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)

We have studied some of the factors involved in the cytotoxic actions of the anticancer anthracycline antibiotics doxorubicin (DOX) and idarubicin (IDA) towards human B-cell lymphoma cells in vitro. IDA was found to accumulate within cells to a greater degree than the related drug DOX for both short (1 h) and long-term (24 h) exposures. Both agents showed a similar capacity for trapping topoisomerase II in intact cells, but cross-linking activity was significantly lower than that induced by the specific poison VP16. IDA was four- to eight fold more potent for the induction of cytostasis and cell cycle arrest and for the instigation of DNA breakdown as a prelude to the full expression of apoptosis. Inhibition of DNA fragmentation at higher drug doses was linked closely with the inhibition of S-phase traverse. The findings suggest that DOX and IDA act in a similar fashion, the latter agent being more effective due to enhanced intracellular accumulation. We conclude that the presence of drug and topoisomerase II-associated DNA damage is not sufficient to induce DNA fragmentation; rather, unregulated commitment to S-phase traverse is an important factor in the activation of programmed cell death.
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PMID:DNA fragmentation as a consequence of cell cycle traverse in doxorubicin- and idarubicin-treated human lymphoma cells. 806 Nov 10

Irinotecan hydrochloride (CPT-11), a DNA topoisomerase-I inhibitor, is now widely used in the treatment of various solid tumors, including colorectal, gastric, breast, lung, and ovarian cancer. Despite the good response shown in the late phase-II study, CPT-11 was not often employed in the treatment of malignant lymphoma, mainly because of severe leukopenia and diarrhea caused by the recommended schedule: 40 mg/m2 of CPT-11 on days 1 to 3, 8 to 10, 15 to 17, then discontinued for at least 2 weeks. In clinical use, administration of CPT-11 had to be ceased on days 15 to 17 in almost all cases, and on days 8 to 10 in a considerable number of patients. Subsequently, a lower dose schedule (less than 40 mg/m2) was developed. Our phase II trial employing a reduced dose of CPT-11 on days 1 and 2, plus ADM on day 3 with 3-week interval in patients with refractory and relapsed NHL showed a fairly good response of relapsed B-cell lymphoma and a substantial response of T-cell lymphoma with acceptable toxicity. The combination of a topoisomerase-I inhibitor (CPT-11) and a topoisomerase-II inhibitor is an interesting concept for the treatment of NHL. Another phase II trial in combination with CPT-11 and other anti-cancer drugs, particularly cisplatin or topoisomerase-II inhibitors, is warranted. A superior salvage chemotherapy regimen could be found in the future by investigating combinations of low-dose CPT-11 and cisplatin or topoisomerase-II inhibitors.
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PMID:Chemotherapy with irinotecan (CPT-11), a topoisomerase-I inhibitor, for refractory and relapsed non-Hodgkin's lymphoma. 1169 85

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

p38 MAPK is mainly activated by stress stimuli and mediates signals that regulate various cellular responses, including cell-cycle progression and apoptosis, depending on cell types and stimuli. Here we examine the role of p38 in regulation of apoptosis and cell cycle checkpoint in Daudi B-cell lymphoma cells treated with the topoisomerase II inhibitor etoposide. Etoposide activated p38, inhibited the G2/M transition with the persistent inhibitory phosphorylation of Cdc2 on Tyr15, and caused apoptosis of Daudi cells. Inducible expression of a dominant negative p38alpha mutant in Daudi cells reduced the inhibition of Cdc2 as well as G2/M arrest and augmented apoptosis induced by etoposide. SB203580, a specific inhibitor of p38alpha and p38beta, similarly reduced the inhibitory phosphorylation of Cdc2 as well as G2/M arrest and augmented apoptosis of Daudi cells treated with etoposide. These results suggest that p38 plays a role in G2/M checkpoint activation through induction of the persistent inhibitory phosphorylation of Cdc2 and, thereby, inhibits apoptosis of Daudi cells treated with etoposide. The present study, thus, raises the possibility that p38 may represent a new target for sensitization of lymphoma cells to DNA-damaging chemotherapeutic agents.
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PMID:p38 MAP kinase plays a role in G2 checkpoint activation and inhibits apoptosis of human B cell lymphoma cells treated with etoposide. 1615 44

