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

More than thirty small guanine nucleotide-binding proteins related to the ras-encoded oncoprotein, termed Ras or p21ras, are known. They regulate many fundamental processes in all eukaryotic cells, such as growth, vesicle traffic and cytoskeletal organization. GTPase-activating proteins (GAPs) accelerate the intrinsic rate of GTP hydrolysis of Ras-related proteins, leading to down-regulation of the active GTP-bound form. For p21ras, two GAP proteins are known, rasGAP and the neurofibromatosis (NF1) gene product. There is evidence that rasGAP may also be a target protein for regulation by Ras and be involved in downstream signalling. We have purified a GAP protein for p21rho, which is involved in the regulation of the actin cytoskeleton. Partial sequencing of rhoGAP reveals significant homology with the product of the bcr (breakpoint cluster region) gene, the translocation breakpoint in Philadelphia chromosome-positive chronic myeloid leukaemias. We show here that the carboxy-terminal domains of the bcr-encoded protein (Bcr) and of a Bcr-related protein, n-chimaerin, are both GAP proteins for the Ras-related GTP-binding protein, p21rac. This result suggest that Bcr could be a target for regulation by Rac and has important new implications for the role of bcr translocations in leukaemia.
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PMID:Bcr encodes a GTPase-activating protein for p21rac. 190 16

We have cloned 70 kb of DNA from chromosome 11p13 at the site of a recurrent translocation in T-cell leukaemia (T-ALL): t(11;14)(p13;q11). The translocation involves the TCR-delta gene on 14q11 and a new site on 11p13. Two new and 10 previously identified translocations all mapped within 25 kb on 11p13, the 11p13 T-cell translocation cluster (11p13 ttc). A search for expressed sequences surrounding the breakpoint cluster region on 11p13 identified a gene telomeric of all breakpoints which is overexpressed in three T-ALL samples with a t(11;14). The gene T-cell translocation gene (TTG-2) encodes a small cysteine-rich protein. Forty-eight per cent of the amino acids are identical with another translocation-deregulated gene, TTG-1 (T-cell translocation gene 1 or rhombotin) in 11p15. There are two copies of a cysteine-rich motif in both proteins. Two tandem copies of the same cysteine-rich motif are also present in the recently described lin-11, isl-1 and mec-3 gene products, and one motif is found in the CRIP protein. Therefore the proteins encoded by these two translocation-deregulated genes belong to this new class of cysteine-rich proteins with the 'LIM' motif, which are important in normal development.
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PMID:TTG-2, a new gene encoding a cysteine-rich protein with the LIM motif, is overexpressed in acute T-cell leukaemia with the t(11;14)(p13;q11). 192 11

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

The development of cancer is generally believed to occur by a multistep process in which critical genetic defects accumulate in a clone of cells, confer a growth advantage, and result in the emergence of more malignant subclones. This paper describes the clonal origin of cells in a patient with Philadelphia-chromosome negative, M-bcr rearrangement-positive chronic myelogenous leukemia, observed in two episodes of lymphoid blast crisis (BC), the intervening chronic phases (CP), and following allogeneic bone marrow transplantation. Serial analysis of immunoglobulin heavy and kappa light chain (IgJH, IgCK), beta-T-cell receptor (beta-TcR) and bcr major breakpoint cluster region (M-bcr) gene rearrangements was performed. Clonal IgJH rearrangements present in cells of the first lymphoblastic crisis (BC1) were altered during the chronic phase post-treatment (CP1), and were again altered in recurrent blast crisis (BC2). In addition, the M-bcr gene rearrangement present in BC1 and CP1 was absent from cells in BC2. These observations suggest that the course of clinical neoplastic disorders may not always be characterized simply by a hierarchical process of clonal evolution, but may also involve clonal succession of malignant cells. Moreover, the deletion of M-bcr in recurrent BC suggests that bcr/abl may not be essential for the maintenance of cell growth in established BC.
Leukemia 1991 Sep
PMID:Clonal succession and deletion of bcr/abl sequences in chronic myelogenous leukemia with recurrent lymphoid blast crisis. 194 28

