Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Aberrant hypermethylation of tumor suppressor genes plays an important role in the development of many tumors. Recently identified new DNA methyltransferase (DNMT) genes, DNMT3A and DNMT3B, code for de novo methyltransferases. To determine the roles of DNMT3A, DNMT3B, as well as DNMT1, in the development of leukemia, competitive polymerase chain reaction (PCR) assays were performed and the expression levels of DNMTs were measured in normal hematopoiesis, 33 cases of acute myelogenous leukemia (AML), and 17 cases of chronic myelogenous leukemia (CML). All genes were constitutively expressed, although at different levels, in T lymphocytes, monocytes, neutrophils, and normal bone marrow cells. Interestingly, DNMT3B was expressed at high levels in CD34(+) bone marrow cells but down-regulated in differentiated cells. In AML, 5.3-, 4.4-, and 11.7-fold mean increases were seen in the levels of DNMT1, 3A, and 3B, respectively, compared with the control bone marrow cells. Although CML cells in the chronic phase did not show significant changes, cells in the acute phase showed 3.2-, 4.5-, and 3.4-fold mean increases in the levels of DNMT1, 3A, and 3B, respectively. Using methylation-specific PCR, it was observed that the p15(INAK4B) gene, a cell cycle regulator, was methylated in 24 of 33 (72%) cases of AML. Furthermore, AML cells with methylated p15(INAK4B) tended to express higher levels of DNMT1 and 3B. In conclusion, DNMTs were substantially overexpressed in leukemia cells in a leukemia type- and stage-specific manner. Up-regulated DNMTs may contribute to the pathogenesis of leukemia by inducing aberrant regional hypermethylation. (Blood. 2001;97:1172-1179)
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PMID:Expression of DNA methyltransferases DNMT1, 3A, and 3B in normal hematopoiesis and in acute and chronic myelogenous leukemia. 1122 58

A collection of analogues of the dimeric natural product psammaplin A that differ in the substitution on the (halo)tyrosine aryl ring, the oxime and the diamine connection has been synthesized. The effects on cell cycle, induction of differentiation and apoptosis of the natural-product inspired series were measured on the human leukaemia U937 cell line. Epigenetic profiling included induction of p21(WAF1), effects on global H3 histone and tubulin acetylation levels as well as in vitro enzymatic assays using HDAC1, DNMT1, DNMT3A, SIRT1 and a peptide domain with p300/CBP HAT activity. Whereas the derivatives of psammaplin A with modifications in the length of the connecting chain, the oxime bond and the disulfide unit showed lower potency, the analogues with changes on the bromotyrosine ring exhibited activities comparable to those of the parent compound in the inhibition of HDAC1 and in the induction of apoptosis. The lack of HDAC1 activity of analogues modified on the disulfide bond suggests that its cleavage must occur in cells to produce the monomeric Zn(2+)-chelating thiol. This assumption is consistent with the molecular modelling of the complex of psammaplin A thiol with h-HDAC8. Only a weak inhibition of DNMT1, DNMT3A and residual activities with SIRT1 and a p300/CBP HAT peptide were measured for these compounds.
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PMID:Epigenetic profiling of the antitumor natural product psammaplin A and its analogues. 2121 47

Abnormal epigenetic regulation has been implicated in oncogenesis. We report here the identification of somatic mutations by exome sequencing in acute monocytic leukemia, the M5 subtype of acute myeloid leukemia (AML-M5). We discovered mutations in DNMT3A (encoding DNA methyltransferase 3A) in 23 of 112 (20.5%) cases. The DNMT3A mutants showed reduced enzymatic activity or aberrant affinity to histone H3 in vitro. Notably, there were alterations of DNA methylation patterns and/or gene expression profiles (such as HOXB genes) in samples with DNMT3A mutations as compared with those without such changes. Leukemias with DNMT3A mutations constituted a group of poor prognosis with elderly disease onset and of promonocytic as well as monocytic predominance among AML-M5 individuals. Screening other leukemia subtypes showed Arg882 alterations in 13.6% of acute myelomonocytic leukemia (AML-M4) cases. Our work suggests a contribution of aberrant DNA methyltransferase activity to the pathogenesis of acute monocytic leukemia and provides a useful new biomarker for relevant cases.
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PMID:Exome sequencing identifies somatic mutations of DNA methyltransferase gene DNMT3A in acute monocytic leukemia. 2144 72

