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

The cytosolic glutathione S-transferases of rat liver have been fractionated by chromatofocusing into 10 distinct fractions based on their reactivity with 2,4-dinitrochlorobenzene. All these fractions were capable of generating leukotriene C4 (LTC4) from leukotriene A4 (LTA4) to some extent. An inhibitor of leukotriene synthesis, U-60,257, inhibited the activity of these enzymes. The cytosolic glutathione S-transferases of rat basophil leukemia (RBL) cells have been similarly fractionated. U-60,257 inhibited the activity of some of these fractions but not that of others. None of the fractions of the enzyme from RBL cells formed LTC4 from LTA4. The microsomal glutathione S-transferase from rat liver also produced LTC4 from LTA4. It differs from the microsomal LTC synthetase of RBL cells in at least two respects: (1) The enzyme from RBL cells did not react with chromophoric substrates like dinitrochlorobenzene while the enzyme from liver did react. (2) Triton X-100 potentiated the activity of the enzyme from basophil leukemia cells and solubilized it, while it inhibited the activity of the leukotriene-synthesizing enzyme in the rat liver preparation. These results, along with a distinctly different inhibitor profile, indicate that LTC synthetase is a new and distinct glutathione S-transferase.
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PMID:Leukotriene C synthetase, a special glutathione S-transferase: properties of the enzyme and inhibitor studies with special reference to the mode of action of U-60,257, a selective inhibitor of leukotriene synthesis. 638 74

Addition of the calcium inophore, A 23187, and cysteine to isolated mononuclear cells from rat peritoneal washings causes a marked increase in the formation of thromboxane B2 (TxB2) along with the formation of leukotrienes C and D (LT's). The formation of LT's in this system was inhibited by 6,9-deepoxy-6,9-(phenylimino)-delta 6,8-prostaglandin I1, U-60,257, or its methyl ester, U-56,467, (ID50 4.6 and 0.31 microM, respectively). There was no inhibition of TxB2 formation. By contrast, two structurally-related compounds, PGI2 and its stable analog, 6-beta-PGI1, did not affect the formation of either LT's or TxB2. The inhibition of LT formation by U-60,257 was rapidly reversed after removal of this compound from the cells. U-60,257 did not inhibit the cyclooxygenase of human polymorphonuclear leukocytes. Nor did it inhibit formation of 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) in human platelets. On the other hand, U-60,257 inhibited glutathione S-transferase activity of rat basophil leukemia cells (ID50, 37 microM), suggesting that this compound may inhibit the last step in LTC biosynthesis. In addition to inhibiting LT synthesis, U-60,257 also appears to be a competitive inhibitor of the action of LT on the guinea pig ileum, although this inhibition requires a higher drug concentration than those ordinarily encountered during assay for LT's in U-60,257-treated incubations.
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PMID:6,9-deepoxy-6,9,-(phenylimino)-delta 6,8-prostaglandin I1, (U-60,257), a new inhibitor of leukotriene C and D synthesis: in vitro studies. 681 65

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and erythropoietin (Epo) are hematopoietic growth factors that regulate proliferation and differentiation of hematopoietic cells. They elicit and control a cascade of biochemical events, the earliest of which is tyrosine phosphorylation of several cellular proteins. Grb2/Ash is composed of SH2 and SH3 domains. The SH2 domain binds to tyrosine-phosphorylated proteins, and the SH3 domains bind to proteins containing proline-rich regions. It is considered that Grb2/Ash functions as an adapter protein linking tyrosine kinases and Ras in downstream of receptors for growth factors in fibroblasts. However, the mechanisms of signal transduction through Grb2/Ash and the roles of proteins associated with Grb2/Ash remain to be determined in hematopoietic cells. By means of the binding experiments using the glutathione S-transferase fusion protein including the full-length Grb2/Ash, we have found that Shc and unidentified 130- and 135-kDa proteins are associated with Grb2/Ash and that they are tyrosine phosphorylated by treatment with GM-CSF or Epo in a human leukemia cell line, UT-7. We have purified the 130-kDa protein (pp130) using the glutathione S-transferase-Grb2/Ash affinity column. The amino acid sequence analysis of the three peptides derived from the in situ protease digestion of the purified pp130 showed that the pp130 was identical to the human c-cbl proto-oncogene product (c-Cbl). c-Cbl constitutively binds to the SH3 domain of Grb2/Ash both in vitro and in vivo but not to the SH2 domain of Grb2/Ash, and the binding of Grb2/Ash to c-Cbl or Sos was not altered by GM-CSF stimulation. Moreover, c-Cbl (pp130) becomes tyrosine phosphorylated rapidly and transiently depending on GM-CSF or Epo stimulation. These findings strongly suggest that c-Cbl is implicated in the signal transduction of GM-CSF or Epo in hematopoietic cells and that c-Cbl is involved in another signaling pathway different from the Ras signaling pathway.
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PMID:The proto-oncogene product c-Cbl becomes tyrosine phosphorylated by stimulation with GM-CSF or Epo and constitutively binds to the SH3 domain of Grb2/Ash in human hematopoietic cells. 753 40

