UMLS:C0023467 - FACTA Search

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Query: UMLS:C0023467 (acute myeloid leukemia)
35,200 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We recently reported an internal tandem duplication of the human flt3 receptor gene (FLT3) as a somatic mutation in 17% of acute myelogenous leukemia (AML). The present study revealed the duplication at the juxtamembrane and the first tyrosine kinase domains of FLT3 in seven of 92 (8%) patients with myelodysplastic syndrome (MDS) and AML with trilineage myelodysplasia (AML/TMDS), the diseases which may represent neoplastic changes of pluripotent stem cells. A tandem duplication of exon 11 of FLT3 was harbored by two of 58 (3%) patients with MDS and five of 34 (15%) with overt leukemia, including MDS-derived leukemia, AML/TMDS and therapy-related leukemia. Although the duplicated regions varied within exon 11 in each case, they occurred in-frame, and altered mRNA expressions were demonstrated by reverse-transcription polymerase chain reaction. Two cases of MDS with a FLT3 duplication transformed to overt leukemia within a few months. Longitudinal analyses in two other patients with leukemia revealed that the duplication was a late genetic event during the disease course; one of whom showed two independent duplications of FLT3 at the terminal therapy-resistant phase. Of seven patients with the FLT3 duplication, six had abnormal karyotypes, and four harbored a point mutation of the N-RAS and/or TP53 genes. Patients with FLT3 mutations have poor prognoses. This study uncovered the fact that the accumulation of genetic events, including FLT3 duplication, correlates with leukemic transformation from antecedent myelodysplasia and with subsequent disease progression.
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PMID:Tandem duplications of the FLT3 receptor gene are associated with leukemic transformation of myelodysplasia. 930 95

FLT3 is a member of receptor tyrosine kinases expressed in leukemia cells, as well as in hematopoietic stem cells. Recently, a somatic alteration of the FLT3 gene was found in acute myeloid leukemia, as an internal tandem duplication (FLT3/ITD) which caused elongation of the juxtamembrane (JM) domain of FLT3. Here we characterized the FLT3/ITD and investigated its clinical significance in acute promyelocytic leukemia (APL). Seventy-four newly diagnosed patients with APL, who were treated with the same protocol in a multi-institutional study, were studied for the FLT3/ITD. Genomic and message sequences of the FLT3 gene were amplified by means of polymerase chain reaction (PCR), and elongated PCR products were sequenced. Fifteen patients (20.3%) had FLT3/ITD, all of which were transcribed in frame. Location of the duplicated fragments (six to 30 amino acids) varied from patient to patient. However, they always contained either Y591 or Y599, but the tyrosine kinase domain was not significantly affected. This finding implied that signal transduction of FLT3 is amplified by the duplication. Clinically, the presence of FLT3/ITD was related to high peripheral white blood cell counts as well as peripheral leukemia cell counts (P < 0.0001), high LDH level (P = 0.04), and low fibrinogen concentration (P = 0.04). These data suggest that FLT3/ITD plays a significant role in progression of APL.
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PMID:Internal tandem duplication of FLT3 associated with leukocytosis in acute promyelocytic leukemia. Leukemia Study Group of the Ministry of Health and Welfare (Kohseisho). 930 96

