Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:5.99.1.2 (topoisomerase)
9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

For a series of antitumor-active 5-substituted 9-aminoacridine-4-carboxamide topoisomerase II poisons, we have used X-ray crystallography and stopped-flow spectrophotometry to explore relationships between DNA binding kinetics, biological activity, and the structures of their DNA complexes. The structure of 5-F-9-amino-[N-(2-dimethylamino)ethyl]-acridine-4-carboxamide bound to d(CGTACG)(2) has been solved to a resolution of 1.55 A in space group P6(4). A drug molecule intercalates between each of the CpG dinucleotide steps, its protonated dimethylamino group partially occupying positions close to the N7 and O6 atoms of guanine G2 in the major groove. A water molecule forms bridging hydrogen bonds between the 4-carboxamide NH and the phosphate group of the same guanine. Intercalation unwinds steps 1 and 2 by 12 degrees and 8 degrees, respectively compared with B-DNA, whereas the central TpA step is overwound by 10 degrees. Nonphenyl 5-substituents, on average, decrease mean DNA dissociation rates by a factor of three, regardless of their steric, hydrophobic, H-bonding, or electronic properties. Cytotoxicity is enhanced on average 4-fold and binding affinities rise by 3-fold, thus there is an apparent association between kinetics, affinity, and cytotoxicity. Taken together, the structural and kinetic studies imply that the main origin of this association is enhanced stacking interactions between the 5-substituent and cytosine in the CpG binding site. Ligand-dependent perturbations in base pair twist angles and their consequent effects on base pair-base pair stacking interactions may also contribute to the stability of the intercalated complex. 5-Phenyl substituents modify dissociation rates without affecting affinities, and variations in their biological activity are not correlated with DNA binding properties, which suggests that they interact directly with the topoisomerase protein.
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PMID:Acridinecarboxamide topoisomerase poisons: structural and kinetic studies of the DNA complexes of 5-substituted 9-amino-(N-(2-dimethylamino)ethyl)acridine-4-carboxamides. 1095 60

An efficient five-step synthetic method was developed to access a homologous series of spermidine-acridine and spermidine-anthracene conjugates. The derivatives were comprised of a spermidine fragment covalently tethered at its N4 position to either an acridine or anthracene nucleus via an aliphatic chain (e.g., spermidine-[aliphatic tether]-acridine). The distance separating the spermidine and aromatic nucleus was altered by using different tethers comprised of four or five methylene units, respectively. These ligands (2-5) were shown to inhibit human DNA topoisomerase-II (TOPO-II) activity at 10 microM. Enzymatic activity was assessed as the ability to unknot (decatenate) and cleave kinetoplast DNA (kDNA). Polyamine conjugation did not disrupt the ability of the acridine-spermidine conjugates 2 and 3 to inhibit TOPO-II activity as compared with the 9-aminoacridine and 9-(N-butyl)aminoacridine controls (at 10 microM). In general, the acridine derivatives (2 and 3) showed higher TOPO-II inhibitory activity than their anthracene counterparts (4 and 5). However, this trend was reversed in a whole cell assay with L1210 (murine leukemia) cells, wherein the anthracene analogues were more potent than their acridine counterparts. In this regard the qualitative enzyme-based assay did not predict the trends in the corresponding IC(50) values. Within either series insertion of an additional methylene unit did not significantly alter activity. While the appended spermidine unit did not disrupt TOPO II inhibition by the tethered DNA intercalator, it did provide an alternative mode of entry into the cell as demonstrated by spermidine protection assays. These results were compared with a spermine-intercalator analogue. Of all the conjugates tested the N(4)-(4-(9-aminoacridinyl)butyl)spermine hexahydrochloride (conjugate 16)resulted in the highest degree of L1210 cell rescue upon cotreatment of the cells with exogenous spermidine. It was concluded that the monoalkylated spermine motif present in 16 holds promise as a better vector than its N4 monoalkylated spermidine counterpart.
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PMID:The effect of polyamine homologation on the transport and cytotoxicity properties of polyamine-(DNA-intercalator) conjugates. 1097 Feb 97

