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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In acute lymphoblastic leukaemia (ALL) the karyotype provides important prognostic information which is beginning to have an impact on treatment. The most significant structural chromosomal changes include: the poor-risk abnormalities; t(9;22)(q34;q11), giving rise to the BCR/ABL fusion and rearrangements of the MLL gene; abnormalities previously designated as poor-risk; t(1;19)(q23;p13), producing the E2A/PBX1 and rearrangements of MYC with the immunoglobulin genes; and the probable good risk translocation t(12;21)(p13;q22), which results in the ETV6/AML1 fusion. These abnormalities occur most frequently in B-lineage leukaemias, while rearrangements of the T cell receptor genes are associated with T-lineage ALL. Abnormalities of the short arm of chromosome 9, in particular homozygous deletions involving the tumour suppressor gene (TSG) p16(INK4A), are associated with a poor outcome. Numerical chromosomal abnormalities are of particular importance in relation to prognosis. High hyperdiploidy (51-65 chromosomes) is associated with a good risk, whereas the outlook for patients with near haploidy (23-29 chromosomes) is extremely poor. In view of the introduction of risk-adjusted therapy into the UK childhood ALL treatment trials, an interphase FISH screening programme has been developed to reveal chromosomal abnormalities with prognostic significance in childhood ALL. Novel techniques in molecular cytogenetics are identifying new, cryptic abnormalities in small groups of patients which may lead to further improvements in future treatment protocols.
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PMID:Acute lymphoblastic leukaemia. 1164 Aug 71

A real-time reverse transcription polymerase chain reaction (RT-PCR) method is described that enabled the detection and quantification of E2A-PBX1 fusion gene transcripts associated with t(1;19). The method was highly reproducible and offered exceptional sensitivity at 5 fg of fusion transcript per reaction, without the need for a nested PCR primer design. To illustrate the usefulness of this new technology the E2A-PBX1 fusion gene transcript expression level for several human leukaemia cell lines that are positive and negative for cytogenetically detectable t(1;19) was determined. The RCH-ACV had a threefold higher expression of E2A-PBX1 transcripts (600 transcripts per cell) than the other t(1;19) positive 697 (150 transcripts per cell). The only other cell line with detectable E2A-PBX1 was CEM, but the level of expression was < 1 transcript per cell.
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PMID:Real-time reverse transcription polymerase chain reaction detection and quantification of t(1;19) (E2A-PBX1) fusion genes associated with leukaemia. 1184 16

Treatment of pediatric acute lymphoblastic leukemia (ALL) is based on the concept of tailoring the intensity of therapy to a patient's risk of relapse. To determine whether gene expression profiling could enhance risk assignment, we used oligonucleotide microarrays to analyze the pattern of genes expressed in leukemic blasts from 360 pediatric ALL patients. Distinct expression profiles identified each of the prognostically important leukemia subtypes, including T-ALL, E2A-PBX1, BCR-ABL, TEL-AML1, MLL rearrangement, and hyperdiploid >50 chromosomes. In addition, another ALL subgroup was identified based on its unique expression profile. Examination of the genes comprising the expression signatures provided important insights into the biology of these leukemia subgroups. Further, within some genetic subgroups, expression profiles identified those patients that would eventually fail therapy. Thus, the single platform of expression profiling should enhance the accurate risk stratification of pediatric ALL patients.
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PMID:Classification, subtype discovery, and prediction of outcome in pediatric acute lymphoblastic leukemia by gene expression profiling. 1208 66

Multi-parameter flow cytometry, molecular genetics, and cytogenetic studies have all contributed to new classification of leukemia. In this review we discuss immunophenotypic characteristics of major genotypic leukemia categories. We describe immunophenotype of: B-lineage ALL with MLL rearrangements, TEL/AML1, BCR/ABL, E2A/PBX1 translocations, hyperdiploidy, and myc fusion genes; T-ALL with SCL gene aberrations and t(5;14) translocation; and AML with AML1/ETO, PML/RARalpha, OTT/MAL and CBFbeta/MYH11 translocations, trisomies 8 or 11 and aberrations of chromosomes 7 and 5. Whereas some genotypes associate with certain immunophenotypic features, others can present with variable immunophenotype. Single molecules (as NG2, CBFbeta/SMMHC and PML/RARalpha proteins) associated with or derived from specific translocations have been described. More often, complex immunophenotype patterns have been related to the genotype categories. Most known associations between immunophenotype and genotype have been defined empirically. Therefore, these associations should be validated in independent patient cohorts before they can be widely used for prescreening of leukemia. Progress in our knowledge on leukemia will show how the molecular-genetic changes modulate the immunophenotype as well as how the expressed protein molecules further modulate cell behavior.
Leukemia 2002 Jul
PMID:Antigen expression patterns reflecting genotype of acute leukemias. 1209 48