In this study, we examined a large number of patients to clarify the distribution and frequency of a recently described FLT3 tandem duplication among hematopoietic malignancies, including 112 acute myelocytic leukemia (AML), 55 acute lymphoblastic leukemia (ALL), 37 myelodysplastic syndrome (MDS), 20 chronic myelogenous leukemia (CML), 30 non-Hodgkin's lymphoma (NHL), 14 adult T cell leukemia, 15 chronic lymphocytic leukemia (CLL) and 38 multiple myeloma (MM). We also evaluated 71 cell lines derived from 11 AML, 31 ALL, two hairy cell leukemia, three acute unclassified leukemia, 10 CML, 12 NHL including six Burkitt's lymphoma, and two MM. Using genomic PCR of exon 11 coding for the juxtamembrane (JM) domain and first amino acids of the 5'-tyrosine kinase (TK) domain, this length mutation was found only in AML (22/112, 20%) and MDS (1/37). According to the FAB subclassification, they were 5/18 (28%) of M1, 4/29 (14%) of M2, 3/17 (18%) of M3, 6/24 (25%) of M4, 4/20 (20%) of M5 and 1/9 of refractory anemia with excess of blast in transformation. In the various cell lines examined, this abnormality was determined in only one derived from AML and never found in other hematological malignancies. The sequence analysis of the abnormal PCR products revealed that 23 of 24 showed internal tandem duplication with or without insertion of nucleotides. In one AML, insertion and deletion without duplication was determined. All 24 lengthened sequences were in-frame. Duplication takes place in the sequence coding for the JM domain and leaves the TK domain intact. In conclusion, we emphasize that the length mutation of FLT3 at JM/TK-I domains were restricted to AML and MDS. Since all these mutations resulted in in-frame, this abnormality might function for the proliferation of leukemic cells.
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PMID:Internal tandem duplication of the FLT3 gene is preferentially seen in acute myeloid leukemia and myelodysplastic syndrome among various hematological malignancies. A study on a large series of patients and cell lines. 932 77

An important step in the oncogenic transformation of hemopoietic cells and the subsequent development of leukemia is the proliferation of tumor cells in the absence of exogenous growth factors. In most cases of chronic myelocytic leukemia and in some cases of acute myelocytic leukemia and acute lymphocytic leukemia, the bcr-abl oncogene is involved in this process. Although the BCR-Abl oncoprotein demonstrates enhanced tyrosine kinase activity in leukemic cells, the mechanism by which this leads to growth factor independence remains poorly defined. One proposed mechanism is the activation of cytokine signal transduction pathways, possibly by an autocrine loop involving IL-3 and/or granulocyte-macrophage CSF. Examination of several different cell lines expressing BCR-Abl demonstrates that some of these cells have constitutive activation of the JAK/STAT signaling pathway. We have found the constitutive activation of STAT5 in most, but not all, cell lines expressing BCR-Abl. This constitutive activation of STAT5 is variably associated with a corresponding activation of JAK kinases. Ab blocking studies show that the activation of STAT5 in these cell lines cannot be attributed to the activation of an IL-3/granulocyte-macrophage CSF-driven autocrine loop. Interestingly, samples of peripheral blood cells derived from patients with acute myelocytic leukemia and chronic myelocytic leukemia, which express BCR-Abl, demonstrate constitutive activation of STAT family members. These studies suggest that in a variety of leukemic states, BCR-Abl may use a bypass mechanism to activate cytokine signal transduction pathways.
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PMID:Constitutive activation of JAKs and STATs in BCR-Abl-expressing cell lines and peripheral blood cells derived from leukemic patients. 936 95

The pattern of expression of the human Emt tyrosine kinase was established in healthy individuals and hematological malignancies by RT-PCR from bone marrow and blood samples, fractionated into T-cells, B-cells, monocytes, granulocytes and thrombocytes. Previously studied mostly in murine samples or established human cell lines, the in vivo correlation was here further clarified. In hematopoietic cells, expression of the EMT gene was associated with T-cell fractions, but Emt was not detected in cord blood CD34+ cells. In fetal tissues, Emt mRNA was strongly expressed in thymus, no expression could be detected in non-hematopoietic tissues. The expression pattern of the 48 malignant bone marrow samples (23 ALL, 1 PLL, 9 AML, 7 CLL and 8 CML cases) paralleled the findings from normal hematopoietic cells: 9/11 T cell associated ALLs, as well as one T-PLL sample, but only 1/12 samples of B-ALL expressed Emt markedly. Only minor signs of Emt expression could be shown in the AML samples, while CML and CLL samples were totally devoid of expression. In addition the Emt protein could be detected by Western blotting from T-lymphocytes and T-cell associated ALL, corresponding to mRNA expression. In conclusion, Emt (Itk) is T-cell associated both in normal and leukemic cells, but is not expressed in cord blood CD34+ cells, suggesting that Emt expression is switched on only later in T-cell development. In addition, an association between Emt and CD2 expression remains even in malignancies.
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PMID:Human Emt tyrosine kinase is specifically expressed both in mature T-lymphocytes and T-cell associated hematopoietic malignancies. 1004 24

