Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Therapy-related acute myeloid leukemia (t-AML), often presenting as myelodysplasia (t-MDS), has become the most serious long-term complication of cancer therapy and offers a unique opportunity to study chemical leukemogenesis. Seven cohorts of patients treated for six different types of primary tumor have been followed closely for leukemic complications, and 115 consecutive patients with t-MDS or t-AML, including 45 cases from the cohorts, have been investigated cytogenetically at our institutions during the past 16 years. In patients primarily treated with alkylating agents, the risk of t-MDS and t-AML increased by approximately 1% per year from 2 to at least 8 years after start of treatment. In most cases, the disease presented as t-MDS with loss of a whole chromosome 5 or 7, or various parts of their long arms, and the leukemias were of FAB-subtypes M1, M2, or M4. In patients treated with drugs targeting at DNA-topoisomerase II, such as etoposide, doxorubicin, 4-epidoxorubicin, or mitoxantrone combined with drugs reacting directly with DNA, such as cisplatin or alkylating agents, the risk of leukemia increased much more steeply from only one year after start of therapy. These early onset cases often presented as overt leukemia of FAB-subtypes M4 or M5 with balanced translocations to chromosome bands 11q23 and 21q22, whereas later onset cases often shared characteristics with cases observed after therapy with alkylating agents alone. Both alkylation of DNA and poisoning of DNA-topoisomerase II may result in development of t-AML with different clinical and cytogenetic characteristics. There may be a synergistic leukemogenic effect between the two types of drug, and in patients with germ cell tumors treated with etoposide, cisplatin and bleomycin, reassessment suggested the risk of leukemia to increase exponentially with increasing doses of cisplatin and etoposide.
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PMID:Therapy-related myelodysplasia and acute myeloid leukemia. Cytogenetic characteristics of 115 consecutive cases and risk in seven cohorts of patients treated intensively for malignant diseases in the Copenhagen series. 825 96

Now that a substantial group of cancer patients has such a favourable prognosis, it has become increasingly important to evaluate the long-term complications of treatment. Of all late effects of treatment, secondary leukaemia is one of the most serious. Increased risk of AML has been observed both after RT and after CT; however, several types of CT have much stronger leukaemogenic properties than RT. Limited field radiation in the therapeutic dose range is associated with very little or no increased risk of leukaemia, which has been attributed to cell killing at the higher radiation doses. With respect to CT, two different syndromes of treatment-related AML have been recognized. Risk of alkylating agent-related AML is highest in the 5-10 year follow-up period and seems to decrease afterwards. This type of leukaemia is often preceded by MDS, and is characterized by deletions of chromosomes 5 and 7. Leukaemias related to treatment with the topoisomerase II inhibitors are characterized by a short induction period, presentation as myelomonocytic or monocytic leukaemia (rather than MDS) and balanced chromosomal translocations involving bands 11q23 and 21q22. This review addresses the risk of secondary AML and MDS following treatment of HD, NHL, testicular cancer, ovarian cancer, breast cancer and paediatric malignancies. In patients with HD, the risk of AML is higher with an increasing number of mechlorethamine-procarbazine-containing cycles, a greater number of CT episodes, and after splenectomy. The majority of data shows that RT does not add to the leukaemia risk from CT, but this issue is still surrounded by some controversy. ABV(D)-treated patients have a very low risk of AML. Generally, patients with NHL, testicular cancer and breast cancer experience much lower risk of AML than patients with HD. NHL and breast cancer treatment regimens with cumulative cyclophosphamide doses of 20 g or less do not confer an appreciable increase of AML. Recently, strongly increased AML risk has been observed following autologous bone marrow transplantation and other dose intensification strategies. Risk factors for this excess remain to be defined. PVB treatment for testicular cancer is not followed by increased leukaemia risk, but modern etoposide-containing regimens do confer excess risk, of which the magnitude at conventional drug doses is not yet well known. High risk of leukaemia has been reported in children treated with epipodophyllotoxins. The leukaemogenic hazards of cancer treatment should be weighed against their therapeutic benefits.
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PMID:Risk of acute myelogenous leukaemia and myelodysplasia following cancer treatment. 873 May 51