Benzene is a human carcinogen; exposure to benzene can result in aplastic anemia and leukemia. Data from animal models are frequently used in the risk assessment for benzene. In rodent studies, mice have been shown to be more sensitive to benzene-induced hematotoxicity than rats. In this regard, we have observed that bone marrow stromal cells from mice were significantly more susceptible to the cytotoxicity induced by the benzene metabolites hydroquinone (HQ) and benzoquinone (BQ) than cells from rats. Since cellular glutathione (GSH) and quinone reductase (QR) are known to play critical roles in modulating HQ-induced cytotoxicity, we have measured the GSH content and the QR and glutathione S-transferase (GST) activity in stromal cells from both species. In rat cells, the GSH content and the QR specific activity were 2 and 28 times as much as those from mice, respectively. GSH and QR in both mouse and rat stromal cells were inducible by 1,2-dithiole-3-thione (D3T). D3T pretreatment of both mouse and rat stromal cells resulted in a marked protection against HQ-induced toxicity. Pretreatment of both mouse and rat stromal cells with GSH ethyl ester also provided a dramatic protection against HQ-induced toxicity. Conversely, dicoumarol, an inhibitor of QR, enhanced the HQ-induced toxicity in stromal cells from both mice and rats, indicating an important role for QR in modulating HQ-induced stromal toxicity in both species. Buthionine sulfoximine (BSO), which depleted GSH significantly in both species, potentiated the HQ-induced toxicity in mouse but not in rat stromal cells. Surprisingly, incubation of stromal cells with BSO resulted in a significant induction of QR, especially in rats. The failure of BSO to potentiate HQ-induced toxicity in rat stromal cells may be due to the concomitant induction of QR by BSO. Overall, this study demonstrates that the differences in stromal cellular GSH content and QR activity between mice and rats contribute to their respective susceptibility to HQ-induced cytotoxicity in vitro, and may be involved in the greater in vivo sensitivity of mice to benzene-induced hematotoxicity.
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PMID:Differences in xenobiotic detoxifying activities between bone marrow stromal cells from mice and rats: implications for benzene-induced hematotoxicity. 756 17

The development of drug resistance is an important factor contributing to failure of chemotherapy in cancer patients. Cyclophosphamide (CP) is a cytostatic drug widely used in the treatment of haematological malignancies and solid tumours. Because CP requires bioactivation to become cytotoxic, an in vivo approach was chosen to generate a subline of the Brown Norway rat acute myelocytic leukaemia (BNML/CPR) highly resistant to CP to serve as a model to investigate the molecular mechanism(s) of cyclophosphamide resistance. The role of the CP-detoxifying enzyme aldehyde dehydrogenase (ALDH) in the molecular mechanism of CP resistance in this subline of the BNML has been investigated. Compared to the parent BNML cell line, the BNML/CPR cell line displayed an approximately 6-fold higher level of ALDH enzyme activity. Pretreatment of leukaemic rats with the ALDH inhibitor disulfiram resulted in a restoration of CP sensitivity of animals carrying the BNML/CPR cells. Furthermore, in vitro incubation of BNML/CPR cells with disulfiram prior to incubation with the activated CP derivative mafosfamide resulted in an extra 2-3 log cell kill as indicated by the survival time of rats which were injected with disulfiram pretreated BNML/CPR cells compared to non-pretreated BNML/CPR cells. Data on the glutathione S-transferases (GSTs) isozyme profiles of cytoplasmic liver and spleen extracts of BNML- and BNML/CPR-carrying leukaemic rats indicated that the total GST enzyme amount was lower in BNML/CPR cells than in parent BNML cells. Furthermore, the BNML/CPR subline proved to be sensitive to phosphoramide mustard, both in vivo and in vitro.
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PMID:Aldehyde dehydrogenase involvement in a variant of the brown Norway rat acute myelocytic leukaemia (BNML) that acquired cyclophosphamide resistance in vivo. 785 14

