Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.10.1 (ERK)
 95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

FLT3/FLK2 is a receptor tyrosine kinase (RTK) which is thought to play an important role in early stages of hematopoiesis. Monoclonal antibodies (mAbs) against the extracellular domain of human FLT3 were generated to study the cell surface expression of this class III RTK on normal bone marrow cells and on leukemic blasts from patients with acute leukemias. Functional analysis of five mAbs (SF1 series) revealed that all of them can mimic to variable extents the activity of the FLT3 ligand (FL) upon receptor activation and modulation, while only one mAb weakly inhibited ligand binding. Using flow cytometry, we detected surface expression of FLT3 on cell lines of the myeloid (4/8) and B lymphoid (7/10) lineages. On normal human bone marrow cells, the expression of FLT3 is restricted, in agreement with a presumed function of this receptor at the level of the stem cells and early committed progenitors. Expression of FLT3 was found on a fraction of CD34-positive and CD34-negative cells. Three-color analysis further revealed that most of the CD34 FLT3+ cells coexpress CD117 (KIT) at a high level. Finally, FLT3 is expressed on leukemic blasts of 18/22 acute myeloid leukemias (AML) and 3/5 acute lymphoid leukemias (ALL) of the B lineage, providing a possible application in diagnosis and therapy of these diseases.
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PMID:Human FLT3/FLK2 receptor tyrosine kinase is expressed at the surface of normal and malignant hematopoietic cells. 863 32

We have evaluated an easy and fast immunomagnetic method for positive selection of cells expressing the CD34 antigen from BM, peripheral blood (PB) and apheresis products (AP) of CML patients and healthy adults (HA) in order to further characterize them by immunophenotypic analysis. From an initial frequency of CD34+ cells in the original sample of 1.8 +/- 1.7%, CD34+ cells were rapidly and efficiently enriched up to 91.5 +/- 6.4% by high-gradient magnetic cell sorting (MACS) (yield 53 +/- 21%). A five-dimensional flow cytometric analysis of the immunomagnetic isolated CD34+ cells demonstrated little overlap between CD34+HLA-DRlo and CD34+CD38lo subpopulations in both BM-HA and in BM-CML. Only 16 and 6% of the CD34+HLA-DRlo and CD34+CD38lo cells respectively, showed lack of expression of both Ag (CD34+HLA-DRloCD38lo) in BM-CML samples. Between 60 and 70% of the CD34+ cells expressed the stem cell factor (SCF) receptor (c-KIT, CD117) and there were no differences between BM-HA and BM-CML patients. Moreover, more than 60% of the CD34+HLA-DRlo cells, co-expressed c-KIT. MACS-enriched BM-CD34+ cells showed normal hematopoietic colony formation in vitro in all the sources analyzed with a higher colony-forming efficiency than the unfractionated sample (MNC).
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PMID:Isolation of CD34+ hematopoietic progenitor cells in chronic myeloid leukemia by magnetic activated cell sorting (MACS). 887 25

