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)

Chemotherapy failure remains a significant medical problem in the treatment of neoplastic disease and is thought to be due to many different factors including membrane transport, p-glycoprotein in multidrug resistance, glutathione and its related enzymes, topoisomerase II and DNA repair. Glutathione is a major constituent of non-protein thiol and participates in detoxification of chemotherapy and radiation. Thus, glutathione concentration is correlated with sensitivity to alkylating agents and radiation, and increased in resistant cell lines. Buthionine sulfoximine (BSO) is an inhibitor of glutathione biosynthesis and may increase cytotoxicities of alkylating agents, including melphalan and cisplatin, and radiation in sensitive and resistant cell lines. We studied effects on cellular glutathione levels and cytotoxicities of cisplatin, carboplatin and radiation by BSO treatment in human stomach cancer cell line (SNU-1) and ovarian cancer cell line (OVCAR-3). The results were as follow: 1) After BSO treatment of 1 mM and 2 mM for 2 days, the intracellular thiol concentration was depleted to 75.7% and 76.2% in SNU-1, and 74.1% and 63.0% in OVCAR-3, respectively. 2) The intracellular thiol concentration in SNU-1 was depleted to 33.4% after BSO 2 mM for only 2 hours incubation and 71.5% after small amount of BSO (0.02 mM) for 2 days. 3) The recovery of intracellular thiol concentration required more than 3 days after BSO removal. 4) BSO inhibited partially the growth of SNU-1 and OVCAR-3. 5) The cytotoxicities of cisplatin and carboplatin were markedly enhanced both in SNU-1 and OVCAR-3 by BSO treatment. 6) The cytotoxicities of radiation was increased in OVCAR-3 and SNU-1 by BSO treatment. Therefore, it is concluded that BSO can deplete effectively the intracellular thiol concentration and enhance the cytotoxicities of cisplatin, carboplatin and radiation.
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PMID:Effects of buthionine sulfoximine treatment on cellular glutathione levels and cytotoxicities of cisplatin, carboplatin and radiation in human stomach and ovarian cancer cell lines. 130 72

Exposure of human ovarian cancer SW626 cell line to 0.08 mumol/l methotrexate or 25 mumol/l aphidicolin for 24 h caused no cytotoxicity but enhanced etoposide cytotoxicity. Methotrexate or aphidicolin treatment induced a reversible blockade at the beginning of S phase which was reversed upon drug removal with a consequent wave of synchronisation. The enhancement of etoposide cytotoxicity was not due to higher etoposide intracellular uptake in the methotrexate or aphidicolin-pretreated cells. The topoisomerase II content in methotrexate or aphidicolin pretreated SW626 cells was higher than in control cells assessed by western blotting or flow cytometry. The higher etoposide cytotoxicity observed after synchronization with methotrexate or aphidicolin was apparently unrelated to the number of drug-induced DNA-topoisomerase II complexes evaluated as DNA double strand breaks or DNA-protein crosslinks. These data support the view that etoposide-induced DNA-topoisomerase II complexes are more cytotoxic in cells which are in S-phase.
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PMID:Potentiation of etoposide cytotoxicity against a human ovarian cancer cell line by pretreatment with non-toxic concentrations of methotrexate or aphidicolin. 131 31

Centrifugal elutriation was used to obtain synchronized cell populations in various cell cycle phases without prior growth-perturbing manipulation. Treatment of these subpopulations with novobiocin (NOVO), a putative inhibitor of the mammalian topoisomerase II enzyme, revealed a unique cell cycle phase-dependent cytotoxicity for this agent. At a concentration of 0.3 mM, NOVO was cytotoxic only to a specific cell subpopulation in the G1-S phase boundary. Cells in other cell cycle phases were completely unaffected. Additionally, S and G2M phase cells progressed through the cell cycle relatively unaffected by NOVO but were blocked at the G1-S boundary. NOVO treatment protected tumor cells from Adriamycin (ADR)-induced lethality but sensitized them to the toxic action of 4-hydroperoxycyclophosphamide, and alkylating agent. These opposing effects of NOVO were demonstrated in all of the four tumor cell lines investigated: A431 and HEp3 (derived from human squamous cell carcinomas); MLS, a human ovarian cancer cell line; and a Chinese hamster ovary cell line. The degree of protection against ADR was the greatest for S-phase cells, intermediate for cells in early G1 and M phases, and the least for late G1 cells. This cell cycle-dependent protection by NOVO, which is identical to the cell cycle-dependent cytotoxicity of ADR, was consistent with the idea that NOVO interfered directly with the cell-killing mechanism of ADR. In contrast, even though the cytotoxic activity of 4-hydroperoxycyclophosphamide exhibited significant cell cycle dependency, NOVO enhanced 4-hydroperoxycyclophosphamide lethality equally for all cell cycle phases.
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PMID:Modulation of the cell cycle-dependent cytotoxicity of adriamycin and 4-hydroperoxycyclophosphamide by novobiocin, an inhibitor of mammalian topoisomerase II. 131 22

