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)

Topoisomerase II is a key target for many anti-cancer drugs used to treat breast cancer. In human cells there are two closely related, but differentially expressed, topoisomerase II isoforms, designated topoisomerase II alpha and beta. Here, we report the production of a new polyclonal antibody raised against a fragment of the C-terminal domain of the 180 kDa form of topoisomerase II (the beta isoform), which does not cross-react with the 170 kDa form (the alpha isoform). Using this antibody, together with a polyclonal antibody specific for the 170 kDa isoform of topoisomerase II, we have examined the relationship between the sensitivity of a panel of human breast cancer cell lines to different classes of topoisomerase II inhibitors and cellular levels of the topoisomerase II alpha and beta proteins. We found that sensitivity to amsacrine showed a correlation with the level of expression of topoisomerase II alpha protein, and that sensitivity to etoposide showed a similar correlation with the level of expression of topoisomerase II beta protein. There was also a relationship between sensitivity of these cell lines to mitoxantrone and the cellular level of both isoforms of topoisomerase II. No relationship was found between the level of mRNA for topoisomerase II alpha or beta, and either sensitivity of breast cancer cell lines to topoisomerase II inhibitors or the level of topoisomerase II protein expression.
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PMID:Relationship between expression of topoisomerase II isoforms and intrinsic sensitivity to topoisomerase II inhibitors in breast cancer cell lines. 851 59

Increased expression of DNA topoisomerase II alpha has been associated with resistance to certain DNA-damaging alkylating agents, but no causal relationship or mechanism has been established. To investigate this observation, we developed a model of topoisomerase II overexpression by transfecting a full-length Chinese hamster ovary topoisomerase II alpha into EMT6 mouse mammary carcinoma. Topoisomerase II alpha-transfected cell lines demonstrated continued topoisomerase II alpha mRNA and protein expression, which were undetectable in vector-only lines, in stationary phase (G0-G1). The topoisomerase II transfectants were approximately 5-10-fold resistant to the alkylating agents cisplatin and mechlorethamine. Upon release from G0-G1, the topoisomerase II transfectants demonstrated more rapid thymidine incorporation and shorter cell-doubling times than control cells. Purified topoisomerase II and nuclear extracts with topoisomerase II-decatenating activity bound to cisplatin-treated DNA with significantly greater affinity than to untreated DNA in a cisplatin concentration-dependent manner. These observations suggest that expression of topoisomerase II alpha may have a role in cellular resistance to antineoplastic alkylating agents. The mechanism for this may involve increased binding of topoisomerase II alpha to alkylating agent-damaged DNA.
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PMID:DNA topoisomerase II alpha expression is associated with alkylating agent resistance. 852 1

Biopsies of superficial bladder cancer were analysed to study the relationship between response to epirubicin and the expression of the human topoisomerase II alpha and beta genes. Tissue samples were obtained prior to treatment and a marker tumour was left in the bladder. Transcript levels of both genes were generally lower in biopsies taken following treatment failure. Levels of topoisomerase II mRNA were uniformly lower in tumour tissue than in biopsies of normal tissue.
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PMID:Response to epirubicin in patients with superficial bladder cancer and expression of the topoisomerase II alpha and beta genes. 854 98

DNA topoisomerase II is the target of a variety of important antitumor agents, including etoposide, adriamycin, and amsacrine. We have constructed a system for analyzing the action of anti-topoisomerase II agents using the yeast Saccharomyces cerevisiae and have constructed vectors for expressing human topoisomerase II functionally in yeast. We have demonstrated that temperature-conditional yeast TOP2 mutants can be complemented by expression of wild-type human topoisomerase II alpha. Furthermore, expression of human topoisomerase II in yeast results in a quantitatively unique pattern of sensitivity to amsacrine. We also have constructed mutations in human TOP2 based on previously identified mutations from a human cell line selected for resistance to teniposide. Our experiments demonstrate that mutation of either arginine 450 or proline 803 of human topoisomerase II can result in an enzyme that has altered sensitivity to anti-topoisomerase II agents, and that a human enzyme carrying both mutations confers a higher level of drug resistance than enzymes carrying either single mutation.
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PMID:Functional expression of human topoisomerase II alpha in yeast: mutations at amino acids 450 or 803 of topoisomerase II alpha result in enzymes that can confer resistance to anti-topoisomerase II agents. 854 81