A group of 9-substituted acridine and azacridine derivatives (m-AMSA analogues) were synthesised following classical procedures as potential antitumour agents with inhibitory effects on DNA topoisomerase II. Some were found to have noticeable cytotoxicity against human HL-60 and HeLa cells grown in culture. Their non-covalent interactions with calf thymus DNA have been studied using fluorescence quenching. We evaluated DNA damage produced by the tested compounds by means of DNA filter elution and protein precipitation techniques. Catalytic studies carried out with purified topoisomerase confirmed these agents as antitopoisomerase inhibitors. Chemotherapy of solid-tumour-bearing mice with tested compounds allowed an aza-analogue (compound IIIb), as potent as m-AMSA but less toxic towards the host, to be recognised.
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PMID:Synthesis and antiproliferative activity of some variously substituted acridine and azacridine derivatives. 1100 84

The structure of the complex formed between d(CGTACG)2 and 9-amino-N-[2-(4-morpholinyl)ethyl]-4-acridinecarboxamide, an inactive derivative of the antitumour agents N-[2-(dimethylamino)ethyl]acridine-4-carboxamide (DACA) and 9-amino-DACA, has been solved to a resolution of 1.8 A using X-ray crystallography. The complex crystallises in the space group P6(4 )and the final structure has an overall R factor of 21.9%. A drug molecule intercalates between each of the CpG dinucleotide steps with its side chain lying in the major groove, and its protonated morpholino nitrogen partially occupying positions close to the N7 and O6 atoms of guanine G2. The morpholino group is disordered, the major conformer adopting a twisted boat conformation that makes van der Waals contact with the O4 oxygen of thymine T3. A water molecule forms bridging hydrogen bonds between the 4-carboxamide NH and the phosphate group of guanine G2. Sugar rings are found in alternating C3'-exo/C2'-endo conformations except for cytosine C1 which is C3'-endo. Intercalation perturbs helix winding throughout the hexanucleotide compared with B-DNA, steps 1 and 2 being unwound by 10 and 8 degrees, respectively, while the central TpA step is overwound by 11 degrees. An additional drug molecule lies at the end of each DNA helix linking it to the next duplex to form a continuously stacked structure. The protonated morpholino nitrogen of this 'end-stacked' drug hydrogen bonds to the N7 atom of guanine G6, and its conformationally disordered morpholino ring forms a C-H...O hydrogen bond with the guanine O6 oxygen. In both drug molecules the 4-carboxamide group is internally hydrogen bonded to the protonated N10 atom of the acridine ring. We discuss our findings with respect to the potential role played by the interaction of the drug side chain and the topoisomerase II protein in the poisoning of topoisomerase activity by the acridinecarboxamides.
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PMID:Crystal structure of 9-amino-N-[2-(4-morpholinyl)ethyl]-4-acridinecarboxamide bound to d(CGTACG)2: implications for structure-activity relationships of acridinecarboxamide topoisomerase poisons. 1180 84