Recombinant human tumor necrosis factor (rHuTNF) synergistically potentiates the cytotoxicity of the topoisomerase I inhibitor camptothecin, and the topoisomerase II inhibitors epidoxorubicin, etoposide, mitoxantrone, ellipticine, actinomycin D and 4'-(9-acridinylamino)methanesulfon-m-anisidide on A2780 human ovarian cancer cell line. Similar synergy was not observed with a combination of rHuTNF and cis-platinum or mitomycin C. When A2780 cells were incubated with rHuTNF simultaneously with camptothecin or mitoxantrone or VP16, increased numbers of DNA single-strand breaks were produced. rHuTNF alone did not induce DNA strand breakage. These data provide evidence that the enhancing effect of rHuTNF is closely related to the DNA damage mediated by topoisomerase-targeted drugs. These observations may have relevance for ovarian cancer treatment.
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PMID:Potentiation of topoisomerase I and II inhibitors cell killing by tumor necrosis factor: relationship to DNA strand breakage formation. 133 89

Significant prolongation of survival time among the patients with advanced ovarian cancer has been brought under the development of surgery and chemotherapy, but even those with clinical remission shows sometimes recurrence. For the recurrent ovarian cancer patients at present there are no definite strategy to treat the recurrent cases. Under these circumstance, we have reviewed the current treatment of cytoreductive surgery and chemotherapy for the recurrent cases. 1) surgical treatment Generally, in the cases of recurrent ovarian cancer, cytoreductive surgery is required to minimize the residual tumour in the abdomen. But sometimes we can find the distant metastasis including liver, lung, and lymph node. This means that surgery is not sufficient for control of recurrent tumor. Further adjuvant chemotherapy will be required to control metastatic tumors. 2) chemotherapy After the detail assessment of the initial treatment of cases, at first we should think about retreatment with CDDP-based regimen and secondly about dose-intensification of CDDP or CBDCA for the CDDP-resistant cases. And as combination regimens, topoisomerase inhibitors, etoposide or CPT-11 are also preferable to use, alkylating agents such as ifosfamide, 5-fluorouracil, and some current trials with new drug, taxol are effective for recurrent cases. In conclusion, further active chemotherapy using platinum compounds, topoisomerase inhibitors, taxol will be achieved for the control of the recurrent cases of ovarian cancer.
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PMID:[Treatment of recurrent ovarian cancer]. 135 32

Recombinant human tumor Necrosis Factor (rHuTNF) produced dose-dependent cytotoxicity against human ovarian cancer cells, OSC and OMC, obtained from fresh ascites. A combination of rHuTNF and the topoisomerase II inhibitor, Mitoxantrone, produced dose-dependent synergistic cytotoxicity on OSC and OMC cells. When OMC cells were incubated simultaneously for one hour with rHuTNF and Mitoxantrone, increased numbers of DNA single-strands breaks were produced. rHuTNF alone did not induce DNA single-strands breaks. These data are consistent with a role for topoisomerase-linked DNA lesions in the rHuTNF mediated potentiation of killing cells by Mitoxantrone.
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PMID:Augmentation of antineoplastic effects by the combination of recombinant human tumor necrosis factor and mitoxantrone on primary culture of human ovarian cancer cells. 144 98

P-glycoprotein (P-gp) expression and DNA topoisomerase (Topo) II are important variables in multidrug resistant tumor cell lines. The aim of this study was to evaluate P-gp expression and Topo I and II activity in benign and malignant epithelial ovarian tumors. P-gp expression was analyzed immunohistochemically in cryostat sections of fresh tumor specimens. In the same specimens Topo I and II activity were measured by, respectively, relaxation of supercoiled plasmid pBR322 DNA and decatenation of kinetoplast DNA. P-gp expression (range, 5-100% positive staining cells) was found in 3 of 6 cystadenomas, 0 of 2 borderline tumors, 15 of 21 untreated ovarian cancers, and 8 of 13 platinum/cyclophosphamide treated ovarian cancers. Median Topo I and II activity were elevated in malignant ovarian tumors compared to benign and borderline tumors. No difference was found between median Topo I activity in untreated ovarian cancer and platinum/cyclophosphamide treated ovarian cancer. High Topo II activity (greater than or equal to 8 x 10(2) units/mg protein) was more frequent in untreated compared to platinum/cyclophosphamide treated samples. Respectively, 8- and 16-fold differences in Topo I and II activity were found in the malignant tumors. Topo II activity in malignant tumors correlated with Topo I activity (r = 0.36, P less than 0.05) and the tumor volume index (r = 0.35, P less than 0.05). However, this last weak correlation cannot explain the 16-fold differences in Topo II activity in malignant tumors. Mitotic index and P-gp expression did not correlate with Topo I or II activity. A large variability in P-gp expression and Topo I and II activity was observed in patients with ovarian cancer.
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PMID:P-glycoprotein expression and DNA topoisomerase I and II activity in benign tumors of the ovary and in malignant tumors of the ovary, before and after platinum/cyclophosphamide chemotherapy. 168 37