During the last decade the frequency of therapy-related acute leukemia (t-leuk) and myelodysplastic syndrome (t-MDS) has been increasingly observed. Over the past 15 years, we treated 56 patients with t-leuk who had received prior chemotherapy (39%), radiotherapy (11%), or both (45%). The drugs received included alkylating agents and topoisomerase II inhibitors. The primary tumors included hematological malignancies (49%) and solid tumors such as breast or ovarian cancer. The median age at diagnosis of the primary tumor was relatively young (43 years +/- 18). Twelve patients had more than one primary tumor and 31 patients had a family history of malignancy. Karyotypic abnormalities were found in 91% of the patients. Prognosis was uniformly poor, with an overall median survival of 10 months. Twelve of the 18 patients examined (67%) had a multidrug resistance phenotype. P53 genes of the leukemic cells, as well as the original tumors, were analyzed in 21 patients using polymerase chain reaction (PCR) with single-stranded conformation polymorphism analysis followed by sequencing. P53 mutations were identified in 38% of these patients, a relatively high prevalence compared with other forms of MDS or de novo acute myeloid leukemia. Mutations were nongermline and restricted to the leukemic cells. We identified different p53 mutations in the various primary tumors of individual patients. The presence of a mutator phenotype was assessed by PCR analysis of microsatellites in eight loci (one trinucleotide repeat sequence, four dinucleotide, and three mononuclear repeat sequences). Microsatellite instability in two to seven loci were found in 15 of 16 (94%) of the patients. This instability is compatible with a mutator phenotype, which predisposes the patients to the development of malignancies including t-leuk.
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PMID:Microsatellite instability and p53 mutations in therapy-related leukemia suggest mutator phenotype. 894 66

Two main types of therapy-related acute myeloid leukemias (tAML) and myelodysplastic syndromes (tMDS) have been described. The first classical type typically occurs late after use of alkylating agents and presents as MDS with -7/del 7q and/or -5/del5q. The second form occurs early after the use of agents targeted at topoisomerase II, and presents as AML with 11q23 or other rearrangements of de novo AML. Recently, we and others reported, in AML and MDS, a strong correlation between cytogenetic rearrangements leading to 17p deletion, a specific type of dysgranulopoiesis and p53 mutation; several of those cases of 17p- syndrome were therapy-related. Over the last 15 years, we observed 25 cases of tAML and tMDS with 17p deletion, which represented 36% of the AML and MDS with 17p deletion diagnosed during that period. Median age was 59 years. Twenty-one patients had tMDS and four tAML. Typical dysgranulopoiesis and p53 mutation and/or overexpression were seen in 22 of 24 and 16 of 19 evaluable patients, respectively. 17p deletion resulted from unbalanced translocations involving 17p (18 cases), monosomy 17 (five cases), i(17q) (one case) or del 17p (one case). Twenty-one patients also had -5/del 5q, and/or -7/del 7q. Median interval from treatment of the first tumor of tAML and tMDS was 94 months (range 19-252). Median survival was only 7 months. Based on primary tumor and antineoplastic agents used, patients could be relatively well divided into two groups: a first group of 11 cases, occurring mainly after a lymphoid neoplasm (eight cases) treated by chemotherapy with an alkylating agent (10 cases), and a second group of 14 cases occurring after essential thrombocythemia (ET) or polycythemia vera (PV) treated mainly by hydroxyurea (10 cases), pipobroman (eight cases), 32P (six cases) but rarely by alkylating agents (two cases). -7/del 7q was found in 10 of the 11 patients in the first group, as compared to three of the 14 patients of the second group (P = 0.0001). Therefore, therapy-related cases represent a high proportion of AML and MDS with the 17p- syndrome. They have many features in common with classical tMDS and tAML, including long interval from the first tumor, a usual preleukemic phase, and frequent occurrence of -5/del 5q. About one half of them, in addition, occur after alkylating agents and generally carry -7/del 7q. The other half, however, occur mainly after ET or PV treated by hydroxyurea or other non-alkylating agents, and usually have no -7/del 7q. These findings bring further support to a possible relationship between prior drugs used and cytogenetic rearrangements in tAML and tMDS.
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PMID:Therapy-related myelodysplastic syndrome and acute myeloid leukemia with 17p deletion. A report on 25 cases. 1002 99

