Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism of death induced by recombinant human tumor necrosis factor (rHuTNF) in L929 tumor cells of C3H mice was investigated. Treatment with rHuTNF led to fragmentation of DNA into nucleosomal oligomers and to induction of the expression of TRPM-2, a programmed cell death-associated gene. Both events preceded cell death by several hours. Treatment with DNA topoisomerase II inhibitors accelerated both the rHuTNF-mediated DNA fragmentation and the elevation in TRPM-2 messenger RNA levels. These results suggest that rHuTNF exerts its cytotoxicity on L929 cells by activating programmed cell death, leading to apoptosis, and that topoisomerase II inhibitors enhance rHuTNF-mediated cytotoxicity by accelerating this process.
J Natl Cancer Inst 1991 Mar 06
PMID:Activation of programmed cell death by recombinant human tumor necrosis factor plus topoisomerase II-targeted drugs in L929 tumor cells. 156 7

The effects of topoisomerase II-reactive epipodophyllotoxins etoposide and teniposide as well as amsacrine on the viability of thymocytes in primary culture has been examined. All three drugs were shown to produce DNA cleavage detectable by resolving isolated DNA by pulsed field agarose gel electrophoresis. The DNA cleavage was found to have two components. The first was due to the interaction of the drugs with topoisomerase II, whereas the second component was due to endonuclease cleavage caused by the drug-induced entry of the thymocytes into programmed cell death or apoptosis. This second component of the DNA cleavage was also detected in thymocytes undergoing apoptosis following exposure to the glucocorticoid analogue, dexamethasone. The effect of the drugs on programmed cell death is dependent upon new protein and RNA synthesis, indicating that topoisomerase II has a role in the very first stages of the process. These results are discussed in terms of the use of this class of topoisomerase II-reactive drugs in chemotherapy.
Cancer Res 1991 Feb 15
PMID:Topoisomerase II-reactive chemotherapeutic drugs induce apoptosis in thymocytes. 184 55

The aim of our work was to investigate whether DNA topoisomerase II participates in the repair-specific incision of UV-irradiated genomic DNA. Therefore, the influence upon DNA incision of the topoisomerase II inhibitors (nalidixic and oxolinic acid, novobiocin and coumermycin A1) as well as the intercalating agent quinacrine has been measured in normal human fibroblasts using the alkaline elution technique. In addition, inhibition by novobiocin has been determined in fibroblast strains from 11 normal donors and from 16 xeroderma pigmentosum (XP) patients belonging to the complementation groups A, C, D, E, and XP variant. Nalidixic and oxolonic acid did not inhibit endonucleolytic cleavage, whereas novobiocin was a potent inhibitor of DNA incision. It was observed that in normal and in all XP strains 50% inhibition by novobiocin occurred on average in the dose range 315-590 microM. Since inhibition by novobiocin was not paralleled by that with the other topoisomerase II inhibitors nalidixic and oxolinic acid, it must be concluded that reduction of enzyme-catalysed breaks was not due to the participation of topoisomerase II in the incision step, but to the displacement of ATP at the binding site of the DNA-incising enzyme. This enzyme absolutely requires ATP as a cofactor for endonucleolytic cleavage. Quinacrine, however, inhibited DNA incision in normal fibroblasts at a mean Ki of 318 microM. Inhibition by this intercalating agent seems to be caused by structural perturbations in DNA, which render it a poor substrate for endonucleolytic cleavage.
J Cancer Res Clin Oncol 1991
PMID:The effects of inhibitors of topoisomerase II and quinacrine on ultraviolet-light-induced DNA incision in normal and xeroderma pigmentosum fibroblasts. 184

