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

Chromosomal translocation within B and T cell malignancies has proven a rich source for proto-oncogenes. The obligate DNA breaks within immunoglobulin (Ig) and T cell receptor (TCR) loci are frequently the sites of recurrent translocations. Burkitt's lymphoma established the paradigm by introducing the myc oncogene from chromosome segment 8q24 into the Ig heavy chain gene locus at 14q32. Molecular cloning of an aberrant Ig rearrangement in follicular lymphoma revealed Bcl-2. Bcl-2 constitutes the first member of a new category of oncogenes: regulators of programmed cell death. Bcl-2 blocks apoptosis and maintains long-term immune responsiveness including B-cell memory. The PRAD1 gene of parathyroid adenomas appears to be the elusive Bcl-1 gene of t(11;14)(q13;q32) bearing lymphomas. It proves to be a novel G1 cyclin. Acute lymphoblastic leukemias (ALL) pre-B phenotype produce a E2A/PBX fusion protein that possesses the leucine zipper of E2A with the homeodomain of PBX. Two molecular forms of the BCR/ABL fusion protein are produced by the Philadelphia chromosome. A deregulated p210 tyrosine kinase is found in chronic myelogenous leukemia, while a p190 form predominates in Ph+ ALL. In contrast, T-cell ALLs introduce a potpourri of genes into their T cell receptor loci. However, a common theme is emerging. These oncogenes (Ttg1, Ttg2, SCL, LylI, H0X11) all belong to classic families of transcription factors, possessing LIM domains, helix-loop-helix motifs, or homeodomains. Provocatively, these transcription factors are normally intended for lineages other than T cells. These genes have widened the horizons of both oncogenesis and normal development.
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PMID:Chromosomal translocations in lymphoid malignancies reveal novel proto-oncogenes. 159 Oct 3

The 9p21 locus has been deleted at a high frequency in a wide variety of tumors. Recently, two genes, p16INK4A and p15INK4B (also called MTS1 and MTS2), have been localized in close proximity at the 9p21 locus, encoding cyclin-dependent kinases 4/6 inhibitors of relative molecular mass 16 kD and 15 kD, respectively and also found to be deleted at a high frequency in tumor cell lines. We analyzed p16INK4A and p15INK4B genes in 178 cases of primary leukemias including 81 cases of chronic lymphocytic leukemia (CLL), seven of hairy cell leukemia (HCL), seven of chronic myelogenous leukemia (CML), 43 of acute myelogenous leukemia (AML), 27 of acute lymphoblastic leukemia (ALL), and 13 of myelodysplastic syndrome (MDS) by Southern blot analyses. The ALL cases showed a relatively high frequency of homozygous deletions (22%, 6 of 27) at the p16INK4A gene locus. Interestingly, of the six cases with p16INK4A homozygous deletions, only three showed homozygous deletions at the p15INK4B gene. In 81 CLL patients, we detected one homozygous and five heterozygous deletions at both the p16INK4A and p15INK4B genes and two heterozygous deletions at the p16INK4A gene alone. Deletion of these two genes in AML cases is relatively low (9%). We did not detect deletions in any of the MDS, HCL, and CML cases examined. Sequence analyses of p16INK4A gene of six CLL cases with heterozygous deletion at this locus showed a 27-bp deletion at the splice acceptor site of intron 1 in one case and changes in the coding sequence in three other cases. The data presented in this report showed that (1) p16INK4A and p15INK4B genes are preferentially deleted homozygously in ALL and heterozygously in CLL cases with frequent mutation in the second allele, and (2) p16INK4A gene appears to be more frequently deleted than p15INK4B gene.
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PMID:p16INK4A and p15INK4B gene deletions in primary leukemias. 779 38

p21 is induced by and mediates the effects of p53 in response to DNA damage arresting the cell in G1 or G2, by inhibiting multiple cyclin-cyclin-dependent kinases (CDK) or binding to proliferating-cell nuclear antigen (PCNA), respectively. To determine whether p21 mutants occur in tumors we examined DNA from 188 primary non-Hodgkin's B-cell lymphoma (NHL) tumors and 84 chronic myelogenous leukemia samples for mutational changes in the coding region of p21 by single-strand conformation polymorphism (SSCP) analysis and direct sequencing of polymerase chain reaction (PCR)-amplified DNA. We did not find mutations in the coding region in these two tumor types. We identified a polymorphic nucleotide change in codon 31 in which a transversion from C to A substituted amino acid arginine for serine. Three of 188 NHL tumors were homozygous for this change, but they were not identified in 84 CMLs or in 97 normal controls. On the other hand, in one CML case a transition from G to A in codon 64 substituted amino acid threonine for alanine. These data do not indicate that derangements in the coding region of p21 contribute to the initiation and/or progression of these tumors.
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PMID:Absence of somatic changes in p21 gene in non-Hodgkin's lymphoma and chronic myelogenous leukemia. 865 61

