Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.3 (topoisomerase)
 9,911 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Alkylating agents, topoisomerase II inhibitors, ionizing radiation, and other hematotoxins induce DNA damage in hematopoietic stem cells that results in lesions such as balanced and unbalanced chromosome rearrangements, -5/del(5q) and/or -7/del(7q), as well as other submicroscopic genetic lesions. Together with epigenetic alterations, these result in dysplasia, clonal expansion, and ultimately myeloid leukemia. Combinations of lesions are required to induce overt leukemia. Altering a small subset of signaling pathways leads to disruption of normal self-renewal, proliferation, differentiation, and apoptotic mechanisms that control the development of hematopoietic stem cells and their differentiation into mature effector cells. Recent studies have shown that cytogenetically normal (CN-) AML is quite heterogeneous at the molecular level. Patients with CN-AML harboring mutations in NPM1, FLT3, CEBPA, WT1 or expressing high levels of BAALC, ERG, or MN1 have distinctly different clinical outcomes. NPM1 mutations are independently associated with higher remission rates and longer disease-free and overall survival in AML. Copy number alterations (CNAs) are deletions or amplifications of single genes. CNAs have been found at the breakpoints of known chromosomal translocations. Fewer CNAs have been detected in AML than in pediatric ALL. Micro-RNAs (miRs) are non-coding small RNA molecules containing about 22 nucleotides that are typically encoded within introns. They hybridize to complementary mRNA targets and modulate protein expression by inhibiting translation and/or inducing degradation of target messenger RNAs. This new class of genes has recently been shown to play a pivotal role in malignant transformation. miRs are down-regulated in many tumors and thus appear to function as tumor suppressor genes. Distinctive genome-wide miR expression profiles have been associated with different subsets of AML. A miR signature that is associated with clinical outcome in patients with high-risk molecular features of AML (those who have FLT3-ITD or wild-type NPM1) has been reported. This subgroup constitutes approximately 65% of patients with CN-AML and one-third of all patients with AML <60 years old. Down-regulation of the miR-181 family contributes to an aggressive leukemia phenotype through mechanisms associated with the activation of pathways of innate immunity mediated by toll-like receptors and interleukin-1beta.
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PMID:Micro-RNAs and copy number changes: new levels of gene regulation in acute myeloid leukemia. 1982 34

To study the characteristics and clinical impact of therapy-related acute myeloid leukemia (t-AML). 200 patients (7.0%) had t-AML and 2653 de novo AML (93%). Patients with t-AML were older (P < .0001) and they had lower white blood counts (P = .003) compared with de novo AML patients; t-AML patients had abnormal cytogenetics more frequently, with overrepresentation of 11q23 translocations as well as adverse cytogenetics, including complex and monosomal karyotypes, and with underrepresentation of intermediate-risk karyotypes (P < .0001); t-AML patients had NPM1 mutations (P < .0001) and FLT3 internal tandem duplications (P = .0005) less frequently. Younger age at diagnosis of primary malignancy and treatment with intercalating agents as well as topoisomerase II inhibitors were associated with shorter latency periods to the occurrence of t-AML. In multivariable analyses, t-AML was an adverse prognostic factor for death in complete remission but not relapse in younger intensively treated patients (P < .0001 and P = .39, respectively), relapse but not death in complete remission in older, less intensively treated patients (P = .02 and P = .22, respectively) and overall survival in younger intensively treated patients (P = .01). In more intensively treated younger adults, treatment-related toxicity had a major negative impact on outcome, possibly reflecting cumulative toxicity of cancer treatment.
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PMID:The impact of therapy-related acute myeloid leukemia (AML) on outcome in 2853 adult patients with newly diagnosed AML. 2112 74

Hodgkin's disease has been treated mainly with two chemotherapy schedules, MOPP (nitrogen mustard, Oncovin, procarbazine and prednisone), which includes alkylating agents, and ABVD (adriamycin, bleomycin, vinblastine and dacarbazine), which includes topoisomerase II inhibitors, either with or without radiation therapy. Due to the types of agents used, patients with Hodgkin's disease often develop secondary leukemias. The alkylating agents included in the MOPP scheme were the first drugs associated with the development of therapy-related myelodysplastic syndrome (t-MDS) and acute myeloid leukemia (t-AML); both entities are the result of the clonal selection of cells with accumulated genomic lesions induced by antineoplastic therapy. In patients who developed t-MDS and t-AML, eight alternative routes with specific cytogenetic and molecular changes have been identified, and the routes are related to the type of therapy, alkylating agents or DNA topoisomerase II inhibitors. At the cytogenetic level, patients treated with alkylating agents show deletion 5q/monosomy 5 and deletion 7q/monosomy 7; in contrast, those who were treated with topoisomerase II inhibitors show 11q23 translocations involving the MLL gene. At the molecular level, there are two types of mutations: Class I, which alter the RAS-BRAF signal transduction pathways and increase cell proliferation; Class II, which disrupt genes that encode transcription factors and NPM1 that are involved in cell differentiation, and the inactivation of p53 tumor suppressor gene. Knowledge of the genetic alterations in these conditions is important for the classification, treatment and prognosis of patients as well as essential for increasing the knowledge of the biology of these diseases, which leads to identifying potential therapeutic targets.
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PMID:Genetic abnormalities in leukemia secondary to treatment in patients with Hodgkin's disease. 2157 43

De novo acute myeloid leukemia with normal karyotype (NK-AML) comprises a large group of patients with no common cytogenetic alterations and with a large variation in treatment response. Single-nucleotide polymorphisms (SNPs) in genes related to the metabolism of the nucleoside analogue AraC, the backbone in AML treatment, might affect drug sensitivity and treatment outcome. Therefore, SNPs may serve as prognostic biomarkers aiding clinicians in individualized treatment decisions, with the aim of improving patient outcomes. We analyzed polymorphisms in genes encoding cytidine deaminase (CDA 79A>C rs2072671 and -451C>T rs532545), 5'-nucleotidase (cN-II 7A>G rs10883841), and deoxycytidine kinase (DCK 3'UTR 948T>C rs4643786) in 205 de novo NK-AML patients. In FLT3-internal tandem duplication (ITD)-positive patients, the CDA 79C/C and -451T/T genotypes were associated with shorter overall survival compared to other genotypes (5 vs. 24 months, P < 0.001 and 5 vs. 23 months, P = 0.015, respectively), and this was most pronounced in FLT3-ITD-positive/NPM1-positive patients. We observed altered in vitro sensitivity to topoisomerase inhibitory drugs, but not to nucleoside analogues, and a decrease in global DNA methylation in cells carrying both CDA variant alleles. A shorter survival was also observed for the cN-II variant allele, but only in FLT3-ITD-negative patients (25 vs. 31 months, P = 0.075). Our results indicate that polymorphisms in genes related to nucleoside analog drug metabolism may serve as prognostic markers in de novo NK-AML.
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PMID:Decreased survival in normal karyotype AML with single-nucleotide polymorphisms in genes encoding the AraC metabolizing enzymes cytidine deaminase and 5'-nucleotidase. 2387 72