Cells from patients with Bloom syndrome, a cancer-prone disorder with cutaneous photosensitivity and spontaneous chromosome breakage, exhibit an abnormally increased number of sister-chromatid exchanges following treatment with 5-bromodeoxyuridine (BrdU). This effect has been postulated to be mediated by abnormal topoisomerase II activity. We used alkaline elution to measure DNA single-strand breakage following prolonged exposure to BrdU. Five-day exposure to BrdU produced equal numbers of alkali-labile sites in normal and Bloom-syndrome fibroblasts. These breaks were not protein-associated but were produced by alkali. Treatment with topoisomerase II inhibitors induced similar frequencies of DNA single-strand breaks in normal and Bloom-syndrome fibroblasts. These findings imply that BrdU incorporation into cellular DNA induces alkali-labile DNA lesions that are independent of topoisomerase II activity in Bloom and normal cells.
 ...
PMID:Relationship of DNA strand breakage produced by bromodeoxyuridine to topoisomerase II activity in Bloom-syndrome fibroblasts. 184 52

DNA topoisomerase inhibitors, camptothecin and 4'-demethylepipodophyllotoxin ethylidene-beta-D-glucoside (VP16) had strong differentiation-inducing activity for all five kinds of leukemia cells examined (human HL60, U937, ML1, and K562 cells and mouse M1 cells) as judged from measurements of various differentiation markers. The characteristics that appeared as a result of differentiation induced by these inhibitors were essentially similar in every cell line. Exposure to VP16 for 2 h induced both differentiation and DNA-strand breaks in K562 cells, whereas podophyllotoxin, which lacks topoisomerase II inhibitory activity, induced neither differentiation nor DNA-strand breaks in these cells. These results suggest a parallelism between the induction of differentiation and that of DNA-strand breaks. The combination of VP16 and recombinant tumor necrosis factor alpha (rTNF alpha) synergistically induced differentiation of human U937, ML1, and M1 cells and had an additive effect on HL60 cells. Simultaneous treatment with rTNF alpha plus camptothecin or VP16, or pretreatment with camptothecin or VP16, followed by rTNF alpha induced marked differentiation of M1 cells. These results indicate that inhibition of topoisomerase (either topoisomerase I or II) followed by the action of rTNF alpha was effective in inducing differentiation of leukemia cells.
Jpn J Cancer Res 1991 Feb
PMID:Topoisomerase inhibitors have potent differentiation-inducing activity for human and mouse myeloid leukemia cells. 184 45

Etoposide (VP-16) resistance is expressed following in vitro exposure of HN-1 and MCF-7 human tumor cells to the drug itself or to fractionated X irradiation. VP-16-selected sublines prove cross-resistant to Adriamycin, amsacrine and actinomycin D, whilst X-ray-pretreated sublines show cross-resistance to only actinomycin D. These differential responses, in the HN-1 series, are not associated with significant differences in amounts of immunoreactive topoisomerase (topo) II, altered topo-II catalytic activity of nuclear extracts or changes in susceptibility of the topo II to VP-16- or amsacrine-induced DNA-protein cross-link formation. Therefore significant modifications in topo II appear not to be implicated in VP-16 resistance in these HN-1 sublines.
Int J Cancer 1991 Apr 01
PMID:A lack of detectable modification of topoisomerase II activity in a series of human tumor cell lines expressing only low levels of etoposide resistance. 184 24

Terpentecin and clerocidin, microbial terpenoides, have been known to be potent antitumor antibiotics. However, the critical biochemical target of these terpenoides has not been identified. Our present studies, using purified mammalian topoisomerase II, have shown that terpentecin and clerocidin induce topoisomerase II-mediated DNA cleavage in vitro with comparable potency to that of demethylepipodophyllotoxin ethylidene-beta-D-glucoside. These terpenoides produced a similar DNA cleavage pattern which is distinctly different from those generated in the presence of the known topoisomerase poisons, demethylepipodophyllotoxin ethylidene-beta-D-glucoside and 4'-(9-acridinylamino)methanesulfon-m-anisidide. Brief heating at 65 degrees C, which abolishes completely the cleavable complex with demethylepipodophyllotoxin ethylidene-beta-D-glucoside, of the reaction mixture containing these terpenoides resulted in slight reduction in DNA cleavage. Thus, differently from other topoisomerase II-active antitumor agents, terpentecin and clerocidin induce formation of a cleavable complex which is stable for heat or salt treatments. The lack of significant DNA binding or intercalation activity of terpentecin and clerocidin suggests that topoisomerase II is a cellular target for these drugs.
Cancer Res 1991 Jun 01
PMID:Induction of a heat-stable topoisomerase II-DNA cleavable complex by nonintercalative terpenoides, terpentecin and clerocidin. 185 67

