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)

A hybrid molecule, which combines an anilinoacridine chromophore related to the antitumour drug amsacrine (m-AMSA) and a bispyrrole moiety analogous to the antiviral agent netropsin, has been examined for its ability to bind chromatin and to modulate the activity of topoisomerase II. The results show that the presence of histones does not alter the bimodal DNA binding process. Intercalation of the acridine and groove binding of the netropsin part of the drug are both observed with chromatin preparations. Moreover, the hybrid has a clear topoisomerase II-DNA cleavable complex-inducing activity close to that of m-AMSA. The role of the two parts of the hybrid ligand is discussed in relation to ternary complex formation. Two cell lines (L1210 leukemia and MCF7 mammary carcinoma) were compared in their sensitivity to the tested ligand. The drug, which appears to be an efficient growth inhibitor of leukemic cells in vitro, reveals moderate activity against P388 leukemia in vivo. The biological activity of the hybrid may derive from a mechanism that involves DNA binding and topoisomerase II inhibition. This study demonstrates that agents which intercalate and bind to the minor groove of DNA simultaneously represent a new class of drugs interfering with topoisomerase II and provide opportunities for the development of new antitumour agents.
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PMID:Biological activity and molecular interaction of a netropsin-acridine hybrid ligand with chromatin and topoisomerase II. 131 80

The present review describes several methods to characterize and differentiate between two different mechanisms of cell death, apoptosis and necrosis. Most of these methods were applied to studies of apoptosis triggered in the human leukemic HL-60 cell line by DNA topoisomerase I or II inhibitors, and in rat thymocytes by either topoisomerase inhibitors or prednisolone. In most cases, apoptosis was selective to cells in a particular phase of the cell cycle: only S-phase HL-60 cells and G0 thymocytes were mainly affected. Necrosis was induced by excessively high concentrations of these drugs. The following cell features were found useful to characterize the mode of cell death: a) Activation of an endonuclease in apoptocic cells resulted in extraction of the low molecular weight DNA following cell permeabilization, which, in turn, led to their decreased stainability with DNA-specific fluorochromes. Measurements of DNA content made it possible to identify apoptotic cells and to recognize the cell cycle phase specificity of the apoptotic process. b) Plasma membrane integrity, which is lost in necrotic but not apoptotic cells, was probed by the exclusion of propidium iodide (PI). The combination of PI followed by Hoechst 33342 proved to be an excellent probe to distinguish live, necrotic, early- and late-apoptotic cells. c) Mitochondrial transmembrane potential, assayed by retention of rhodamine 123 was preserved in apoptotic but not necrotic cells. d) The ATP-dependent lysosomal proton pump, tested by the supravital uptake of acridine orange (AO) was also preserved in apoptotic but not necrotic cells. e) Bivariate analysis of cells stained for DNA and protein revealed markedly diminished protein content in apoptotic cells, most likely due to activation of endogenous proteases. Necrotic cells, having leaky membranes, had minimal protein content. f) Staining of RNA allowed for the discrimination of G0 from G1 cells and thus made it possible to reveal that apoptosis was selective to G0 thymocytes. g) The decrease in forward light scatter, paralleled either by no change (HL-60 cells) or an increase (thymocytes) of right angle scatter, were early changes during apoptosis. h) The sensitivity of DNA in situ to denaturation, was increased in apoptotic and necrotic cells. This feature, probed by staining with AO at low pH, provided a sensitive and early assay to discriminate between live, apoptotic and necrotic cells, and to evaluate the cell cycle phase specificity of these processes. i) The in situ nick translation assay employing labeled triphosphonucleotides can be used to reveal DNA strand breaks, to detect the very early stages of apoptosis.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Features of apoptotic cells measured by flow cytometry. 133 43