The oral antitumor drugs against hematological malignancies are summarized. Sobuzoxane, a topoisomerase II inhibitor, is useful for the treatment of lymphoma, especially adult T cell leukemia/lymphoma. Sobuzoxane has an effect to protect against doxorubicin cardiotoxicity. Cytarabine ocfosfate, a derivative of cytosine arabinoside, is a useful agent against acute leukemia and MDS, especially RAEB, RAEB in T, CMMoL. The JALSG AML 92 study for APL with all-trans retinoic acid resulted in a 89% CR rate in 196 and 64% 4-year DFS in CR cases. Hydroxycarbamide is can control the WBC in CML. This agent is also effective for other myeloproliferative disorders, such as acute leukemia and MDS. Oral administration of 50 mg etoposide daily showed a good outcome in old patients with malignant lymphoma. For old patients and those with refractory hematological malignancies, oral administration of these agents can offer a new form of palliative therapy to allow them to remain at home while maintaining a high quality of life.
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PMID:[Oral antitumor drugs for hematological malignancies]. 1006 91

Drug resistant cells often have an increased capacity to repair their DNA after damage by cytotoxic agents. Aphidicolin can inhibit this DNA repair. We describe a study of the effect of aphidicolin to modulate the sensitivity to cytotoxic drugs of blast cells from 13 patients with AML, 11 with de novo disease on presentation and 2 secondary to MDS. Three patients had relapsed following previous therapy and samples were received from 1 patient both on presentation and relapse. Blast cells were exposed to anthracyclines, antimetabolites or etoposide +/- aphidicolin (15 microM) for 48 hours. The MTT assay was used to measure cell survival and the LC50 (concentration of drug required for 50% cell kill) was calculated. Overall, there was a significant increase in sensitivity to ara-C on co-incubation with aphidicolin in 12/14 samples (p = 0.007). The median increase in sensitivity was 3.88-fold (range 1.26- to 80-fold). Interestingly, when patients were grouped according to in vitro sensitivity to ara-C, cells from resistant patients demonstrated the greatest increase in sensitivity (median 14-fold compared to 2-fold for the sensitive group, p = 0.02). Despite the documented evidence for altered DNA repair as a mechanism of resistance to the topoisomerase II inhibitors, we found no significant increase in sensitivity to daunorubicin, doxorubicin or etoposide on co-incubation with aphidicolin. Nevertheless, we believe the unparalleled modulation of ara-C warrants further investigation.
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PMID:Aphidicolin markedly increases the in vitro sensitivity to ara-C of blast cells from patients with AML. 1050 Aug 35

Clinically distinct features in both alkylating agents--and topoisomerase II (topo II)-induced secondary leukemias (SL) are reviewed with special reference to the increasing frequencies observed in relation to advances in modern cancer chemotherapy. Topo II interacts with, and then stabilizes the cleavable complex that ultimately results in double strand breaks. In patients with SL, breakpoints in MLL gene are clustered within SARs of 3' bcr. However, mechanisms by which the former type of SL is caused remain to be elucidated. Since alkylating agents often induce profound marrow dysplasia, long-lived lesions induced on hematopoietic stem cells are of potential relevance to the development of SL. This process may be partially demonstrated by the variety of mitotic modifications found in MDS. Recently, the association has been investigated between certain enzyme polymorphisms related to activation or detoxification of anticancer agents and SL. These studies have potential importance, since individuals with a certain genotype may be at increased risk for SL.
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PMID:[Secondary leukemias: their clinical features, incidence among populations at risk, mechanisms and new strategy for prediction]. 1058 63

