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)

Resistance of tumors due to restricted drug accumulation and reversal of DNA lesions in tumor cells as well as normal tissue toxicity limit the efficacy of topoisomerase inhibition based anticancer drugs. It has been proposed that selective inhibition of energy dependent repair processes and enhanced retention of drug in cancer cells can significantly improve the therapeutic efficacy. The purpose of these studies was to verify this proposition by investigating the effects of 2-deoxy-D-glucose (2-DG) an inhibitor of the glycolytic ATP production on the cytotoxicity of certain topoisomerase inhibitors in human tumor cell lines. Human glioma (BMG-1 and U-87) and squamous carcinoma (4197 and 4451) cell lines were investigated with topo-poisons like etoposide (topo II inhibitor), camptothecin (topo I inhibitor) and hoechst-33342 (topo I and II inhibitor). DNA damage induction (halo assay), cell survival (macro colony assay), cytogenetic damage (micronuclei) and apoptosis (morphological analysis) were investigated. Presence of 2-DG for 2 h following exposure to the topoisomerase inhibitors enhanced the cell death (macro colony assay) in a concentration dependent manner and a 2-3-fold increase was observed at 5 mM (equimolar with glucose). Halo assay revealed that 2-DG inhibited the reversal of cleavable complex leading to the accumulation of DNA strand breaks. Under these conditions 2-DG enhanced the drug-induced micronuclei formation by nearly 2 folds with etoposide and hoechst-33342 and a 4-fold increase in delayed apoptosis was observed in case of etoposide. These results clearly demonstrate that presence of 2-DG for a few hours following exposure to topo-inhibitors enhances the cytotoxicity, primarily by increasing the cytogenetic damage.
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PMID:2-deoxy-D-glucose enhances the cytotoxicity of topoisomerase inhibitors in human tumor cell lines. 1525 10

Earlier studies have shown that 2-deoxy-D-glucose (2-DG), a glucose analogue and inhibitor of glycolytic ATP production significantly enhances the cytotoxic effects of anticancer agents like topoisomerase inhibitors (etoposide and camptothecin) and a radiomimetic drug (bleomycin) in established human tumor cell lines. Therefore, combination of 2-DG and DNA damage causing cytotoxic agents could be very useful in enhancing local tumor control. The purpose of the present studies was to investigate the therapeutic effects of etoposide and 2-DG in Ehrlich ascites tumor (EAT) bearing mice, grown as solid tumor as well as in the ascites form. Cell growth, cell cycle perturbations (flow cytometry), cytogenetic damage (micronuclei assay) and apoptosis (DNA content, morphological changes) were studied as parameters of cellular response, while delay in tumor growth and cure rate (tumor free survival) were evaluated as parameters of systemic response. Body weight and general condition as well as the damage to bone marrow and spleen was monitored to evaluate normal tissue toxicity. Intraperitoneal administration of etoposide (30 mg/Kg b. wt.) resulted in significant tumor growth delay and cure (approximately 11%) only in subcutaneous tumors leading to local tumor control. When etoposide was combined with 2-DG (2 g/Kg b. wt.; i.v./i.p.; 4 h after etoposide injection), these effects were further enhanced resulting in a cure rate of approximately 22% in case of subcutaneous tumors and 20% in ascites bearing mice. Analysis of cells obtained from ascitic fluid as well as solid tumors during follow up clearly showed that etoposide induced cell death was mainly due to apoptosis, which was enhanced further by 2-DG. Although, there was a significant level of toxicity revealed by reduced animal survival, decrease in body weight and damage to sensitive organ status like spleen and bone marrow at 60 mg/Kg b. wt. of etoposide, it was not significant at 30 mg/Kg b.wt. 2-DG, however, did not enhance the etoposide toxicity at both the doses. These results indicate that the administration of 2-DG can improve the local control of tumors without increasing normal tissue toxicity, thereby enhancing the therapeutic efficacy of topoisomerase inhibitor based anticancer drugs like etoposide.
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PMID:The glycolytic inhibitor 2-deoxy-D-glucose enhances the efficacy of etoposide in ehrlich ascites tumor-bearing mice. 1571 Nov 25

