Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023467 (acute myeloid leukemia)
 35,200 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The function of the steel factor receptor, p145c-kit, in patient-derived acute myeloblastic leukemia (AML) cells was investigated. Steel factor stimulation of AML cells coexpressing p145c-kit and the progenitor cell antigen CD34 resulted in complete receptor down-regulation, a marked decrease of CD34 antigen expression, and the induction of the granulocyte lineage antigen CD15. These changes in surface marker expression paralleled morphological differentiation to granulated blasts and promyelocytes. Interestingly, the same phenotype was achieved by IL-3 stimulation of AML cells. p145c-kit extracellular domain-specific antibodies had either blocking or enhancing effects on ligand binding, receptor phosphorylation and down-regulation, and induction of cell proliferation. Correlations of these phenomena with distinct effects of antibody stimulation on cell substrate phosphorylation provide clues for the dissection of the p145c-kit signal and the analysis of its relevance for AML.
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PMID:Modulation of p145c-kit function in cells of patients with acute myeloblastic leukemia. 768 35

Cell kinetic studies of acute myeloid leukemia (AML) have provided evidence for the presence of nonproliferating cells. Hemopoietic growth factors (GF) can regulate proliferation of leukemic cells, furnishing new possibilities for recruiting quiescent cells into the cycle and overcoming cytokinetic resistance in AML. To assess the role of the novel identified cytokine, mast cell growth factor (MGF), in enhancing cytosine arabinoside (Ara-C) cytotoxicity, we have primed AML blasts with MGF and then exposed these cells to the S phase specific agent Ara-C. Other growth factors such as PIXY, interleukin 3 (IL-3), granulocyte-macrophage colony stimulating factor (GM-CSF) and granulocyte CSF (G-CSF) and the combination of MGF plus PIXY were also tested. Cytokinetic changes and clonogenic growth of leukemic colony forming unit (CFU-L) cells in methylcellulose were used to detect proliferative and cytotoxic effects on AML blasts. Expression of MGF receptor, the c-kit protein, was also measured by flow cytometry. We report in this preliminary study that MGF is able to increase proliferation in 75% of the samples studied and enhance Ara-C cytotoxicity in some of these cases. When MGF proliferative activity was compared with other GFs, individual cases showed heterogeneity in response, although the combination of MGF plus PIXY was always the most effective.
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PMID:Effects of mast cell growth factor on Ara-C mediated acute myeloid leukemia cell killing. 769 32

The MTT assay, a colorimetric assay, is found to be suitable for chemosensitivity testing. Recently, it has been suggested that hematopoietic growth factors (HGF) may enhance the effects of cytostatic drugs in acute myeloid leukemia (AML). We therefore studied the effects of granulocyte colony-stimulating factor (G-CSF), interleukin 3 (IL-3), and granulocyte-macrophage colony-stimulating factor (GM-CSF) combined with cytosine arabinoside (Ara-C), daunorubicin (DNR), mitoxantrone (MXT), or etoposide (VP-16) by using the MTT assay. The results were compared with in vitro clonogenic assays. Briefly, AML cells of nine patients were incubated in the presence or absence of G-CSF, IL-3, or GM-CSF under serum-free conditions for 24 hours. Next, for the MTT assay, Ara-C (final dilution range: 0.0024-240 micrograms/ml), DNR (final dilution range: 0.05-3.2 micrograms/ml), MXT (final dilution range: 0.05-3.2 micrograms/ml), or VP-16 (final dilution range: 0.1-100 micrograms/ml) were added and incubated for 48 hours. Cell survival was determined and IC75 values (75% reduction as compared to control cultures) were calculated. For clonogenic assays, the three lowest drug concentrations were used. After 48 hours, the clonogenic response was determined in serum-free, semi-solid cultures with G-CSF, IL-3, or GM-CSF. The results obtained by the MTT assay showed no significant enhancement of cytotoxicity by HGF on cytostatic drug preincubated cells compared to cytostatic drugs alone. The results obtained by the clonogenic assays showed increased cytotoxicity of Ara-C combined with G-CSF, IL-3, or GM-CSF. The median IC75 values of Ara-C decreased from 0.056 to 0.0168 microgram/ml with G-CSF (p = 0.01), from 0.108 to 0.0168 microgram/ml with IL-3 (p = 0.004) and from 0.12 to 0.0204 microgram/ml for GM-CSF (p = 0.02). Only moderate enhanced cytotoxicity was observed when VP-16 was combined with IL-3 (p = 0.036) or GM-CSF (p = 0.036), but not with G-CSF. No enhanced cytotoxicity of DNR and MXT to clonogenic AML cells was found when these agents were combined with HGF stimulation. The results indicate that the MTT assay underestimates HGF enhanced cytotoxicity of Ara-C or VP-16 to clonogenic cells. Therefore, the assay is not useful for accurately detecting differences of clonogenic response due to the proliferative status of cells. In this paper, the potential explanations for the failure of the MTT assay are discussed.
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PMID:Enhanced chemosensitivity in acute myeloid leukemia by hematopoietic growth factors: a comparison of the MTT assay with a clonogenic assay. 769 94