The breakpoint localization was analyzed in 61 patients with Philadelphia chromosome (Ph) positive chronic myelogenous leukemia to compare the breakpoint localization and clinical course. All patients were treated with interferon alfa (IFN alpha) or IFN alpha plus IFN gamma at the time of the study. Thirty-three of the patients had been pretreated with other cytostatic drugs. Sixty-nine per cent of the breakpoints were located in the 5' region of the major breakpoint cluster region (M-bcr), 29% in the 3' part. There was no significant difference between these two groups with respect to response to IFN(s), clinical course or conversion to blast crisis, nor survival.
Leukemia 1991 Jun
PMID:Breakpoint localization within the M-bcr and clinical course do not correlate in patients with chronic myelogenous leukemia undergoing alfa interferon therapy. 205 69

Acute lymphoblastic leukemia (ALL) patients with a Philadelphia chromosome (Ph+ ALL) were treated with a combination of antineoplastic drugs recommended for both myeloid and lymphoid leukemia (BHAC-DMPV: behenoylcytosine arabinoside, daunorubicin, 6-mercaptopurine, prednisolone, and vincristine). Ph+ ALL patients with chromosome breaks which occur within the major breakpoint cluster region (M-BCR rearranged Ph+ ALL) were treated with natural interferon-alpha (IFN-alpha) after entering complete remission. In this study, four of seven patients with Ph+ ALL had M-BCR rearrangement, and all achieved complete remission with karyotypic normalization. Subsequent cytogenetic analysis during complete remission in two ALL patients with M-BCR rearrangement revealed that the percentage of bone marrow cells with the Ph chromosome increased, while the bone marrow maintained remission status. This cytogenetic-hematological discrepancy led us to consider that M-BCR rearranged Ph+ ALL might be a variant of chronic myelogenous leukemia, therefore, three Ph+ ALL patients with M-BCR rearrangement were treated with IFN-alpha after achieving complete remission. In contrast, only one of three patients with M-BCR non-rearranged Ph+ ALL obtained complete remission.
Leukemia 1991 Jul
PMID:Treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia: a pilot study which raises important questions. 207 47

The Philadelphia (Ph) chromosome translocation, t(9:22) (q34;q11) is found in some acute lymphoid leukaemias (ALL) and acute myeloid leukaemias (AML). Although cytogenetically all pH chromosomes appear similar, the 22q11 breakpoints found in acute leukaemias are of two kinds, those within the major breakpoint cluster region (Mbcr-1) of the BCR gene as found in chronic myelogenous leukaemia (CML), and those within the first intron of this gene. In the former group the molecular events are the same as those found in CML, p210 bcr-abl, encoded by 8.5 kb mRNA; however, a new aberrant protein, p190 bcr-abl, is found in the latter group. Ph translocation is also found in a few cases with malignant lymphoma, but it has not been characterized at the molecular level. We describe here a non-Hodgkin's lymphoma case with primary splenic presentation, which showed a complex Ph translocation. Neoplastic cells were of a B-cell origin (HLA-DR+, sIgM+, sIg lambda +, CALLA-). Molecular studies revealed the expression of p190 bcr-abl with no Mbcr-1 rearrangement. Our case indicates that the same Ph translocation as seen in acute leukaemias can be found in haematologic disorders other than leukaemias, suggesting that a c-abl gene activating mechanism may be involved in the pathogenesis of wide spectrum of haematologic malignancies.
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PMID:Philadelphia chromosome positive B-cell type malignant lymphoma expressing an aberrant 190 kDa bcr-abl protein. 209 24

