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)

Amsacrine is a DNA intercalating agent which is active against a number of tumours in mice and is used for the treatment of leukaemia in humans. In its DNA-bound form, amsacrine efficiently quenches the fluorescence of ethidium. Fluorescence lifetime studies demonstrate two populations of DNA-bound ethidium. The first, whose fluorescence lifetime is constant at approx. 3 ns and whose proportion increases with increasing amsacrine binding ratio, may comprise molecules bound in close proximity to amsacrine. The second, whose fluorescence lifetime is longer and variable (10-24 ns) and whose proportion decreases with increasing amsacrine binding ratio, may comprise molecules three or more base-pairs away from ethidium. Studies with a number of derivatives of 9-anilinoacridine containing different anilino substituents suggest that the observed wide variation in quenching capacity is correlated with the magnitude of the substituent dipole moment in a particular direction. Consideration of the geometry of the DNA-binding complex indicates that the negative pole of a dipole established in the anilino ring is directed towards a positively charged site on the ethidium molecule. Quenching of ethidium fluorescence may therefore occur where an electron-transfer complex has formed between ethidium and amsacrine molecules. To ascertain whether electron-transfer complex formation is biologically important in the amsacrine series, ethidium quenching has been quantitated and compared with activity against a transplantable neoplasm in mice, the Lewis lung carcinoma. Compounds which strongly quench ethidium fluorescence are in general highly active antitumour agents. The results are discussed in terms of a model where amsacrine has both a DNA-binding and a protein-binding domain, the latter possibly interacting by formation of an electron-transfer complex. The most likely protein-binding domain is on the enzyme topoisomerase II, the target for its cytotoxic activity.
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PMID:The possible role of electron-transfer complexes in the antitumour action of amsacrine analogues. 220 43

Ellipticine derivatives have been shown to induce DNA strand breaks by trapping DNA-topoisomerase II (Topo II) in an intermediary covalent complex between Topo II and DNA which could be related to their cytotoxic effects. We report here that Celiptium and Detalliptinium, two ellipticine derivatives clinically used for their antitumoral properties against breast cancer, exhibit the highest in vitro activity on Topo II DNA cleavage reaction and decatenation among a series of 14 ellipticine derivatives. The in vitro cleavage site specificity in pBR 322 plasmid DNA and in a human c-myc gene inserted in a lambda phage DNA is identical for both ellipticines, but different from m-AMSA, another Topo II related antitumoral agent. Recently, it has been shown that the ellipticine derivative Celiptium presents a strong cytotoxic activity in vitro on different human tumors including small cell lung carcinoma (SCLC). However, the studies that involved Topo II as a target for ellipticine derivatives have been performed only by using animal tumor cell lines. Therefore we have studied the in vivo DNA cleavage activity of Celiptium and Detalliptinium on a human SCLC cell line, NCI N417, comparatively to that obtained with m-AMSA. The respective IC50 on cell growth are 9, 8 and 1 microM for Celiptium, Detalliptinium and m-AMSA, respectively. Using the alkaline elution technique, we have observed that Celiptium and Detalliptinium exhibit a weak cleavage activity on genomic DNA from whole cells. The ellipticines are about 50 times less potent than m-AMSA in inducing DNA strand breaks. Analysis of in vivo c-myc gene cleavage by Southern blot hybridization also demonstrates a lack of activity of the ellipticine derivatives as no gene cleavage could be detected up to 50 microM of the drug. With m-AMSA, c-myc gene cleavage is detected at a concentration of 0.2 microM, which indicates that this methodology is less sensitive in detecting DNA strand breaks than is the alkaline elution. Further studies of the drug effect on isolated nuclei by alkaline elution also show that the DNA cleavage activity of Celiptium and Detalliptinium is increased when compared to whole cells. Our data indicate that these two drugs have a weaker cytotoxic effect than m-AMSA on NCI N417 cell line, due to a limited access to the cell nucleus rather than to a lack of activity on Topo II as assessed by in vitro and isolated nuclei experiments.
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PMID:Topoisomerase II-mediated DNA cleavage activity induced by ellipticines on the human tumor cell line N417. 254 83

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

N-[2-(Dimethylamino)ethyl]acridine-4-carboxamide (AC; NSC 601316) is a chemically novel antitumour agent which is thought to interact with DNA topoisomerase II and which has DNA binding properties which are distinct from other acridine derivatives such as amsacrine and its disubstituted analogue CI-921. AC is one of the most active agents, experimental or clinical, against the Lewis lung carcinoma in mice. AC is the first acridine derivative in our hands to show higher activity against cultured Lewis lung cells than against leukaemia lines. AC is more active against two human leukaemia cell lines (U-937 and Jurkat) than against a melanoma line (MM-96) and is inactive against the HT-29 human colon line. With all cell lines tested, cytotoxicity was higher at AC concentrations of 3-6 microM than at 15-20 microM. AC at a concentration of 20 microM inhibited the cytotoxicity of amsacrine and CI-921, but not that of another topoisomerase-directed drug doxorubicin. A Lewis lung line which had been cultured for a long period was less sensitive than a line freshly isolated from mice, but sensitivity of the cultured line recovered after it was multiply passaged in vivo. Long-term cultures may therefore be less appropriate than short-term cultures for predicting effectiveness of AC in vivo.
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PMID:Selectivity of N-[2-(dimethylamino)ethyl]acridine-4-carboxamide towards Lewis lung carcinoma and human tumour cell lines in vitro. 270 82

