Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sulfhydril compounds, some of them with immunomodulatory activity have also been shown to modulate the induction of apoptosis. This study was performed to assess the possible apoptosis inhibitory effect of the immunomodulatory compound tri-(2-thioureido-S-ethyl)-amine (K-1) in U-937 and HL-60 leukaemia cell lines as model systems. Treatment of U-937 and HL-60 cells with K-1 inhibited etoposide (ETO)-induced apoptosis in both cell lines in a dose-dependent manner, IC(50)=200 microg/ml. The results indicate that inhibition of ETO-induced apoptosis occurs downstream of ETO-mediated cleavable complex formation but early in, or at the level of the mitochondria events of the apoptotic pathway. Further, like other isothioureas, K-1 proved to be a potent inhibitor of nitric oxide synthase. This raises the possibility that where the activation of nitric oxide synthase is involved in apoptosis induction, K-1 might also be effective. These findings suggest that K-1 may serve as a potent inhibitor of apoptosis initiated by ETO or nitric oxide.
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PMID:Apoptosis inhibitory effect of the isothiourea compound, tri-(2-thioureido-S-ethyl)-amine. 1070 7

The expression of nitric oxide synthase (NOS) isoforms was investigated in the established ESKOL hairy cell line and in leukemic cells of patients with hairy cell leukemia (HCL). By reverse transcription-polymerase chain reaction (RT-PCR), these cells were found to spontaneously express inducible NOS (iNOS)-specific mRNA, but not endothelial constitutive NOS (ecNOS) mRNA. The iNOS protein was detected by immunofluorescence in the cytoplasm of permeabilized leukemic cells and ESKOL cells, using different anti-iNOS monoclonal antibodies. A protein of 135 kDa was identified by Western blotting in ESKOL and HCL lysates, confirming the presence of an iNOS in these cells. Cytosolic homogenates displayed NOS catalytic activity, as measured by the conversion of 14C-labelled L-arginine into 14C L-citrulline and by detection in situ using the DAF-2DA (diaminofluorescein diacetate) NO-sensitive fluorescent probe. Ligation of CD23 (low affinity IgE receptor) was found to increase iNOS expression in ESKOL and conversely to decrease the percentage of cells undergoing apoptosis, as measured by the percentage of cells expressing annexin V. These results indicate that, as in chronic B cell lymphocytic leukemia cells (B-CLL) a functional iNOS is expressed constitutively in hairy cells that contributes to protecting these tumoral cells from apoptosis.
Leukemia 2000 Apr
PMID:Expression of a functional inducible nitric oxide synthase in hairy cell leukaemia and ESKOL cell line. 1076 57

B cell chronic lymphocytic leukaemia (B-CLL) is characterised by defective apoptosis that cannot be explained solely on the basis of the known chromosomal abnormalities. We and other have now reported that the leukemic cells spontaneously display the inducible isoform of nitric oxide synthase, iNOS. Inhibition of the iNOS pathway leads to increased apoptosis of the tumoral cells in vitro, indicating that the endogenous release of NO contributes to their resistance to the normal apoptotic process. The factors that induce the expression of iNOS in vivo in the leukemic cells are not yet identified. Yet, as interaction of B-CLL leukemic cells with bone marrow stromal cells promotes their survival, the involvement of adhesion molecules and integrins may be suspected. The engagement of CD23 stimulates iNOS activation in the tumoral cells, suggesting that in vivo interaction of CD23 with one of its recognised ligands may contribute to iNOS induction. A role for CD40-CD40 ligand interaction may also be hypothesised. The mechanisms involved in the anti-apoptotic role of NO are not fully understood, but may implicate the inhibition of caspase activity, hence the impairment of the Fas pathway. In addition, the mitochondrial membrane potential disruption appears to be a NO-sensitive step in the apoptosis cascade. The presence of a NOS displaying anti-apoptotic properties has now been recognised in different cell types, including various leukaemia. A better knowledge of the mechanisms governing the ultimate fate of NO, anti- versus pro-apoptotic would allow the development of new therapeutic approaches for the treatment of these diseases.
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PMID:Contribution of nitric oxide to the apoptotic process in human B cell chronic lymphocytic leukaemia. 1142 46

