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 mitochondrial permeability transition and oxidative stress seem to be critical alterations in cellular physiology that take place during programmed cell death. Failure to undergo apoptosis is associated with drug resistance in acute myeloid leukemia and other cancers. Therefore, it is important to establish causal relationships between the physiological changes that take place in apoptosis, because these are potential targets for novel treatment strategies to overcome this form of drug resistance. We describe the use of multilaser flow cytometry methods to make correlated measurements of mitochondrial membrane potential (MMP), the generation of reactive oxygen intermediates, the cellular content of reduced glutathione (GSH), intracellular calcium, and exposure of phosphatidylserine on the cell surface. Using these combined methods, we have mapped a "death sequence" that occurs after treatment of leukemic blasts with clinically relevant concentrations of 1-beta-D-arabinofuranosylcytosine (ara-C). Dual labeling of MMP and cellular glutathione content showed that loss of MMP, indicative of the permeability transition, took place in cells that were depleted of glutathione. The loss of MMP coincided with phosphatidylserine exposure and preceded a state of high reactive oxygen generation. Finally, there was an increase in intracellular calcium. These results demonstrate that the mitochondrial permeability transition takes place during ara-C toxicity but suggest that this occurs downstream of the loss of GSH. Thus, oxidative stress after ara-C-induced toxicity seems to be a biphasic phenomenon, with the permeability transition occurring after a depletion of GSH and preceding a state of high reactive oxygen generation.
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PMID:Relationships between the mitochondrial permeability transition and oxidative stress during ara-C toxicity. 919 24

Using an autodigestion method, we investigated endogenous endonuclease(s) in leukemia cells freshly obtained from pediatric patients with various types of leukemia. Endonucleolytic activity was found to cause both high molecular weight and internucleosomal DNA fragmentation at a neutral pH in whole cell lysates of all common acute lymphoblastic leukemia (cALL) blasts, which was Mg2+-dependent and Ca2+-independent. Whole lysates from most acute myeloblastic leukemia (AML) cells possessed similar endonuclease activity, but both Mg2+ and Ca2+ were required for the activity. Our results suggest that leukemia cells of different lineages have distinct constitutive endonucleases, which may play a role in the occurrence of apoptosis in these cells.
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PMID:Constitutive endonuclease to induce high molecular weight or internucleosomal DNA fragmentation in freshly isolated leukemia cells. 923 28

Epidemiological studies have indicated a modestly increased risk for the development of acute myeloid leukaemia in children who live close to high-voltage power-lines. Recent evidence has suggested that a common property shared by a number of known and suspected tumour promoters is their ability to block the process of apoptosis. Therefore, one possible mechanistic explanation for the apparent leukaemogenic effect of weak, low-frequency magnetic fields, such as emitted by power-lines and electrical appliances, would be their expression of tumour-promoting activity by interfering with the regulation of apoptosis in multipotent haemopoietic progenitor cells. In order to test this hypothesis, we have employed the well-characterized multipotential haemopoietic progenitor cell line FDCP-mix(A4). These cells are non-leukaemic and undergo apoptosis when deprived of appropriate growth factors such as Interleukin-3. We have tested a series of different regimes of weak, low-frequency magnetic fields: nulled fields, Ca2+-ion cyclotron resonance conditions at 50 Hz, and vertical 50 Hz fields of 6 microT(RMS), 1 mT(RMS) and 2 mT(RMS), exposing the cells for 2 hours, 24 hours, 4 days or 7 days under various culture conditions. We have not seen any significant alteration in apoptosis induced by any of the exposure regimes tested. We therefore conclude that the regulation of viability and apoptosis in FDCP-mix(A4) cells is not disturbed by weak magnetic fields of the magnitude and type indicated.
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PMID:Apoptosis in haemopoietic progenitor cells exposed to extremely low-frequency magnetic fields. 935 66

The hormonally active form of vitamin D is 1alpha, 25-dihydroxyvitamin D3 [1,25(OH)2D3], which is a principal regulator of calcium homeostasis. It also affects hormone secretion, cell differentiation, and proliferation by a mode of action that involves stereospecific interaction with an intracellular vitamin D receptor (VDR). We recently found that retinoids, which are vitamin A derivatives, exert anticoagulant effects by upregulating thrombomodulin (TM) and downregulating tissue factor (TF) expression in acute promyelocytic leukemia cells and monoblastic leukemia cells. Both the VDR and retinoid receptors belong to the same family of receptors. A heterodimer consisting of the retinoid X receptor and the VDR binds to vitamin D responsive elements on genes regulated by vitamin D. To determine whether 1,25(OH)2D3 would exhibit anticoagulant effects similar to retinoids, we measured the antigen level, activity, and mRNA level of TM and TF in human leukemic cells, vascular endothelial cells, and monocytes treated with 1,25(OH)2D3. We found that 1,25(OH)2D3 upregulates antigen expression, activity, and mRNA levels of TM and downregulates antigen expression, activity, and mRNA levels of TF in human monocytic leukemia cells, some acute myelogenous leukemia cells, and monocytes, but not in umbilical vein endothelial cells. Transient transfection studies with reporter plasmids in monocytic leukemia cells and mobility gel-shift assay showed interaction with 1,25(OH)2D3 and functional retinoic acid responsive elements present in the 5'-flanking region of the TM gene. However, auxiliary factors or other elements in the TM gene may contribute to VDR specificity and transactivation of the gene in specific target cells. These findings indicate that 1,25(OH)2D3 resembles the retinoids in its control of the transcription of the TM and TF genes in human monocytic cells. Analogs of 1,25(OH)2D3 with anticoagulant activity may serve as adjunctive antithrombotic agents in monocytic leukemia and atherosclerotic disease.
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PMID:Anticoagulant effects of 1alpha,25-dihydroxyvitamin D3 on human myelogenous leukemia cells and monocytes. 963 12

