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

Joining of the BCR and ABL genes is an essential feature of the group of human leukemias characterized by the Philadelphia chromosome and there is recent evidence that the human BCR-ABL fusion gene induces leukemia in experimental animals. Joining of these two genes is the result of cytogenetic translocation, usually the t(9;22)(q34;q11), but sometimes of more complex translocations involving one or more chromosomes in addition to chromosomes 9 and 22. The leukemic cells of some patients carry the BCR-ABL fusion gene but have an apparently normal karyotype. Recent studies show that these cells conceal complex chromosome rearrangements. Because the BCR-ABL fusion gene appears to be the result of cytogenetic rearrangement in all cases of these leukemias, the causes and mechanism of chromosome rearrangement will be relevant to the development of leukemia in man. We examine mechanisms of chromosome rearrangement and propose that both simple and complex chromosome translocations result from a single, though sometimes complex, interchange event.
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PMID:Complex chromosomal translocations in the Philadelphia chromosome leukemias. Serial translocations or a concerted genomic rearrangement? 175 91

To determine the role of the BCR-ABL gene in the proliferation of blast cells of patients with chronic myelogenous leukemia, leukemia blast cells were exposed to synthetic 18-mer oligodeoxynucleotides complementary to two identified BCR-ABL junctions. Leukemia colony formation was suppressed, whereas granulocyte-macrophage colony formation from normal marrow progenitors was unaffected. When equal proportions of normal marrow progenitors and blast cells were mixed, exposed to the oligodeoxynucleotides, and assayed for residual colony formation, the majority of residual cells were normal. These findings demonstrate the requirement for a functional BCR-ABL gene in maintaining the leukemic phenotype and the feasibility of gene-targeted selective killing of neoplastic cells.
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PMID:Selective inhibition of leukemia cell proliferation by BCR-ABL antisense oligodeoxynucleotides. 185 87

A patient is described with de novo acute non-lymphocytic leukemia of megakaryoblastic lineage with tri-lineage myelodysplasia. This patient was studied cytogenetically and using molecular genetic techniques throughout her clinical course. She had an N-ras mutation at diagnosis which persisted despite a bone marrow transplant, and acquired a Philadelphia chromosome associated with a P190 BCR-ABL transcript at clinical relapse 3 months post-transplantation.
Leukemia 1991 Aug
PMID:Megakaryoblastic leukemia with an N-ras mutation and late acquisition of a Philadelphia chromosome. 188 21

Chronic myelogenous leukemia (CML) is the best understood human cancer. The molecular basis of CML involves activation of a cellular proto-oncogene--ABL. The consequence is to increase tyrosine kinase activity. This results in a marked clonal increase in the myeloid mass. Later on, cellular maturation is blocked and the decrease eventuates in acute leukemia. Abnormalities of other proto-oncogenes or antioncogenes, like P53, may be involved in leukemia progression. Treatment of CML involves chemotherapy and, more recently, interferon. Whether this treatment prolongs survival or increases the likelihood of cure is unknown but either result seems unlikely. Bone marrow transplants which cure about 50% of persons with CML are most effective when performed in chronic phase.
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PMID:Chronic myelogenous leukemia: molecule to man. 189 3

The first consistent karyotypic abnormality found to be associated with neoplastic disease was the Philadelphia (Ph) chromosome (Nowell & Hungerford, 1960). Furthermore, the best-studied example of translocation-mediated gene activation occurs in leukaemia patients bearing this abnormality (reviewed by Kurzrock et al, 1988). In these individuals, the Ph translocation (t(9;22)(q34;q11)) results in transposition of the ABL proto-oncogene from chromosome 9q34 to 22q11, where it is fused with part of the BCR gene. It is now known that as a result of the Ph translocation, p160BCR and p145ABL (the normal BCR and ABL gene products) are replaced by p210BCR-ABL. This aberrant protein constitutes the molecular fingerprint of CML. The enhanced tyrosine phosphokinase enzymatic activity (a property possessed by some growth factor receptors and transformation-inducing oncogenes) of p210BCR-ABL implicates a direct role for this molecule in the pathogenesis of CML. Because the Ph translocation is present in the early chronic phase, the union of the BCR and ABL genes is probably involved in the initiation of the leukaemic process. The secondary molecular forces driving progression of CML to blast crisis are however unknown, and may differ from patient to patient. Approximately 10% of CML patients lack a Ph chromosome. One-half of these individuals have bcr rearrangement and express p210BCR-ABL. Ph+ and Ph- bcr+ (p210+) CML are identical and should be treated the same. Molecular follow-up of diploid bcr+ CML patients is essential for detection of persistent malignancy after therapy. The presence of a specific marker--the BCR-ABL message--permits the development of new diagnostic approaches for CML. For instance, detection of a BCR-ABL message with the use of the highly sensitive polymerase chain reaction, a technique capable of detecting up to one leukaemia cell amongst one million normal cells, yields important information about minimal residual disease. Finally, the use of therapy directed against the BCR-ABL product may be a worthwhile strategy which deserves investigation, and may prompt a new era of tumour-specific treatment.
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PMID:The molecular pathology of chronic myelogenous leukaemia. 193 6

