title: Effect of polyamine depletion by alpha-difluoromethylornithine or (2R,5R)-6-heptyne-2,5-diamine on drug-induced topoisomerase II-mediated DNA cleavage and cytotoxicity in human and murine leukemia cells.
abstract: The effects of alpha-difluoromethylornithine (DFMO), an ornithine analogue which is an ornithine decarboxylase inhibitor, on the actions of the topoisomerase II-reactive agents 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) and etoposide (VP-16) were investigated in 2 murine L1210 leukemia lines and 2 human HL-60 leukemia lines. One of the human lines was resistant to the cytotoxic and DNA cleaving effects of m-AMSA (HL-60/AMSA). In all 4 lines, alpha-DFMO depleted cellular putrescine and spermidine to nondetectable levels. VP-16-induced DNA cleavage (quantified using alkaline elution) was decreased in all lines following alpha-DFMO treatment. The m-AMSA-induced DNA cleavage was decreased in one of the L1210 lines and in the HL-60 line sensitive to m-AMSA; m-AMSA-induced DNA cleavage was increased in the other L1210 line. The low frequency of m-AMSA-induced DNA cleavage produced in HL-60/AMSA was unaffected by alpha-DFMO treatment. Alterations in drug-mediated DNA effects induced by alpha-DFMO could not be uniformly explained by alpha-DFMO-induced alterations in m-AMSA or VP-16 cellular uptake, as indicated by direct measurements of cell-associated drug or results of DNA cleavage assays in nuclei isolated from alpha-DFMO-treated cells. Exogenous putrescine prevented the effects of alpha-DFMO on drug-induced DNA cleavage, substantiating polyamine depletion as the cause of the altered frequency of DNA cleavage. Cytotoxicity assays in 2 of the lines demonstrated that drug-induced reductions in colony-forming ability paralleled drug-induced DNA cleavage. (2R,5R)-6-heptyne-2,5-diamine, a putrescine analogue which is also an ornithine decarboxylase inhibitor, was also used to deplete polyamine levels in HL-60. (2R,5R)-6-heptyne-2,5-diamine was more potent than alpha-DFMO and produced effects on m-AMSA- and VP-16-induced DNA cleavage and cytotoxicity identical to those produced by alpha-DFMO.
authors.affiliation: Department of Medical Oncology, University of Texas, M.D. Anderson Hospital and Tumor Institute, Houston 77030.
authors.forename: M
authors.initials: M
authors.lastname: Bakic
authors.forename: D
authors.initials: D
authors.lastname: Chan
authors.forename: E J
authors.initials: EJ
authors.lastname: Freireich
authors.forename: L J
authors.initials: LJ
authors.lastname: Marton
authors.forename: L A
authors.initials: LA
authors.lastname: Zwelling
mesh_terms: D000480:Alkynes; D000677:Amsacrine / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004247:DNA / Q000187:drug effects / Q000378:metabolism*; D004249:DNA Damage; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D003959:Diamines / Q000494:pharmacology*; D000518:Eflornithine / Q000494:pharmacology*; D005047:Etoposide / Q000494:pharmacology; D006801:Humans; D007939:Leukemia L1210 / Q000235:genetics / Q000378:metabolism; D015470:Leukemia, Myeloid, Acute / Q000235:genetics / Q000378:metabolism; D051379:Mice; D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000187:drug effects*
chemical_list: D000480:Alkynes; D000970:Antineoplastic Agents; D003959:Diamines; D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines; D000677:Amsacrine; D005047:Etoposide; C039613:6-heptyne-2,5-diamine; D004247:DNA; D004250:DNA Topoisomerases, Type II; D000518:Eflornithine