Arsenic is generally recognized as a nonmutagenic carcinogen because sodium arsenite induces DNA damage only at very high concentrations. In this study we demonstrate that arsenite concentrations above 0.25 microM induce DNA strand breaks in both human leukemia cells and Chinese hamster ovary cells. Therefore, DNA damage may be involved in arsenic-induced carcinogenesis. Formamidopyrimidine-DNA glycosylase and proteinase K greatly increased DNA strand breaks in arsenite-treated cells, providing evidence that a large portion of arsenite-induced DNA strand breaks come from excision of oxidative DNA adducts and DNA-protein cross-links. Because DNA strand breaks appear only temporarily during excision repair, the level of detectable DNA strand breaks will be low at any given time point. For this reason many previous studies have only detected low levels of DNA strand breaks. We also show that catalase, and inhibitors of calcium, nitric oxide synthase, superoxide dismutase, and myeloperoxidase, could modulate arsenite-induced DNA damage. We conclude that arsenite induces DNA adducts through calcium-mediated production of peroxynitrite, hypochlorous acid, and hydroxyl radicals.
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PMID:Arsenite induces oxidative DNA adducts and DNA-protein cross-links in mammalian cells. 1146 69

It is generally accepted that the vascular endothelial growth factor (VEGF) signal system has no role in the maintenance of normal blood cell formation, although it obviously regulates the development of primitive hematopoiesis during an early stage of embryogenesis. The VEGF signaling pathway, however, might have some role in malignant hematopoiesis, since malignant hematopoietic cells, including acute myeloid leukemia (AML) cells, have been shown to express VEGF and its receptors. In endothelial cells, the VEGF/Flk-1/KDR signal system is a very important generator of nitric oxide (NO) through the activation of its downstream effectors phosphatidylinositol-3-OH-kinase (PI3-K), Akt kinase and endothelial NO synthase (eNOS). It is known that NO regulates hematopoiesis and modulates AML cell growth. The role of the VEGF signaling pathway in the control of AML cell growth through eNOS, however, has not been studied. By using the OCI/AML-2 cell line, which expresses VEGF receptor-2, ie Flk-1/KDR, eNOS and VEGF, as analyzed by flow cytometry, and produces VEGF into growth medium, as analyzed by ELISA, we showed that the Akt kinase and NOS activities in these cells were decreased by the inhibitors of VEGF, Flk-1/KDR and PI3-K, and NOS activity also by the direct inhibitor of NOS. The decreased NOS activity led to inhibition of clonogenic cell growth and, to some extent, induction of apoptosis. We also found that blast cells of bone marrow samples randomly taken from 14 AML patients uniformly expressed Flk-1/KDR and to varying degrees eNOS and VEGF, as analyzed by immunohistochemistry. We conclude that autocrine VEGF through Flk-1/KDR, by activating eNOS to produce NO through PI3-K/Akt kinase, maintains clonogenic cell growth in the OCI/AML-2 cell line. Since the patient samples did not express VEGF in all cases, it is possible that in vivo the regulatory connection between these two signal systems is also mediated via endocrine VEGF in addition to autocrine or paracrine VEGF.
Leukemia 2001 Sep
PMID:Regulation of the acute myeloid leukemia cell line OCI/AML-2 by endothelial nitric oxide synthase under the control of a vascular endothelial growth factor signaling system. 1151 4