As part of an ongoing rational drug design programme aiming to develop monosubstituted anthracenyl-peptides as potential anticancer drugs, three novel dipeptide conjugates have been synthesized and evaluated as inhibitors of topoisomerase (topo) I and II. Each of the three conjugates (designated NU/ICRF 600-602) was shown to inhibit the catalytic activity of both topoisomerase I and II, of which NU/ICRF 602 was the most active [100% inhibition of both enzymes at 5 micrograms/ml (approximately 15 microM) or less]. In a topo I/DNA unwinding assay, none of the compounds bound to DNA, suggesting genuine inhibition of catalytic activity. NU/ICRF 600 stabilized topo I cleavable complexes, although none of the compounds induced topo II-mediated DNA cleavage. Using a panel of Chinese hamster ovary cell lines along with the human ovarian cancer cell line, A2780, none of the three compounds were actively cytotoxic at concentrations < 100 microM. Subsequent drug uptake studies with NU/ICRF 600 and 602, using a method developed to correlate the chemosensitivity of A2780 cells with the uptake of anthracenyl-amino acid conjugates, revealed a lack of cellular uptake for both dipeptide conjugates. The significance of this finding in relation to drug design and the future development of this series of compounds is discussed.
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PMID:Identification of anthracenyl-dipeptide conjugates as novel topoisomerase I and II inhibitors and their evaluation as potential anticancer drugs. 749 76

30 years ago an anthracycline antibiotic was shown to have antineoplastic activity. This led to the development of well over 1000 analogues with a vast spectrum of biochemical characteristics. Many biological actions have been described. The original anthracyclines are active against many types of cancer and are an integral part of several curative combinations. They are ineffective against other tumours. Although some analogues show an altered spectrum of activity or an improved therapeutic index relative to the older agents, it is not clear that cardiotoxicity can be totally avoided with these agents. Primary and secondary resistance to anthracyclines remain major clinical problems. Pharmacokinetic studies have been of limited help in explaining this. Overexpression of a surface-membrane permeability glycoprotein (Pgp) was identified in ovarian cancer of patients who had clinical multidrug resistance in 1985. This led the way for the discovery of a number of resistance mechanisms in vitro. Some of these have been found in more than 1 type of cell line, and more than 1 mechanism may exist in a single cell. Additional resistance proteins have been identified, qualitative and quantitative alterations of topoisomerase II have been described, and some mechanisms in other systems have not yet been identified. Some of these may prove to be important in clinical drug resistance. Drugs such as calcium antagonists and cyclosporin, studied initially for their ability to block the Pgp pump, appear to be heterogeneous in this capacity and may have additional sites of action. It will be critical for clinical studies to define the precise resistance mechanism(s) that must be reversed. To date this has been difficult, even in trials ostensibly dealing with the original Pgp. Liposomes can potentially alter toxicity and target drug delivery to specific sites. In addition, they may permit the use of lipophilic drugs that would otherwise be difficult to administer systemically. Resistant tumours may be sensitive to anthracyclines delivered by liposomes. To reduce cardiac toxicity, administering doxorubicin (adriamycin) by slow infusion through a central-venous line should be considered whenever feasible. Monitoring of cardiac ejection fraction and the use of endomyocardial biopsy will permit patients to be treated safely after they reach the dose threshold at which heart failure begins to be a potential risk. A number of structurally modified anthracyclines with the potential advantages of decreased cardiotoxicity and avoidance of multidrug resistance mechanisms are entering clinical trials. Meanwhile, the vast weight of clinical experience leaves doxorubicin as a well tolerated and effective choice for most potentially anthracycline-sensitive tumours.
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PMID:Anthracycline antibiotics in cancer therapy. Focus on drug resistance. 751 99

Doxorubicin, ellipticine and etoposide are antineoplastic drugs with topoisomerase II inhibitory activity. The relationship between drug-induced sister-chromatid exchanges (SCEs) or chromosomal aberrations (CAs) and cytotoxicity, or drug-induced DNA double-strand breaks (DSBs) and cytotoxicity, or drug-induced SCEs and DSBs was investigated in human ovarian cancer cells sensitive (A2780) and resistant (A2780-DX3) to topoisomerase II inhibitors. 30-min drug treatments produced SCEs, CAs and DSBs in sensitive cells, doxorubicin being more potent than etoposide at equimolar concentrations. The same treatments of resistant (A2780-DX3) cells did not produce chromosomal damage (SCEs, CAs, DSBs) and no cytotoxicity was observed. A plot of cytotoxicity versus SCEs indicated a good correlation between these two parameters for topoisomerase II inhibitors and not for mytomicin C. The plot of DSBs versus SCEs also showed a very good correlation.
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PMID:Sister-chromatid exchanges, chromosomal aberrations and cytotoxicity produced by topoisomerase II-targeted drugs in sensitive (A2780) and resistant (A2780-DX3) human ovarian cancer cells: correlations with the formation of DNA double-strand breaks. 752 71


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