Leukemia cells from adults with Philadelphia (Ph1)-chromosome positive chronic myelogenous leukemia (CML) have a characteristic molecular rearrangement between the BCR and ABL genes whereby major breakpoint cluster region (Mbcr) exons 2 or 3 are joined to ABL exon II. Ph1-chromosome positive CML is uncommon in children and it is unknown whether these children have similar rearrangements. We studied 17 children with Ph1-chromosome positive CML. Five were studied for Mbcr rearrangement using Southern blotting, nine for the presence of chimeric BCR-ABL mRNA using reverse transcription and polymerase chain reaction, and three for both. All eight children studied by Southern blotting had BCR rearrangement. Of 12 children in whom BCR-ABL mRNA was studied, 10 had Mbcr exon 2 joined to ABL exon II, one had Mbcr exon 3 joined to ABL II, and one had both Mbcr-ABL junctions. These data indicate a similarity to adult CML. However, mRNA processing in children may preferentially splice Mbcr exon 2 to ABL exon II. No child had BCR exon 1 joined to ABL exon II, the rearrangement typical of childhood Ph1-chromosome positive acute lymphoblastic leukemia.
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PMID:BCR-ABL rearrangements in children with Philadelphia chromosome-positive chronic myelogenous leukemia. 193 52

Previous studies have revealed a consistent defect in the cycling behavior of primitive neoplastic progenitor cells in patients with Philadelphia chromosome (Ph1)-positive chronic myeloid leukemia (CML). This is manifested both in vivo and in long-term cultures of CML cells as an increased rate of turnover amongst Ph1-positive progenitor cell types whose counterparts in normal individuals are mainly quiescent. To determine whether this deregulated proliferative activity of primitive Ph1-positive cells might be explained by a perturbation in the production of growth factors that regulate the turnover of primitive normal cells, the possibility of either autocrine or paracrine mechanisms of Ph1-positive cell stimulation was investigated. Northern blot analysis of total cellular RNA extracted from various CML blood cell populations showed no evidence of increased expression of granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage-CSF (GM-CSF), interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-3, IL-6, or tumor necrosis factor-alpha (TNF-alpha) compared with analogous normal peripheral blood cell populations in which transcripts for most of these growth factors are not detectable. A similar analysis of RNA extracted from the adherent layer of 4-week-old long-term cultures established from CML marrow (in which the Ph1-positive cells typically disappear) or from CML blood seeded onto normal marrow adherent layers (in which Ph1-positive cells typically persist) also revealed no difference in growth factor production compared with analogous cultures established with exclusively normal cells. For some of the growth factors studied, the assessment of bioactivity detectable in the medium confirmed the RNA data. There was also no evidence of a decreased production of putative inhibitors of primitive hematopoietic cells, i.e. transforming growth factor-beta and macrophage inflammatory protein-1 alpha by CML versus normal cells or cultures. These results do not support the existence of BCR-ABL induced autocrine or paracrine mechanisms in CML and suggest that constitutive activation of events normally dependent on growth factor receptor stimulation is more likely to underlie the lack of proliferation control exhibited by primitive Ph1-positive cells.
Leukemia 1991 Oct
PMID:Lack of evidence for abnormal autocrine or paracrine mechanisms underlying the uncontrolled proliferation of primitive chronic myeloid leukemia progenitor cells. 196 Oct 20