Human saphenous veins were cultured to characterize neointima formation and feasibility of gene transfer to inhibit the intimal proliferative response to injury. Mechanical injury was introduced by abrading the luminal surface of the vein patch with a sterile cotton bud. Both injured and non-injured vein patches were cultured and transduced with retroviral vectors carrying marker or therapeutic genes. After a 14-day culture, the thickness of the intimal layer of non-injured vein patches reached 90+/-28 microm at the edge and 61+/-22 microm at the center (n=29) from the original 22+/-12 microm at harvest (n=6, P=0.02). Mechanical injury to the intimal surface prior to culture resulted in an exaggerated proliferative response. The intimal thickness of injured vein patches increased from 3.4+/-1 microm right after injury to 128+/-23 microm (n=12, P<0.001) at the edge after 14-day culture. Genes were transduced efficiently into a luminal layer of cultured veins using a pseudotyped murine leukemia viral vector. Transduction of gene encoding nitric oxide synthase resulted in reduction of neointima formation to 33+/-7 microm (n=12) at the edge after 14-day culture compared to 90 microm (P<0.01) seen in untransduced non-injured vein patches. Marker gene transduction did not alter intimal proliferative response or its immunohistochemical profile. The data suggest that cultured vein can be used as a model for studying the effects of injury to blood vessels and to evaluate the effects of candidate therapeutic genes.
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PMID:Injury induced neointima formation and its inhibition by retrovirus-mediated transfer of nitride oxide synthase gene in an in-vitro human saphenous vein culture model. 1188 23

Nitric oxide (NO) is a biological mediator that is synthesized from L-arginine by the nitric oxide synthase (NOS) family. We investigated the expression of iNOS in bone marrow (BM) mononuclear cells (MNCs) using a reverse transcriptase polymerase chain reaction (RT-PCR) assay and the concentration of NO from BM serum by measuring the metabolite NO(2)(-) in 13 patients with aplastic anemia (AA) compared with 10 normal controls who were donors for allogeneic bone marrow transplantation (BMT). All samples of BM MNCs in patients with AA expressed iNOS mRNA, but iNOS was not expressed in patients who were treated successfully with allogeneic BMT. Normal control samples and samples from leukemia patients who had bone marrow aplasia after chemotherapy did not show significant iNOS expression. When we measured the density of bands for both iNOS and beta(2)-microglobin expressed as the iNOS/beta(2)-microglobin density ratio, there was a significant difference in the ratio between AA and normal controls (0.88+/-0.15 vs 0.26+/-0.05, P<0.001). The BM serum NO(2)(-) concentration in the patients with AA was significantly higher than that of normal controls (88.1+/-32.8 microM vs 48.8+/-8.6 microM, P=0.002). In addition, there was a significant correlation between the NO(2)(-) concentration and the calculated iNOS/beta(2)-microglobin density ratio (r=0.567, P=0.01). These findings suggest that upregulation of iNOS expression for local NO production may contribute in part to the pathogenesis of AA.
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PMID:Increased inducible nitric oxide synthase expression and nitric oxide concentration in patients with aplastic anemia. 1260 89

Flavopiridol, an inhibitor of cyclin-dependent kinases and other protein kinases, induces in vitro apoptosis of malignant cells from B-cell chronic lymphocytic leukemia (B-CLL). Previously, we reported that nitric oxide (NO), produced by an inducible NO synthase (iNOS), spontaneously expressed by the B-CLL cells, contributed to their deficiency in apoptosis. In the present work, we show that ex vivo treatment of leukemic cells from B-CLL patients with flavopiridol results in the inhibition of iNOS expression, as determined by immunofluorescence and Western blotting, and in a marked inhibition of NO production measured in situ with a specific fluorescent probe (DAF-2 DA). These effects are accompanied by membrane, mitochondrial and nuclear events of apoptosis. Flavopiridol exposure also results in the stimulation of caspase 3 activity and in caspase-dependent cleavage of p27(kip1), a negative regulator of the cell cycle, which is overexpressed in B-CLL. Thus, flavopiridol is capable of downregulating both iNOS and p27(kip1) expression in B-CLL cells. Furthermore, flavopiridol-promoted apoptosis is partly reverted by an NO donor, suggesting that inhibition of the NO pathway could participate in the apoptotic effects of flavopiridol on the leukemic cells.
Leukemia 2003 Dec
PMID:Flavopiridol downregulates the expression of both the inducible NO synthase and p27(kip1) in malignant cells from B-cell chronic lymphocytic leukemia. 1467 37