The effects of the granulocyte (G) and macrophage (M) colony-stimulating factors (CSFs) on the growth of purified subpopulations of human fetal liver progenitors were investigated. In contradiction to the characterization of these cytokines as CSFs acting late in the course of hematopoiesis, both G-CSF and M-CSF were most potent in promoting the growth of fetal liver colony-forming cells (CFCs) that express high levels of CD34 and CD38 (CD34++CD38+) and are depleted of cells expressing a panel of lineage markers (Lin-). Cultures of these cells in serum-deprived conditions generated a mean of 11.2 and 39.1 low-proliferative potential (LPP)-CFCs per 1.0 x 10(3) CD34++CD38+Lin- cells grown in G-CSF and M-CSF, respectively. Cultures of more mature progenitors, isolated based on a lower level of CD34 expression (CD34+ Lin-), generated few LPP-CFCs and 6.3 and 4.7 clusters per 1.0 x 10(3) CD34+Lin- cells in response to G-CSFs and M-CSF, respectively. G-CSF was also found to synergistically enhance colony growth by either kit-ligand (KL) or fit-3/flk-2 ligand (FL) in cultures of CD34++CD38+Lin- cells as well as the more primitive compartment of CD34++CD38-Lin- cells. Synergism between G-CSF and KL or FL was also observed in liquid cultures of CD34++CD38-Lin- cells. The effects of G-CSF on CD342++CD38-Lin- cells were further demonstrated by the ability of G-CSF to support the short-term survival of these cells in clonal cultures. In contrast, M-CSF did not affect the growth or survival of CD34++CD38-Lin- cells, a finding that was also supported by the observation that the receptor for M-CSF (CD115 or fms) was only expressed on CD34++CD38+Lin- cells. G-CSF receptor expression and flt-3/flk-2 expression were detected by flow cytometry on both the CD38- and CD38+ subpopulations of CD34++Lin- cells, but these receptors were not detected on CD34+ cells. Receptors for KL (CD117) and interleukin-3 (CD123), for which the ligands are active on a broad range of fetal liver progenitors, were detected on cells expressing both high and low levels of CD34. These data help to define the potential roles of cytokines in human fetal hematopoiesis.
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PMID:Colony-forming cells expressing high levels of CD34 are the main targets for granulocyte colony-stimulating factor and macrophage colony-stimulating factor in the human fetal liver. 913 Oct 1

It has been supposed in de novo AML that malignant transformation occurs at the level of committed progenitors. Recent data of our group and others provide evidence that in AML malignant transformation may regularly occur at the level of stem cells. These cells can be discriminated by function and specific surface molecules. CD34, a glycophosphoprotein, is a cellular surface antigen characteristically expressed by stem cells. CD34+ stem cells can be further subdivided by the expression of additional surface molecules like CD38 and CD117. In this article we present results from cytogenetic examinations of FACS-isolated stem cell subpopulations in eight patients (four AML and four MDS). Six of them displayed clonal karyotype abnormalities at the time of first diagnoses in the native bone marrow (5q-; 5q- and complex abnormalities; +8; inv(16) and +8; i(17q) and -21; i(21q)). We used CD117, the receptor for the stem cell factor (also KIT oncogene) as a new cellular surface marker. CD34+/CD117+/- stem cell subpopulations were examined in two patients with AML and three patients with MDS. We found leukemic stem cells in every type of stem cell subpopulation examined (CD34+/CD38-, CD34+/CD38+, CD34+/CD117-, CD34+/CD117+). Secondary, progression-associated chromosome abnormalities likewise were demonstrable in CD34+ cells. In three patients a mosaic of normal and abnormal metaphases was found in the highly purified stem cell subpopulations. We conclude that in AML and MDS stem cells are the target of leukemogenic genetic defects. CD117 as a new marker to isolate different CD34+ subpopulations was not sufficient to discriminate between normal and leukemic stem cells. Our findings have implications for autologous stem cell transplantation, high-dose chemotherapy and the pathogenetic concept of leukemogenesis.
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PMID:Cytogenetic analysis of CD34+ subpopulations in AML and MDS characterized by the expression of CD38 and CD117. 918 Feb 91