N-[2-(Dimethylamino)ethyl]acridine-4-carboxamide (NSC 601316) is a DNA intercalating experimental antitumour agent which is curative against the Lewis lung carcinoma in mice. Its action has been compared with amsacrine, its inactive isomer oAMSA, the solid tumour active derivative CI-921 (NSC 343499), a C-6 methylene chain-linked bisacridine (NSC 210733), 9-aminoacridine and quinacrine. All compounds inhibited the unknotting of phage P4 DNA by topoisomerase II in nuclear extracts prepared from L1210 cells. NSC 601316 inhibited growth of cultured L1210, P388, P/AMSA (P388 resistant to amsacrine) and P/ACTD (resistant to actinomycin D) cell lines at concentrations of 87, 150, 2020 and 150 nM respectively. A 1 h drug exposure to 0.85 microM NSC 601316 killed 50% of L1210 cells. L1210 cells treated for 1 h with NSC 601316 accumulated DNA breaks and protein-DNA cross-links. There was a good correlation between DNA breakage and cytotoxicity, but the relationship between drug concentration and number of protein-DNA cross-links was non-linear and differed from that of amsacrine and CI-921. There was also a positive correlation between the degree of cross-resistance of P/AMSA cells (which have altered topoisomerase II function) and ability to induce DNA breakage or protein-DNA complexes. The results suggest that topoisomerase II is the target of action of NSC 601316.
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PMID:Cell line selectivity and DNA breakage properties of the antitumour agent N-[2-(dimethylamino)ethyl]acridine-4-carboxamide: role of DNA topoisomerase II. 285 Jan 93

The specific inhibition of eukaryote DNA topoisomerase II by the anti-cancer drugs VP16, VM26, and 21 other congeners of podophyllotoxin has been extensively studied in this laboratory through the use of alkaline elution and other techniques. A structure-activity relationship has been established for cytotoxicity, single and double strand DNA breakage, and inhibition of the DNA strand passing activity of topoisomerase II. Furthermore, topoisomerase inhibition was measured in four naturally sensitive and resistant human lung carcinoma cells by quantifying the amount of single and double strand DNA breakage produced by VP16 and VM26 in cells and isolated nuclei. A direct correlation between double but not single strand DNA breaks and cytotoxicity was observed for the analogs in A549 human lung adenocarcinoma cells. In fact, some analogs were capable of producing substantial single strand DNA breakage without producing cytotoxicity. A similar correspondence was observed between double strand DNA breaks and cytotoxicity produced by VP16 and VM26 in the naturally sensitive and resistant cell lines. Evidence is also presented suggesting that the association of the drug with enzyme-DNA intermediate complex and the formation of the enzyme-DNA complex alone both reflected equilibrium governed conditions that were readily reversible. These studies support a model based on the proposal that the actual cytotoxic events are genetic alterations caused by possible heterologous subunit exchanges occurring between adjacent enzyme molecules, which result from the stabilization of the intermediate complex, rather than the actual loss of topoisomerase II activity caused by the inhibition. The resistance of normal cells and cells with acquired resistance to the possible clastogenic effects of topoisomerase inhibition may be, in part, related to the low topoisomerase II levels found in such cells. Topoisomerase II may also play a role in gene amplification and tumor cell heterogeneity by serving as a vehicle through which genetic recombination events may occur.
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PMID:Inhibitors of topoisomerase II: structure-activity relationships and mechanism of action of podophyllin congeners. 285 48

Several antitumor drugs including DNA intercalative and non intercalative agents induce in vitro and in vivo double-stranded DNA breaks by stabilization of a topoisomerase II-DNA complex. In order to locate cleavage sites in an actively transcribed oncogene, N417 cells, originating from a human small cell lung carcinoma and containing 45-50 copies of c-myc oncogene, were treated with mAMSA, 9 hydroxyellipticine and VM 26. The presence of DNA lesions in c-myc was investigated by Southern blot hybridization with a human c-myc probe. In addition to normal bands, DNA patterns of drug treated-cells revealed the presence of new bands most likely corresponding to topoisomerase II-mediated cleavage as these bands were not found in untreated control DNA and in DNA treated with oAMSA, a biologically inactive stereoisomer of mAMSA. Major cleavage sites induced by drugs in the N417 cell c-myc locus were located in the 5' end of the c-myc exon 1 closely to some DNAse I hypersensitive sites which are assumed to reflect an activity of the gene. Therefore our data suggest that TopoII-mediated drug activity correlates with gene activity.
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PMID:In vivo stimulation by antitumor drugs of the topoisomerase II induced cleavage sites in c-myc protooncogene. 301 77