The BCR gene, on chromosome 22, is involved in the Philadelphia (Ph1) chromosome which is a characteristic cytogenetic marker of chronic myeloid leukaemia (CML). Breakpoints in CML occur within the M-bcr region (5.8 kb) which encompasses exons 12-15 (b1-b4), and the M-bcr can be conveniently divided into five zones by restriction mapping. One of these zones (3) contains exon b3 which can be either present or absent from the hybrid mRNA, even if it is present in the chimaeric gene. We have mapped the breakpoints around BCR exon b3 and related this to the type of RNA splice site expressed, in CML patients at diagnosis. Breakpoints within zone 3 were restriction mapped to one of six sub-zones and the site related to the type of RNA splice site. Two clusters of breakpoints within zone 3 were observed. One cluster was located around exon b3 and often resulted in deletion of exon b3 from the chimaeric gene. The majority of this cluster expressed b2-a2 spliced RNA, usually as a consequence of a deletion removing exon b3. The second cluster occurred within two sub-zones that spanned an Alu sequence, and 90% of this cluster exhibited b3-a2 spliced RNA. Furthermore, a greater number of patients had entered blast crisis if the RNA contained BCR exon b3 (8 of 10 patients), compared to those with b2-a2 spliced RNA (3 of 12 patients). The high degree of heterogeneity in the site of the breakpoint within zone 3 of the M-bcr, combined with the type of BCR-ABL hybrid mRNA expressed, further implicates BCR exon b3 in the pathogenesis of CML.
Leukemia 1991 Nov
PMID:Mapping of breakpoints, and relationship to BCR-ABL RNA expression, in Philadelphia-chromosome-positive chronic myeloid leukaemia patients with a breakpoint around exon 14 (b3) of the BCR gene. 196 Oct 34

The Philadelphia (Ph1) chromosome is present in greater than 90% of patients with chronic myelogenous leukemia (CML) and in 2% to 20% of those with acute leukemias, for which it is an important prognostic marker too. The chimeric BCR-ABL mRNAs resulting from the translocation encode either a 210-Kd or a 190-Kd protein. The techniques used to detect Ph1 chromosome include karyotyping, Southern analysis to demonstrate bcr rearrangement, and polymerase chain reaction to amplify the BCR-ABL transcripts. However, the routine performance of these methods by clinical laboratories is cumbersome, time consuming, and exposes laboratory personnel to radioisotopes. We describe here the clinical application of a new method, the hybridization protection assay (HPA), which uses chemiluminescent acridinium-ester-labeled probes in conjunction with PCR for detection of the amplified BCR-ABL sequences. The method is sensitive, specific, and can reliably distinguish between the transcripts for P190BCR-ABL and P210BCR-ABL. In contrast to the 2 days or longer required for conventional hybridization, HPA analysis can be completed in less than 30 minutes. We have successfully used this method to analyze 60 leukemia samples (34 from Ph1-negative acute leukemias; 6 from Ph1-positive acute leukemias; and 20 from CML) with complete correlation (of BCR-ABL positivity or negativity) with the results of karyotype or Southern Blot analysis of genomic DNA for bcr rearrangement. Therefore, the HPA, in conjunction with PCR, appears to provide a rapid and reliable test for the diagnosis of Ph1-positivity.
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PMID:Hybridization protection assay: a rapid, sensitive, and specific method for detection of Philadelphia chromosome-positive leukemias. 198 90

The Philadelphia chromosome (Ph) is the cytogenetic hallmark of chronic myeloid leukemia (CML) and as such has been used to confirm the diagnosis of CML based on morphological and clinical criteria. We have investigated 12 patients who were considered to have clinical and morphological features of CML and who did not have detectable abnormalities of chromosomes 9q34 or 22q11. In six of the 12 patients, rearrangement within the 5.8 kb major breakpoint region (M-bcr) and amplification of CML specific M-bcr-ABL cDNA sequences by the polymerase chain reaction (PCR) was demonstrated. Six other CML patients did not have rearrangement of the M-bcr gene or amplification of BCR-ABL by PCR. These patients had atypical CML. They were significantly older, most had less than 10% immature granulocytic cells (metamyelocytes, myelocytes and promyelocytes) and had various degrees of marrow fibrosis. Three of these six patients died of blastic transformation at 4, 15 and 54 months from diagnosis.
Leukemia 1991 Mar
PMID:Molecular diagnosis of Philadelphia negative CML using the polymerase chain reaction and DNA analysis: clinical features and course of M-bcr negative and M-bcr positive CML. 201 77


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