The t(1;19) translocation yields a fusion between E2A and PBX1 genes and occurs in 5% of acute lymphoblastic leukemia in children and adults. We used chromosomal translocations and Ig heavy chain (IGH)/T cell antigen receptor (TCR) rearrangements to develop an understanding of the etiology and natural history of this subtype of leukemia. We sequenced the genomic fusion between E2A and PBX1 in 22 preB acute lymphoblastic leukemias and two cell lines. The prenatal origin of the leukemia was assessed in 15 pediatric patients by screening for the clonotypic E2A-PBX1 translocation in neonatal blood spots, or Guthrie cards, obtained from the children at the time of birth. Two patients were determined to be weakly positive for the fusion at the time of birth, in contrast to previously studied childhood leukemia fusions, t(12;21), t(8;21), and t(4;11), which were predominantly prenatal. The presence of extensive N-nucleotides at the point of fusion in the E2A-PBX1 translocation as well as specific characteristics of the IGH/TCR rearrangements provided additional evidence for a postnatal, preB cell origin. Intriguingly, 16 of 24 breakpoints on the 3.2-kb E2A intron 14 were located within 5 bp, providing evidence for a site-specific recombination mechanism. Breakpoints on the 232-kb PBX1 intron 1 were more dispersed but highly clustered proximal to exon 2. In sum, the translocation breakpoints displayed evidence of unique temporal, ontological, and mechanistic formation than the previously analyzed pediatric leukemia translocation breakpoints and emphasize the need to differentiate cytogenetic and molecular subgroups for studies of leukemia causality.
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PMID:Site-specific translocation and evidence of postnatal origin of the t(1;19) E2A-PBX1 fusion in childhood acute lymphoblastic leukemia. 1241 13

Cyclin-dependent kinase inhibitors (CDKIs) have been shown to block human immunodeficiency virus and herpes simplex virus. It is hypothesized that CDKIs block viral replication by inhibiting transcription of specific cellular genes. Here we find that three CDKIs, flavopiridol, purvalanol A, and methoxy-roscovitine, block Moloney murine leukemia virus (MLV) transcription events. Using gene expression microarray technology to examine the inhibitory effects of CDKIs, we observed a cellular gene, the pre-B-cell leukemia transcription factor 1 (Pbx1) gene, down-regulated by CDKI treatment. The PBX consensus element (PCE), TGATTGAC, is conserved in the long terminal repeats of several murine retroviruses, including Moloney MLV. Mutations in the PCE completely inhibited viral transcription whereas overexpression of PBX1 and a PBX1-associated protein, PREP1, enhanced viral transcription. The interaction between the PCE and PBX1-PREP1 proteins was confirmed by gel shift experiments. Blocking PBX1 protein synthesis resulted in a significant decrease in viral transcription. Collectively, our results represent the first work demonstrating that the homeodomain proteins PBX1 and PREP1 are cellular factors involved in Moloney MLV transcription regulation.
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PMID:Identification of homeodomain proteins, PBX1 and PREP1, involved in the transcription of murine leukemia virus. 1252 89

Molecular and cytogenetic studies performed in 305 adult acute lymphoblastic leukaemia (ALL) patients enrolled in the gimema (Gruppo Italiano Malattie EMatologiche dell'Adulto) multicentric protocols identified an E2A-PBX1 fusion and/or t(1;19) in 10 patients (3.3%). All had common ALL, were mostly CyIg+ and were CD34/CD13/CD33-. Nine patients achieved a complete remission (CR); five patients showed a haematological relapse after 7 months (median). Four patients are alive in first CR with a median follow-up of 29 months; three patients are molecularly negative. This abnormality is frequently associated with early treatment failure. E2A-PBX1+ adult ALL should be considered for intensified treatment strategies and monitoring of minimal residual disease.
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PMID:E2A-PBX1 fusion in adult acute lymphoblastic leukaemia: biological and clinical features. 1258 Sep 65