Solid tumors are often placed under stress conditions, such as glucose starvation which may result in topoisomerase II drug resistance. In this study, we investigated whether glucose deprivation or substitution by fructose regulates tumor cell apoptosis induced by 2-acetyl furanonaphthoquinone (FNQ). We now show that FNQ exerts much greater antitumor activity than either 7-methoxy 2-ethyl FNQ or 2-ethyl FNQ. Whereas 0.8 microM FNQ induces apoptosis after 16 hours in glucose-supplemented conditions irrespective of bcl-2 overexpression in K1735 melanoma, 0.5 microM FNQ is also effective within 12 hours in low glucose or in fructose-supplemented medium. Under the latter conditions, apoptosis-associated PARP cleavage and cytosolic cytochrome C are increased, together with induction and partial translocation to mitochondria of phosphorylated Jun-N-terminal kinase and massive upregulation of mitochondrial Mn superoxide dismutase. We propose that mitochondrial colocalization of these activities is important in this synergistic anti-tumor effect of FNQ and glucose depletion. Since glucose limitation slows proliferation and decreases efficacy of some genotoxic drugs that trigger apoptosis in rapidly dividing cells, we propose evaluating FNQ as a novel therapeutic anti-cancer adjuvant against slowly proliferating tumors.
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PMID:Decreased glycolytic metabolism accelerates apoptosis in response to 2-acetyl furanonaphthoquinone in K1735 melanoma irrespective of bcl-2 overexpression. 1584 99

Doxorubicin executes apoptosis, a process known to produce leakage of cytochrome c and opening of the mitochondrial permeability transition pores. To define the loss of mitochondrial function by apoptosis, we monitored cellular respiration during continuous exposure to doxorubicin. A phosphorescence analyzer capable of stable measurements over at least 5 h was used to measure [O(2)]. In solutions containing glucose and cells, [O(2)] declined linearly with time, showing that the kinetics of oxygen consumption was zero order. Complete inhibition of oxygen consumption by cyanide indicated that oxidations occurred in the respiratory chain. A decline in the rate of respiration was evident in Jurkat and HL-60 cells exposed to doxorubicin. The decline was abrupt, occurring after about 2 h of incubation. The inhibition was concentration-dependent and was completely blocked by the pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone. Respiration in resistant HL-60/MX2 cells, characterized by an altered topoisomerase II activity, was not inhibited by doxorubicin. A decline in cellular ATP was measured in Jurkat cells after 2-4 h of incubation with 20 microM doxorubicin, paralleling the decline in respiration rate. Thus, cells incubated with doxorubicin exhibit caspase-mediated inhibition of oxidative phosphorylation.
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PMID:Inhibition of cellular respiration by doxorubicin. 1691 44

DE-310 is a novel macromolecular prodrug of the topoisomerase-I inhibitor DX-8951. DX-8951 is covalently linked to carboxymethyl dextran polyalcohol (CM-Dex-PA) via a Gly-Gly-Phe-Gly (GGFG) tetrapeptide spacer. The present study was conducted to identify the portions of DX-8951 linked to DE-310, as well as to quantify the number of DX-8951 molecules associated with DE-310. Two different structures terminated with either glycolaldehyde (CM-GA-GGFG-DX-8951) or glycerol (CM-Glr-GGFG-DX-8951) are obtained when the polymer backbone is fragmented with 1 M HCl. The two products, i.e., CM-GA-GGFG-DX-8951 and CM-Glr-GGFG-DX-8951, indicate linkage of GGFG-DX-8951 with carboxymethyl (CM) group at C-2 and C-4 position of the glucose units, respectively. In the present study, CM-GA-GGFG-DX-8951 was reduced to CM-ethyleneglycol (EG)-GGFG-DX-8951 in order to improve stability prior to HPLC analysis. Hydrolysis results revealed that the amount of CM-GA-GGFG-DX-8951 liberated was 84.7 nmol/mg DE-310 and the amount of CM-Glr-GGFG-DX-8951 was 71.8 nmol/mg DE-310. Considering the ratio of generation between CM-GA-GGFG-DX8951 and CM-Glr-GGFG-DX8951, it suggested that slightly larger amount of GGFG-DX-8951 was linked to carboxymethyl groups at the C-2 position of glucose units in DE-310. The sum of the amounts of CM-GA-GGFG-DX-8951 and CM-Glr-GGFG-DX-8951 agrees well with the amount of G-DX-8951 produced from DE-310 by alpha-chymotrypsin treatment (157.5 nmol/mg DE-310). The data indicate that the established hydrolysis give a quantitative evaluation of the DX-8951 linked to DE-310.
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PMID:Quantitative acid hydrolysis of DE-310, a macromolecular carrier system for the camptothecin analog DX-8951f. 1712 25