Evidence suggests that the anticancer agents etoposide (VP16-213) and teniposide (VM26) produce DNA breaks and cytotoxicity by interaction with type II topoisomerase. Therefore, levels of type II topoisomerase may influence sensitivity to VP16-213 and VM26. We have characterized four lung carcinoma-derived cell lines for natural sensitivity or resistance to VP16-213 and VM26. Included in this study were two small cell lung carcinoma lines (SW900 and SW1271), an adenocarcinoma line (A549), and a large cell carcinoma (H157). SW1271 was the most sensitive line with a median inhibitory concentration for cell proliferation of 0.5 microM for VM26 and 2.7 microM for VP16-213, and SW900 was the most resistant with median inhibitory concentration values of 2.0 and 16 microM, respectively. A549 and H157 cells were intermediate in sensitivity to these drugs. Alkaline elution techniques were used to study in vivo formation and repair of single and double strand DNA breaks. Single strand DNA breaks were observed in SW1271 cells exposed to as little as 10 nM VM26 or 100 nM VP16-213 for 1 h, whereas SW900 cells required exposure to 10-fold higher concentrations of VM26 or VP16-213 to produce similar results. Single strand DNA breaks predominated only in SW1271 and A549 cells and then, only at low drug concentrations, whereas the ratios between single and double strand DNA breaks decreased at higher drug concentrations. Plots of cytotoxicity versus single and double strand DNA breakage revealed that cytotoxicity produced by both drugs was more closely related to double strand DNA break formation in all four cell lines. DNA breaks appeared rapidly upon addition of drug, reaching plateaus in DNA breaks within 30 min, and repair of both single and double strand DNA breaks occurred rapidly with time to repair one-half of the DNA breaks of 20 to 60 min in all four cell lines upon removal of drug, arguing against repair as a mechanism for drug resistance. DNA breakage was also observed in nuclei isolated from SW900 and SW1271 cells in similar magnitude to that observed in the respective cells. Results indicate that DNA breakage plateaus may reflect a steady-state equilibrium established between the drug and its nuclear target, possibly type II topoisomerase, and suggest that natural resistance to VP16-213 and VM26 may be due to different enzyme levels in sensitive and naturally resistant cells.
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PMID:DNA breakage in human lung carcinoma cells and nuclei that are naturally sensitive or resistant to etoposide and teniposide. 301 77

In a human small cell lung carcinoma cell line, GLC4, Adriamycin (ADR) resistance was induced. In the resistant cell line, GLC4/ADR, a 45% decreased intracellular ADR level was found compared to GLC4, but this could not fully explain the resistance. Evaluation of DNA damage in both cell lines after incubation with ADR by alkaline and neutral elution revealed single-strand breaks, DNA-protein cross-links, and double-strand breaks (DSB). At all incubation concentrations there was a decreased amount of all types of DNA damage in GLC4/ADR. The number of DSB was decreased also when corrected for the decreased intracellular concentration. This can at least partly be explained by the decreased stability of ADR induced DSB. After removal of ADR, 80% of DSB was repaired in 1 h in GLC4/ADR against no repair in GLC4. X-ray induced DSBs were also repaired faster: in GLC4/ADR t1/2 = 10 min and in GLC4 t1/2 = 23 min. Ratios for single strand breaks/DSBs and single strand breaks/DNA-protein cross-links between GLC4 and GLC4/ADR after exposure to ADR differed; these differences were compatible with differences in the distribution of the various types of DNA damage induced in the cell lines due to an altered ADR-topoisomerase II interaction. In this human small cell lung carcinoma cell line the resistance is multifactorial with decreased intracellular ADR levels, increased DNA repair, and altered ADR-topoisomerase interaction.
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PMID:Multifactorial drug resistance in an adriamycin-resistant human small cell lung carcinoma cell line. 302 13

A number of new anilino ring variants of the anti-tumour drug amsacrine have been synthesised and their anti-tumour activity evaluated. In vitro selectivity, as measured by the logarithmic ratio of IC50 growth inhibition assays against P388 leukaemia and Lewis lung carcinoma cells, was significantly correlated with the increase in life span in vivo with the P388 leukaemia and Lewis lung lines, whereas the growth inhibition IC50 values alone correlated with the dose potency in mice. It was thus possible to predict both in vivo anti-tumour activity and dose potency, identifying compounds with high therapeutic activity, using a combination of two in vitro assays. Two new compounds have been identified which provide, along with an acridine-substituted analogue of amsacrine which is at present in clinical trial (CI-921), a high proportion of cures against the Lewis lung tumour in vivo. Since amsacrine is thought to interact with the enzyme topoisomerase II, and because the anilino group of 9-anilinoacridine derivatives is thought to project from the DNA intercalation site of the drug-DNA complex, these compounds may be of particular interest in mode of action studies.
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PMID:In vitro and in vivo assessment of activity of new anilino-substituted analogues of amsacrine against Lewis lung carcinoma. 345 Feb 94


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