Progression of eukaryotic cells through major cell cycle transitions is mediated by sequential assembly and activation of regulators, the cyclin-dependent CDKkinases (CDKs). Recent studies have identified different CDK inhibitory genes (CDKis), and two of them, p16ink4a/MTS1/CDKN2 and p15ink4b/MTS2 are both mapped to chromosome 9p21 and inhibit cyclin D-CDK4 and -CDK6 complexes. A feedback regulatory loop involving pRb, p16ink4a, and CDKs seems to regulate G1/S phases transition. p16ink4a and p15ink4b are deleted in high frequency in human cell lines and in some fresh solid tumors. Point mutations of p16ink4a have also been sequenced, especially in familial melanomas and digestive cancers but preferential mechanism of p16ink4a/p15ink4b inactivation seems to be biallelic deletion. In hematological malignancies, homozygous deletions of p16ink4a and p15ink4b occur frequently in acute lymphoblastic leukemia (ALL) (14-40%), lymphoid type blast crisis of chronic myeloid leukemia (CML), and adult T cell leukemia (ATL), but p16ink4a deletions are more frequent than p15ink4b deletions, and hemizygous deletions of either p16ink4a and p15ink4b are rare. In ALL an association of homozygous deletions of p16ink4a and p15ink4b, and T-lineage, 9p abnormalities, and prognostic factors was found in some but not all reports. This review presents recent data on p16ink4a and p15ink4b functions and analyses their implications in hematological malignancies.
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PMID:p16ink4a gene and hematological malignancies. 872 24

Cell proliferation control is ensured by a group of proteins named cyclin-dependent kinases (CDKs), the activation of which is dependent on phosphorylation and cyclin association. In parallel, these CDKs are negatively controlled by two distinct groups of inhibitory proteins, the cyclin-dependent kinase inhibitors (CKIs). The first group, including p16Ink4a, p15Ink4b, p18Ink4c and p19Ink4d, is specific for the G1 CDKs, CDK4 and CDK6, inhibiting the kinase activity of cyclin D/CDK4-CDK6 complexes on pRb. p16Ink4a, down-regulated by pRb, inhibits G1 CDKs by competition with cyclin D; p15Ink4b, the synthesis of which is induced by TGF beta, seems to be a mediator of TGF beta-mediated cell cycle arrest. Furthermore, p18Ink4c inhibits CDK6 phosphorylation and activation by CAK. The second CKIs family is constituted by p21Waf1, p27Kip1 and p57Kip2. Their inhibitory action concerns a large range of cyclin/CDK complexes involved in G1 and S phase. p21Waf1, induced in part by p53, is up-regulated by senescence, DNA damage and cellular differentiation. p21Waf1 forms quaternary complexes with CDKs, cyclins and PCNA. Its inhibitory action, preventing CDK from phosphorylation, depends on the stoichiometry of the components. As p15Ink4b, p27Kip1 causes late G1 cell cycle arrest after TGF beta treatment and contact inhibition. The implications of CKIs in hematological malignancies are function of deletions or mutations of their genes. p16Ink4a and p15Ink4b genes, localized on 9p21, present frequent homozygous deletions in ALL T, ATL and lymphoblastic acutisation of CML. The other CKIs present very rare homozygous deletions or mutations, particularly p21Waf1 and p27Kip2. However, reduction of inhibitory activity due to hemizygous deletions might favour leukemogenesis.
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PMID:Cyclin-dependent kinase inhibitors (CKIs) and hematological malignancies. 889 23

Bcr-Abl is a constitutively active tyrosine kinase that is expressed in Philadelphia chromosome (Ph1)-positive human leukemias. Bcr-Abl has been shown to inhibit apoptosis and cause anchorage independent growth. However, its ability to activate mitogenic signaling pathways is controversial. Here we show that Bcr-Abl signaling prevents down-regulation of cyclin-dependent kinase activity and cell cycle arrest after growth factor deprivation of hematopoietic progenitor cells. Using an inducible system to regulate Bcr-Abl expression, we also demonstrate that Bcr-Abl expression is sufficient to induce G1-to-S phase transition, DNA synthesis, and activation of cyclin-dependent kinases in cells that were arrested in G0 by growth factor deprivation. Furthermore, Bcr-Abl activates Ras, Erk, and Jnk pathways as a primary consequence of expression. These data show that Bcr-Abl is one of a select group of oncogenes that is capable of both inhibiting apoptosis and deregulating cell proliferation. The combination of these activities is likely to be important for the progression of CML.
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PMID:The Bcr-Abl tyrosine kinase activates mitogenic signaling pathways and stimulates G1-to-S phase transition in hematopoietic cells. 939 77

The selective and conspicuous absence of a novel receptor-Ck (having affinity for cholesterol moiety in lipoproteins and intrinsic tyrosine kinase activity) in various leukemic cell lines/patients, prompted us to explore the nature of interrelationship between receptor-Ck deficiency and over-expression of genes coding for bcl-2, cyclin 'D', chimeric bcr-abl, c-myc and LDL-receptor in the human promyelocytic leukemic cell line (HL-60). This study revealed unambiguously that deregulated expression of these genes is primarily due to the inability of these cells to express the receptor-Ck gene. Based upon the observations we propose that 'receptor-Ck' deficiency may be responsible for the initiation of chronic myeloid leukemia.
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PMID:Receptor-Ck-dependent regulation of genes in HL-60 cell line. 944 38

