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

The chromosomal translocation involving 3q27 has been recently described in B-cell malignancies, especially in diffuse large cell lymphomas. We have previously cloned the breakpoint cluster region of 3q27 designated as the BCL6 locus, previously known as BCL5, and subsequently cloned the cDNA for the BCL6 (we previously reported it as BCL5) gene encoding a novel Cys2-His2 zinc-finger protein, which locates adjacent to the breakpoints and is activated through the translocation. To elucidate whether rearrangements occur within the BCL6 gene, we characterized the genomic structure of the gene. The BCL6 gene encompasses about 26 kilobases (kb) and consists of nine exons. Translation start site is located in exon 3 and zinc-finger motif is distributed in the exons 6 to 9. We have identified at least two types of mRNA alternatively spliced, which contain or do not contain exon 2 of 134 bp coding for the 5' untranslated region. A large intron 1 of 9 kb is not efficiently spliced out, which might result in the creation of minor 10-12-kb transcripts observed in the Northern blot analysis in addition to major 3.8-kb transcripts. The breakpoints are clustered around the first exon, and the putative regulatory region of the BCL6 gene is removed through the translocation, leading to the over-expression of the gene.
Leukemia 1994 Aug
PMID:The organization of the BCL6 gene. 805 68

Seven patients with acute leukemia and translocation involving band 11q23 have been studied by fluorescence in situ hybridization (FISH) using YAC probes spanning the HRX gene. While hybridization signal was split by translocation between the rearranged 11 and the partner chromosomes in five patients, only one signal on the derivative 11 was observed in two patients, one with t(9;11)(p21-22;q23) and the other with t(6;11)(q27;q23). Having shown that HRX was rearranged in these two cases, the distal part of 11q23 was investigated using other YACs containing markers for this region. This showed that a 600-700 kb deletion, distal to the HRX breakpoint cluster region, had occurred in the two cases. This study supports the notion that the 5' end of HRX is the important part in the chimeric genes resulting from 11q23 translocations and suggests that deletions of the 3' part are not uncommon.
Leukemia 1994 Apr
PMID:Hunting 11q23 deletions with fluorescence in situ hybridization (FISH). 815 54

A child with T-cell acute lymphoblastic leukemia (ALL) is presented who at relapse acquired two Philadelphia chromosomes (Ph). Molecular studies at relapse revealed a rearrangement of the major breakpoint cluster region (M-bcr) on chromosome 22. No rearrangements of the immunoglobulin heavy chain or T-cell beta receptor gene loci were demonstrated. This case supports the hypothesis that leukemogenesis in Ph-positive malignancies is a multi-step process, the first step of which may not necessarily involve acquisition of the Ph.
Leukemia 1994 May
PMID:Late-developing Philadelphia chromosomes in a case of T-cell acute lymphoblastic leukemia. 818 46

Chronic myelogenous leukemia (CML) is a myeloproliferative disorder associated with the Philadelphia chromosome (Ph1) in more than 95% of these patients. The Ph1 and the resulting BCR-ABL fused genes are markers for this type of leukemia. In CML, the product of the fused BCR-ABL gene is typically a protein of approximately 2,000 amino acids termed P210 BCR-ABL. We have developed an assay for the BCR-ABL protein involving Western blotting of circulating white blood cells (WBC) with an anti-ABL monoclonal antibody that can detect P210 BCR-ABL and P145 ABL in peripheral blood cells from chronic phase Ph1-positive leukemia patients. This assay was used to analyze the BCR-ABL protein content of circulating WBC from CML patients before and after various treatments. In parallel to changes in percentages of Ph1-positive blood cells as determined by cytogenetic analyses of bone marrow samples, BCR-ABL protein expression in blood cells decreased or increased as patients entered remission or underwent relapse. Of interest, six Ph1-negative CML patients were BCR-ABL protein-positive. All except one had a rearrangement in the major breakpoint cluster region and that patient expressed P185 BCR-ABL and not P210. Our results indicate that the BCR-ABL Western blotting assay has clinical applications for both diagnosis and prospective evaluation of Ph1-positive and Ph1-negative CML patients.
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PMID:BCR-ABL protein expression in peripheral blood cells of chronic myelogenous leukemia patients undergoing therapy. 820 87