A cell separation system based on the calcium-dependent interaction of calmodulin (CM) with a calmodulin-binding peptide (CBP) has been developed. The prototype of this system utilizes an indirect method to label the target cell population. Cells are first labeled with a primary monoclonal antibody directed to a specific cell surface antigen, then with a secondary affinity reagent, consisting of a polyclonal goat anti-mouse IgG (GAM-IgG) that has been cross-linked to a CBP derived from the sequence of the rabbit skeletal muscle myosin light chain kinase. In the presence of Ca2+, the CBP on the cells labeled with GAM-IgG-CBP binds to biotinylated calmodulin (CM-Biotin) with high affinity. The target cells are then captured with a solid-phase streptavidin. The unbound non-target cells are washed away and the immobilized target cells are released by chelating Ca2+ with EGTA. The specificity of the GAM-IgG-CBP and CM-Biotin and the feasibility of using this system to separate cells was demonstrated using the KG-1 human acute myelogenous leukemia cell line. KG-1 cells were fractionated on the basis of cell surface expression of HLA-DR. The cell selection reagents and the cell separation process did not affect KG-1 cell viability while cells selected by this procedure were 90% pure with a yield of 75%. This cell separation system also was used for rare cell isolation from normal human peripheral blood mononuclear cells. T cells expressing the Vbeta5 T cell receptor, which represent < 5% of the unfractionated cells, were isolated with 89% viability, 72% purity, 80% yield, and retained the ability to respond to activation signals as measured by blast transformation. The results from this study show that a cell selection system based on the reversible interaction between CM and a CBP can be applied to gently and efficiently isolate cells from a heterogeneous starting population that are free of the solid matrix without exposure to the stresses of mechanical or enzymatic release.
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PMID:Cell separation based on the reversible interaction between calmodulin and a calmodulin-binding peptide. 967 Nov 54

The glutathione-depleting agent buthionine sulfoximine (BSO) was found to be toxic to some AML blast populations. This toxicity was manifested as the appearance of high levels of reactive oxygen generation in GSH-depleted cells, and later by the loss of mitochondrial membrane potential and an increase in intracellular calcium. Striking heterogeneity in BSO sensitivity was observed in a series of four human AML cell lines, and in fresh leukemic blasts obtained from eight AML patients. In some cases, toxicity was seen at BSO concentrations as low as 1 microM; approximately 100-fold less than the plasma levels achieved in patients treated with BSO as a drug resistance reversing agent. Based on these results we propose that some AML blast populations are unusually dependent on GSH-based antioxidant mechanisms, due to high intrinsic rates of reactive oxygen generation. The mitochondrial respiratory chain is the most likely source of this reactive oxygen. Because toxicity is seen at clinically achievable concentrations of BSO, this agent might have antileukemic activity in patients.
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PMID:Antileukemic action of buthionine sulfoximine: evidence for an intrinsic death mechanism based on oxidative stress. 976 98

OCI/AML-2 acute myeloid leukemia cells were found to undergo apoptosis after treatment with y rays from a 137Cs source. Multilaser flow cytometry techniques using probes for live cell function were used to monitor the biochemical changes that occurred prior to the loss of surface membrane integrity. These showed increases in the generation of reactive oxygen species (ROS) and in the glutathione (GSH) content of irradiated cells. An additional population of cells that showed a further increase in ROS and depletion of GSH was seen in irradiated cells but not in controls. This population showed loss of mitochondrial membrane potential (deltapsim), indicative of the mitochondrial permeability transition, and exposure of phosphatidylserine on the cell surface. Increases in intracellular calcium were observed in a proportion of these low-deltapsi(m)/high-ROS cells. Similar findings were seen using the antileukemia drug cytosine arabinoside (ara-C), although cell cycle analysis showed that the loss of deltapsi(m) occurred mainly in G1 phase with ara-C treatment, and mainly in G2 phase with irradiation. Furthermore, the protective effect of overexpression of BCL2 was more pronounced after ara-C treatment than with radiation. Cells of the TP53 (formerly known as p53)-null human AML line OCI M2 showed growth arrest in G2 phase after radiation treatment, with no loss of deltapsi(m) or morphological changes indicative of apoptosis. The flavine-dependent oxidoreductase inhibitor diphenylene iodonium failed to inhibit generation of ROS in irradiated OCI/AML-2 cells, indicating that the mechanism is unlikely to involve the TP53-induced gene PIG3. These results show that oxidative stress can occur in irradiated human leukemia "blasts", and may play a direct role in radiation-induced apoptosis.
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PMID:An oxidative stress-mediated death pathway in irradiated human leukemia cells mapped using multilaser flow cytometry. 984 Jan 83

