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)

The natural product of the Red Sea sponge Verongia sp., identified as 3,5,8-trihydroxy-4-quinolone, was found to be a potent inhibitor of the RNA-directed DNA synthesis of the reverse transcriptases (RTs) of human immunodeficiency viruses type 1 and type 2 (HIV-1 and HIV-2, respectively). This inhibition was unaffected by the nature of the primer template used for DNA synthesis. The DNA-dependent DNA polymerase activity was inhibited to a lesser extent, whereas the ribonuclease H (RNase H) function associated with both HIV RTs was only slightly inhibited. The inhibition by the trihydroxyquinolone is reversible and noncompetitive with respect to both substrates--dTTP and the template primer poly(rA)n.oligo(dT)12-18. The inhibitor binds HIV-1 RT with a high affinity (Ki = 0.46 microM). This compound was shown also to inhibit the catalytic activities of the RT of murine leukemia virus, establishing the general inhibitory effect on retroviral RTs. Introductions of acetyl or methoxy moieties at positions with potential activity have generated three synthetic analogs of the natural compound. Only one analog, 5,8-dimethoxy-4-quinolone, exhibited an inhibition potency similar to that of the unmodified compound. Analysis of the three analogs has led us to the conclusion that the hydroxyl group at the ortho position to the carbonyl group in the pyridinone ring is a key structural element for the inhibitory activity. Thus, it could well be that the inhibitor interacts with the enzyme through a hydrogen bond of this hydroxyl group. We hope that the identification of the inhibitory site of the compound might be an important step toward the rational design of new potent anti-HIV RT drugs.
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PMID:3,5,8-Trihydroxy-4-quinolone, a novel natural inhibitor of the reverse transcriptases of human immunodeficiency viruses type 1 and type 2. 751 Sep 44

Fifty-seven Thai herbs and spices were examined for their retroviral reverse transcriptase inhibitory activity. All herbs and spices were extracted with hot-water and methanol. Reverse transcriptase inhibitory activity of the extracts was determined by using Moloney Murine Leukemia Virus reverse transcriptase (M-MuLV-RT) reacted with 3H-dTTP and radioactivity measured with a scintillation counter. Eighty-one per cent (46/57) of hot-water extracts and 54% (31/57) of methanol extracts showed inhibitory activities. At a concentration of 125 micrograms/ml, 13% (6/46) of hot-water extracts, namely Eugenia caryophyllus Bullock et Harrison, Phyllanthus urinaria Linn., Terminalia belerica Roxb., Nelumbo nucifera Gaertn., Psidium guajava Linn. and Lawsonia inermis Linn., had a relative inhibitory ratio (IR) over 50%. They showed ratios of 100%, 91%, 75%, 74%, 61% and 60%, respectively. For methanol extracts, only 10% (3/31) had IR values over 50%. They were T. belerica, E. caryophyllus and N. nucifera which exhibited IR values of 83%, 54% and 54%, respectively.
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PMID:Retroviral reverse transcriptase inhibitory activity in Thai herbs and spices: screening with Moloney murine leukemia viral enzyme. 752 65

G-->A hypermutation is a remarkable phenomenon resulting from retroviral reverse transcription in the presence of highly biased dNTP concentrations. Of the three reverse transcriptases (RTases) available, those of human immunodeficiency virus type 1 (HIV-1), avian myeloblastosis virus (AMV) and Moloney murine leukemia virus (MoMLV), the HIV-1 enzyme showed the greatest sensitivity to biased [dCTP]/[dTTP] ratios. The HIV-1 RTase was able to discriminate between dUTP, dITP and the four DNA precursors and was insensitive to pH. There was little preference for nucleotide contexts. A few exceptionally modified sequences were found presumably resulting from G-->A hypermutation and multiple strand transfer. This particular predilection of the HIV-1 and, by extrapolation, the lentiviral RTases towards G-->A hypermutation suggests that the phenomenon may have contributed to the remarkably elevated A content of these retroviral genomes.
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PMID:Reverse transcriptase and substrate dependence of the RNA hypermutagenesis reaction. 754 58