Two-thirds of patients with Philadelphia (Ph) chromosome-positive acute lymphoblastic leukaemia (ALL) have a breakpoint in the minor breakpoint cluster region (m-bcr) of the BCR gene, which results in an e1a2 transcript and a P190BCR-ABL fusion protein. This type of genomic rearrangement occurs very rarely in chronic myeloid leukaemia (CML); it has been reported in only four cases. We describe here a fifth case of P190 CML in which the cytomorphological characteristics were intermediate between CML and chronic myelomonocytic leukaemia (CMML). This case, and the four reported previously, had a consistent and significant monocytosis with a low neutrophil/monocyte ratio in the peripheral blood, resembling CMML. On the other hand, they also had a high percentage of circulating immature granulocytes, basophilia and low neutrophil alkaline phosphatase (NAP) score, which are more commonly found in classical CML. Thus, P190 CML may be a specific form of CML, in which the myeloproliferative process includes the monocytic, as well as the granulocytic lineage. Since the molecular defect in CML is thought to involve a pluripotent stem cell, the different effects of P210BCR-ABL and P190BCR-ABL in CML must reflect the somewhat wider spectrum of activity of the P190BCR-ABL. Other patients with atypical CML or CMML who lack a Ph chromosome may also have an m-bcr breakpoint which would not be detected on standard Southern blots, but which would be detectable by polymerase chain reaction amplification of reverse transcribed RNA.
Leukemia 1994 Jan
PMID:P190BCR-ABL chronic myeloid leukaemia: the missing link with chronic myelomonocytic leukaemia? 793 80

In acute lymphoblastic leukemia (ALL), it is unclear whether variant Philadelphia (Ph) translocations have the same molecular and clinical implications as the classical translocation. Two children with Ph+ ALL with variant translocations are described. One, in whom cytogenetic remission was not achieved, had evidence of translocation of c-abl to chromosome 22, rearrangement of minor breakpoint cluster region (mBCR) and expression of hybrid bcr/abl transcripts. In the other case, no gene rearrangement was found and complete remission was achieved. Variant Ph translocations in childhood ALL are heterogeneous at the molecular level. Molecular studies coupled with observations of clinical outcome are needed in larger numbers of such children to determine whether poor clinical response correlates with bcr/abl involvement and to allow planning of appropriate therapeutic strategies.
Leukemia 1994 Feb
PMID:Molecular heterogeneity of variant Philadelphia translocations in childhood acute lymphoblastic leukaemia. 830 52

We performed cytogenetic and molecular analysis of the BCR-ABL rearrangement by polymerase chain reaction (PCR) in 39 consecutive cases of adult acute lymphoblastic leukemia (ALL). Eleven patients had a Philadelphia (Ph) chromosome. Thirteen patients had a BCR-ABL rearrangement, involving minor breakpoint cluster region (m-bcr, situated in intron 1 of the BCR gene) in 11 cases, and major breakpoint cluster region (M-bcr, 'specific' of chronic myeloid leukemia) in the remaining two cases. All of the 12 BCR-ABL cases studied immunologically were of early B, CALLA-positive immunophenotype. The 13 BCR-ABL positive cases included the 11 Ph-positive cases, and two patients with normal karyotype at diagnosis. In the two Ph-negative BCR-positive cases, seven (patient 1) and 18 (patient 2) mitoses had been examined at diagnosis. In patient 1, Ph negativity at diagnosis could certainly be explained by the small number of mitoses analyzed, as a Ph chromosome was found at relapse. This was less probable in patient 2, who raised the issue of whether authentic Ph-negative BCR-ABL-positive ALL exists (as in the chronic myeloid leukemia model) or not. Whatever the explanation, our results suggest that molecular detection of BCR-ABL should be more widely used in B-lineage ALL.
Leukemia 1993 Jul
PMID:Philadelphia negative, BCR-ABL positive adult acute lymphoblastic leukemia (ALL) in 2 of 39 patients with combined cytogenetic and molecular analysis. 832 Oct 20