Effect of low-density lipoprotein (LDL) on the expression of Bcl-2 as well as cyclin 'D' genes was studied in Receptor 'Ck' (+ve) and Receptor 'Ck'(-ve) human lymphocytes. LDL had no effect upon the elevated levels of Bcl-2 and cyclin 'D' gene products in Receptor 'Ck' (-ve) lymphocytes (from untreated CML patients), whereas in Receptor 'Ck' (+ve) lymphocytes (from normal subjects), the exposure to LDL regulated the level of cyclin 'D' gene product without initiating the expression of bcl-2 gene product. However, blockage of Receptor 'Ck' in normal lymphocytes, through its specific antibody (Ab-RCk) in presence or absence of LDL, resulted in the induction of both cyclin 'D' (at 4 h interval) and bcl-2 (at 12 h interval) gene products. Based upon these results, we propose that Receptor 'Ck' deficiency in cells may inherit defective apoptosis and capacity proliferation leading to leukemic transformation.
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PMID:LDL-dependent regulation of Bcl-2 and cyclin 'D' gene expression in lymphocytes from normal and CML patients. 957 Mar 62

Chronic myeloid leukemia (CML) is characterized by an increased proliferative activity of the leukemic progenitors that produce an elevated number of mature granulocytes. Nevertheless, cell cycle-active agents, even in very high doses, are alone unable to eradicate the leukemic clone, suggesting the presence of a rare subset of quiescent leukemic stem cells. To isolate such cells, we first used Hoechst 33342 and Pyronin Y staining to obtain viable G(0) and G(1)/S/G(2)/M fractions of CD34(+) cells by fluorescence-activated cell sorting (FACS) from 6 chronic-phase CML patients' samples and confirmed the quiescent and cycling status of the 2 fractions by demonstration of expected patterns of Ki-67 and D cyclin expression. Leukemic (Ph(+)/BCR-ABL(+)) cells with in vitro progenitor activity and capable of engrafting immunodeficient mice were identified in the directly isolated G(0) cells. Single-cell reverse transcriptase-polymerase chain reaction (RT-PCR) analysis showed that many leukemic CD34(+) G(0) cells also expressed BCR-ABL mRNA. CD34(+) from 8 CML patients were also labeled with carboxyfluorescein diacetate succinimidyl diester (CFSE) before being cultured (with and without added growth factors) to allow viable cells that had remained quiescent (ie, CFSE(+)) after 4 days to be retrieved by FACS. Leukemic progenitors were again detected in all quiescent populations isolated by this second strategy, including those exposed to a combination of flt3-ligand, Steel factor, interleukin-3, interleukin-6, and granulocyte colony-stimulating factor. These findings provide the first direct and definitive evidence of a deeply but reversibly quiescent subpopulation of leukemic cells in patients with CML with both in vitro and in vivo stem cell properties.
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PMID:Isolation of a highly quiescent subpopulation of primitive leukemic cells in chronic myeloid leukemia. 1047 35

Chronic myeloid leukemia (CML) is a malignant stem cell disease characterized by an expansion of myeloid progenitor cells expressing the constitutively activated Bcr-Abl kinase. This oncogenic event causes a deregulation of apoptosis and cell cycle progression. Although the molecular mechanisms protecting from apoptosis in CML cells are well characterized, the cell cycle regulatory event is poorly understood. An inhibitor of the cyclin-dependent kinases, p27, plays a central role in the regulation of growth factor dependent proliferation of hematopoietic cells. Therefore, we have analyzed the influence of Bcr-Abl in the regulation of p27 expression in various hematopoietic cell systems. An active Bcr-Abl kinase causes down-regulation of p27 expression in murine Ba/F3 cells and human M07 cells. Bcr-Abl blocks up-regulation of p27 after growth factor withdrawal and serum reduction. In addition, p27 induction by transforming growth factor-beta (TGF-beta) is completely blocked in Bcr-Abl positive M07/p210 cells. This deregulation is directly mediated by the activity of the Bcr-Abl kinase. A Bcr-Abl kinase inhibitor completely abolishes p27 down-regulation by Bcr-Abl in both Ba/F3 cells transfected either with a constitutively active Bcr-Abl or with a temperature sensitive mutant. The down-regulation of p27 by Bcr-Abl depends on proteasomal degradation and can be blocked by lactacystin. Overexpression of wild-type p27 partially antagonizes Bcr-Abl-induced proliferation in Ba/F3 cells. We conclude that Bcr-Abl promotes cell cycle progression and activation of cyclin-dependent kinases by interfering with the regulation of the cell cycle inhibitory protein p27. (Blood. 2000;96:1933-1939)
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PMID:Bcr-Abl kinase down-regulates cyclin-dependent kinase inhibitor p27 in human and murine cell lines. 1096 97


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