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)

Acute promyelocytic leukemia (APL) is characterized by a specific chromosome translocation t(15;17). Recently, using molecular biology techniques, a number of laboratories have demonstrated that the gene coding for the retinoic acid receptor alpha (RARA), normally located on chromosome 17, is disrupted by the t(15;17) and fused with the PML gene on chromosome 15. The chromosome 17 breaks were mapped consistently within the second intron of the RARA gene while the chromosome 15 breaks were clustered in two limited regions within the PML gene. Molecular cloning and sequence analysis of the PML gene demonstrated a complex splicing pattern and this gene may encode a transcription factor. Different isoforms of the PML-RARA fusion transcripts were discovered which are produced as a result of distinct PML gene rearrangements. Sequence analysis of the reciprocal products of the translocation t(15;17) in some APL cases suggested the implication of topoisomerase II in mediating the DNA recombination. The RT/PCR procedure has been established to characterize the expression patterns of the PML-RARA fusion gene and to detect minimal residual disease (MRD). The biological activity of the PML-RARA fusion gene and its isoforms should be further explored.
Leuk Lymphoma 1992 Nov
PMID:RARA and PML genes in acute promyelocytic leukemia. 133 47

The epipodophyllotoxins, etoposide and teniposide, have been used in leukemias and malignant lymphomas for the past 15 years. Although etoposide has acquired a place in many first-line protocols for lymphomas and, more recently, for leukemias, the role of teniposide has remained limited. Teniposide is a more potent inhibitor of topoisomerase II than etoposide, and has a less toxic effect on hematopoietic progenitor cells. Both drugs have been regarded as equitoxic and cross-resistant. The role of teniposide in front-line treatment of leukemias has only been established in childhood acute lymphoblastic leukemia (ALL). Some promising results have been obtained in small numbers of patients with refractory adult ALL and acute monoblastic leukemia. However, the remission rates and remission duration were not significantly different from those of other combination regimens. Data on teniposide in untreated acute nonlymphoblastic leukemia are very scarce. In non-Hodgkin's lymphoma, the antineoplastic activity of teniposide has been demonstrated in studies by the European Organization for Research and Treatment of Cancer and in two large studies conducted by the Australian and New Zealand Lymphoma Co-operative Chemotherapy Study Group. In these studies, teniposide had comparable but not significantly better activity than vincristine. The dose-dependent antineoplastic activity of teniposide has led to its use in several conditioning regimens in bone marrow transplantation for leukemias and lymphomas. The limited clinical data currently available on teniposide seem to warrant further clinical trials with this agent in leukemias and lymphomas.
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PMID:Teniposide in lymphomas and leukemias. 141 40

The t(4;11)(q21;q23) has been associated with marked lineage heterogeneity. Most of the reported cases were classified as acute lymphoblastic leukemia (ALL). The t(4;11) is one of the commonest specific chromosomal translocations in ALL, occurring in 2% of childhood and 5% of adult cases. In childhood ALL, this translocation is associated with female sex, age less than 1 year, hyperleukocytosis, CD10-/CD19+ B-precursor cell immunophenotype, and myeloid-associated antigen (CD15) expression. There also appears to be an age-related difference in treatment outcome. Adults had the worst prognosis, and children aged 1 to 9 years appeared to have a better outcome than infants or adolescents. Reported cases of acute myeloid leukemia (AML) or secondary leukemia with the t(4;11) have not been well characterized. It is intriguing that virtually all of the reported cases with secondary leukemia had received epipodophyllotoxins or doxorubicin, agents that affect topoisomerase II and are associated with secondary AML characterized by 11q23 abnormalities. Identification of the involved gene(s) in the t(4;11) will provide a molecular approach permitting more accurate classification of these cases.
Leuk Lymphoma 1992 Jun
PMID:Acute leukemias with the t(4;11)(q21;q23). 147 45