Previous work in our laboratory showed that UFT (mixed compound of tegafur and uracil, molar ratio 1:4, respectively) caused the prolonged reduction of dTTP in L1210 leukemia cells in comparison with 5-fluorouracil (5-FU). The purpose of this study was to assess the effect of UFT on cell cycle distribution and thymidylate synthase activity of a leukemia cell line as compared with 5-FU. UFT and 5-FU were orally given to BDF1 mice bearing L1210 ascites tumor on day 3 after the tumor inoculation. Cell cycle distribution patterns at 24 hr after the drug administration showed a higher percentage of S phase in tumor cells treated with UFT than in those treated with 5-FU. Until 6 hr after the oral administration of the drugs, UFT inhibited the incorporation of [3H] deoxyuridine into DNA more long than 5-FU did. These results indicated that UFT has longer and stronger inhibitory effects on DNA replication than 5-FU in vivo under the employed experimental conditions (i.e., low and single doses of these fluorinated pyrimidines).
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PMID:Effects of UFT (mixed compound of tegafur and uracil) on cell kinetics and inhibition of thymidylate synthase in L1210 ascites tumor. 755 12

The N-pyridinyl and N-quinolinyl substituted derivatives of phthalimides and succinimides demonstrated cytotoxicity against the growth of a number of cultured cell lines. The substituted succinimides were more effective than the unsubstituted succinimide derivative in reducing cell growth. On the other hand, phthalimide demonstrated more potent cytotoxicity than its N-substituted derivatives. Three representative examples N-[2-pyridinyl-1-oxide) methyl] phthalimide 8, 1-[N-2-phthalimidoethyl]-3,4-dihydroiso-quinoline 12, and 1-[N-(2-(1,2,3,4-tetrahydro-2-quinolinyl)] ethylphthalimide 14 were shown to inhibit L1210 leukemia DNA synthesis whereas RNA synthesis was not inhibited at 25-100 uM. All three agents inhibited the activities of DNA polymerase alpha, PRPP-amido transferase, nucleoside kinases, and dihydrofolate reductase. The cellular pool levels of d[GTP], d[CTP], and d[TTP] were reduced after 60 minutes incubation at 100 uM. The DNA molecule itself was not a target of these agents.
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PMID:The cytotoxicity of N-Pyridinyl and N-quinolinyl substituted derivatives of phthalimide and succinimide. 757 4

Deoxycytidine kinase is a key anabolic enzyme for the activation of ara-C and other antitumor drugs, as well as normal purine and pyrimidine deoxynucleotides. Previously, two forms of the kinase have been identified; deoxycytidine kinase I (70 kDa) and deoxycytidine kinase II (70 kDa). Deoxycytidine kinase I utilized dCyd and ara-C as substrates, while deoxycytidine kinase II used dCyd and dThd as substrates. Deoxycytidine kinase kinase II had very low activity on ara-C as a substrate. We report a procedure for the purification of a novel deoxycytidine kinase (52 kDa) from isolated human peripheral blood leukemia cell mitochondria. This enzyme has activity similar to deoxycytidine kinase II. The enzyme was extracted from the mitochondria with digitonin (1 mg/8 mg protein) and 0.3 M NaCl, and the extract was purified by DEAE-cellulose chromatography and thymidine-Sepharose affinity chromatography. This procedure produced a near homogeneous enzyme preparation with a yield of 70%. The mitochondrial deoxycytidine kinase was localized to the outer mitochondrial membrane. The enzyme phosphorylated dCyd (Km = 17 microM), however, ara-C was not a good substrate for the mitochondrial deoxycytidine kinase. ATP was the best phosphate donor, whereas dCTP and dTTP were potent inhibitors of mitochondrial deoxycytidine kinase. In contrast, phosphorylation of ara-C by deoxycytidine kinase I utilized GTP, dGTP, or ATP as a phosphate donor.
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PMID:Purification and characterization of deoxycytidine kinase from acute myeloid leukemia cell mitochondria. 839 94

The effect of mutational loss of thymidine kinase (TK) on the sensitivity to alkylating agents was investigated in promyelocytic, HL-60, and T-lymphoblastoid, Molt-3, human leukemia cell lines. Although both cell lines exhibited approx. 1% residual TK activity, only HL-60 TK deficient cells had a decreased intracellular TTP pool, i.e., 20% of that of the wild-type. When treated with N-methyl-N'-nitronitrosoguanidine or ethyl methanesulfonate, HL-60 TK deficient cells showed significantly increased killing and mutation frequencies at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus relative than did wild-type. Pretreatment of cells with O6-benzylguanine, an inhibitor of O6-alkylguanine-DNA alkyltransferase, partially abolished those differences. Molt-3 wild-type and TK deficient cells had similar cell survivals and HGPRT mutation frequencies following treatment with alkylating agents. These results indicate that TK deficiency, only when a concomitant decrease of TTP pool is detected, plays a pivotal role in the sensitivity to the cytotoxic and mutagenic effects of alkylating agents.
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PMID:Thymidine kinase deficient cells with decreased TTP pools are hypersensitive to DNA alkylating agents. 853 43