The class III receptor tyrosine kinase FLT3/FLK2 (FLT3; CD135) represents an important molecule involved in early steps of hematopoiesis. Here we compare cell-surface expression of FLT3 on bone marrow (BM) and cord blood (CB) cells using monoclonal antibodies (MoAbs) specific for the extracellular domain of human FLT3. Flow cytometric analysis of MACS-purified BM and CB cells showed that 63% to 82% of BM CD34+ and 88% to 95% of the CB CD34+ cells coexpress FLT3. Clonogenic assays and morphological characterization of FACS-sorted BM CD34+ cells demonstrate that colony-forming unit-granulocyte-macrophage (CFU-GM) and immature myelo-monocytic precursor cells are enriched in the subpopulation staining most brightly with the FLT3 MoAb whereas the majority of the burst-forming units-erythroid (BTU-E) and small cells with lymphoid morphology are found in the FLT3- population. In contrast, statistically indistinguishable proportions of CFU-granulocyte-erythrocyte-megakaryocyte-macrophage (CFU-GEMM) and more primitive cobblestone area forming cells (CAFC) were detected in both fractions, albeit the FLT3+ fraction consistently showed more CAFC activity than the FLT3- fraction. Although in both, BM and CB the majority of CD34+CD117+ (KIT+), CD34+CD90+ (Thy-1+), and CD34+CD109+ cells coexpress FLT3, three-color phenotypic analyses are consistent with the functional findings and suggest that the most primitive cells defined as CD34+CD38-, CD34+CD71low, CD34+HLA-DR-, CD34+CD117low, CD34+CD90+, and CD34+CD109+ express low levels of cell-surface FLT3 and were therefore not enriched to a statistically significant extent with the bright versus negative sorting scheme. Thus, clear segregation of the most primitive progenitors from BM CD34+ cells was confounded by low apparent levels of FLT3 cell-surface expression on these cells, whereas myeloid progenitors unambiguously segregated with the FLT3 brightest cells and erythroid progenitors with the FLT3 dimmest. Additional phenotypic analyses using MoAbs against progenitor/stem cell markers including the mucinlike molecule MGC-24v (CD164), the receptor tyrosine kinases TIE, FMS (CD115), and KIT (CD117) further illustrate the differences in surface antigen expression profiles of BM and CB CD34+ cells. Notably, CD115 is rarely detected on CB CD34+ cells, whereas 20% to 25% of the BM CD34+FLT3+ cells are CD115+. Furthermore, 80% to 95% of the CB CD34+CD117+ but only 60% to 75% of the BM CD34+CD117+ cells coexpress FLT3. Only a negligible amount of CD34+CD19+ are detected in CB, while in BM 20% to 30% of CD34+CD19+ presumed pro/pre-B cells coexpress FLT3. In contrast, the majority of the CD34+CD164+ and CD34+TIE+ subsets in both CB and BM coexpress FLT3. Analysis of unseparated cells showed that FLT3 expression is not restricted to CD34+ subsets. About 65% to 70% of lymphocyte-gated BM CD34-FLT3+ cells are positive for the monocytic marker CD115 whereas 25% to 30% of these cells consist of CD10 expressing B-cell precursors. Finally, CD34- monocytes in BM, CB, and PB express FLT3 whereas granulocytes are FLT3-. Our data show that detectable FLT3 appears first at low levels on the surface of primitive multilineage progenitor cells and disappears during defined stages of B-cell development, but is upregulated and maintained during monocytic maturation.
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PMID:Functional and phenotypic characterization of cord blood and bone marrow subsets expressing FLT3 (CD135) receptor tyrosine kinase. 920 45

In this report we evaluated the exact expression pattern of c-Kit on mobilized peripheral blood (PB) CD34+ cells. Using a monoclonal antibody against CD117 antigen (95C3), flow cytometric analysis revealed that approximately 25% of the mobilized PB CD34+ cells coexpress c-Kit. This cell fraction showed a considerable heterogeneity with respect to c-Kit expression, consisting of a small fraction with high levels of c-Kit (4.2%) (CD34+/CD117high fraction) and a larger proportion of cells expressing low levels of this antigen (21.0%) (CD34+/CD117low fraction). Clonogenic assays showed that CD34+/CD117high cell fraction consisted almost exclusively of erythroid progenitors, in contrast to CD34+/CD117low cell subset which gave rise mostly to granulocyte-monocyte colonies. The majority of CFU-GEMM and the most primitive week 6 cobblestone area forming cells (CAFCs) segregated in the CD34+/CD117low cell subset, suggesting the highest content of multipotential progenitors within this cell fraction. None of the sorted cell subsets was able to produce reactive oxygen intermediates (ROI). However, ex vivo expansion of the sorted subsets with interleukin 3, stem cell factor and FLT3 ligand for 2 weeks resulted in a significant production of O2- and H2O2/HOCl by CD34+/CD117low cell fraction, compared to the same sorted but not expanded counterparts. According to the major content of multipotential hematopoietic progenitors and highest capacity to generate sufficient amounts of ROI after ex vivo expansion, we suggest that CD34+/CD117low cell subset would be one of the most potential candidates for transplantation in patients with acute lymphoblastic leukemia, which lack c-Kit antigen expression.
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PMID:Phenotypic and functional characterization of mobilized peripheral blood CD34+ cells coexpressing different levels of c-Kit. 966 40