We have analyzed the configuration of the immunoglobulin heavy (IgH) chain gene and the T cell receptor (TCR) chain (beta, gamma, and delta) genes in a group of 22 leukemia patients with the Philadelphia (Ph) chromosome. The group consisted of 14 patients with chronic myelogenous leukemia in blast crisis (CML-BC) and eight with Ph-positive acute leukemia (Ph + AL); these diagnoses were based on hematologic and cytogenetic features. In CML-BC patients, an IgH joining region rearrangement was detected only in patients with CD10 expression; TCR-beta, -gamma, or -delta rearrangements were associated with IgH involvement. In contrast, five of the eight Ph+ AL patients had breaks within the major breakpoint cluster region (M-BCR), and four of them had IgH involvement. Of the remaining three Ph+ M-BCR nonrearranged AL patients, only one showed IgH rearrangement. In addition, TCR-beta involvement was sometimes detected in Ph+ AL patients (two of the eight patients) with or without rearranged M-BCR, and no PH+ AL case displayed rearranged TCR-gamma. These findings suggest that genotypic changes in CML-BC are usually associated with phenotypic results of the neoplastic cells: the expression of CD10 in CML-BC patients is accompanied by the involvement of IgH with frequent TCR rearrangements which possibly are due to the common recombinase activity. On the other hand, the mechanism of the involvement of IgH in Ph+ AL patients without rearranged M-BCR seems different from that observed in Ph+ leukemia patients with rearranged M-BCR, although TCR involvement could occur whether or not the leukemia cells had a rearranged M-BCR in Ph+ AL patients.
Leukemia 1990 Aug
PMID:Immunoglobulin and T cell receptor gene rearrangements in Philadelphia chromosome-positive leukemia: a different involvement pattern in blast crisis and acute leukemia. 214 95

Chronic and blastic phase chronic myelogenous leukaemia cells have been studied by northern and Southern blot analysis. DNA from matched chronic and blastic phase cells obtained from the same patient demonstrated that the rearrangement site within the breakpoint cluster region did not change at the time of blastic crisis. A search for a mutation in a controlling region of the first exon of c-myc also failed to demonstrate any new abnormality at the time of blastic crisis. While some differences in the transcript levels for several genes (c-myc, p53, histone H3, MRS) were detected, these differences could be ascribed to differences in the proportions of immature cells during the chronic and blastic phases. The data suggested that the c-myc transcripts in blastic phase cells and in immature chronic phase cells differ in that the latter contain some c-myc transcripts that are not polyadenylated. Differences in c-myc transcript half-life could contribute to the differences in the behaviour of chronic phase and blastic phase immature cells.
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PMID:Studies of proto-oncogene expression in the chronic and blastic phases of chronic myelogenous leukemia. 214 22

We report two cases of Philadelphia (Ph1) chromosome positive acute mixed lineage leukemia (AMLL) with breakpoint cluster region (bcr) (M-BCR-1) rearrangement. A 31 year-old-man (case 1) and a 42 year-old-woman (case 2) were admitted to our hospital for further evaluation of leucocytosis with atypical blasts. Each case was diagnosed as having bilineal type of AMLL because: (1) blasts in each case consisted of larger myeloid cells positive for myeloperoxidase and small lymphoid cells positive for PAS, and blasts in case 2 were positive for TdT; (2) blasts in case 1 expressed B lymphoid associated antigen; (3) Southern analysis in each case showed clonal rearrangements of both the immunoglobulin heavy chain and the T cell receptor beta gene. These two cases demonstrated the Ph1 chromosome and rearrangement of the bcr (M-BCR-1) gene, but none of splenomegaly, basophilia, and additional chromosome abnormalities were observed. In addition, after achieving remissions, they didn't revert to chronic phase of chronic myelogenous leukemia (CML) and showed normal neutrophil alkaline phosphatase scores, and the Ph1 chromosome disappeared completely in case 1 and coexisted with the normal chromosome in case 2. These findings suggest that diagnosis of both cases should not be CML blast crisis (BC) but Ph1 positive acute leukemia, and Ph1 positive AMLL may be a distinct clinical entity to be distinguished from CML-BC.
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PMID:[Philadelphia chromosome positive acute mixed lineage leukemia with bcr (M-BCR-1) rearrangement]. 215 95


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