Murine L1210 and human HL-60 leukemia cells grown for 5-7 days in medium containing 1% serum without selenium supplementation [Se(-) cells] were severely depressed in selenoperoxidase (SePX) activity relative to selenium-supplemented controls [Se(+) cells]. Catalase (CAT) activity in Se(-) cells was unaffected up to this point, but thereafter began to increase. Two manifestations of this increase have been differentiated for both cell lines: (a) short-term induction of CAT (up to approx. twofold) after 2-3 weeks, followed by (b) long-term selection for cells that irreversibly express much higher levels of CAT, e.g., > 100 times (L1210) and > 10 times (HL-60) the levels observed in Se(+) controls after approximately 20 weeks. Although superoxide dismutase, glutathione S-transferase, and glucose-6-P dehydrogenase activities were unchanged in Se(-) cells, GSH levels were elevated by 50-100%; like short-term CAT elevation, this could be reversed by supplying Se. Short-term Se(-) cells were more sensitive to H2O2-induced killing than Se(+) cells, evidently because SePX activity was important for peroxide detoxification. However, long-term Se(-) cells were markedly more resistant to H2O2 than Se(+) counterparts, consistent with the much higher levels of CAT in the former. Southern blot analysis revealed that the copy number of CAT DNA in a clone of long-term Se(-) L1210 cells was four- to fivefold greater than that in an Se(+) clone. Northern blot analysis of RNA from the same Se(-) clone showed a CAT mRNA level that was at least 40 times higher than that of the Se(+) control. Similar trends were observed for HL-60 cells. These results suggest that elevated CAT during long-term Se deprivation is a reflection of amplification and greater transcription of the CAT gene.
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PMID:Amplification and hyperexpression of the catalase gene in selenoperoxidase-deficient leukemia cells. 787 6

The cytokine melanoma growth-stimulating activity (MGSA) is a growth factor for melanoma cells and a chemotaxin for neutrophils. Known purification procedures of MGSA from human sources or expression systems give a low yield and require multiple chromatography steps. Here, a fast and high-yield method for the purification of recombinant MGSA is described. Approximately 500 micrograms MGSA were recovered from the bacterial lysate of a 10 liter culture within a day. For this purpose, total mRNA of Hs294T melanoma cells was isolated and cDNA of MGSA was obtained by reverse transcription and polymerase chain reaction. The cDNA of MGSA was subcloned into the expression vector pGEX-2T, generating a fusion with the Schistosoma japonicum glutathione S-transferase gene. The fusion protein was expressed in E. coli DH5a and purified from the bacterial lysate using glutathione-sepharose beads. MGSA was cleaved from the complex of fusion protein and glutathione-sepharose beads with thrombin and purified to homogeneity by anion-exchange high-performance liquid chromatography with a Mono-S-column. The bioactivity of the recombinant MGSA was assessed by chemotactic migration and triggered [Ca2+]i-transients in human neutrophils. In addition, [125I]MGSA bound specifically to undifferentiated human leukemia cells HL-60 transfected with the cDNA of the interleukin-8 (IL-8) receptor beta with similar properties as [125I]IL-8. Thus, this described method might be a powerful tool to generate large amounts of cytokines in a short time.
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PMID:Single-step purification of recombinant melanoma growth-stimulating activity by anion-exchange high-performance liquid chromatography. 792 55