Alterations in DNA methylation have been implicated in the pathogenesis of myelodysplastic syndromes (MDS), although the underlying mechanism remains largely unknown. Methylation of CpG dinucleotides is mediated by DNA methyltransferases, including DNMT1, DNMT3A and DNMT3B. DNMT3A mutations have recently been reported in patients with de novo acute myeloid leukemia (AML), providing a rationale for examining the status of DNMT3A in MDS samples. In this study, we report the frequency of DNMT3A mutations in patients with de novo MDS, and their association with secondary AML. We sequenced all coding exons of DNMT3A using DNA from bone marrow and paired normal cells from 150 patients with MDS and identified 13 heterozygous mutations with predicted translational consequences in 12/150 patients (8.0%). Amino acid R882, located in the methyltransferase domain of DNMT3A, was the most common mutation site, accounting for 4/13 mutations. DNMT3A mutations were expressed in the majority of cells in all tested mutant samples regardless of myeloblast counts, suggesting that DNMT3A mutations occur early in the course of MDS. Patients with DNMT3A mutations had worse overall survival compared with patients without DNMT3A mutations (P=0.005) and more rapid progression to AML (P=0.007), suggesting that DNMT3A mutation status may have prognostic value in de novo MDS.
Leukemia 2011 Jul
PMID:Recurrent DNMT3A mutations in patients with myelodysplastic syndromes. 2175 May 60

DNA methylation and its influence on gene expression are key in understanding cancer pathogenesis. Even though it is becoming clear that DNA methylation strongly interacts with other components of the epigenetic machinery such as histone modifications, aberrant DNA methylation can still be regarded as a crucial hallmark of cancer by itself. In Acute Myeloid Leukemia (AML), aberrations of DNA methylation also rank among the most frequent alterations observed. Recent studies revealed that specific patterns of DNA methylation characterize AML and help to distinguish AML subtypes. The contribution of this epigenetic dysregulation to leukemogenesis in AML is currently unclear. However, interactions between mutated transcription factors and epigenetic networks have already been shown to be partially responsible for leukemic transformation, for e.g. in acute promyelocytic leukemia (APL). Also, direct mutations in the epigenetic master regulators EZH2 and DNMT3A were recently identified in AML and in diseases leading to secondary leukemia. These findings strengthen the view that dysregulated epigenetic networks can induce AML. Correspondingly, epigenetic therapies e.g. hypomethylating drugs show significant activity in AML. While benefit is observed in many patients, DNA hypomethylating therapy by itself is not curative. Furthermore, it is not clear whether the drugs' effects are solely epigenetic in nature since in vitro studies suggest different mechanisms of action. Current clinical trials aim to improve efficacy of DNA hypomethylating drugs for e.g. by combination with standard AML chemotherapy. Taken together, targeting the epigenetic machinery seems to be the way towards more effective therapies in AML.
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PMID:DNA methylation as a pathogenic event and as a therapeutic target in AML. 2161 74

To study the prevalence and prognostic importance of mutations in NADH dehydrogenase subunit 4 (ND4), a mitochondrial encoded transmembrane component of the electron transport chain respiratory Complex I, 452 AML patients were examined for ND4 mutations by direct sequencing. The prognostic impact of ND4 mutations was evaluated in the context of other clinical prognostic markers and genetic risk factors. In all, 29 of 452 patients (6.4%) had either somatic (n=12) or germline (n=17) ND4 mutations predicted to affect translation. Somatic mutations were more likely to be heteroplasmic (P<0.001), to occur in predicted transmembrane domains (P<0.001) and were predicted to have damaging effects upon translation (P<0.001). Patients with somatically acquired ND4 mutations had significantly longer relapse-free survival (P=0.017) and overall survival (OS) (P=0.021) than ND4(wildtype) patients. Multivariate analysis also demonstrated a tendency for increased survival in patients with somatic ND4 mutations (RFS: hazard ratio (HR) 0.25, confidence interval (CI) 0.06-1.01, P=0.052; OS: HR 0.29, CI 0.74-1.20, P=0.089). Somatic ND4(mutated) patients had a higher prevalence of concomitant DNMT3A mutations (P=0.023) and a higher percentage of the NPM1/FLT3-ITD low-risk genotype (P=0.021). Germline affected cases showed higher BAALC (P=0.036) and MLL5 (P=0.051) expression levels. Further studies are warranted to validate the favorable prognostic influence of acquired ND4 mutations in AML.
Leukemia 2012 Feb
PMID:Prognostic implications and molecular associations of NADH dehydrogenase subunit 4 (ND4) mutations in acute myeloid leukemia. 2182 63

