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Query: UMLS:C0023473 (chronic myeloid leukemia)
 18,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Philadelphia chromosome (Ph') is found in the blood cells of about 90% of patients with chronic myeloid leukaemia (CML) and usually results from the reciprocal chromosome translocation t(9;22). This translocation relocates the proto-oncogene c-abl, normally found on chromosome 9q34, to within the breakpoint cluster region (bcr) on chromosome 22q11 (refs 3-8). The juxtaposition of c-abl and the 5' portion of bcr appears to be the critical genomic event in CML and results in a novel 8-kilobase (kb) fused abl/bcr transcript and a c-abl-related protein of relative molecular mass 210,000 (ref.11). About 10% of adult patients diagnosed as CML lack the Ph' chromosome; they represent a heterogeneous group of disorders which are difficult to diagnose precisely. We have examined five patients with CML whose leukaemic cells have a normal karyotype. We report here that two of the patients showed the same genomic change as occurs in Ph'-positive CML, but the change resulted from a mechanism other than chromosomal translocation. The remaining three patients showed no genomic rearrangement. This genomic diversity correlated with the clinical differences between the patients.
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PMID:Genomic diversity correlates with clinical variation in Ph'-negative chronic myeloid leukaemia. 300 92

The Philadelphia chromosome translocation, which is present in 90-95% of chronic myelogenous leukemia patients, involves translocation of the c-abl protooncogene to chromosome 22 and is accompanied by activation of embryonic globin gene expression in the K562 chronic myelogenous leukemia cell line. To test directly if the protein products of the translocated c-abl protooncogene can activate embryonic globin gene expression, we transfected the v-abl oncogene (which shares the property of autophosphorylation with the translocated c-abl protooncogene) into mouse erythroleukemia cells. v-abl-transfected mouse erythroleukemia cells, which contained multiple copies of the v-abl transgenome, exhibited activation of mouse embryonic globin gene expression. These results suggest that the translocated c-abl protooncogene of the Philadelphia chromosome translocation is central to the pathogenesis of chronic myelogenous leukemia and that it may result in the activation of embryonic globin genes in some chronic myelogenous leukemia cell lines.
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PMID:v-abl activates embryonic globin gene expression in mouse erythroleukemia cells. 300 48

To examine whether determination of (1) the copynumber or restriction pattern of certain oncogenes or (2) the mutational activation of the N-ras gene might contribute to the risk classification of acute lymphoblastic leukemia of childhood (ALL), we investigated DNA isolated from lymphoblasts of untreated patients. Restriction enzyme analysis of cellular oncogenes was performed on DNA of 25 patients. No rearrangements could be demonstrated within or near the genes c-myc, c-myb, c-abl, bcr, c-Ki-ras, and N-ras. No amplifications of these genes nor of N-myc or c-Ha-ras were present. Eight of 21 patients were heterozygote for "rare" Ha-ras allelic restriction fragments that have been associated with an increased risk of developing a malignancy. These patients were clinically indistinguishable from patients lacking these fragments. The breakpoint cluster region (bcr) that is rearranged in all patients with Philadelphia chromosome positive chronic myeloid leukemia, was normal in all cases, including at least one patient with Philadelphia chromosome positive ALL. A 2.8 kb HindIII fragment of a hitherto unknown gene or pseudogene related to v-myb probably derives from the Y chromosome. Nineteen patients were examined for point mutations in the N-ras gene, using a novel synthetic oligonucleotide hybridization assay. In two patients activating point mutations were present, both in positions 1 of the 12th codon. Both patients were somewhat older than the others (16 and 11 years), had L2 morphology, and were shown to have high growth fractions of tumor in their bone marrow.
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PMID:Absence of oncogene amplifications and occasional activation of N-ras in lymphoblastic leukemia of childhood. 301 Nov 51