Hydroxyurea is an antineoplastic drug with a broad spectrum of clinical activity and minimal nonhematopoietic toxicity. It potentiates the cytotoxicity of alkylating agents and topoisomerase II active drugs in vitro and in vivo. It is not susceptible to alkylating agent-specific or multidrug-type resistance. We have therefore added high-dose oral hydroxyurea to widely used autologous bone marrow transplantation combination chemotherapy regimens for large cell lymphoma and metastatic breast cancer. Seventeen patients with primary-refractory or refractory-relapse large cell lymphoma received oral hydroxyurea (1.5 g/m2 every 6 hours for 12 doses) added to carmustine/cyclophosphamide/etoposide (BCV). Twelve patients with metastatic breast cancer received the same dose oral hydroxyurea added to cyclophosphamide and thiotepa. Mucositis severe enough to require parenteral narcotics was seen in over half of the patients, but none required intubation for airway maintenance. A thrombotic thrombocytopenic purpura-like hemorrhagic syndrome occurred in six patients and was fatal for three. With the BCV/hydroxyurea regimen, this syndrome was seen with the same frequency as with BCV alone. Death from rapidly progressive disease or toxicity occurred in seven of 29 patients (24%). For patients with 6 months' minimum follow-up, four of 12 (33%) of the metastatic breast cancer patients remain in complete response (median follow-up, 15 months), and four of 17 (24%) refractory large cell lymphoma patients remain in complete response (median follow-up, 10 months). High-dose hydroxyurea may increase the effectiveness of standard autologous bone marrow transplantation regimens without substantially increasing toxicity.
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PMID:High-dose hydroxyurea in autologous bone marrow transplantation: a promising "new" agent. 164 52

Hydroxyurea is a potent inhibitor of the enzyme ribonucleotide reductase. Due to its effects on cellular deoxyribonucleotide pools, hydroxyurea can modulate the activity of several pyrimidine and purine antimetabolites. As an inhibitor of DNA repair, it can potentially interact with DNA-damaging agents such as alkylating agents or inhibitors of topoisomerase II. Both cytokinetic and biochemical interactions occur between hydroxyurea and cytarabine (ara-C), which account for their synergistic cytotoxicity. Inhibition of ribonucleotide reductase by hydroxyurea depletes cellular deoxycytidine triphosphate pools, thereby enhancing ara-C uptake and phosphorylation to ara-C triphosphate. In a phase II clinical trial, the combination of hydroxyurea and ara-C produced a 43% response rate in patients with refractory malignant lymphoma. Studies in murine leukemia models have demonstrated therapeutic synergy when hydroxyurea is combined with fluoropyrimidines. High levels of deoxyuridine monophosphate that have been associated with resistance to 5-fluorouracil can be suppressed by hydroxyurea, leading to greater inhibition of thymidylate synthase. Despite the strong biochemical rationale for the use of hydroxyurea and 5-fluorouracil in combination, few clinical trials have been conducted thus far. Antimetabolites and topoisomerase II inhibitors have also been shown to be synergistic in vitro. Hydroxyurea has been shown to enhance the formation of DNA strand breaks produced by amsacrine and to produce synergistic cytotoxicity with etoposide. A phase I clinical trial of these drugs has demonstrated bone marrow suppression to be the major toxicity of the combination. In summary, hydroxyurea has been shown to undergo cytokinetic and biochemical interactions with a number of established antitumor agents. Clinical trials of hydroxyurea in combination with these agents have identified doses and schedules of administration that produce acceptable levels of clinical toxicity and appear feasible for further testing.
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PMID:Laboratory and clinical studies of biochemical modulation by hydroxyurea. 164 59