Physiological cell conditions such as glucose deprivation and hypoxia play roles in the development of drug resistance in solid tumors. These tumor-specific conditions cause decreased expression of DNA topoisomerase IIalpha, rendering cells resistant to topo II target drugs such as etoposide. Thus, targeting tumor-specific conditions such as a low glucose environment may be a novel strategy in the development of anticancer drugs. On this basis, we established a novel screening program for anticancer agents with preferential cytotoxic activity in cancer cells under glucose-deprived conditions. We recently isolated an active compound, AA-98, from Streptomyces sp. AA030098 that can prevent stress-induced etoposide resistance in vitro. Furthermore, LC-MS and various NMR spectroscopic methods identified AA-98 as mithramycin, which belongs to the aureolic acid group of antitumor compounds. We found that mithramycin prevents the etoposide resistance that is induced by glucose deprivation. The etoposide-chemosensitive action of mithramycin was just dependent on strict low glucose conditions, and resulted in the selective cell death of etoposide-resistant HT-29 human colon cancer cells.
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PMID:Mithramycin inhibits etoposide resistance in glucose-deprived HT-29 human colon carcinoma cells. 1809 71

Microchip-based systems have many desirable characteristics and can be used in much cellular biochemical analysis. Glucose-regulated protein 78 (GRP78), an endoplasmic reticulum chaperone, has a critical role in chemotherapy resistance of some cancers. This work aimed at analyzing the correlation between the expression of GRP78 and an anticancer drug, topoisomerase II inhibitor-VP-16, in human lung cancer cell line NCI-H460 using this microchip-based system. The cells were cultured on a PDMS chip, the expression of GRP78 at both protein and mRNA levels for the cells under the condition with or without the induction of A23187 were assayed by immunofluorescence and chip electrophoresis, respectively. Then the cells were treated by VP-16, percentages of apoptosis and the cycle distributions of the cells were detected by flow cytometry. The cells cultured on the PDMS attached and spread well to micro-channels with high viability. Compared with the non-induced cells, the expression of GRP78 at both protein and mRNA levels for the A23187-induced cells were increased greatly. After treatment by VP-16, the percentage of apoptotic cells decreased nearly threefold for the A23187-induced cells in contrast to the non-induced cells (13.15 +/- 3.84% versus 34.03 +/- 11.45%), and the cells distributed in S phase reduced dramatically (11.96 +/- 1.27% versus 20.76 +/- 3.05%) whereas in G(1) phase increased greatly (74.16 +/- 0.95% versus 57.06 +/- 4%). GRP78 is correlated to the resistance to VP-16 in human lung cancer cell line. The microchip-based system has the potential application and feasibility for cell culture and its functional research.
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PMID:The analysis of chemotherapy resistance in human lung cancer cell line with microchip-based system. 1836 95

2-acetyl furanonaphthoquinone (FNQ) is a naturally occurring drug with enhanced toxicity versus glucose-starved tumor cells, which frequently show topoisomerase II drug resistance. Since loss of p53 tumor suppressor function or overexpression of the anti-apoptotic bcl-2 gene can decrease susceptibility to some cancer therapies, we now investigated the effect of FNQ against genetically matched C8161 melanoma cell lines transduced to express unequal levels of Bcl-2, or engineered to harbour a functional wt p53 for comparison with dominant-negative mutant p53 R175H. Cells with differing p53 genotype showed susceptibility to FNQ. However, this response was attenuated in those overexpressing mutant p53, although a brief p53 induction was early seen in FNQ-treated wt p53 cells. Cells susceptible to FNQ showed cleavage of anti-apoptotic Mcl-1, sustained activation of the c-Jun N-terminal Kinase (p-JNK), and apoptosis-associated PARP fragmentation, all of which were counteracted in bcl-2 overexpressing cells. Suppression of JNK activation with the specific inhibitor, SP600125 also prevented FNQ-mediated cell death. Our data suggests that Bcl-2, persistent JNK phosphorylation and cleavage of anti-apoptotic Mcl-1 are key events controlling susceptibility to FNQ.
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PMID:Mcl-1 cleavage and sustained phosphorylation of c-Jun-N-terminal kinase mediate melanoma apoptosis induced by 2-acetyl furanonaphthoquinone: roles of Bcl-2 and p53. 1845 32