Mutation or deletion of the retinoblastoma tumor suppressor gene (Rb) or abnormal Rb protein expression is found in many types of human solid tumors. Low or absent levels of Rb protein are usually found in the leukemic cells of patients with acute myelogenous leukemia (AML) who have an extremely poor prognosis. The absence of Rb protein in these AML cells could result from defects in the Rb gene or from abnormal cell cycle regulation that affects Rb expression. To test these possibilities and to examine whether a low level of Rb protein in AML cells could be up-regulated, we studied the effect that growth factors interleukin 3 (IL3) and granulocyte-macrophage colony stimulating factor (GM-CSF) had on the levels of Rb protein and Rb phosphorylation in AML cells from patients with low Rb or no Rb protein expression. We observed three responses to growth factor-stimulation in leukemic cells taken from patients with AML: (1) some AML cell samples entered a proliferative phase, and Rb protein levels increased with the appearance of normally phosphorylated forms of Rb protein and positive nuclear staining for Rb protein; (2) some AML cell samples became more proliferative, but the levels of Rb protein remained low or absent; and (3) some AML cell samples showed no response. These results indicate that at least two different mechanisms may be responsible for the lack of Rb protein in the leukemic cells of some patients with AML.
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PMID:Growth-factor stimulation reveals two mechanisms of retinoblastoma gene inactivation in human myelogenous leukemia cells. 771 26

We investigated the effect of 2-chlorodeoxyadenosine (2-CdA) in concentrations: 10, 20, 50, 100, 150 and 300 nM/l on the clonal growth of acute myeloid leukemia clonogenic cells (L-CFU), after 24 h preincubation with recombinant granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin-1 alpha (IL-1 alpha) or interleukin 3 (IL-3) and in conditioned medium obtained from phytohemagglutin stimulated lymphocytes (PHA-LCM). 2-CdA in concentration 300 nM/l significantly reduced (30%) the number of blast colonies in comparison with control experiments (p < 0.05). After preincubation of blast cells with cytokines (20% PHA-LCM, or GM-CSF--100 ng/ml, or IL-3--5 U/ml) an increase of 2-CdA cytotoxic effect on L-CFU clonal growth was observed. In experiments with 2-CdA (300 nM/l) and GM-CSF or PHA-LCM or IL-3 the number of blast colonies was reduced in 70%, 50% and 50%, respectively, (p < 0.05). Preincubation of blasts with IL-1, did not effect the 2-CdA--induced growth inhibition of CFU.
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PMID:[Cytokines modify 2-chlorodeoxyadenosine (2-CdA) toxicity in acute myeloid leukemia clonogenic cells (L-CFU)]. 774 65