We surveyed 20 Philadelphia chromosome (Ph1) positive chronic myelogenous leukemia (CML) samples by Southern blot hybridization to determine the location of the breakpoints that occur on chromosomes 9 and 22 in the Ph1 translocation. Only 3 of 20 samples exhibited breakpoints on chromosome 9 within 18 kilobases (kb) of the v-abl homologous sequences. Mapping of these three chromosome 9 breakpoints indicates that each is at a separate location within this 18-kb region, indicating that there are no breakpoint "hot spots" in this area. In contrast, all 20 CML samples exhibited breaks on chromosome 22 within a 5.0-kb Bgl II fragment that lies within the previously described breakpoint cluster region (bcr). Several patients with CML blast crisis exhibiting multiple Ph1 chromosomes/metaphase exhibited amplified and rearranged c-abl-related fragments. These additional Ph1 chromosomes in blast crisis cells do not arise from a second, independent 9:22 translocation but rather result from a duplication of the preexisting Ph1 chromosome.
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PMID:Breakpoints on chromosomes 9 and 22 in Philadelphia chromosome-positive chronic myelogenous leukemia (CML). Amplification of rearranged c-abl oncogenes in CML blast crisis. 302 20

In the DNAs of all Ph1-positive chronic myelocytic leukemia patients studied to date, a breakpoint on chromosome 22 (the Ph1 chromosome) can be demonstrated with a probe from the bcr (breakpoint cluster region). Although the K562 cell line was established from cells of a chronic myelocytic leukemia patient, we have been unable to detect the Ph1 chromosome by cytogenetic means. Employing a probe from the 5' region of bcr, we have cloned an amplified Ph1 breakpoint fragment from K562. This demonstrates that K562 contains multiple remnants of a Ph1 chromosome with a breakpoint within bcr and thus may serve as a model system for the study of Ph1-positive chronic myelocytic leukemia at a molecular level. The isolation of bcr cDNA sequences shows that parts of bcr encode a protein. Employing K562, we demonstrate the presence of an abnormally sized mRNA species hybridizing to c-abl and to a bcr cDNA probe, indicating the possible consequence of the Ph1 translocation on a transcriptional level in chronic myelocytic leukemia. The isolation and sequencing of a cDNA containing the breakpoint area of this mRNA provide further evidence for its chimeric structure. Cloning of large stretches of chromosomal DNA flanking bcr and c-abl sequences in K562 and identification of the exons participating in the formation of the chimeric mRNA shows that a splice of at least 99 kilobases is made to fuse the 3' bcr exon to the 5' c-abl exon. Furthermore two chimeric cDNAs were isolated containing chromosome 9 sequences that map 43.5 kilobases downstream from the K562 breakpoint. These chromosome 9 sequences neither hybridize to the 8.5-kilobase chimeric c-abl mRNA nor to normal c-abl mRNAs in Hela cells and probably represent incorrect splicing products present in the K562 cell line.
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PMID:The chronic myelocytic cell line K562 contains a breakpoint in bcr and produces a chimeric bcr/c-abl transcript. 302 59

Chronic myelogenous leukemia (CML) is associated with the Philadelphia (Ph) chromosome, which results from a reciprocal translocation between chromosomes 9 and 22. This activates the abl oncogene by moving it from chromosome 9 and combining it with sequence located on chromosome 22. The new fusion gene, with chromosome 22 sequence at its 5' end and chromosome 9-abl sequence at its 3' end, generates a new messenger RNA (mRNA) and protein that are implicated in the pathogenesis of CML. The breakpoint near the c-abl locus on chromosome 9 can occur within a large area. In contrast, the breakpoints on chromosome 22 are concentrated within a 6 kilobase (kb) region termed the breakpoint cluster region (bcr). This study was designed to determine whether chronic-phase and blast crisis patients had identifiable differences in the structure of their Ph chromosomes. Restriction mapping of the chromosome 22 translocation breakpoints performed for 26 patients showed that the breakpoints of eight of the nine patients in blast crisis were in the 3' portion of the bcr, whereas the breakpoints in the 17 patients in the chronic phase were clustered in the 5' portion of the bcr. This suggests a strong correlation between a 3' bcr breakpoint and blast crisis in CML.
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PMID:CML patients in blast crisis have breakpoints localized to a specific region of the BCR. 303 13