We investigated whether the expression of protein kinase C (PKC) isoenzymes, topoisomerase II alpha, II beta, multidrug resistance associated protein (MRP), p53 or the activity of glutathione-S- transferase (GST) are additional factors contributing to the resistance mediated by multidrug resistance gene 1 (mdr 1). the cell lines employed for these studies were human lymphoblastoid CCRF cells selected for resistance with actinomycin D, vincristine and adriamycin, KB-3-1 and matched resistant KB-8-5 and KB-C1 cells (selected with colchicine), and a HeLa cell line, in which the resistance was obtained by transfection with the mdr1-gene. Analysis of PKC isozymes showed that there is no correlation of a specific isoenzyme with resistance, although minor differences in the expression were observed. In vincristine and adriamycin selected cells, topoisomerase II alpha- and II beta-MRNA levels were reduced, and in vincristine selected cells the MRP-mRNA was elevated compared with the sensitive line. In KB cells the levels of topoisomerase II alpha and II beta mRNA were increasing with the resistance. Expression of p53 did not correlate with Pgp levels. In summary, MRP and topoisomerase II may contribute to the mdr1 -mediated resistance in some cell lines, but PKC, p53 and GST seem to be of minor or no importance.
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PMID:Protein kinase C isoenzymes, p53, accumulation of rhodamine 123, glutathione-S-transferase, topoisomerase II and MRP in multidrug resistant cell lines. 861 23

The mechanism of action of the antitumor drug amsacrine involves intercalation of the acridine chromophore into DNA and inhibition of topoisomerase II. The substituent at position 1' on the aniline is believed to be essential to the formation of the topoisomerase II/DNA cleavable complex and therefore to the cytotoxicity of the drug. To further delineate the role of the 1'-substituent, we investigated the effects on topoisomerase II activities of three anilinoacridine derivatives that differ only by the nature of the substituent at position 1'. The results of the cytotoxicity assays performed with cells sensitive (DC-3F) and resistant [DC-3F/9-hydroxy-ellipticine (9-OH-E)] to topoisomerase inhibitors are correlated with the effects of the drugs on topoisomerase II-mediated DNA cleavage in vitro. The influence of topoisomerase II alpha on the mechanism of action of the drugs was examined using resistant DC-3F/9-OH-E cells transfected with a plasmid carrying a wild-type human topoisomerase II alpha cDNA. Depending on the nature of the 1'-substituent of the drugs, the restoration of normal topoisomerase II alpha catalytic activity in human topoisomerase II alpha cDNA-transfected DC-3F/9-OH-E cells either does not modify the susceptibility of the cells to the drug or partially reverses the resistance phenotype. The molecular and cellular studies reveal that topoisomerase II alpha is implicated in the cytotoxicity of amsacrine and confirm that the substituent at position 1' on the anilino ring of amsacrine governs the interaction with topoisomerase II.
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PMID:The 1'-substituent on the anilino ring of the antitumor drug amsacrine is a critical element for topoisomerase II inhibition and cytotoxicity. 863 68

We have developed a method to quantify topoisomerase (topo) II activities in partially purified nuclear extracts from human leukemia cells. By virtue of their different pH optima in the reaction buffer, two different topo II activities were found with activity optima at pH 7.9 and at pH 8.9 under high stringency conditions. The activities could be identified as topo II beta activity (pH 7.9) and topo II alpha activity (pH 8.9) by their different sensitivities to topo II alpha inhibitors, dephosphorylation experiments and immunoprecipitation with polyclonal antibodies. Seventy-two bone marrow or blood samples from patients with acute myeloid leukemias have been examined and their in vitro sensitivities to anthracyclines and epipodophyllotoxines correlated to the activities of topo II alpha and topo II beta. Although the topo II alpha activity could be directly inhibited by incubation of the cells with the mentioned drugs, no correlation between the topo II alpha activity and the sensitivity of the cells could be found. In contrast, the topo II beta activity which was not substantially inhibited by the drugs inversely correlated with the sensitivity of the cells. These findings were statistically significant for idarubicin (P=0.017) and daunorubicin (P=0.006). Vice versa, resistant cells (IC90 > median) had a higher topo II beta activity. Clinical relevance might be indicated by the finding that cells from patients that relapsed after initial treatment with anthracyclin-containing regiments had a significantly higher topo II alpha/beta activity ratio (P=0.0276). Obviously, the sensitivity of AML cells is substantially influenced by the activity of the resistant topo II (topo II beta) which gives evidence that the remaining topo II activity after treatment helps the cell to survive the DNA repair phase.
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PMID:Topoisomerase II activities in AML blasts and their correlation with cellular sensitivity to anthracyclines and epipodophyllotoxines. 865