The TOPRIM domain found in many nucleotidyl transferases contains a DxD motif involved in magnesium ion coordination for catalysis. Medium- to high-copy-number plasmid clones of Yersinia pestis topoisomerase I (YpTOP) with Asp-to-Asn substitution at the first aspartate residue (D117N) of this motif could not be generated in Escherichia coli without second-site mutation even when expression was under the control of the tightly regulated BAD promoter and suppressed by 2% glucose in the medium. Arabinose induction of a single-copy YpTOP-D117N mutant gene integrated into the chromosome resulted in approximately 10(5)-fold of cell killing in 2.5 h. Attempt to induce expression of the corresponding E. coli topoisomerase I mutant (EcTOP-D111N) encoded on a high-copy-number plasmid resulted in either loss of viability or reversion of the clone to wild type. High-copy-number plasmid clones of YpTOP-D119N and EcTOP-D113N with the Asn substitution at the second Asp of the TOPRIM motif could be stably maintained, but overexpression also decreased cell viability significantly. The Asp-to-Asn substitutions at these TOPRIM residues can selectively decrease Mg(2+) binding affinity with minimal disruption of the active-site geometry, leading to trapping of the covalent complex with cleaved DNA and causing bacterial cell death. The extreme sensitivity of the first TOPRIM position suggested that this might be a useful site for binding of small molecules that could act as topoisomerase poisons.
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PMID:Asp-to-Asn substitution at the first position of the DxD TOPRIM motif of recombinant bacterial topoisomerase I is extremely lethal to E. coli. 1901 70

Mitochondrial dysfunction has a significant role in the development and complications of diabetic cardiomyopathy. Mitochondrial dysfunction and mitochondrial DNA (mtDNA) mutations are also associated with different types of cancer and neurodegenerative diseases. The goal of this study was to determine if chronically elevated glucose increase in mtDNA damage contributed to mitochondrial dysfunction and identify the underlying basis for mtDNA damage. H9c2 myotubes (a cardiac-derived cell line) were studied in the presence of 5.5, 16.5, or 33.0 mM glucose for up to 13 days. Tests of mitochondria function (Complex I and IV activity and ATP generation) were all significantly depressed by elevated media glucose. Intramitochondrial superoxide and intracellular superoxide levels were transiently increased during the experimental period. AnnexinV binding (a marker of apoptosis) was significantly increased after 7 and 13 days of high glucose. Thirteen days of elevated glucose significantly increased mtDNA damage globally and across the region encoding for the three subunits of cytochrome oxidase. Using mitochondria isolated from cells chronically exposed to elevated glucose, we observed significant increases in topoisomerase-linked DNA cleavage. Mitochondria-dependent DNA cleavage was significantly exacerbated by H(2)O(2) and that immunoprecipitation of mitochondrial extracts with a mtTOP1 antibody significantly decreased DNA cleavage, indicating that at least part of this activity could be attributed to mtTOP1. We conclude that even mild increases in glucose presentation compromised mitochondrial function as a result of a decline in mtDNA integrity. Separate from a direct impact of oxidative stress on mtDNA, ROS-induced alteration of mitochondrial topoisomerase activity exacerbated and propagated increases in mtDNA damage. These findings are significant in that the activation/inhibition state of the mitochondrial topoisomerases will have important consequences for mitochondrial DNA integrity and the well being of the myocardium.
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PMID:Chronically elevated glucose compromises myocardial mitochondrial DNA integrity by alteration of mitochondrial topoisomerase function. 2112 31


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