CD164 is a novel 80- to 90-kD mucin-like molecule expressed by human CD34(+) hematopoietic progenitor cells. Our previous results suggest that this receptor may play a key role in hematopoiesis by facilitating the adhesion of CD34(+) cells to bone marrow stroma and by negatively regulating CD34(+) hematopoietic progenitor cell growth. These functional effects are mediated by at least two spatially distinct epitopes, defined by the monoclonal antibodies (MoAbs), 103B2/9E10 and 105A5. In this report, we show that these MoAbs, together with two other CD164 MoAbs, N6B6 and 67D2, show distinct patterns of reactivity when analyzed on hematopoietic cells from normal human bone marrow, umbilical cord blood, and peripheral blood. Flow cytometric analyses revealed that, on average, 63% to 82% of human bone marrow and 55% to 93% of cord blood CD34(+) cells are CD164(+), with expression of the 105A5 epitope being more variable than that of the other identified epitopes. Extensive multiparameter flow cytometric analyses were performed on cells expressing the 103B2/9E10 functional epitope. These analyses showed that the majority (>90%) of CD34(+) human bone marrow and cord blood cells that were CD38(lo/-) or that coexpressed AC133, CD90(Thy-1), CD117(c-kit), or CD135(FLT-3) were CD164(103B2/9E10)+. This CD164 epitope was generally detected on a significant proportion of CD34(+)CD71(lo/-) or CD34(+)CD33(lo/-) cells. In accord with our previous in vitro progenitor assay data, these phenotypes suggest that the CD164(103B2/9E10) epitope is expressed by a very primitive hematopoietic progenitor cell subset. It is of particular interest to note that the CD34(+)CD164(103B2/9E10)lo/- cells in bone marrow are mainly CD19(+) B-cell precursors, with the CD164(103B2/9E10) epitope subsequently appearing on CD34(lo/-)CD19(+) and CD34(lo/-)CD20(+) B cells in bone marrow, but being virtually absent from B cells in the peripheral blood. Further analyses of the CD34(lo/-)CD164(103B2/9E10)+ subsets indicated that one of the most prominent populations consists of maturing erythroid cells. The expression of the CD164(103B2/9E10) epitope precedes the appearance of the glycophorin C, glycophorin A, and band III erythroid lineage markers but is lost on terminal differentiation of the erythroid cells. Expression of this CD164(103B2/9E10) epitope is also found on developing myelomonocytic cells in bone marrow, being downregulated on mature neutrophils but maintained on monocytes in the peripheral blood. We have extended these studies further by identifying Pl artificial chromosome (PAC) clones containing the CD164 gene and have used these to localize the CD164 gene specifically to human chromosome 6q21.
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PMID:CD164, a novel sialomucin on CD34(+) and erythroid subsets, is located on human chromosome 6q21. 968 Mar 53

C-KIT, TIE and HKT expression on leukemic cells from patients were simultaneously analyzed using flow cytometry. Consistent with previous reports, leukemic cells from most patients with de novo acute myeloid leukemia (AML) were C-KIT-positive (28/35), while those from patients with B-lineage acute lymphoid leukemia (B-ALL) were C-KIT-negative (0/9). In the B-ALL patients, leukemic cells trom seven patients had one or more myeloid antigen such as CD13, CD15 and CD33. In contrast to C-KIT expression, leukemic cells from only one patient with acute monocytic leukemia were TIE-positive. Similarly, leukemic cells from only two patients (one, B-ALL with t(4;11)(q21;q23) and one, essential thrombocythemia in myeloblastic transformation (ET-MBT)) were HTK-positive. These results suggest that among the three receptor tyrosine kinases, C-KIT is the most useful marker for identifying AML.
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PMID:Analysis of C-KIT, TIE and HTK expression on leukemic cells using flow cytometry: a preliminary report. 971 14