We have used stopped-flow spectrophotometry and the sodium dodecyl sulfate sequestration technique to study the kinetics of dissociation of DNA complexes of the mixed topoisomerase I/II poison N-[2-(dimethylamino)ethyl]acridine-4-carboxamide (termed DACA) and a range of related linear tricyclic carboxamides with neutral chromophores. Complexes of DACA and related acridine and phenazinecarboxamides bearing an N,N-dimethylaminoethyl side chain dissociate from calf thymus DNA by a kinetic pathway involving four discernible steps in a manner similar to complexes of N-[(2-dimethylamino)ethyl]-9-aminoacridine-4-carboxamide (termed 9-amino-DACA). We infer from these findings that the side chains of DACA, its phenazine homologue, and 9-amino-DACA make comparable interactions with the DNA base pairs. In the case of 9-amino-DACA, a selective topoisomerase II poison, these are known, by crystallographic analysis, to involve hydrogen-bonding interactions between the protonated dimethylammonium group of the side chain and the O6/N7 atoms of guanine and to include a bridging water molecule hydrogen bonded to the carboxamide group and a phosphate oxygen. By contrast, we find that other linear tricyclic carboxamides with neutral chromophores which lack a peri nitrogen atom and are biologically inactive dissociate from DNA by a different mechanism in which it appears their side chains fail to interact with guanine. We conclude that the ability of the carboxamide group to lie preferentially in the plane of the chromophore, so facilitating the dimethylammonium-guanine hydrogen bond and ensuring maintenance of the water-bridged carboxamide-phosphate interaction, is a critical requirement for antitumor activity among ligands of the linear tricyclic carboxamide class. However, unlike the situation for 9-amino-DACA, for ligands with uncharged chromophores containing peri nitrogen atoms such as DACA, this outcome is possible with the 4-carboxamide group rotated cis or trans with respect to the ring nitrogen. This difference may have relevance to the ability of DACA to be a dual poison of both topoisomerases I and II.
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PMID:Kinetic studies of the binding of acridinecarboxamide topoisomerase poisons to DNA: implications for mode of binding of ligands with uncharged chromophores. 1183 1

Acridine derivatives are one of the oldest classes of bioactives, widely used as antibacterial and antiprotozoal agents. Some work in these areas continues, but recent research has focused mainly on their use as anticancer drugs, because of the ability of the acridine chromophore to intercalate DNA and inhibit topoisomerase enzymes.
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PMID:Acridine derivatives as chemotherapeutic agents. 1217 48

Acridines have been used as chemotherapeutic agents against bacteria, protozoa and fungi, and they now find important use as anticancer drugs. There is a paucity of crystal structures of acridine-DNA complexes above the dinucleotide level, but recent structures of acridinecarboxamide topoisomerase II poisons complexed to hexanucleotides have allowed a molecular rationalization of their structure-activity relationships for cytotoxicity and for their kinetics of DNA binding.
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PMID:Crystal structures of acridines complexed with nucleic acids. 1217 49

We have synthesized two podophyllotoxin-acridine conjugates-pACR6 and pACR8. In these compounds an 9-acridinyl moiety is beta linked to the C4 carbon of the four ring system in 4'-demethylepipodophyllotoxin (epiDPT) via eighter an N-6-aminohexanylamide linker (pACR6) or via an N-8-aminooctanylamide linker containing two more carbon atoms (pACR8). The acridine-linker moiety occupies the position where different glucoside moieties, dispensable for activity, are normally linked to epiDPT in the well known epipodophyllotoxins VP-16 and VM-26. As with VP-16 and VM-26, pACR6 and pACR8 show evidence of being topoisomerase II poisons as they stimulate topoisomerase II mediated DNA cleavage in vitro and induce DNA damage in vivo. This in vivo DNA damage, as well as pACR6/pACR8 mediated cytotoxicity, is antagonized by the catalytic topoisomerase II inhibitors ICRF-187 and aclarubicin, demonstrating that topoisomerase II is a functional biological target for these drugs. Despite their structural similarities, pACR6 was more potent than pACR8 in stimulating topoisomerase II mediated DNA cleavage in vitro as well as DNA damage in vivo and pACR6 was accordingly more cytotoxic towards various human and murine cell lines than pACR8. Further, marked cross-resistance to pACR6 was seen among a panel of multidrug-resistant (MDR) cell lines over-expressing the MDR1 (multidrug resistance protein 1) ABC drug transporter, while these cell lines remained sensitive towards pACR8. pACR8 was also capable of circumventing drug resistance among at-MDR (altered topoisomerase II MDR) cell lines not over-expressing drug transporters, while pACR6 was not. Two resistant cell lines, OC-NYH/pACR6 and OC-NYH/pACR8, were developed by exposure of small cell lung cancer (SCLC) OC-NYH cells to gradually increasing concentrations of pACR6 and pACR8, respectively. Here, OC-NYH/pACR6 cells were found to over-express MDR1 and, accordingly, displayed active transport of 3H-labeled vincristine, while OC-NYH/pACR8 cells did not, further suggesting that pACR6, but not pACR8, is a substrate for MDR1. Our results show that the spatial orientation of podophyllotoxin and acridine moieties in hybrid molecules determine target interaction as well as substrate specificity in active drug transport.
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PMID:Linker length in podophyllotoxin-acridine conjugates determines potency in vivo and in vitro as well as specificity against MDR cell lines. 1237 83