We established a real-time PCR method that can simultaneously detect 10 different fusion transcripts (major, minor and micro BCR/ABL, AML1/MTG8, PML/RARalpha, CBFbeta/MYH11, TEL/AML1, E2A/PBX1, MLL/AF4, and MLL/AF9) together with Wilms' tumor gene (WT1) transcripts. This screening method allowed the processing of six specimens concomitantly and required only one working day from RNA extraction to final results. Fifty-seven bone marrow (BM) samples from patients with acute leukemia were retrospectively screened for the presence of fusion and WT1 transcripts without knowledge of the cytogenetic data, and the fusion transcripts were detected in 20 of 57 samples (35.1%). The concordance between the present method and cytogenetic analysis was examined in 38 samples in which the cytogenetic data were available. In 12 of 38 samples, the PCR results agreed with the cytogenetic data, whereas in 4 of the remaining 26 samples, the translocations were detected by real-time PCR alone because of the insufficient number of metaphases obtained and presumably the submicroscopic or masked translocations. The WT1 levels ranged from 400 to 690,000 copies/microg RNA in BM from leukemia patients, whereas 0-470 copies/microg RNA were found in BM cells from BMT donors. This real-time PCR method enables rapid and efficient characterization of acute leukemia in addition to subsequent evaluation of minimal residual diseases.
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PMID:Rapid screening of leukemia fusion transcripts in acute leukemia by real-time PCR. 1261 15

The gene E2A on chromosome 19 is involved in recurrent chromosomal rearrangements associated with pediatric acute lymphoblastic leukemia. The resulting fusion of 5' E2A sequences with 3' portions of other genes leads to the expression of two well-characterized fusion proteins: E2A-PBX1 and E2A-HLF. Since the E2A, PBX1 and HLF proteins all appear to function as transcription factors, it appears likely that the oncogenic fusion proteins contribute to leukemia development by causing abnormal transcriptional regulation of key target genes. Furthermore, since the E2A portion of the fusion proteins contains transcriptional activation domains, and the PBX1 and HLF portions contain DNA binding domains, leukemogenesis may be due, at least in part, to excessive transcriptional induction of target genes defined by PBX1 or HLF. However, recent findings suggest that this model is simplistic and possibly incorrect. In this article, I review the evidence pertaining to leukemogenesis by the well-characterized E2A-fusion proteins and consider its mechanistic implications.
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PMID:E2A basic helix-loop-helix transcription factors in human leukemia. 1270 34

Multiple genes have been shown to be independently hypermethylated in lymphoid malignancies. We report here on the extent of concurrent methylation of E-cadherin, Dap-kinase, O(6)MGMT, p73, p16, p15 and p14 in 129 pediatric ALL cases. While most of these genes demonstrated methylation in a proportion of cases, O(6)MGMT, p16 and p14 were infrequently methylated (11, 7 and 3%, respectively). Methylation of at least one gene was found in the vast majority (83%) of cases. To determine the extent and concordance of methylation we calculated a methylation index (MI=number of methylated genes/number of studied genes) for each sample. The average MI was 0.28, corresponding to 2/7 methylated genes. MI was correlated with standard prognostic factors, including immunophenotype, age, sex, WBC and presence of specific translocations (TEL-AML1, BCR-ABL, E2A-PBX1 or MLL-AF4). We determined that children >/=10 years old and children presenting with high WBC (>/=50 x 10(9)/l) both associated with a higher MI (P<0.01 and <0.05, respectively). T-ALLs demonstrated a lower MI (median=0.17) than precursor B ALLs (median=0.28). Among the different molecular subgroups, MLL-ALLs had the highest MI (mean=0.35), while ALLs carrying the t(1;19) had the lowest MI (mean=0.07). The most common epigenetic lesion in childhood ALL was methylation of E-cadherin (72%) independent of the molecular subtype or other clinicopathological factors.
Leukemia 2003 Sep
PMID:Concurrent methylation of multiple genes in childhood ALL: Correlation with phenotype and molecular subgroup. 1297 Jul 85


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