The Philadelphia (Ph) chromosome, the main product of the (9;22)(q34;q11) translocation, is the cytogenetic hallmark of chronic myeloid leukemia (CML), a clonal myeloproliferative disorder of the hematopoietic stem cell; the Ph chromosome is also found in a sizeable portion of acute lymphoblastic leukemia (ALL) patients and in a small number of acute myeloid leukemia (AML) cases. At the molecular level, the t(9;22) leads to the fusion of the BCR gene (on chromosome 22) to the ABL gene (translocated from chromosome 9); this fusion gene BCR-ABL with its elevated tyrosine kinase activity must to be central to the pathogenesis of these disorders. Three different breakpoint cluster regions are discerned within the BCR gene on chromosome 22: M-bcr, m-bcr, and mu-bcr. Ph + leukemia cell lines are important tools in this research area. More than 20 ALL-and more than 40 CML-derived Ph + leukemia cell lines have been described. Furthermore, three Ph + B-lymphoblastoid cell lines, established from patients with Ph + ALL or CML, are available. Molecular analysis has documented BCR-ABL fusion genes in three apparently Ph chromosome-negative cell lines, all three derived from CML. Nearly all Ph + ALL cell lines have the m-bcr e1-a2 fusion gene (only two ALL cell lines have a b3-a2 fusion) whereas all CML cell lines, but one carry the M-bcr b2-a2, b3-a2 or both hybrids. The mu-bcr e19-a2 has been detected in one CML cell line. Four cell lines display a three-way translocation involving chromosomes 9, 22 and a third chromosome. Additional Ph chromosomes (up to five) have been found in four Ph + ALL cell lines and in 18 CML cell lines; though in some cell lines the extra Ph chromosome(s) might be caused by the polyploidy (tri- and tetraploidy) of the cells. Another modus to acquire additional copies of the BCR-ABL fusion gene is the formation of tandem repeats of the BCR-ABL hybrid as seen in CML cell line K-562. Both mechanisms, selective multiplication of the der(22) chromosome and tandem replication of the fusion gene BCR-ABL, presumably lead to enhanced levels of the fusion protein and its tyrosine kinase activity (genetic dosage effect). The availability of a panel of Ph + cell lines as highly informative leukemia models offers the unique opportunity to analyze the pathobiology of these malignancies and the role of the Ph chromosome in leukemogenesis.
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PMID:Leukemia cell lines: in vitro models for the study of Philadelphia chromosome-positive leukemia. 1007 Oct 72

Mitogen-activated protein (MAP) kinases act as transducers of extracellular signaling via tyrosine kinase-growth factor receptors and G-protein-linked receptors to transcription factors. Constitutive activation of MAP kinase has been observed in a variety of solid tumors including renal cancer and breast cancer. Recently, we have reported that constitutively activated MAP kinase was observed in 50% of human primary acute myeloid leukemia (AML) cells. Ras is one of the components of G-proteins and transduces the signal from cytokine receptors to raf-1 theoretically resulting in the activation of MAP kinase pathway. In the present study, we have examined the correlation of Ras mutations and the activation of MAP kinase pathway in patients with AML. Twenty out of 22 AML cases with activating N-Ras mutations showed no phosphorylated forms of ERK2. ERK2 phosphorylation was tightly correlated with ERK1 phosphorylation and MAP kinase activity detected by in vitro kinase assay. Three samples with N-Ras mutations were stimulated with IL-3, GM-CSF and G-CSF separately but ERK2 activation was induced in none of these samples stimulated with these cytokines. In contrast, ERK2 was constitutively activated in all of four pancreatic carcinoma cases with K-Ras mutation at codon 12. These results suggest that function of the Ras mutations may be different between solid tumors, such as pancreatic carcinoma and colorectal carcinoma, and AML. Mutated Ras does not always stimulate MAP kinase pathway constitutively and may rather inhibit classical MAP kinase cascade in AML blasts from leukemia patients.
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PMID:Lack of constitutive activation of MAP kinase pathway in human acute myeloid leukemia cells with N-Ras mutation. 1021 65

