title: DNA topoisomerase II as the target for the anticancer drug TOP-53: mechanistic basis for drug action.
abstract: TOP-53 is a promising anticancer agent that displays high activity against non-small cell lung cancer in animal tumor models [Utsugi, T., et al. (1996) Cancer Res. 56, 2809-2814]. Compared to its parent compound, etoposide, TOP-53 is considerably more toxic to non-small cell lung cancer cells, is more active at generating chromosomal breaks, and displays improved cellular uptake and pharmacokinetics in animal lung tissues. Despite the preclinical success of TOP-53, several questions remain regarding its cytotoxic mechanism. Therefore, this study characterized the basis for drug action. Results indicate that topoisomerase II is the primary cytotoxic target for TOP-53. Furthermore, the drug kills cells by acting as a topoisomerase II poison. TOP-53 exhibits a DNA cleavage site specificity that is identical to that of etoposide. Like its parent compound, the drug increases the number of enzyme-mediated DNA breaks by interfering with the DNA religation activity of the enzyme. TOP-53 is considerably more efficient than etoposide at enhancing topoisomerase II-mediated DNA cleavage and exhibits high activity against human topoisomerase IIalpha and IIbeta in vitro and in cultured cells. Therefore, at least in part, the enhanced cytotoxic activity of TOP-53 can be attributed to an enhanced activity against topoisomerase II. Finally, TOP-53 displays nearly wild-type activity against a mutant yeast type II enzyme that is highly resistant to etoposide. This finding suggests that TOP-53 can retain activity against systems that have developed resistance to etoposide, and indicates that substituents on the etoposide C-ring are important for topoisomerase II-drug interactions.
authors.affiliation: Department of Biochemistry and Medicine (Hematology/Oncology), Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Byl
authors.forename: S D
authors.initials: SD
authors.lastname: Cline
authors.forename: T
authors.initials: T
authors.lastname: Utsugi
authors.forename: T
authors.initials: T
authors.lastname: Kobunai
authors.forename: Y
authors.initials: Y
authors.lastname: Yamada
authors.forename: N
authors.initials: N
authors.lastname: Osheroff
mesh_terms: D000951:Antigens, Neoplasm; D000972:Antineoplastic Agents, Phytogenic / Q000633:toxicity*; D004249:DNA Damage / Q000187:drug effects; D011088:DNA Ligases / Q000037:antagonists & inhibitors; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D004271:DNA, Fungal / Q000378:metabolism; D004268:DNA-Binding Proteins; D005047:Etoposide / Q000031:analogs & derivatives* / Q000633:toxicity*; D006801:Humans; D006868:Hydrolysis / Q000187:drug effects; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D013329:Structure-Activity Relationship; D059005:Topoisomerase II Inhibitors; D014407:Tumor Cells, Cultured
chemical_list: D000951:Antigens, Neoplasm; D000972:Antineoplastic Agents, Phytogenic; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D007527:Isoenzymes; D011994:Recombinant Proteins; C099874:TOP 53; D059005:Topoisomerase II Inhibitors; D005047:Etoposide; D004250:DNA Topoisomerases, Type II; D011088:DNA Ligases