The outcome of classical Hodgkin lymphoma (cHL) patients may be related to the tumor microenvironment, which in turn may be influenced by Epstein-Barr virus (EBV) infection. To characterize the cHL microenvironment, a set of 63 cHL tissue samples was profiled using DNA microarrays. Their gene expression profile differed from that of histiocyte T cell-rich B-cell lymphoma (H/TCRBCL) samples that were used as controls, mainly due to high expression of PDCD1/PD-1 in H/TCRBCL. EBV(+) cHL tissues could be distinguished from EBV(-) samples by a gene signature characteristic of Th1 and antiviral responses. Samples from cHL patients with favorable outcome overexpressed genes specific for B cells and genes involved in apoptotic pathways. An independent set of 146 cHL samples was analyzed using immunohistochemistry. It showed a significant adverse value in case of high percentage of either TIA-1(+)-reactive cells or topoisomerase-2(+) tumor cells, whereas high numbers of BCL11A(+), FOXP3(+), or CD20(+) reactive cells had a favorable influence. Our results suggest an antitumoral role for B cells in the cHL microenvironment and a stronger stromal influence of the PD1 pathway in H/TCRBCL than cHL. The observation of Th1/ antiviral response in EBV(+) cHL tissues provides a basis for novel treatment strategies.
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PMID:Molecular profiling of classical Hodgkin lymphoma tissues uncovers variations in the tumor microenvironment and correlations with EBV infection and outcome. 1909 12

DT40 is a B-cell lymphoma-derived avian cell line widely used to study cell autonomous gene function because of the high rates with which DNA constructs are homologously recombined into its genome. Here, we demonstrate that the power of the DT40 system can be extended yet further through the use of RNA interference as an alternative to gene targeting. We have generated and characterized stable DT40 transfectants in which both topo 2 genes have been in situ tagged using gene targeting, and from which the mRNA of both topoisomerase 2 isoforms can be conditionally depleted through the tetracycline-induced expression of short hairpin RNAs. The cell cycle phenotype of topo 2-depleted DT40 cells has been compared with that previously reported for other vertebrate cells depleted either of topo 2alpha through gene targeting, or depleted of both isoforms simultaneously by transient RNAi. In addition, the DT40 knockdown system has been used to explore whether excess catenation arising through topo 2 depletion is sufficient to trigger the G2 catenation (or decatenation) checkpoint, proposed to exist in differentiated vertebrate cells.
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PMID:Studying vertebrate topoisomerase 2 function using a conditional knockdown system in DT40 cells. 1949 82

In the highly active antiretroviral therapy era, an increasingly large number of HIV-infected patients are developing non- AIDS-defining cancers (NADCs). As patients survive longer, long-term therapy-related complications take on greater importance. Herein, we describe a patient with AIDS who presented to medical attention with pancytopenia 48 months postchemotherapy with etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab (R-EPOCH) for diffuse large B-cell lymphoma. Bone marrow biopsy showed a moderately hypocellular marrow; 51% of the nucleated cells were blasts with myelomonocytic differentiation. Cytogenetic studies revealed an abnormal karyotype with deletion of the long arm of chromosome 11 (11q21) and 2 additional copies of the MLL gene attached to the short arms of chromosome 10 in 80% of the metaphase cells examined. With the diagnosis of therapy-related acute myeloid leukemia (AML) secured, he began induction chemotherapy with idarubicin and cytarabine. Two weeks later, he died of fungal septicemia and multiorgan failure. Through a literature search, we were able to identify 4 additional cases of therapy-related AML in AIDS patients following chemotherapy for lymphomas. The median age of these patients at the time of AML diagnosis was 39 years (range, 33-59 years), the median time from the treatment of lymphoma to AML was 18 months (range, 11-48 months), and the median survival following induction chemotherapy was 4 weeks (range, 2-16 weeks). With many HIV-infected patients surviving alkylator and topoisomerase inhibitor-based treatment and radiation therapy for AIDS-defining cancers and NADCs, long-term follow-up for therapy-related complications assumes greater importance.
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PMID:Therapy-related acute myeloid leukemia following HIV-associated lymphoma. 1971 83

