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)

Patients with the autosomal recessive disorder Fanconi anemia (FA) present with progressive pancytopenia, skeletal abnormalities and a predisposition to leukemia. In addition to elevated rates of spontaneous chromosome aberrations occurring in cultured fibroblasts and lymphoblastoid cell lines, an increased susceptibility to DNA cross-linking agents and oxygen has been found. To explain this hypersensitivity to clastogenic agents a defective function of DNA topoisomerase I or II could be invoked, a suggestion which is supported by the co-localization of the DNA topoisomerase I gene and a putative FA gene to chromosome 20q. In order to investigate the function of DNA topoisomerases in FA, the sensitivity of lymphoid B-cell lines derived from FA patients and control cell lines to inhibitors of DNA topoisomerases I and II was compared using continuous bromodeoxyuridine labeling and bivariate Hoechst/ethidium bromide flow cytometry. Both agents inhibited cell proliferation mainly by arresting cells in the G2 phase of the cell cycle. However, no difference was found in sensitivity towards both DNA topoisomerase inhibitors between control and FA cell lines.
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PMID:Cell cycle effects of the DNA topoisomerase inhibitors camptothecin and m-AMSA in lymphoblastoid cell lines from patients with Fanconi anemia. 138 35

DNA topoisomerases modify supercoiled DNA through concerted breaking and rejoining of the DNA strands and consequently play a key role in DNA biosynthesis and processing. It has been suggested that topoisomerases may facilitate access to damaged sites of excision repair enzymes due to their property to relax supercoiled DNA. We show here that treatment with nalidixic acid and novobiocin, which affects topoisomerase II activity among other targets, impairs the incision of 8-methoxypsoralen photoinduced DNA interstrand cross-links in normal human fibroblasts. Since cells derived from Fanconi anemia (FA) demonstrate hypersensitivity to DNA cross-linking agents associated with a reduced repair efficiency of cross-links, we compared the effects of different topoisomerase I and II inhibitors on FA and normal lymphoblasts. No differences were found in growth inhibition or induction of chromosome aberrations between FA and normal cells. The specificity of inhibitors is questionable and even if topoisomerases are indeed inhibited alternative pathways may be involved. However, our observations provisionally suggested that topoisomerases activities are normal in FA cells.
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PMID:Comparison of the effects of DNA topoisomerase inhibitors on lymphoblasts from normal and Fanconi anemia donors. 752 5

A case of therapy-related acute non-lymphocytic leukemia (t-ANLL) in a 70-year-old female patient is reported. An operation for lung cancer was performed in February 1991, and she was treated with etoposide (VP-16), a topoisomerase II inhibitor. Nineteen months after the start of chemotherapy, she complained of palpitations, and anemia and thrombocytopenia developed. The myelogram revealed 41.2% leukemic cells, and a diagnosis of t-ANLL induced by VP-16 was made. The karyotype of bone marrow cells showed 46, XX, t(7;11) (p13;p15), 16p+. She obtained complete remission (CR) by treatment with low dose cytosine arabinoside (Ara-C) and cytarabine ocfosfate (SPAC). Karyotype with t-ANLL induced by alkylate agents frequently shows unbalanced abnormalities. The difference of cytogenetic findings suggest the difference of mechanisms. Detailed chromosomal analysis make clear the oncogenesis of t-ANLL. It is reported that the prognosis of patients with t-ANLL treated by conventional chemotherapy is poor. Considering that elderly cases of acute leukemia have a lower probability of achieving CR than non-elderly cases, because of complications and side effects of chemotherapy such as bone marrow suppression, treatment with low dose Ara-C and SPAC is thought to be indicated in elderly patients with t-ANLL.
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PMID:[Therapy-related acute non-lymphocytic leukemia (M2) with 7;11 chromosome translocation induced into complete remission by low dose cytosine arabinoside and cytarabine ocfosfate therapy]. 807 12

Etoposide produces reversible inhibition of topoisomerase II, leading to cleavage of DNA, and thereby has an antitumor effect. This mechanism suggests that the longer treatment is continued, the greater the antitumor effect will be. In the present study, both therapeutic and adverse effects of long-term treatment with low-dose oral etoposide were studied in 29 patients aged > or = 65 years with non-Hodgkin's lymphoma (NHL) for whom standard chemotherapy was not effective or refractory. These patients received etoposide at a dose of 50 mg/d for as long as possible. Treatment was continued until white blood cell count decreased to < or = 2,000/microL or the platelet count decreased to < or = 5 x 10(4)/microL. According to the World Health Organization (WHO) criteria of therapeutic effects, 6 (20.7%) of the 29 patients achieved complete remission and 13 patients (44.8%) had partial remission, for a response rate of 65.5%. Adverse effects of > or = grade 3 included leukopenia in 24 patients (82.8%) and anemia in 7 (24.1%). Granulocyte colony-stimulating factor (G-CSF) was given in combination with etoposide to eight patients because of leukopenia (granulocyte count < or = 1,000/microL). In view of the excellent subjective tolerance, low incidence of serious adverse effects, and good activity, single agent oral etoposide given continuously over prolonged periods represents a useful treatment for elderly patients with NHL.
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PMID:Evaluation of long-term daily administration of oral low-dose etoposide in elderly patients with relapsing or refractory non-Hodgkin's lymphoma. 916 61