This study was designed to investigate the biologic and molecular basis of the aggressive behavior of high-grade post-thymic T-cell malignancies. Freshly frozen tumor tissues from (1) human T-cell leukemia/lymphoma virus type I (HTLV-I)-positive adult T-cell lymphoma (ATL) (7 cases), (2) HTLV-I-negative aggressive T-cell lymphoma (12 cases), and (3) HTLV-I-negative nonaggressive T-cell lymphoma (11 cases) were studied for the expression of several growth-related genes or proliferation antigens including interleukin-2 receptor (IL-2R), Ki-67, transforming growth factor-beta (TGF-beta), topoisomerase, and the multidrug resistance (MDR) gene by immunohistochemistry and Northern blot hybridization. Our results showed that tumor cells associated with HTLV-I and anaplastic morphology had an enhanced expression of Ki-67, TGF-beta, and topoisomerase, as compared to nonaggressive T-cell lymphoma. The expression of IL-2R was limited to ATL and one Ki-1 lymphoma. The MDR gene was frequently expressed in ATL, but only infrequently in other, HTLV-I-negative, malignancies. Clinical progression or relapse was associated with the expression of MDR, in addition to an increased expression of Ki-67. We therefore conclude that the aggressive clinical behavior of high-grade T-cell lymphoma may result mainly from the high proliferative activity of tumor cells, but the association with HTLV-I and clinical relapse is further complicated by the development of drug resistance.
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PMID:Expression of growth-related genes and drug-resistance genes in HTLV-I-positive and HTLV-I-negative post-thymic T-cell malignancies. 167 81

Etoposide, a derivative of epipodophyllotoxin, is one of the most important new drugs that was introduced into the management of the malignant lymphomas during the past decade. A growing number of specific protocols include this useful agent in the management of malignant lymphoma, both at the time of primary treatment and at relapse. The broad activity of etoposide across several histologic subtypes of malignant lymphoma and Hodgkin's disease indicates a potential that is only now being fully exploited. Used according to optimal doses and schedules, etoposide has single-agent activity that rivals earlier drugs such as the alkylating agents and doxorubicin. Functioning as a protein synthesis and topoisomerase II inhibitor, it offers the potential for non-cross-resistant cytotoxicity. After a brief comment on the single-agent activity of etoposide, this report will focus on the integration of etoposide into multiagent protocols used in the primary treatment of malignant lymphoma and Hodgkin's disease. The specific findings from protocols such as prednisone, methotrexate, doxorubicin, cyclophosphamide, etoposide-cytarabine, bleomycin, vincristine, and methotrexate (Pro-MACE-CytaBOM) (US National Cancer Institute [NCI]) and etoposide, doxorubicin, cyclophosphamide, vincristine, prednisone, and bleomycin (VACOP-B) (Vancouver) for the primary treatment of malignant lymphoma, and vinblastine, etoposide, cyclophosphamide, doxorubicin, bleomycin, vincristine, and prednisone (VECABOP) (Vancouver) for the treatment of previously untreated patients with advanced Hodgkin's disease will be discussed.
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PMID:The evolving role of etoposide in the management of lymphomas and Hodgkin's disease. 198 27

Mitoxantrone, an anthracenedione derivative, has been used for preclinical and clinical studies from the end of the 1970s. Several working mechanisms are suggested such as intercalation and electrostatic interactions with DNA with or without involvement of topoisomerase II, immunosuppressive effects and inhibition of prostacyclin synthesis. Efficacy of mitoxantrone alone or in combination with other chemotherapeutic drugs has been especially demonstrated in patients with breast cancer, leukemia and lymphoma. Locoregional (but not intrathecal) therapy with this drug is possible because it is not a vesicant. It has an improved tolerability profile compared with doxorubicin. Dose-limiting toxicity is myelotoxicity and mucositis. Therefore this drug has recently also been used in high doses with bone marrow support and in combination with hematopoietic growth factors. Cardiotoxicity is less frequent than after doxorubicin and daunorubicin. However, cardiac function tests are warranted after cumulative doses greater than 160 mg/m2 or earlier if additional risk factors, namely previous mediastinal irradiation, anthracycline therapy or cardiovascular disease, are present.
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PMID:Mitoxantrone: bluebeard for malignancies. 215 49