Many human cancers are associated with characteristic chromosomal rearrangements, especially hematopoietic cancers such as leukemias and lymphomas. The first and most critical step in the rearrangement process is the induction of two DNA double-strand breaks (DSB). In all cases, at least one of the two DSBs is generated by a pathologic process, such as (1) randomly-positioned breaks due to ionizing radiation, free radical oxidative damage, or spontaneous hydrolysis; (2) breaks associated with topoisomerase inhibitor treatment; or (3) breaks at direct or inverted repeat sequences, mediated by unidentified strand breakage mechanisms. In lymphoid cells, one of the two requisite DSBs is often physiologic, the result of V(D)J recombination or class switch recombination (CSR) at the lymphoid antigen receptor loci. The RAG complex, which causes the DSBs in V(D)J recombination, can cause (4) sequence-specific, pathologic DSBs at sites that fit the consensus of their normal V(D)J recombination signal targets; or (5) structure-specific, pathologic DSBs at regions of single- to double-strand transition. CSR occurs specifically in the B-cell lineage, and requires (6) activation-induced cytidine deaminase (AID) action at sites of single-stranded DNA, which may occur pathologically outside of the normal target loci of class switch recombination regions and somatic hypermutation (SHM) zones. Recent work proposes a seventh mechanism: the sequential action of AID and the RAG complex at CpG sites provides a coherent model for the pathologic DSBs at some of the most common sites of translocation in human lymphoma - the bcl-2 gene in follicular lymphoma and diffuse large B-cell lymphoma, and the bcl-1 gene in mantle cell lymphoma.
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PMID:Mechanisms of chromosomal rearrangement in the human genome. 2015 66

Manipulation of the activity of the p53 tumor suppressor pathway has demonstrated potential benefit in preclinical mouse tumor models and has entered human clinical trials. We describe here an improved, extensive small-molecule chemical compound library screen for p53 pathway activation in a human cancer cell line devised to identify hits with potent antitumor activity. We uncover six novel small-molecule lead compounds, which activate p53 and repress the growth of human cancer cells. Two tested compounds suppress in vivo tumor growth in an orthotopic mouse model of human B-cell lymphoma. All compounds interact with DNA, and two activate p53 pathway in a DNA damage signaling-dependent manner. A further screen of a drug library of approved drugs for medicinal uses and analysis of gene-expression signatures of the novel compounds revealed similarities to known DNA intercalating and topoisomerase interfering agents and unexpected connectivities to known drugs without previously demonstrated anticancer activities. These included several neuroleptics, glycosides, antihistamines and adrenoreceptor antagonists. This unbiased screen pinpoints interference with the DNA topology as the predominant mean of pharmacological activation of the p53 pathway and identifies potential novel antitumor agents.
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PMID:Identification of novel p53 pathway activating small-molecule compounds reveals unexpected similarities with known therapeutic agents. 2088 94

Secondary acute lymphoblastic leukemia (sALL) following chemotherapy and/or radiotherapy of previous malignancies represents 2-10% of all cases of ALL. A 72-year-old female patient was diagnosed with acute lymphoblastic leukemia following chemotherapy for a diffuse large B cell lymphoma. Banding cytogenetics showed a t(t(5;11)(q23-31;q23) in 20 of the 21 metaphases examined and fluorescent in situ hybridization confirmed rearrangement of MLL. Long distance inverse-polymerase chain reaction revealed an in-frame fusion between 5'MLL and 3'PRRC1. Sixty-five cases of sALL associated with 11q23/MLL rearrangement, including 47 with a t(4;11)(q21;q23), were retrieved from the literature. Drug regimen used to treat the primary neoplasm was available for 54 patients; 52 had received a topoisomerase II inhibitor, known to induce MLL rearrangement.
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PMID:MLL partner genes in secondary acute lymphoblastic leukemia: report of a new partner PRRC1 and review of the literature. 2520 3


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