We report the in vitro suppression of the IL-3-dependent MO-7 acute myeloid leukemia proliferation by an interleukin-3 antagonist. The antagonist was generated by alkylation to inactivate catalytic His-residues of native human interleukin-3. The resulting inhibitor caused a factor 7 inhibition of the growth-response curve of the IL-3 control-stimulated proliferation of a MO-7 leukemia cell line. A 40% inhibition of the MO-7 proliferation could be achieved with a partially alkylated inhibitor in presence of a factor 30 excess of native IL-3. Therefore, the inhibitor had a substantially improved affinity for the IL-3 receptor on these leukemia cells. At a concentration of as low as 0.1 ng/ml it still caused a 2-fold inhibition of the native IL-3-stimulated proliferation response curve. Thus it can be concluded that this alkylate IL-3 is a potent IL-3 antagonist. Based on the reported specific zinc binding of IL-2, IL-6, GM-CSF and gamma-interferon this suggests that more leukemias and even other forms of cancer can be effectively suppressed by alkylated growth factors.
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PMID:In vitro suppression of leukemia by alkylated interleukin-3. 776 58

Thrombopoietin (TPO), a lineage-specific cytokine affecting the proliferation and maturation of megakaryocytes from committed progenitor cells, is believed to be the major physiological regulator of circulating platelet levels. Recently we have isolated a cDNA encoding a ligand for the murine c-mpl protooncogene and shown it to be TPO. By employing a murine cDNA probe, we have isolated a gene encoding human TPO from a human genomic library. The TPO locus spans over 6 kb and has a structure similar to that of the erythropoietin gene (EPO). Southern blot analysis of human genomic DNA reveals a hybridization pattern consistent with a single gene locus. The locus was mapped by in situ hybridization of metaphase chromosome preparations to chromosome 3q26-27, a site where a number of chromosomal abnormalities associated with thrombocythemia in cases of acute myeloid leukemia have been mapped. A human TPO cDNA was isolated by PCR from kidney mRNA. The cDNA encodes a protein with 80% identity to previously described murine TPO and is capable of initiating a proliferative signal to murine interleukin 3-dependent BaF3 cells expressing the murine or human TPO receptor.
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PMID:Human thrombopoietin: gene structure, cDNA sequence, expression, and chromosomal localization. 780 66

The GM-CSF receptor belongs to the cytokine receptor superfamily. The high-affinity receptors of this class are lacking intrinsic tyrosine kinase domains. The GM-CSF receptor consists of alpha and beta subunits. The beta subunit is shared with the receptors of IL-3 and IL-5. In addition to the membrane bound forms the receptors have been found to possess soluble isoforms. Since retroviral infection of the human GM-CSF dependent cell line, TF-1, leads to factor independent growth by increased expression of the GM-CSF receptor alpha chain in a subgroup of infected clones, we were interested in studying the role of this chain in human AML. Further considering that a point mutation in the extracellular domain of the erythropoietin receptor, also a member of the cytokine receptor superfamily, resulted in constitutive activation of a murine cell line, we investigated the possibility that a point mutation of the GM-CSF receptor was responsible for autonomous growth of AML cells. We sequenced a segment of the receptor coding for the extracellular domain of the alpha subunit. cDNA was prepared from peripheral blood or bone marrow cells from 24 patients with AML, from four patients with MDS and from three human myeloid cell lines. The region of interest was amplified with two rounds of PCR reactions with nested primers, covering five overlapping fragments, and directly sequenced using a non-radioactive technique. No point mutations were found in the investigated samples. Thus, point mutations in this segment of the GM-CSF receptor gene do not seem to play an important role in the transformation process of human acute leukemia.
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PMID:Absence of point mutations in the extracellular domain of the alpha subunit of the GM-CSF receptor in a series of patients with acute myeloid leukemia (AML). 784 15

