title: Enhanced topoisomerase II targeting by annamycin and related 4-demethoxy anthracycline analogues.
abstract: Targeting topoisomerase II (topo II) is regarded as an important component of the pleiotropic mechanism of action of anthracycline drugs. Here, we show that 4-demethoxy analogues of doxorubicin, including annamycin, exhibit a greater ability to trap topo II cleavage complexes than doxorubicin and some other 4-methoxy analogues. In leukemic CEM cells with wild-type topo II, annamycin induced substantial levels of topo II-mediated DNA-protein cross-links (15-37% of total DNA for 0.5-50 micromol/L drug), whereas doxorubicin-induced DNA-protein cross-links were marginal (0-4%). In CEM/VM-1 cells that harbor mutated, drug-resistant topo II, both 4-methoxy and 4-demethoxy drugs produced marginal DNA-protein cross-links. Annamycin, but not doxorubicin, formed topo II-mediated DNA-protein cross-links also in isolated CEM nuclei. In disparity with the unequal DNA-protein cross-link induction, both drugs induced comparable levels of DNA strand breaks in CEM cells. Compared with CEM, drug cytotoxicity against CEM/VM-1 cells was reduced 10.5- to 13.8-fold for 4-demethoxy analogues but only 3.8- to 5.5-fold for 4-methoxy drugs. Hence, growth inhibition by 4-demethoxy analogues seems more dependent on the presence of wild-type topo II. The enhanced topo II targeting by 4-demethoxy analogues was accompanied by a profound induction of apoptotic DNA fragmentation in leukemic CEM cells. Normal WI-38 fibroblasts, however, were markedly more resistant to annamycin-induced DNA-protein cross-links, apoptosis, and growth inhibition. The enhanced topo II targeting by 4-demethoxy doxorubicin analogues underscores the mechanistic diversity of anthracycline drugs. This diversity needs to be recognized as a factor in responses to drugs such as annamycin and doxorubicin.
authors.affiliation: Department of Radiation Oncology, University of Texas Health Science Center, San Antonio, TX 78245, USA.
authors.forename: Alex V
authors.initials: AV
authors.lastname: Trevino
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Woynarowska
authors.forename: Terence S
authors.initials: TS
authors.lastname: Herman
authors.forename: Waldemar
authors.initials: W
authors.lastname: Priebe
authors.forename: Jan M
authors.initials: JM
authors.lastname: Woynarowski
mesh_terms: D018943:Anthracyclines / Q000737:chemistry* / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D004247:DNA / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004317:Doxorubicin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D015394:Molecular Structure; D011485:Protein Binding
chemical_list: C500024:4-demethoxyanthracycline; D018943:Anthracyclines; D004791:Enzyme Inhibitors; D004317:Doxorubicin; D004247:DNA; D004250:DNA Topoisomerases, Type II; C080315:annamycin