP-16. In a clonogenic assay, we found that the cytotoxicity induced by VP-16 in SCLC cells was inhibited when cells were postincubated with aclarubicin. The addition of aclarubicin at any time in relation to VP-16 was able to stop further cytotoxicity induced by the topoisomerase II (topo-II) targeting drug. Aclarubicin was also found to antagonize the cytotoxicity induced by VM-26 (teniposide), and m-AMSA. With the alkaline elution technique we found that postincubating the cells with aclarubicin inhibited VP-16-induced DNA strand break formation. In an in vitro system with purified topo-II and naked DNA we likewise found, that postincubation with aclarubicin prevented VP-16 induced cleavage. In the same in vitro system, also baseline cleavage induced by topo-II was inhibited when aclarubicin was present. Importantly, aclarubicin exerted the antagonism to topo-II targeting drugs both when administered prior to and after the topo-II targeting agents. Thus, our data suggest that sequential rather than simultaneous administration of aclarubicin and topo-II targeting agents may be superior with respect to net-cytotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Institute of Pathological Anatomy, University of Copenhagen, Denmark.
authors.forename: L N
authors.initials: LN
authors.lastname: Petersen
authors.forename: P B
authors.initials: PB
authors.lastname: Jensen
authors.forename: B S
authors.initials: BS
authors.lastname: Sørensen
authors.forename: S A
authors.initials: SA
authors.lastname: Engelholm
authors.forename: M
authors.initials: M
authors.lastname: Spang-Thomsen
mesh_terms: D015250:Aclarubicin / Q000494:pharmacology*; D000818:Animals; D018288:Carcinoma, Small Cell; D004249:DNA Damage / Q000187:drug effects*; D004273:DNA, Neoplasm / Q000187:drug effects; D005047:Etoposide / Q000037:antagonists & inhibitors*; D006801:Humans; D008175:Lung Neoplasms; D051379:Mice; D013997:Time Factors; D059005:Topoisomerase II Inhibitors; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
chemical_list: D004273:DNA, Neoplasm; D059005:Topoisomerase II Inhibitors; D005047:Etoposide; D015250:Aclarubicin