As recurrent chromosome abnormalities in leukemia are highly associated with particular subtypes, the genetic events of specific chromosome alteration must be associated with leukemogenesis and characteristics of the disease. The chromosomal breakpoints involved in inv(16) and t(16;16) have been shown to generate the fusion gene PEBP2beta(CBFbeta)/MYH11. The PEBP2beta/MYH11 fusion transcripts in all 8 patients with M4Eo, 2 of 18 with M4, and one CML in the blastic phase were detected by using RT-PCR and Southern blotting. We demonstrated the marked expression of CD34 and c-KIT (CD117) antigens in myelomonoblastic leukemia cells from all patients carrying this fusion gene, which was in contrast to the patients with M4 but without the fusion gene. These results indicate that immunophenotypic analysis is useful for detection of leukemia with the fusion gene, and that the PEBP2beta/MYH11 fusion gene is involved in immature cells expressing CD34 and c-KIT antigens.
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PMID:Acute myelomonoblastic leukemia carrying the PEBP2beta/MYH11 fusion gene. 972 Jul 17

We report on a series of 26 patients diagnosed with primary (de novo) plasma cell (PC) leukemia (PCL) in whom we analyzed the clinicobiologic characteristics of the disease together with the immunophenotype, DNA cell content, proliferative index, and numeric chromosomal aberrations of the neoplastic PC, and compared them with 664 multiple myeloma (MM) patients at diagnosis. The median age, sex ratio, and bone lesion extension were similar, but PCL cases displayed a higher prevalence of clinical stage III, extramedullary involvement, and Bence Jones cases, with fewer IgA cases than for MM patients. In addition, according to several prognostic indicators (beta2-microglobulin serum level, proportion of S-phase PCs, proteinuria, calcium serum level, lactate dehydrogenase [LDH] and renal function), the incidence of adverse prognostic factors was significantly higher in PCL versus MM. Immunophenotypic expression was similar for CD38, CD138, CD2, CD3, CD16, CD10, CD13, and CD15, but PCL differed from MM in the expression of CD56, CD9 HLA-DR, CD117, and CD20 antigens. Twenty-two PCL cases were diploid and one was hypodiploid, while most MM cases (57%) showed DNA hyperdiploidy. With the fluorescent in situ hydridization (FISH) technique, 12 of 13 PCL cases displayed the numeric aberrations, -13 (86%), +/-1 (57%), +18 (43%), and -X in women (25%), but they lacked several numeric aberrations usually found in MM such as +3, +6, +9, +11, and +15. PCL cases had a lower overall response to therapy than MM cases (38% v 63%, P =.01332). Among PCL patients, a trend for a worse response was observed in cases treated with melphalan and prednisone (MP) versus polychemotherapy. Overall survival was significantly worse in PCL versus MM patients (8 v 36 months, P <.0001), but it was significantly better in PCL patients treated with polychemotherapy versus MP (18 v 3 months, P =.0137). By contrast, MM patients did not show significant differences in overall survival according to the treatment used, MP or polychemotherapy. Ten variables seemed to predict survival in PCL patients, but only the beta2-microglobulin level and S-phase PCs retained an independent value in multivariate analysis. In summary, our study illustrates that PCs from PCL display singular phenotypic, DNA cell content, and cytogenetic characteristics that lead to a different disease evolution versus MM.
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PMID:Primary plasma cell leukemia: clinical, immunophenotypic, DNA ploidy, and cytogenetic characteristics. 1061 Jan 15


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