The change in cellular reducing potential, most likely reflecting an oxidative burst, was investigated in arachidonic acid- (AA) stimulated leukocytes. The cells studied included the human leukemia cell lines HL-60 (undifferentiated and differentiated into macrophage-like and polymorphonuclear-like cells), Jurkat and Raji, and thymocytes and macrophages from rat primary cultures. The oxidative burst was assessed by nitroblue tetrazolium reduction. AA increased the oxidative burst until an optimum AA concentration was reached and the burst decreased thereafter. In the leukemia cell lines, optimum concentration ranged from 200 to 400 microM (up to 16-fold), whereas in rat cells it varied from 10 to 20 microM. Initial rates of superoxide generation were high, decreasing steadily and ceasing about 2 h post-treatment. The continuous presence of AA was not needed to stimulate superoxide generation. It seems that the NADPH oxidase system participates in AA-stimulated superoxide production in these cells since the oxidative burst was stimulated by NADPH and inhibited by N-ethylmaleimide, diphenyleneiodonium and superoxide dismutase. Some of the effects of AA on the oxidative burst may be due to its detergent action. There apparently was no contribution of other superoxide-generating systems such as xanthine-xanthine oxidase, cytochromes p-450 and mitochondrial electron transport chain, as assessed by the use of inhibitors. Eicosanoids and nitric oxide also do not seem to interfere with the AA-stimulated oxidative burst since there was no systematic effect of cyclooxygenase, lipoxygenase or nitric oxide synthase inhibitors, but lipid peroxides may play a role, as indicated by the inhibition of nitroblue tetrazolium reduction promoted by tocopherol.
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PMID:Arachidonic acid triggers an oxidative burst in leukocytes. 1457 10

Viruses have developed strategies to counteract the apoptotic response of the infected host cells. Modulation of apoptosis is also thought to be a major component of viral persistence and progression to leukemia induced by retroviruses like human T-lymphotropic virus type 1 (HTLV-1) and bovine leukemia virus (BLV). Here, we analyzed the mechanism of ex vivo apoptosis occurring after isolation of peripheral blood mononuclear cells from BLV-infected sheep. We show that spontaneous apoptosis of ovine B lymphocytes requires at least in part a caspase 8-dependent pathway regardless of viral infection. Cell death is independent of cytotoxic response and does not involve the tumor necrosis factor alpha/NF-kappaB/nitric oxide synthase/cyclooxygenase pathway. In contrast, pharmaceutical depletion of reduced glutathione (namely, gamma-glutamyl-l-cysteinyl-glycine [GSH]) by using ethacrynic acid or 1-pyrrolidinecarbodithioic acid specifically reverts inhibition of spontaneous apoptosis conferred indirectly by protective BLV-conditioned media; inversely, exogenously provided membrane-permeable GSH-monoethyl ester restores cell viability in B lymphocytes of BLV-infected sheep. Most importantly, intracellular GSH levels correlate with virus-associated protection against apoptosis but not with general inhibition of cell death induced by polyclonal activators, such as phorbol esters and ionomycin. Finally, inhibition of apoptosis does not correlate with the activities of GSH peroxidase and GSH reductase. In summary, our data fit into a model in which modulation of the glutathione system is a key event involved in indirect inhibition of apoptosis associated with BLV. These observations could have decisive effects during therapeutic treatment of delta-retroviral pathogenesis.
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PMID:Involvement of glutathione as a mechanism of indirect protection against spontaneous ex vivo apoptosis associated with bovine leukemia virus. 1516 11


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