Topoisomerase II is a key target for several anti-cancer drugs used for breast cancer therapy, including doxorubicin, epirubicin and mitoxantrone. Two isoforms of topoisomerase II (alpha and beta) have been described in human cells which differ in their subcellular localisation, biochemical properties and susceptibility to inhibition by anti-cancer drugs. The relative level of expression of the alpha and beta isoforms may contribute to the degree of tumour responsiveness to different chemotherapeutic agents. To assess the relationship between expression of topoisomerase II isoforms and established prognostic factors and pathological variables, 56 primary breast tumour samples were studied. The expression of the two topoisomerase II genes was apparently not co-ordinately regulated in these tissue samples. There was no relationship between any of the commonly used pathological variables [tumour size, lymph node status, S-phase fraction (SPF)] and the level of expression of topoisomerase II beta mRNA. However, high topoisomerase II alpha gene expression was significantly associated with a high SPF (sign-rank test; P = 0.01). Moreover, the ratio of mRNA levels for topoisomerase II alpha and beta showed a stronger relationship to SPF (median raito 0.62 for tumours with SPF < 10, and 1.64 for SPF > 10; P = 0.0021, sign-rank test). As expected from previous studies, an SPF > 10 was associated with poor overall survival (P = 0.01). Immunohistochemical analysis revealed that topoisomerase II beta was widely distributed ( > 90% positive tumour cells), but that topoisomerase II alpha expression was less widely expressed, with a pattern of expression similar to that of the proliferation-dependent antigen recognised by Ki67. Because topoisomerase II gene expression showed a log-normal distribution, log-transformed data were used in multivariate analysis of relapse-free survival. This showed that lymph node status and topoisomerase II beta mRNA expression were the only significant survival factors (P = 0.001 and 0.05, respectively, with relative risks of 1.3 and 1.8). These results indicate that topoisomerase II alpha, but not beta, expression is dependent upon cellular proliferation status, but that the more widely expressed topoisomerase II beta protein may play a significant role as a target for anti-tumour therapy.
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PMID:Differential expression of the topoisomerase II alpha and beta genes in human breast cancers. 866 22

We have developed a method to quantify topoisomerase (topo) II activities in partially purified nuclear extracts from human leukemia cells. By virtue of their different pH optima in the reaction buffer, two different topo II activities were found with activity optima at pH 7.9 and at pH 8.9 under high stringency conditions. The activities could be identified as topo II beta activity (pH 7.9) and topo II alpha activity (pH 8.9) by their different sensitivities to topo II alpha inhibitors, dephosphorylation experiments and immunoprecipitation with polyclonal antibodies. Seventy-two bone marrow or blood samples from patients with acute myeloid leukemias have been examined and their in vitro sensitivities to anthracyclines and epipodophyllotoxines correlated to the activities of topo II alpha and topo II beta. Although the topo II alpha activity could be directly inhibited by incubation of the cells with the mentioned drugs, no correlation between the topo II alpha activity and the sensitivity of the cells could be found. In contrast, the topo II beta activity which was not substantially inhibited by the drugs inversely correlated with the sensitivity of the cells. These findings were statistically significant for idarubicin (P= 0.017) and daunorubicin (P = 0.006). Vice versa, resistant cells (IC50 > median) had a higher topo II beta activity. Clinical relevance might be indicated by the finding that cells from patients that relapsed after initial treatment with anthracyclin-containing regiments had a significantly higher topo II alpha/beta activity ratio (P=0.0276). Obviously, the sensitivity of AML cells is substantially influenced by the activity of the resistant topo II (topo II beta) which gives evidence that the remaining topo II activity after treatment helps the cell to survive the DNA repair phase.
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PMID:Topoisomerase II activities in AML and their correlation with cellular sensitivity to anthracyclines and epipodophyllotoxines. 868 99

The examination of topoisomerase II alpha content by Western blot analysis or topoisomerase II catalytic activity by decatenation of kDNA requires a large number of cells, but it is difficult to collect sufficient cells for these biochemical analyses from lung cancer patients by transbronchial brushing or aspiration. In this study, we explored the relationship between these biochemical analyses and topoisomerase II immunostaining in cytospin preparations of three lung adenocarcinoma cell lines. The levels of topoisomerase II alpha content were about 8.4 for A549, 2.9 for PC-3 and 1 for RERF-LC-MS, and the levels of topoisomerase II catalytic activity were about 4, 2, and 1, respectively. The percentages of strongly positive cells for topoisomerase II immunostaining were 60.9% for A549, 33.3% for PC-3, and 14.3% for RERF-LC-MS, and these were compatible with the levels of topoisomerase II alpha content or topoisomerase II catalytic activity. Our results indicate that topoisomerase II immunostaining can be utilized in place of biochemical analysis.
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PMID:Quantitative immunocytochemical assays of topoisomerase II in lung adenocarcinoma cell lines. Correlation to topoisomerase II alpha content and topoisomerase II catalytic activity. 869 54


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