The eradication of minimal residual blast populations by activation of autologous cytotoxic cells with interleukin 2 (IL-2) is a new promising tool in the treatment of acute myelocytic leukemia (AML). However, the immunological effector cells are not yet clearly defined. The present study was designed to investigate the presence of cytotoxic precursor cells in active AML and to identify phenotypical and functional characteristics of autologous anti-leukemic cytotoxic effector cells. For this purpose, mononuclear cells (MNC) containing at least 70% leukemic blasts were isolated from bone marrow of untreated AML and cultured in the presence of 3000 IU/ml recombinant IL-2 (rIL-2) for 6-8 weeks. Under these conditions, T-cells were selected in the bone marrow cultures and overgrew the leukemic blasts. The resulting T-cell populations were cloned by limiting dilution and the clones obtained were characterized for their phenotypical and functional patterns. Totally, cloning resulted in 68 clones and a few cell lines. The clonality was verified by RT PCR analysis of TCR V beta gene expression. All clones obtained stained positive for CD2, CD3, DR and CD56. The vast majority (68%) of T-cell clones/lines was CD4+, a few clones expressed CD8 (19%) or CD4 and CD8, and four clones were of TCR gamma delta origin. Seven of 15 clones tested, including three CD4+, two CD8+ and two TCR gamma delta(+)-clones were found to be cytotoxic against autologous leukemic blast cells. All except one clone expressed oncolytic activities against allogeneic blasts too. One of the TCR gamma delta(+)-clones demonstrated NK activity by lysis of K562 targets. The majority of the T-cell-clones released IL-2, IL-8, TNF-alpha, GM-CSF but only a few IFN gamma and expressed high levels of mRNA for IL-2, TGF-beta and IL-10. None of the clones was found to produce IL-3, IL-4, IL-7 and TNF-beta. The data provide evidence of the existence of T-cell precursors in untreated AML bone marrow differentiating to cytotoxic cells with activity against autologous and allogeneic AML blast cells.
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PMID:Bone marrow-derived T-cell clones obtained from untreated acute myelocytic leukemia exhibit blast directed autologous cytotoxicity. 786 44

P-glycoprotein (P-gp) expression in mononuclear bone marrow cells was analyzed in 119 patients, including 60 with chronic myelogenous leukemia (CML), 48 with myelodysplastic syndromes (MDS), and 11 with acute myelogenous leukemia (AML). For P-gp measurement an immunocytological method using monoclonal antibodies C219, 4E3, and MRK 16 and the reverse transcription-polymerase chain reaction technique were applied. According to our results obtained in healthy volunteers using the immunocytological method, the limit for P-gp overexpression was set at > or = 10% P-gp-positive mononuclear bone marrow cells and at > or = 30% P-gp-positive mononuclear peripheral blood cells. All 42 CML patients in chronic phase had normal P-gp expression. P-gp overexpression was demonstrated in four of six patients in accelerated myelogenous blast cell phase and in four of 12 CML-BC patients. Of eight CML patients in blast crisis (BC) with normal P-gp expression, partial remission was achieved in three and minor response in five after prednisone/vindesine therapy. All four of the 12 CML-BC patients with P-gp overexpression did not respond to this therapy. Normal P-gp expression was seen in 41 (85.4%) of 48 untreated MDS patients. While P-gp overexpression did not develop during therapy in any of the myelodysplastic syndrome patients treated with low-dose ara-C alone, four of eight treated with low-dose ara-C plus GM-CSF and four of 11 treated with low-dose ara-C and IL-3 developed P-gp overexpression after therapy. Furthermore, 11 AML patients at primary diagnosis, including five AML patients with P-gp overexpression, who were treated with idarubicin, vepesid, and cytarabine V (ara-C) showed a complete remission. Additionally, one daunorubicin-cytarabine-pretreated refractory AML patient was treated with the oral form of the P-gp modulator drug dexniguldipine and achieved complete remission for a duration of 7 months. Our results suggest that in CML patients in BC, P-gp expression influences outcome after therapy. Further more, studies in a larger series of patients are necessary to prove the efficacy and toxicity of idarubicin/vepesid and cytardbine--or dexniguldipine-containing--therapy in relation to P-gp expression of AML patients.
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PMID:Clinical importance of P-glycoprotein-related resistance in leukemia and myelodysplastic syndromes--first experience with their reversal. 791 49


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