The benign phase of chronic myelogenous leukemia (CML) typically is characterized by an overproduction of myeloid cells that eventually progresses to a more acute stage termed blast crisis. This latter stage can exhibit either myeloid or lymphoid blast clones. Our recent results have demonstrated the presence of the P210 BCR-ABL protein in blood cells from benign phase CML patients (Guo et al., Cancer Research 51:3048, 1991). This protein is the product of an 8.5 kb chimeric RNA encoded by fused BCR-ABL genes produced by the formation of the Philadelphia (Ph) chromosome. Using this new assay we have identified a patient with benign-phase CML who produces P190 BCR-ABL, the form of the BCR-ABL protein found in about 50% of cases of acute lymphocytic leukemia (ALL). This patient lacked detectable P210 BCR-ABL protein and did not contain a DNA rearrangement in the major breakpoint cluster region of the BCR gene. Consistent with this result, polymerase chain reaction (PCR) analyses detected a BCR-ABL mRNA with BCR exon 1 fused to ABL exon 2. No BCR-ABL mRNAs with 2'- or 3'-bcr exon to ABL exon 2 fusions were detected in these analyses. Blood cells from this patient lost P190 BCR-ABL after the patient underwent an allogeneic bone marrow transplant, but regained this protein although the patient was still in chronic phase after a subsequent autologous transplant as treatment for graft failure. These findings indicate that P190 BCR-ABL alone is not sufficient to induce a blast crisis phenotype in leukemia patients who are Ph chromosome-positive.
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PMID:Acute lymphoid leukemia molecular phenotype in a patient with benign-phase chronic myelogenous leukemia. 834 Feb 87

Two patients with chronic myeloid leukemia (CML) presenting with the hematologic features of essential thrombocythemia (ET) are reported. At diagnosis they showed extremely high platelet counts (4985 and 2800 x 10(9)/l, respectively) and moderate leukocytosis (21 and 17 x 10(9)/l, respectively). In both cases, in addition to the Philadelphia chromosome (Ph), a rearrangement within the major breakpoint cluster region on chromosome 22 was demonstrated, with the breakpoint in the 3' extreme. In patient 1 the disease initially responded to radioactive phosphorus and hydroxyurea, but during the evolutive course a progressive increase in the white blood cell counts was noted, reaching values typical of the chronic phase of CML, and the patient eventually died from blast crisis 45 months after diagnosis. In patient 2, although good control of the platelet counts was achieved with hydroxyurea, the disease also evolved into a blast crisis four months after diagnosis. In both cases monoclonal antibodies and electron microscopy studies demonstrated the megakaryocytic nature of the blast cells. The above features are not consistent with the present and similar cases being Ph-positive ET. Instead, they should be regarded as a special form of CML characterized by a marked protagonism of the megakaryocytic component.
Leukemia 1993 Feb
PMID:Ph-positive chronic myeloid leukemia mimicking essential thrombocythemia and terminating into megakaryoblastic blast crisis: report of two cases with molecular studies. 842 85

The Philadelphia (Ph) translocation [t(9;22)(q34;q11)] is the most common genetic abnormality in human leukemia; a transposition of the ABL gene to the major-breakpoint cluster region (M-BCR) is associated with the pathogenesis in Ph+ chronic myelogenous leukemia (Ph+ CML) and in some cases of Ph+ acute leukemia (Ph+ AL). Our current understanding of the methylation of human genomes allows us to consider the association between the epigenetic phenomenon and the control of differentiation and proliferation in mammalian cells. In order to determine whether the methylation status of the M-BCR is associated with breakpoint-localization in this region and with the lineage of hematopoietic cells, we have examined 28 patients with Ph+ leukemias, including nine with Ph+ AL, six patients with acute myeloblastic leukemia without Ph (Ph- AML), and five patients with Ph- acute lymphoblastic leukemia (Ph- ALL); using the restriction endonuclease isochizomers, MspI and HpaII. In CML patients in the chronic phase, the hypomethylated status within the normal M-BCR allele is heterogeneous. In contrast, patients with Ph+ CML in the lymphoid blast crisis phase exhibited a 2.5/2.7 kb band with a complete disappearance of the germline M-BCR fragment (type L). This pattern is consistently noted in Ph- ALL cells, and the pattern is quite different from that found in myeloid blast crisis or Ph- AML (type M). In patients with M-BCR-nonrearranged Ph+ ALL, it is suggested that the M-BCR methylation patterns are cell-lineage specific but some Ph+ ALL cells had a hypomethylation pattern that was identical to that observed in Ph- AML, suggesting a distinction of genetic diversity of leukemia cells with the Ph chromosome, especially Ph+ AL.
Leukemia 1993 Jun
PMID:The methylation status of the major breakpoint cluster region in human leukemia cells, including Philadelphia chromosome-positive cells, is linked to the lineage of hematopoietic cells. 850 75


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