In an attempt to characterize and overcome tumor cell resistance to amsacrine (m-AMSA), we studied the structure-activity relationships for amsacrine and seven of its analogs. Using the human leukemic cell line, CCRF-CEM, and its derivatives that express either P-glycoprotein (Pgp)-associated multidrug resistance (MDR) (CEM/VLB100) or altered topoisomerase II-associated MDR (at-MDR) (CEM/VM-1), we assessed antitumor effects of these drugs in a 48-hr growth inhibition assay. We also measured drug-topoisomerase II interactions in an intact cell assay that permits quantitation of drug-stabilized DNA-topoisomerase II complexes. We found that among the tested compounds, amsacrine has an intermediate effect on cell growth in all three cell lines. The CEM/VM-1 cells were 8.6-fold cross-resistant to m-AMSA, and the cross-resistance to the analogs was from 3.0- to 10.5-fold. In the CEM/VLB100 cells, the resistance pattern was different: several analogs, including amsacrine, showed little or no cross-resistance (0.5- to 2.8-fold), whereas for those compounds with substituents at position 3 on the acridine ring, resistance was relatively higher (9.9- or 16.2-fold). Substituents at this position substantially decrease the lipophilicity of the two compounds examined, probably because they both contain amino groups that would be charged at physiologic pH. Compound 12489, having a 1'-NHSO2C6H4NH2 substituent, was very potent in the three cell lines, showing only a slightly higher IC50 value in the CEM/VM-1 line and a lower IC50 value in the CEM/VLB100 and in the CEM cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Structure-activity studies of amsacrine analogs in drug resistant human leukemia cell lines expressing either altered DNA topoisomerase II or P-glycoprotein. 136 24

A new series of DNA bis-intercalators is reported in which acridine moieties are connected by rigid and extended pyridine-based linkers of varied length. Cross-linking of DNA by bis-intercalation is inferred from the unwinding and folding of linear DNA induced by the compounds; after ligation and removal of the bis-intercalator, superhelical circles, catenanes and knots that bear a residual imprint of the bis-intercalator are observed. These novel bis-intercalators are of interest because they can be used to probe the spatial organization of DNA, especially near sites of replication, recombination or topoisomerase action where two duplexes must be in close proximity. Preliminary results on the effects of the various compounds on the cloning efficiency of bacteria and replication by permeabilized human cells are also presented.
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PMID:Evidence for cross-linking DNA by bis-intercalators with rigid and extended linkers is provided by knotting and catenation. 154 10

Analogues of the phenylbisbenzimidazole dye pibenzimol bind tightly to the minor groove of DNA. A clonogenic assay has been used to investigate the effects of these compounds on the cytotoxicity of the topoisomerase II directed anti-cancer drugs amsacrine, CI-921 (an amsacrine analogue), acridine carboxamide, etoposide and doxorubicin. Although pibenzimol itself was inactive, several of its analogues reduced the toxicity of etoposide, amsacrine and CI-921 towards a Lewis lung mouse tumour line at concentrations between 1 and 20 mumol/l. Doxorubicin cytotoxicity was unaffected, suggesting that this drug has a distinct mechanism of action. At concentrations below 1 mumol/l, some of these dyes potentiated the cytotoxicity of etoposide and CI-921 towards Lewis lung cells. Potentiation of CI-921 activity was also found with the human tumour lines HT29 (colon), SW620 (colon) and FME (melanoma). Novel treatments may arise from the potentiation of topoisomerase II directed cytotoxicity.
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PMID:Potentiation by phenylbisbenzimidazoles of cytotoxicity of anticancer drugs directed against topoisomerase II. 169 74