We describe a boy with Fanconi anemia (FA) who developed acute lymphoblastic leukemia (ALL) (FAB-LI) followed by acute myeloid leukemia (AML) (FAB-M5) at relapse. The patient was diagnosed with early pre-B-cell ALL without preceding aplastic anemia and was treated with ALL-oriented chemotherapy which included doxorubicin (a total dose of 140 mg/m(2) administered), which is a topoisomerase II inhibitor. Complete remission was obtained, but after 38 weeks AML developed. The karyotype of ALL cells at diagnosis showed 46,XY, and that of AML cells at relapse was 46,XY, t(11;16)(q23;p13). An MLL gene rearrangement and MLL-CBP chimeric mRNA were found in AML, but not in ALL. A diagnosis of FA was confirmed by an increased number of chromosomal breaks and rearrangements in peripheral blood lymphocytes cultured with mitogen in the presence of mitomycin C. We conclude that this FA patient developed ALL followed by a therapy-related t(11;16)-AML resulting in an MLL-CBP fusion. Further examination of such patients would shed light on leukemogenesis in FA patients. Genes Chromosomes Cancer 27:264-269, 2000.
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PMID:MLL-CBP fusion transcript in a therapy-related acute myeloid leukemia with the t(11;16)(q23;p13) which developed in an acute lymphoblastic leukemia patient with Fanconi anemia. 1067 15

The binding of camptothecin (CPT) to the DNA-topoisomerase complex is reversible, but it needs to be maintained for maximal inhibitory activity. It is also dependent on the chemical structure of CPT. The lactone form is thought to be necessary for the activity. In human serum, the equilibrium between lactone and carboxylate is in favor of the latter. For these reasons, alternative administration of CPT analogues is being evaluated. The ideal compound would remain in lactone form and would expose the host for long periods of time to its effects. Oral administration of irinotecan (CPT-11) and topotecan (TPT) is discussed by other investigators. We studied oral rubitecan and reported a low lactone to total drug area under the plasma concentration-time curve (AUCP) ratio (14.7%), with low plasma concentration over time despite repeated administrations and the presence of an enterohepatic cycle. Aerosolization of a liposomal formulation of rubitecan is currently under study. Six patients have been treated once a day for 5 days every 3 weeks. The dose was 6.7 micrograms/kg/day. Plasma levels are dose for dose higher than those after oral administration, but the ratio of lactone versus total drug is low. No toxicity was observed. The study will continue with increasing doses and lengths of administration. Intrathecal administration of topotecan has been studied in a phase I trial in children. Doses of 0.4 mg are tolerated without toxicity, and clinical responses have been seen in patients with refractory meningial carcinomatosis. Phase II studies are planned. Intraperitoneal (i.p.) administration of topotecan has been studied in a phase I trial as a 24-hour infusion in 5% dextrose at pH 3.5 every 21 days. Dose-limiting toxicity is 4 mg/m2. Toxic effects are neutropenia, anemia, emesis, fever, and pain. Five of 10 patients with ascites had symptomatic relief. Pharmacokinetic analysis demonstrates a second-order kinetics with elimination half-lives of 0.49 and 2.7 hours. The peritoneal to plasma AUC ratio was 31.2. Intramuscular, transdermal, and subcutaneous administrations have been extensively studied in the mouse.
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PMID:Alternative administration of camptothecin analogues. 1119 99

Recurrent or metastatic squamous carcinoma of the head and neck (RMSCHN) is a modestly chemoresponsive tumor; however, currently available agents have failed to improve survival. New active agents are needed for the treatment of this disease. Topotecan is a topoisomerase inhibitor that demonstrated initial promising activity in squamous carcinoma of the head and neck. The Eastern Cooperative Oncology Group conducted a phase II trial of topotecan to determine the efficacy and toxicity of a weekly treatment schedule in patients with RMSCHN. Patients with metastatic or locally recurrent squamous carcinoma of the head and neck were treated with topotecan 1.5 mg/m2 x 24 hours by continuous infusion on days 1, 8, 15, and 22 of each 35-day cycle. Patients were stratified in two cohorts: chemonaive and previously treated. Sixteen chemonaive and 16 previously treated patients were registered on study. Grade III/IV neutropenia and anemia occurred in 16% and 18% of patients, respectively. No responses were observed in either cohort. Median survival for previously untreated patients was 4.6 months and 3.2 months for previously treated patients. Topotecan failed to demonstrate efficacy in patients with RMSCHN. Further evaluation of this agent is not planned.
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PMID:Lack of efficacy of topotecan in the treatment of metastatic or recurrent squamous carcinoma of the head and neck: an Eastern Cooperative Oncology Group Trial (E3393). 1123 52