1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU) resistance has been mostly studied in vitro. In an attempt to better understand BCNU resistance in the in vivo situation, we compared the principal drug-metabolizing enzyme systems in two L1210 leukemia lines, one sensitive and one resistant to BCNU (L1210/BCNU), passaged in vivo in mice. The following enzymes were assayed by immunoblotting: cytochromes P-450 (1A1/1A2, 2B1/2B2, 2C8-10, 2E1, 3A), epoxide hydrolase (EH) and glutathione S-transferase (GST-alpha, -mu and -pi). The following enzymes and cofactors were assayed fluorometrically or spectrophotometrically: 1-chloro-2-4 dinitrobenzene-GST (CDNB-GST), total glutathione (GSH), UDP-glucuronosyltransferase, beta-glucuronidase, sulfatase and sulfotransferase. Results showed that cytochrome P-450 1A1/1A2 was the only isoenzyme detected in both L1210 and L1210/BCNU. CDNB-GST activity was significantly higher in L1210/BCNU compared with L1210. The isoenzyme GST-alpha was more abundant in L1210/BCNU compared with L1210, whereas GST-pi was expressed less in the BCNU-resistant leukemia line. GST-mu was not detected in either L1210 leukemia lines. GSH levels were similar in the two L1210 lines. No significant difference was observed between the two leukemia lines for the conjugative enzymes UDP-glucuronosyltransferase and sulfotransferase, whereas their corresponding hydrolytic enzymes beta-glucuronidase and sulfatase were about two-fold lower in the BCNU-resistant leukemia line. Epoxide hydrolase was 1.3-fold higher in L1210/BCNU compared with L1210 and this level was about three-fold higher than in mouse liver. In conclusion, these studies showed the presence of cytochrome P-450 1A1/1A2 in the two L1210 leukemia lines studied, and indicated noteworthy differences between the two leukemia lines for many enzyme systems such as GST, beta-glucuronidase, sulfatase and epoxide hydrolase. These data are of importance to better understand the mechanisms of drug resistance to nitrosoureas in vivo.
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PMID:Principal drug-metabolizing enzyme systems in L1210 leukemia sensitive or resistant to BCNU in vivo. 796 9

Retroviral integration involves two DNA substrates that play different roles. The viral DNA substrate is recognized by virtue of specific nucleotide sequences near the end of a double-stranded DNA molecule. The target DNA substrate is recognized at internal sites with little sequence preference; nucleosomal DNA appears to be preferred for this role. Despite this apparent asymmetry in the sequence, structure, and roles of the DNA substrates in the integration reaction, the existence of distinct binding sites for viral and target DNA substrates has been controversial. In this report, we describe the expression in Escherichia coli and purification of Moloney murine leukemia virus integrase as a fusion protein with glutathione S-transferase, characterization of its activity by using several model DNA substrates, and the initial kinetic characterization of its interactions with a model viral DNA substrate. We provide evidence for functionally and kinetically distinct binding sites for viral and target DNA substrates and describe a cross-linking assay for DNA binding at a site whose specificity is consistent with the target DNA binding site.
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PMID:Characterization of recombinant murine leukemia virus integrase. 798 42

Human proenkephalin gene transcription is transactivated by human T-cell leukemia virus type I (HTLV-I) Tax in human Jurkat T lymphocytes. This transactivation was further enhanced in Jurkat cells treated with concanavalin A, cyclic AMP, or 12-O-tetradecanoylphorbol-13-acetate. Deletion and cis-element transfer analyses of the human proenkephalin promoter identified a cyclic AMP-responsive AP-1 element (-92 to -86) as both necessary and sufficient to confer Tax-dependent transactivation. Different AP-1 or cyclic AMP-responsive element-binding protein (CREB)/activating transcription factor (ATF) proteins which bind this element were expressed in murine teratocarcinoma F9 cells to identify those capable of mediating Tax-dependent transactivation of human proenkephalin gene transcription. Although CREB, c-Fos, c-Jun, and JunD did not have significant effects, JunB inhibited the Tax-dependent transactivation. In contrast, ATF3 dramatically induced Tax-dependent transactivation, which was further enhanced by protein kinase A. Electrophoretic mobility shift assays with recombinant fusion proteins expressed and purified from bacteria indicate that the DNA-binding activity of ATF3 is also dramatically enhanced by Tax. Chimeric fusion proteins consisting of the DNA-binding domain of the yeast transcription factor Gal4 and the amino-terminal domain (residues 1 to 66) of ATF3 were able to mediate Tax-dependent transactivation of a Gal4-responsive promoter, which suggests a direct involvement of this region of ATF3. Recombinant fusion proteins of glutathione S-transferase with either the amino- or carboxy-terminal (residues 139 to 181) domain of ATF3 were able to specifically interact with Tax. Furthermore, specific antisera directed against Tax coimmunoprecipitated ATF3 only in the presence of Tax.
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PMID:Novel interactions between human T-cell leukemia virus type I Tax and activating transcription factor 3 at a cyclic AMP-responsive element. 800 91


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