It is known that alkylating agents and topoisomerase II inhibitors can cause distinct forms of therapy-related leukemia and myelodysplastic syndrome (TRL/MDS). Although several reports have been made on each of these agents separately, no study has yet been conducted to evaluate the effect of these two types of agents in the same population. In a nationwide, large-scale population study, the clinical and cytogenetic features as well as the prognostic factors in 256 patients with TRL/MDS were assessed. Median age was 61 years, and the median period of latency from primary malignancies was 47.9 months. The latency period was significantly shorter in patients undergoing chemotherapy, especially that of topoisomerase II inhibitors, for primary cancer. The morphological diagnosis of TRL/MDS was acute myeloid leukemia in 59% and MDS in 41% of patients. Chromosome abnormalities that frequently involved chromosomes 5, 7 or 11 were documented in 77% of the 189 patients examined. MLL gene rearrangements were detected in 11 of 58 subjects and were correlated with a borderline significance (P = 0.072) with topoisomerase II inhibitor administration. Overall median survival was only 9.7 months. Survival was similar in cases with or without MLL gene rearrangement. Multivariate analysis identified chromosome 5 abnormalities, hypoproteinemia, poor therapy outcomes for primary cancer, C-reactive protein, and thrombocytopenia as being significantly poor prognostic factors (P < 0.05). This large-population study provided a comprehensive update of TRL/MDS status in Japan, identified significant prognostic factors, and enabled the clinical significance of MLL gene rearrangement to be assessed.
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PMID:Therapy-related leukemia and myelodysplastic syndrome: a large-scale Japanese study of clinical and cytogenetic features as well as prognostic factors. 1074 24

Chromosomal aberrations are frequently associated with therapy-related myelodysplastic syndromes and acute myelogenous leukemia (t-MDS/AML) and are thought to result from exposure to genotoxic drugs, including alkylating agents and DNA topoisomerase II poisons. The NUP98 gene on chromosome band 11p15 is involved in several different chromosomal aberrations that have been associated with t-MDS/AML. We have cloned the translocation breakpoints from two cases of t-MDS harboring a t(11;20)(p15;q11). Sequence analysis of the breakpoints from both cases revealed almost perfectly balanced translocations between NUP98 and TOP1. There were no known recombinogenic sequences identified at or near the breakpoints. However, four bp microduplications present at the translocation crossover points suggested that these translocations may have been initiated by 4 bp staggered double-stranded DNA breaks, which are known to be associated with the action of topoisomerase II. Given the history of patient exposure to topoisomerase II poisons, and the fact that these drugs stabilize staggered breaks with a 4 bp overhang, it seems possible that drug-induced topoisomerase II cleavage and subunit exchange was involved in these translocations. These results suggest that NUP98 is a recurrent target for therapy-related malignancies induced by multiagent chemotherapy, and suggest a role for DNA topoisomerase II poisons in the generation of these translocations. Published 2000 Wiley-Liss, Inc.
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PMID:Potential role for DNA topoisomerase II poisons in the generation of t(11;20)(p15;q11) translocations. 1095 88

The incidence of secondary myelodysplastic syndromes and acute leukemia (MDS/AL) was reported for 395 patients autografted for Hodgkin's disease (HD) (n = 96) and non-Hodgkin's lymphoma (NHL) (n = 299) between 1987 and 1998. Eleven patients developed secondary MDS/AL (crude rate at 2.8%) including two lymphoblastic AL cases. The mean time of occurrence was at 32 months after autologous stem cell transplantation (ASCT) and 71 months after diagnosis. The estimated actuarial incidence at 10 years was at 6.3% (+/-4%). Karyotyping revealed complex chromosomal aberrations in only one patient, and two translocations [t(8;21) and t(8;16)]. No features of topoisomerase II inhibitor-related leukemia were found. Only one patient had received ASCT in first remission. The remaining 10 patients had received multiple courses of chemotherapy before stem cell collection and four had relapsed after ASCT and before the occurrence of secondary MDS/AL. Five of 11 patients had received localized radiotherapy and five others received TBI in their conditioning regimen. Ten patients died despite chemotherapy and/or supportive care and only one patient is alive and well after genoidentical allogeneic transplantation. We suggest a cumulative leukemogenic role of pre-ASCT radiation and chemotherapy in the occurrence of these secondary MDS/AL more than the high-dose therapy itself.
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PMID:Myelodysplasias and leukemias after autologous stem cell transplantation for lymphoid malignancies. 1096 73


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