Gene mutations and epigenetic changes have been shown to play significant roles in the pathogenesis of myelodysplastic syndromes. Recently, mutations in DNMT3A were identified in 22.1% of patients with acute myeloid leukemia. In this study, we analyzed the frequency and clinical impact of DNMT3A mutations in a cohort of 193 patients with myelodysplastic syndromes. Mutations in DNMT3A were found in 2.6% of patients. The majority of mutations were heterozygous missense mutations affecting codon R882. Patients with DNMT3A mutations were found to have a higher rate of transformation to acute myeloid leukemia. When assessing the global methylation levels in patients with mutated versus unmutated DNMT3A and healthy controls no difference in global DNA methylation levels between the two groups was seen. Our data show that in patients with myelodysplastic syndromes, DNMT3A mutations occur at a low frequency and may be a risk factor for leukemia progression.
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PMID:Rare occurrence of DNMT3A mutations in myelodysplastic syndromes. 2188 Jun 36

Rapid advances in molecular technologies are continually re-shaping the way we view and understand the mechanisms driving oncogenesis. The last decade has witnessed unparalleled change in the biology and therapy of the myelodysplastic syndromes (MDS), a heterogeneous collection of clonal myeloid disorders characterised by ineffective haematopoiesis and susceptibility to acute leukaemia transformation. Pivotal studies demonstrating the positive effects of hypomethylating agents on clinical outcome have brought an 'epigenomics revolution' to this disease, emphasising the importance of epigenetic mechanisms to the underlying pathogenesis of MDS. One of the most important future challenges in the MDS field will be to determine whether epigenetic therapies can be made more 'targeted' through identification of biomarkers which define subsets of patients most likely to benefit from treatment. A wave of novel mutations have recently been reported in MDS and other myeloid disorders, several of which regulate endogenous methylation networks within cells (including TET2, DNMT3A, IDH and EZH2). The relevance of these lesions in being able to predict response to epigenetic modulators and their correlation with epigenetic signatures in MDS are beginning to emerge.
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PMID:The epigenomics revolution in myelodysplasia: a clinico-pathological perspective. 2188 38

Somatic mutations of DNMT3A gene have recently been reported in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). We examined the entire coding sequences of DNMT3A gene by high-resolution melting analysis and sequencing in Chinese patients with myeloid malignancies. R882 mutations were found in 12/182 AML and in 4/51 MDS, but not in either 79 chronic myeloid leukemia (CML), or 57 myeloproliferative neoplasms (MPNs), or 4 chronic monomyelocytic leukemia. No other DNMT3A mutations were detected in all patients. R882 mutations were associated with old age and more frequently present in monoblastic leukemia (M4 and M5, 7/52) compared to other subtypes (5/130). Furthermore, 14/16 (86.6%) R882 mutations were observed in patients with normal karyotypes. The overall survival of mutated MDS patients was shorter than those without mutation (median 9 and 25 months, respectively). We conclude that DNMT3A R882 mutations are recurrent molecular aberrations in AML and MDS, and may be an adverse prognostic event in MDS.
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PMID:Recurrent DNMT3A R882 mutations in Chinese patients with acute myeloid leukemia and myelodysplastic syndrome. 2206 15

While acute megakaryoblastic leukaemia (AMKL) occurs in children with (DS-AMKL) and without (paediatric non-DS-AMKL) Down syndrome, it can also affect adults without DS (adult non-DS-AMKL). We have analysed these subgroups of patients (11 children with DS-AMKL, 12 children and four adults with non-DS-AMKL) for the presence of molecular lesions, including mutations and chromosomal abnormalities studied by sequencing and single nucleotide polymorphism array-based karyotyping, respectively. In children, AMKL was associated with trisomy 21 (somatic in non-DS-AMKL), while numerical aberrations of chromosome 21 were only rarely associated with adult AMKL. DS-AMKL was also associated with recurrent somatic gains of 1q (4/11 DS-AMKL patients). In contrast to trisomy 21 and gains of 1q, other additional chromosomal lesions were evenly distributed between children and adults with AMKL. A mutational screen found GATA1 mutations in 11/12 DS-AMKL, but mutations were rare in paediatric non-DS-AMKL (1/12) and adult AMKL (0/4). JAK3 (1/11), JAK2 (1/11), and TP53 mutations (1/11) were found only in patients with DS-AMKL. ASXL1, IDH1/2, DNMT3A, RUNX1 and CBL mutations were not found in any of the patient group studied, while NRAS mutation was identified in two patients with paediatric non-DS-AMKL.
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PMID:Molecular lesions in childhood and adult acute megakaryoblastic leukaemia. 2212 69


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