The mechanism underlying the cytotoxicity mediated by a human CD4(+) cytotoxic T-lymphocyte (CTL) clone directed against a peptide derived from the acute myelogenous leukemia-associated fusion protein, DEK-CAN, was investigated. A DEK-CAN fusion peptide-specific CD4(+) Th0 CTL clone, designated HO-1, was established from the peripheral blood lymphocytes of a healthy individual. HO-1 exerted direct but not "innocent bystander" cytotoxicity within 2 hours. The cytotoxicity mediated by HO-1 was completely Ca2+-dependent. Because HO-1 lysed peptide-loaded Fas-deficient target cells derived from a patient with a homozygous Fas gene mutation, its cytotoxicity appeared to be mediated by a Fas-independent pathway. In addition, its cytotoxicity was only partially inhibited by treatment with concanamycin A and strontium ions, which are inhibitors of the perforin-based cytotoxic pathway. Although membrane-bound type of tumor necrosis factor-alpha (TNF-alpha) was expressed on HO-1, an anti-TNF-alpha antibody had no effect on HO-1-mediated cytotoxicity. HO-1 expressed mRNA for apoptosis-inducing mediators, including perforin, granzyme B, Fas ligand, TNF-alpha, and lymphotoxin; however, no DNA fragmentation was detected in target cells incubated with HO-1 by 5-[125I]Iodo-2'-deoxyuridine release assay and agarose gel electrophoresis of DNA. Although it has been suggested that the Fas/Fas ligand system is the main pathway by which CD4(+) CTL-mediated cytotoxicity is exerted in murine systems, HO-1 produced peptide-specific and HLA-restricted cytotoxicity via a Fas-independent and nonapoptotic pathway. The present study thus describes a novel mechanism of cytotoxicity mediated by CD4(+) CTL.
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PMID:Fas-independent and nonapoptotic cytotoxicity mediated by a human CD4(+) T-cell clone directed against an acute myelogenous leukemia-associated DEK-CAN fusion peptide. 992 Aug 42

Human recombinant CK2 subunits were incubated for different times with the two main cytosolic proteases m-calpain and 20 S proteasome. Both, m-calpain in a calcium dependent manner and the 20 S proteasome, were able to degrade CK2 subunits in vitro. In both cases, CK2alpha' was more resistant to these proteases than CK2alpha. When these proteases were assayed on the reconstituted (alpha2beta2 holoenzyme), a 37 kDa alpha-band, analogous to that observed in AML extracts, was generated which was resistant to further degradation. No degradation was observed when the 26 S proteasome was assayed on free subunits. Studies with CK2alpha deletion mutants showed that m-calpain and the 20 S proteasome acted on the C-terminus end of CK2alpha. These results pointed to cytosolic proteases as agents involved in the control of the amount of free CK2 subunits within the cell, which becomes evident when CK2 is overexpressed as in AML cells.
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PMID:Multiple forms of protein kinase CK2 present in leukemic cells: in vitro study of its origin by proteolysis. 1009 13

Using a newly developed PCR-based technique called methylated CpG island amplification, we have identified several DNA fragments that are aberrantly methylated in a colon cancer cell line. One of the fragments, termed MINT31, mapped to human chromosome 17q21, where frequent loss of heterozygosity is detected in various human tumors. By characterizing the genomic sequence around this area, we identified a gene encoding a T-type calcium channel, CACNA1G, as a target for hypermethylation in human tumors. By reverse transcriptase-PCR we detected expression of CACNA1G in normal colon and bone marrow, but expression was absent in the five tumor cell lines in which methylation was found. After treatment with the methylation inhibitor 5-deoxyazacytidine, the expression of CACNA1G was restored in all five cell lines. Detailed methylation mapping of the 5' CpG island by bisulfite-PCR revealed that methylation of a region 300-800 bp upstream of the translation initiation site closely correlated with the inactivation of CACNA1G. This region contained the transcription start site, as determined by 5' rapid amplification of cDNA ends analysis. Aberrant methylation of CACNA1G was also examined in various human primary tumors and was detected in 17 of 49 (35%) colorectal cancers, 4 of 16 (25%) gastric cancers, and 3 of 23 (13%) acute myelogenous leukemia cases. Inactivation of CACNA1G may play a role in cancer development by modulating calcium signaling, which potentially affects cell proliferation and apoptosis.
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PMID:Inactivation of CACNA1G, a T-type calcium channel gene, by aberrant methylation of its 5' CpG island in human tumors. 1049 2


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