Acute myeloid leukaemia (AML) is characterized by a block in differentiation and an unregulated proliferation of myeloid progenitor cells. While the cause of AML in children is unknown, risk factors that have been identified include exposure to toxins such as ethanol, pesticides and dietary topoisomerase II inhibitors, prior chemotherapy with alkylating agents or topoisomerase II inhibitors, constitutional disorders such as Down's syndrome and type I neurofibromatosis, and haematopoietic failure syndromes such as Fanconi anaemia and severe congenital neutropenia. With intensified chemotherapy including high-dose Ara-C, followed in many cases by bone marrow transplantation, and with improvements in supportive care, current survival rates approach 50%. Future advances in paediatric AML will include better risk stratification to determine optimal treatment and targeted cytotoxic therapy.
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PMID:Acute myeloid leukaemia in children. 1135 25

Hepatitis C virus (HCV) infection has been found to be strikingly associated with autoimmune phenomena. The aim of the present study was to investigate the presence of various autoantibodies in patients with HCV infection. Anti-neutrophil cytoplamic antibody (ANCA), anti-dihydrolipoamide dehydrogenase (anti-E3), rheumatoid factor (RF), anti-dihydrolipoamide acetyltransferase (anti-E2), anti-SS-A/Ro (60 kD), anti-SS-A/Ro (52 kD), anti-SS-B/La, anti-topoisomerase II (anti-topo II), anti-cardiolipin (aCL), anti-dsDNA, anti-ssDNA, anti-nuclear antibodies (ANA), anti-proteinase 3 (anti-Pr3) and anti-myeloperoxidase (anti-MPO) were determined in sera from 516 patients with HCV infection, 11 with primary biliary cirrhosis (PBC) and 44 healthy controls. Assays employed were indirect immunofluoresence, the particle latex agglutination test, enzyme-linked immunosorbent assay (ELISA) and immunoblotting. ANCA, anti-E3 antibody and RF were positive in 278/516 (55.6%), 276/516 (53.3%) and 288/516 (56%) patients with HCV infection, respectively. Positivity for ANA was present in 15.8%, anti-ssDNA in 15.6%, anti-dsDNA in 8.5%, aCL in 5%, anti-SS-B/La in 4.1%, anti-SS-A/Ro (60 kD) in 3.9%, anti-E2 in 3.3% and anti-SSA/Ro (52 kD) in 1.2%, anti-MPO in 4.8%, anti-Topo II and anti-actinin in 0%. All sera with ANCA showed c-ANCA patterns and contained anti-PR3 specificity. HCV patients with ANCA showed a higher prevalence of skin involvement, anaemia, abnormal liver function and alpha-Fetoprotein (alpha-FP). HCV patients with anti-E3 antibodies showed a higher prevalence of liver cirrhosis, arthritis, abnormal liver function and elevated alpha-FP levels. The prevalence of autoantibodies was not affected by treatment with interferon-alpha (IFN-alpha). In conclusion, autoantibodies are commonly found in patients with HCV infection. There is a high prevalence of anti-E3, ANCA and RF in these patients. Proteinase 3 and E3 are the major target antigens in HCV infection. HCV may be regarded as a possible causative factor in ANCA-related vasculitis.
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PMID:Proteinase 3 and dihydrolipoamide dehydrogenase (E3) are major autoantigens in hepatitis C virus (HCV) infection. 1198 26

Preliminary results indicate that inhibitors of the nuclear enzyme topoisomerase (topo) I, such as topotecan, may be active in non-Hodgkin's lymphoma (NHL). Pre-clinical studies have shown sequential administration of a topo I and II inhibitor has supra-additive anti-tumor effects in some model systems, and that greater cytotoxicity occurs if the topo I inhibitor is given first. We enrolled, 22 eligible patients with relapsed or refractory intermediate grade NHL in a phase II study ofsequential administration of topotecan 1.25 mg/m2 days 1-5 and etoposide 50 mg po b.i.d. days 6-12, every 28 days without G-CSF. Most patients had diffuse large B-cell lymphoma and all had received only one prior regimen (CHOP, 20 patients, or equivalent, 2 patients). Patients with stable or responding disease were allowed to proceed to high-dose therapy and autologous stem-cell transplant after 2 cycles of therapy. The 22 patients received a total of 62 cycles of topotecan + etoposide (median 2, range 1-6), and 4/22 completed all six planned cycles. Hematologic toxicity was significant and resulted in incomplete etoposide dosing in half of all cycles in 16/22 patients. Nineteen of twenty-two patients had grade 3/4 neutropenia, 12 had grade 3/4 thrombocytopenia, and 6 grade 3/4 anemia. Eleven patients had at least one episode of febrile neutropenia or had documented infection. Non-hematologic toxicity was mild. Four patients had a partial response (PR) (18.2%), nine had stable disease and seven progressed; three patients with stable disease went on to ABMT. The combination of topotecan and etoposide as given in this study has modest activity in relapsed/refractory aggressive histology NHL, and produces marked myelosuppression. Other doses and schedules combining topo I and II inhibitors, or topo I inhibitors with alkylating agents, should be explored with the addition of hematopoietic growth factors in this patient population.
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PMID:Phase II study of sequential topotecan and etoposide in patients with intermediate grade non-Hodgkin's lymphoma: a National Cancer Institute of Canada Clinical Trials Group study. 1240 Jun


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