DACA (N-[2-(dimethylamino)ethyl]acridine-4-carboxamide dihydrochloride) has high experimental antitumor activity and has completed phase I/II clinical trials. It targets both topoisomerase (topo) I and II, but the roles of each of these enzymes in the antitumour action of DACA are not known. We have used a series of DACA analogues (mainly monosubstituted halogen derivatives) to relate in vitro and in vivo biological activity. We measured topo II selectivity by comparing the inhibition of Jurkat human leukaemia cell lines with high and low topo II content. We determined survival curves following exposure of H460 human lung carcinoma cells for 1 h. We used plasmid DNA to compare the effects of DACA analogues on isolated topo I and II, measuring in particular the inhibition of topo I- and II-mediated DNA relaxation. The results indicate that 5-halogen substituted derivatives are the most active in clonogenic cytotoxicity assays and that this activity is related to their selective activity towards Jurkat cells with high topo II activity. In isolated topo assays, 5-halogen substituted derivatives were also the most potent and in each case the concentration required for inhibition of topo II relaxation was greater than that for inhibition of topo I relaxation. The drug concentration providing efficient cytotoxicity corresponded to that which suppressed the activity of topo I but not of topo II. We hypothesize that DACA analogues act both in vitro and in vivo to simultaneously poison topo II and inhibit topo I catalytic activity, and that this combination contributes to the high antitumour activity of DACA analogues.
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PMID:Topoisomerase I/II selectivity among derivatives of N-[2-(dimethylamino)ethyl]acridine-4-carboxamide (DACA). 1237 84

Amsacrine is an acridine derivative drug applied in haematological malignancies. It targets topoisomerase II enhancing the formation of a cleavable DNA-enzyme complex and leading to DNA fragmentation in dividing cancer cells. Little is known about other modes of the interaction of amsacrine with DNA, by which it could affect also normal cells. Using the alkaline comet assay, we showed that amsacrine at concentrations from the range 0.01 to 10 microM induced DNA damage in normal human lymphocytes, human promyelocytic leukemia HL-60 cells lacking the p53 gene and murine pro-B lymphoid cells BaF3 expressing BCR/ABL oncogene measured as the increase in percentage tail DNA. The effect was dose-dependent. Treated cells were able to recover within a 120-min incubation. Amifostine at 14 mM decreased the level of DNA damage in normal lymphocytes, had no effect on the HL-60 cells and potentiated the DNA-damaging effect of the drug in BCR/ABL-transformed cells. Vitamin C at 10 and 50 microM diminished the extent of DNA damage in normal lymphocytes, but had no effect in cancer cells. Pre-treatment of the cells with the nitrone spin trap, N-tert-butyl-alpha-phenylnitrone or ebselen, which mimics glutathione peroxidase, reduced the extent of DNA damage evoked by amsacrine in all types of cells. The cells exposed to amsacrine and treated with endonuclease III and 3-methyladenine-DNA glycosylase II, the enzymes recognizing oxidized and alkylated bases, respectively, displayed greater extent of DNA damage than those not treated with these enzymes. The results obtained suggest that free radicals may be involved in the formation of DNA lesions induced by amsacrine. The drug can also methylate DNA bases. Our results indicate that the induction of secondary malignancies should be taken into account as diverse side effects of amsacrine. Amifostine may potentate DNA-damage effect of amsacrine in cancer cells and decrease this effect in normal cells and Vitamin C can be considered as a protective agent against DNA damage in normal cells.
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PMID:Free radical scavengers can differentially modulate the genotoxicity of amsacrine in normal and cancer cells. 1254 80


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