DNA filter elution assays have proved useful in studies of DNA strand breaks and crosslinks produced in mammalian cells or tissues by a wide variety of carcinogenic and cancer chemotherapeutic agents. The basic types of DNA lesions that can be measured include single and double-strand breaks, interstrand crosslinks and DNA-protein crosslinks. DNA filter elution has also been adapted to the assay of other lesions such as alkali-labile sites and the protein-associated strand breaks of topoisomerase DNA cleavage complexes. The essential concepts and theory of the technique are discussed and the applications of the technique to various types of studies are critically reviewed.
 ...
PMID:Principles and practice of DNA filter elution. 185 88

Starting with the V79 cell line, two poly(ADP-ribose) polymerase deficient mutants, designated ADPRT 54 and ADPRT 351, had been shown to be hypersensitive to x- and UV-irradiation and to topoisomerase I inhibitors but to be resistant to topoisomerase II inhibitors (Chatterjee, S.; Cheng, M. F.; Berger, N. A. Hypersensitivity to clinically useful alkylating agents and radiation in poly(ADP-ribose) polymerase-deficient cell lines. Cancer Commun. 2:401-407;1990). We now report that these mutants were hypersensitive to a series of different alkylating agents, including alkylsufonates, alkylnitrosoureas, and nitrosoguanidine. In addition, they were hypersensitive to the UV-mimetic agent 4-nitroquinoline-1-oxide. Our findings provide strong evidence that poly(ADP-ribose) polymerase was involved in the repair of alkylating agent induced DNA damage as well as in the damage induced by UV- and x-irradiation and radiomimetic agents. The poly(ADP-ribose) polymerase deficient cell lines showed a marked decrease in the shoulder region of their survival curves, suggesting that poly(ADP-ribose) polymerase was involved in the repair of alkylating agent induced sublethal damage.
Cancer Commun 1991 Mar
PMID:Alkylating agent hypersensitivity in poly(adenosine diphosphate-ribose) polymerase deficient cell lines. 190 Apr 26

In order to understand the cellular events associated with cell death after the formation of topoisomerase II-DNA cleavable complexes, we compared the induction of endonucleolytic DNA fragmentation by etoposide and its more potent analog, teniposide (VM-26) in the human cell lines HT-29 and HL-60. A new filter-binding assay is described, which allows rapid quantification of nonprotein-linked DNA fragmentation involved in apoptosis. Both cell lines showed similar loss of colony formation ability following 30 min of treatment with various VM-26 concentrations even though the initial topoisomerase II-mediated DNA single-strand break frequency was higher in HL-60 cells. DNA repair studies following drug removal indicated that VM-26-induced DNA breaks reversed rapidly and completely in HT-29 cells, while in HL-60 cells, the initial lesions persisted at and above 5 microM VM-26. In both cell lines, topoisomerase II cleavage complexes, as measured by DNA-protein cross-links by alkaline elution, reversed rapidly and completely within 2-3 h. Secondary DNA fragmentation resembling chromatin endonucleolytic cleavage by apoptosis could be detected in HL-60 cells 3 h after VM-26 or etoposide treatment but not in HT-29 cells. Secondary DNA fragmentation was also induced in the human colon cancer cell lines COLO 320, which have c-myc amplification. Since HL-60 cells also have c-myc amplification and HT-29 do not, it is possible that c-myc overexpression may be involved in secondary DNA fragmentation. Finally, our results indicate heterogeneity of cell death mechanisms after exposure to topoisomerase II inhibitors among human cancer cell lines.
Cancer Res 1991 Dec 01
PMID:Differential induction of secondary DNA fragmentation by topoisomerase II inhibitors in human tumor cell lines with amplified c-myc expression. 193 88


<< Previous 1 2 3 4 5 6 7 8 9 10