The present study was designed to determine and compare the clastogenicity of m-AMSA and camptothecin (CAMP) in vivo in mouse bone marrow and peripheral blood lymphocytes (PBLs), and in vitro in mouse lymphoma L5178Y cells. m-AMSA interferes with topoisomerase II to induce double-strand DNA breaks. CAMP interferes with topoisomerase I to induce single-strand DNA breaks. Thus, we expected the two drugs to induce different types of chromosomal aberrations (CAs). However, both drugs produced quantitatively and qualitatively similar numbers and types of aberrations under similar experimental conditions. In mouse bone marrow exposed over and 18-h period, both drugs (3 mg/kg) induced approximately 30 damaged cells, with an average of 0.4 chromatid breaks per cell (in 100 cells analyzed/mouse). In addition, both drugs induced only chromatid-type aberrations in mouse bone marrow in vivo when exposure occurred during G2. Cell cycle specificity was indicated by the absence of CAs when exposure to the drugs occurred in vivo in mouse PBLs during G0. In L5178Y cells, m-AMSA was considerably more potent for the induction of mutations and somewhat more potent for the induction of CAs than CAMP was. In contrast to the in vivo bone marrow results, the drugs induced high levels of both chromatid- and chromosome-type aberrations in vitro. The ultimate types of chromosomal damage induced by m-AMSA and CAMP result from a complex interaction of (i) cell cycle specific variations in topoisomerase enzyme levels, (ii) the abilities of these drugs to interfere with the orderly DNA breakage/reunion associated with topoisomerase activity, and (iii) the processing of the damage resulting from these interactions.
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PMID:Genotoxicity of inhibitors of DNA topoisomerases I (camptothecin) and II (m-AMSA) in vivo and in vitro. 217 33

Mitoxantrone, a cytotoxic anthracenedione derivative, has given clinical evidence of beneficial activity in breast cancer, lymphoma and leukaemia. Several different mechanisms of action have been suggested to account for this. In addition to intercalation, biological effects such as electrostatic interactions with DNA, DNA-protein cross-links, immunosuppressive activities, inhibition of topoisomerase II, prostaglandin biosynthesis and calcium release have been described. Various methods of drug monitoring in biological fluids and tissues are available: the highest sensitivity has been achieved with high performance liquid chromatography with electrochemical detection, radioimmunoassay and enzyme linked immunosorbent assay. Early pharmacokinetic studies of mitoxantrone in experimental animals using radioactive material showed an extensive tissue distribution and a long terminal plasma half-life. The best fit for the plasma concentration-time curve in humans is achieved in a 3-compartment model. All studies reported a short absorption half-life of between 4.1 and 10.7 minutes, with the distribution phase being between 0.3 and 3.1 hours. In contrast, the values of the terminal half-life are quite variable, ranging from 8.9 hours to 9 days. Differences might be attributed to assay sensitivity, number and weighting of data points beyond 24 hours and coadministration drugs. Many studies showed a very large volume of distribution with sequestration of mitoxantrone in a deep tissue compartment. In autopsy studies, relatively high tissue concentrations have been measured in liver, bone marrow, heart, lung, spleen and kidney. Bile is the major route for the elimination of mitoxantrone, with lesser amounts excreted in the urine. Several metabolites have been separated, 2 of which were identified as the monocarboxylic and dicarboxylic acid derivatives. Mitoxantrone is usually administered by rapid intravenous infusion at 3-weekly intervals; other regimens include continuous infusion, daily repeated doses or weekly administration. In peritoneal carcinosis, the pharmacological advantage of intraperitoneal administration is clear. The optimal regimen for different disease categories with respect to efficacy and side-effects remains to be determined in future clinical trials.
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PMID:Pharmacokinetics and metabolism of mitoxantrone. A review. 218 7


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