We report the clinical evaluation of an improved DNA probe assay for the characteristic genetic marker of human CML, observed by cytogenetics and designated the Philadelphia chromosome (Ph1). The Ph1 chromosome results from the fusion of c-abl proto-oncogene sequences from chromosome 9 to phl gene sequence on chromosome 22. (The phl gene is often referred to as bcr. However, for clarity we prefer to reserve the designation "bcr" for the region within the phl gene in which translocation breakpoints have been found to occur. We also find it useful to distinguish between two such regions in phl, bcr-210 and bcr-190, named after the 210- and 190-kDa phl/abl fusion proteins resulting from translocations with breakpoints in the respective regions. We refer to the corresponding chromosomal translocations as Ph1(bcr-210) and Ph1(bcr-190).) DNA, extracted from peripheral blood (PB) or bone marrow (BM) and digested with restriction endonuclease BglII, is hybridized with a probe (phl/bcr-3) spanning a breakpoint cluster region within phl. Rearrangements are revealed by the presence of one or two novel junction fragments. Clinical specimens from leukemic patients with active disease were compared by cytogenetic and DNA probe analysis at seven centers in the United States and Europe. The probe assay identified the phl rearrangement in 190 of 191 cases of Ph1-positive CML, as well as in 12 of 27 clinically diagnosed CML specimens lacking a typical Ph1 chromosome. DNA rearrangements also were seen in two of six cases of Ph1-positive ALL. No false positive results were obtained among 93 non-leukemic controls. Mixing experiments showed that the DNA probe assay can detect as few as 1% leukemic cells in a specimen. A preliminary study of CML patients in remission after allogeneic BM transplantation revealed a small fraction of residual Ph1-positive leukemic cells in a significant number of such patients.
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PMID:Clinical evaluation of a DNA probe assay for the Philadelphia (Ph1) translocation in chronic myelogenous leukemia. 305 Feb 93

We report a case of 62-year-old Japanese male with a myelodysplastic syndrome (MDS) with a Philadelphia (Ph) chromosome. Cytogenetic analysis revealed the bone marrow cells to contain a Ph chromosome due to t(?;11;22) (?;q11;q11), as well as -5, -7, +8, -12 and an extra Ph, in addition to cells with a normal karyotype. Molecular analysis using breakpoint cluster region probes (5' bcr and 3' bcr) did not detect a rearrangement within the bcr DNA sequences, indicating that the breakpoint at 22q11 occurred outside the bcr. Furthermore, the bone marrow cells from this patient did not express an 8.5 kb c-abl mRNA. Thus, the Ph translocation in this case differs from that of Ph-positive chronic myelogenous leukemia.
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PMID:Molecular implications of Ph (+) myelodysplastic syndrome. 306 68

In an attempt to further substantiate the involvement of the c-abl oncogene in the genesis of chronic myelogenous leukemia (CML) and acute lymphocytic leukemia (ALL), we performed in-situ hybridization with the c-abl probe on metaphase chromosomes of a healthy control, a karyotypically normal non-CML leukemia, three cases of CML with t(9;22), t(13;22) and t(3;9;22), one blast phase CML with t(9;22), Ph, + Ph, and one ALL with t(9;22), Ph, + Ph. The aberrant 9q could be cytogenetically identified in all cases except t(13;22). The molecular data clearly demonstrated the involvement of the c-abl in t(13;22) and the karyotype was revised to t(9;13;22). All patients, except the control, showed the altered c-able/bcr rearrangement that has been demonstrated in the Ph-chromosome from the standard t(9;22) translocation. These findings suggest that genomic diversities have important clinical differences in these two diseases. The amalgamation of information from cytogenetic and molecular data on cases where translocations are not precise or difficult to identify, will lead towards a deeper understanding of leukemias.
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PMID:Further evidence of the involvement of the c-abl oncogene in chronic myelogenous leukemia and acute lymphocytic leukemia. 307 67

Cytogenetic and enzymatic studies have shown that chronic myeloid leukemia (CML) represents the clonal proliferation of a pluripotent stem cell. The Philadelphia chromosome (Ph') is the characteristic karyotypic abnormality seen in this disease, although the exact role of this clonal marker in the pathogenesis of CML is uncertain. At a molecular level, the Ph' has recently been shown to represent the translocation of c-abl to a limited (breakpoint cluster region, bcr) on chromosome 22. We have used probes for the bcr gene to obtain molecular evidence for the clonal origin of blast crisis in 2 patient with CML. In both cases, the first with myeloid and the second with lymphoid blast crisis, there was rearrangement of the bcr gene. The patterns of rearrangement varied between patients but were identical when comparing acute and chronic phases within the same individual. As the Ph' translocation is thought to represent a random recombination event these data not only provide further evidence for the clonal origin of blast crisis in CML, but also suggest that in the second patient this translocation event had already occurred at the pluripotent stem cell.
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PMID:Molecular evidence for the clonal origin of blast crisis in chronic myeloid leukaemia. 308 1


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