The c-kit proto-oncogene encodes a 145 kd tyrosine kinase transmembrane receptor, which plays a key role in haemopoiesis. The c-kit has been classified as CD117 and is especially useful in the differential diagnosis of acute myelogenous leukemia (AML) and acute lymphoblastic leukemia (ALL). We analysed 104 consecutive cases (55 AML, 23 B-cell lineage ALL, three T-cell ALL, 11 blast crisis of chronic myeloproliferative disorders and 12 cases of myelodysplastic syndromes with more than 10% of blasts) referred to our Hospital for immunophenotypic diagnosis and compared the expression pattern of CD13, CD33 and CD117 using the same fluorochrome (phycoerythrin-PE). The recommendations of the EGIL group were followed in order to establish lineage involvement of the blastic population. The threshold used to assign positivity for CD117 was 10%. Bcr/abl, TEL/AML-1 and MLL rearrangements were assessed by molecular methods. CD117 expression was detected in 91% of AML and MDS. All the negative cases corresponded to acute monocytic leukemias. The calculated specificity for myeloid involvement was 0.86 for CD117, 0.36 for CD13 and 0.44 for CD33 (P < 0.005). CD117 was also positive in four cases of ALL. None of these cases showed bcr/abl or MLL rearrangements. In the light of these findings, CD117 expression should yield a higher score, at least one point, in the system currently applied for the diagnosis of biphenotypic acute leukemias (BAL) as its myeloid specificity is greater than that of CD13 and CD33. Moreover, its absence in AML could identify two subgroups of M5b cases. The coexpression of CD117 with cytoplasmic CD79a is often associated with CD7 reactivity, suggesting a stem cell disorder. CD117 should be included on a routine basis for the immunophenotypic diagnosis of acute leukemias.
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PMID:Enhanced myeloid specificity of CD117 compared with CD13 and CD33. 1022 19

Recently, in-frame internal tandem duplications have been reported within the regions coding for the juxtamembrane through the first tyrosine kinase domain of the Flt3 gene. These duplications have been reported to lead to autophosphorylation of the receptor. In this study we investigated the effect of such mutations in the Flt3 gene on the in vitro proliferation of human acute myeloid leukemia cells. The mutations were detected in 10 out of 59 AML bone marrow samples analyzed and were not restricted to a specific FAB class or cytogenetic aberration. PCR analysis of those samples showed all mutations to be present in exon 11 of the gene. Whilst samples without a mutation of the Flt3 gene showed an increased cell production in response to either IL-3 and G-CSF or IL-6, SCF, TPO and Flt3L in long-term stroma supported cultures, mutant samples failed to do so. As we could not find a relationship between the absence of a response and either FAB class or cytogenetic aberrations, we interpret these results as an indication that the internal tandem duplications in the Flt3 gene are the prime cause of this unresponsiveness. Although our study does not explain the mechanism by which these mutations cause this unresponsiveness it does suggest that AML cells need a wild-type Flt3 for optimal in vitro proliferation.
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PMID:Human acute myeloid leukemia cells with internal tandem duplications in the Flt3 gene show reduced proliferative ability in stroma supported long-term cultures. 1040 Apr 23

The Ets variant gene 6 (ETV6/TEL) gene is rearranged in the majority of patients with 12p13 translocations fused to a number of different partners. We present here a case of acute myeloid leukemia M4 with eosinophilia (AML-M4Eo) positive for the CBFb/MYH11 rearrangement and carrying a t(1;12)(q25;p13) that involves the ETV6 gene at 12p13. By 3'rapid amplification of cDNA ends-polymerase chain reaction (3'RACE-PCR), a novel fusion transcript was identified between the ETV6 and the Abelson-related gene (ARG) at 1q25, resulting in a chimeric protein consisting of the HLH oligomerization domain of ETV6 and the SH2, SH3, and protein tyrosine kinase (PTK) domains of ARG. The reciprocal transcript ARG-ETV6 was also detected in the patient RNA by reverse transcriptase-polymerase chain reaction (RT-PCR), although at a lower expression level. The ARG gene encodes for a nonreceptor tyrosine kinase characterized by high homology with c-Abl in the TK, SH2, and SH3 domains. This is the first report on ARG involvement in a human malignancy.
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PMID:The tyrosine kinase abl-related gene ARG is fused to ETV6 in an AML-M4Eo patient with a t(1;12)(q25;p13): molecular cloning of both reciprocal transcripts. 1059 83

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