Acridine-induced frameshift mutations in bacteriophage T4 occur at the precise location in the DNA at which acridines stimulate DNA cleavage by the T4-encoded type II topoisomerase in vitro. The mutations are duplications or deletions that begin precisely at the broken phosphodiester bond. In vivo, acridine-induced frameshift mutagenesis is reduced nearly to background levels when the topoisomerase is genetically inactivated. These observations are consistent with a model in which cleaved DNA, induced by the topoisomerase and acridine, serves as the substrate for the production of frameshift mutations at the same site. Our model predicts that the specificity and frequency of cleavage direct the specificity and frequency of mutagenesis. This prediction was tested by examining the influence of DNA sequence changes on topoisomerase-mediated cleavage and on mutagenesis in the T4 rIIB gene. The model successfully predicted the results. When DNA sequence changes altered the position of acridine-induced, topoisomerase-mediated DNA cleavage in vitro, frameshift mutations were found at the new positions. DNA sequence changes that strongly decreased in vitro cleavage also reduced mutagenesis at that site. These results demonstrate that acridine-induced frameshift mutation specificity is directed by the characteristics of the acridine-topoisomerase reaction and do not suggest that slipped pairing in repeated sequences plays a major role in acridine-induced frameshifts in bacteriophage T4.
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PMID:The specificity of topoisomerase-mediated DNA cleavage defines acridine-induced frameshift specificity within a hotspot in bacteriophage T4. 164 2

Acridine and its derivatives are planar polycyclic aromatic molecules which bind tightly but reversibly to DNA by intercalation, but do not usually covalently interact with it. Acridines have a broad spectrum of biological activities, and a number of derivatives are widely used as antibacterial, antiprotozoal and anticancer drugs. Simple acridines show activity as frameshift mutagens, especially in bacteriophage and bacterial assays, by virtue of their intercalative DNA-binding ability. Acridines bearing additional fused aromatic rings (benzacridines) show little activity as frameshift mutagens, but interact covalently with DNA following metabolic activation (forming predominantly base-pair substitution mutations). Compounds where the acridine acts as a carrier to target alkylating agents to DNA (e.g. the ICR compounds) cause predominantly frameshift as well as base-pair substitution mutations in both bacterial and mammalian cells. Nitroacridines may act as simple acridines or (following nitro group reduction) as alkylating agents, depending upon the position of the nitro group. Acridine-based topoisomerase II inhibitors, although frameshift mutagens in bacteria and bacteriophage systems, are primarily chromosomal mutagens in mammalian cells. These mutagenic activities are important, since the compounds have considerable potential as clinical antitumour drugs. Although evidence suggests that simple acridines are not animal or human carcinogens, a number of the derived compounds are highly active in this capacity.
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PMID:The genetic toxicology of acridines. 188 2

(N-[2-(Dimethylamino)ethyl]acridine-4-carboxamide (acridine carboxamide; NSC 601316) is an acridine-derived experimental antitumour agent with curative properties against Lewis lung carcinoma in mice. Although it intercalates into DNA and also appears to interact with topoisomerase II, its DNA binding properties appear distinct from other acridine derivatives such as the clinical antitumour drug, amsacrine. The mutagenic properties of acridine carboxamide, together with three related compounds containing either 9-aminoacridine or phenazine chromophores, were studied at the 6-thioguanine and ouabain loci in cultured V79 Chinese hamster fibroblasts. Each compound, when tested at concentrations causing up to 90% kill, had weak but significant activity at the 6-thioguanine but not at the ouabain locus. All drugs were potent inducers of micronuclei, indicating high clastogenic activity. There was a highly significant relationship between mutation frequency (as resistance to 6-thioguanine) and either cytotoxicity (measured as D37 in a clastogenicity assay) or clastogenicity. A broader range of compounds was also tested for microbial mutagenicity. In Salmonella typhimurium strains, none were mutagenic in TA98, TA100 or TA102 but several were mutagenic in TA1537, a frameshift tester strain. Some drugs also caused 'petite' mutagenesis in Saccharomyces cerevisiae. In general, compounds with the phenazine chromophore, which has no positive charge, were the most mutagenic in these systems. However, activity was not related to mammalian mutagenicity or antitumour effect. The results suggest that in mammalian cells, the cytotoxicity, clastogenicity and mutagenic activity of these drugs are mediated by similar mechanisms to those for amsacrine analogues, probably involving the enzyme DNA topoisomerase II.
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PMID:Genetic toxicology of tricyclic carboxamides, a new class of DNA binding antitumour agent. 214 58

Murine P388 (P) leukemia cell lines resistant to amsacrine (P/AMSA), dactinomycin (P/DACT), and doxorubicin (P/DOX) were compared with the parental strain in their sensitivity to a number of derivatives of amsacrine. The P/DACT cell line, which shows the characteristics of a transport-mediated multidrug-resistant cell line, was cross-resistant to vincristine, doxorubicin, etoposide, and a number of acridine-substituted amsacrine derivatives, but was sensitive in vitro and in vivo to amsacrine and its analog CI-921. The P/DOX cell line was cross-resistant to amsacrine but showed a similar pattern of cross-resistance to that of P/DACT in its in vitro response to amsacrine derivatives. In contrast, the P/AMSA line was substantially cross-resistant (from 27- to 146-fold) to all acridine-substituted amsacrine derivatives. However, when the substituents on the anilino side chain of amsacrine were changed, the in vitro cross-resistance of the P/AMSA line could be substantially reduced and even overcome. Derivatives with low cross-resistance ratios were tested in vivo against the P/AMSA leukemia and, in contrast to amsacrine and CI-921, were found to be active. Since the target enzyme for amsacrine action, topoisomerase II, is thought to be structurally modified in the P/AMSA line as well as in some other multidrug-resistant lines, these results suggest the feasibility of tailoring topoisomerase II-directed drugs specifically for the altered enzymes in resistant cells. New drug design approaches are therefore available for overcoming two major types of multidrug resistance.
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PMID:Design of DNA intercalators to overcome topoisomerase II-mediated multidrug resistance. 215 84

A new cytotoxic acridine alkaloid that exhibited antitumor activity in vivo was isolated from a marine Dercitus species sponge collected at a depth of 160 m in the Bahamas. This violet alkaloid, designated dercitin, inhibited the proliferation of cultured murine and human leukemia, lung, and colon tumor cells at nM concentrations (IC50 values of 63-150 nM) and prolonged the life of mice bearing ascitic P388 tumors (%T/C = 170, 5 mg/kg, i.p., QD1-9). Dercitin was also active against i.p. B16 melanoma and modestly inhibited the growth of s.c. Lewis lung carcinoma on the same schedule. DNA blocked the antiproliferative effects of the agent in culture, and incorporation studies indicated that dercitin disrupted DNA and RNA synthesis with less effects on protein synthesis, similar to the effects of known DNA intercalators. After 1-h exposure to 400 nM dercitin, the rates of incorporation of [3H]uridine, [3H]thymidine, and [3H]leucine by cultured P388 cells were inhibited 83, 61, and 23%, respectively. Equilibrium dialysis indicated that dercitin bound calf thymus DNA with an affinity of 3.1 microM and maximal binding of 0.20 mol dercitin/mol base pair. Binding involved intercalation as evidenced by ability to relax supercoiled phi X174 DNA (half maximal concentration for dercitin relaxation was 36 nM). The effects of dercitin on DNA mobility were reversible, and complete relaxation of DNA with topoisomerase I in the presence of dercitin followed by phenol extraction resulted in the appearance of supercoiled DNA. Dercitin, at microM concentrations, had a small effect in the K+-sodium dodecyl sulfate assay using cultured P388 cells, suggesting minimal inhibition of topoisomerase activity. But, dercitin completely inhibited DNA polymerase I/DNase nick translation of DNA at 1 microM. Relaxation of DNA at a given concentration was greater than inhibition of nick translation suggesting that the effects of dercitin on enzyme activity were secondary to changes in DNA conformation. Results indicate that dercitin is a new marine natural product that probably exerts its biological effects through intercalation into nucleic acids.
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PMID:Antitumor activity and nucleic acid binding properties of dercitin, a new acridine alkaloid isolated from a marine Dercitus species sponge. 254 17


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