A non-radioactive 96-well microtitre plate reverse transcriptase (RT) assay, based on the use of covalently bound riboadenosine homopolymer in the wells and 5-bromodeoxyuridined 5'-triphosphate (BrdUTP) as dNTP, is described. The whole assay is performed in a single well, including the quantitative detection of incorporated BrdU, which is performed immunologically using alkaline phosphatase-conjugated anti-BrdU antibody and colorometric reading. The system also allows the use of variable amounts of primer. The kinetics and characteristics of the assay using BrdUTP is similar to the use of [3H]dTTP. The sensitivity of the assay can be varied either by altering the duration of RT assay time and/or by prolonging the alkaline phosphatase reaction. Thus the assay can detect < 0.02 pg of recombinant human-immunodeficiency-virus (HIV) type I RT, < 0.005 m unit of avian-myeloblastosis-virus RT or < 0.02 m unit of recombinant Moloney-murine-leukaemia-virus RT. The assay was found to be useful with various types of cell-culture material, and a comparative study of 16 HIV-infected lymphocyte cultures, using 10 microliters of supernatant medium for RT assay and 22.5 microliters for p24 antigen assay showed that the new RT assay was at least 25-fold more sensitive than the p24 antigen assay. The results also show a good correlation between the RT activities found and the p24-antigen level detected, with exception for HIV2 isolates, as they only became positive in the RT assay. The technical performance and the capacity of the test compared with other available RT kits is discussed, as well as its use for other applications.
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PMID:A sensitive assay for the quantification of reverse transcriptase activity based on the use of carrier-bound template and non-radioactive-product detection, with special reference to human-immunodeficiency-virus isolation. 863 77

Cytosine arabinoside (Ara-C) is used to treat leukemias, with complete remission induced by combination chemotherapy in approximately 70% of cases of acute myelogenous leukemia (AML). Ara-CTP acts as a competitive inhibitor of DNA polymerase and may also be incorporated into DNA. Accumulation of deoxyribonucleoside triphosphates (dNTPs) induced by Ara-C may indicate disruption of DNA synthesis in susceptible leukemia cells. A procedure has been developed for the quantification of Ara-CTP and dNTPs from small samples of leukaemia cells from patients (4 x 10(7) cells) activated with concanavalin A (10 micrograms/ml, 48 hr) and grown in the presence of [32P]orthophosphate (1.1 microM, 9 x 10(6) Ci/mol, 16 hr). The susceptibilities to Ara-C of the human leukemia cell lines CCRF-CEM (IC50 = 6.30 nM), CCRF-HSB-2 (IC50 = 10.4 nM) and MOLT-4 (IC50 = 10.0 nM) may be correlated with their abilities to accumulate high concentrations of Ara-CTP (> 1000 amol/cell) with increases of between 1.3- and 3.4-fold in dATP, dGTP and dTTP for the four cell lines, while dCTP decreased between 0.23- and 0.78-fold. By contrast, an Ara-C-resistant derivative of HL-60 cells (IC50 = 400 nM) accumulated only low concentrations of Ara-CTP (71 amol/cell) without significant changes in dNTPs. High concentrations of Ara-CTP in leukemia cells induce accumulations of dATP, dGTP and dTTP due to inhibition of DNA synthesis, and depletion of dCTP. This imbalance in the pools of the four dNTPs could lead to genetic miscoding and cell death.
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PMID:Effects of cytosine arabinoside on human leukemia cells. 893 Jan 29

Following exposure to 9-(2-phosphonylmethoxyethyl)adenine (an inhibitor of the cellular DNA polymerases alpha, delta and epsilon), human erythroleukemia K562, human T-lymphoid CEM and murine leukemia L1210 cells markedly accumulated in the S phase of the cell cycle. In contrast to DNA replication, RNA synthesis (transcription) and protein synthesis (mRNA translation) were not affected by 9-(2-phosphonylmethoxyethyl)-adenine. The ribonucleoside triphosphate pools were slightly elevated, while the intracellular levels of all four deoxyribonucleoside triphosphates were 1.5-4-fold increased in 9-(2-phosphonylmethoxyethyl)adenine-treated K562, CEM and L1210 cells. The effect of 9-(2-phosphonylmethoxyethyl)adenine on de novo (thymidylate synthase-mediated) and salvage (thymidine kinase-mediated) dTTP synthesis was investigated using radio-labelled nucleoside precursors. The amount of thymidylate synthase-derived dTTP in the acid soluble pool was 2-4-fold higher in PMEA-treated than in untreated K562 cells, which is in accord with the 3-4-fold expansion of the global dTTP level in the presence of 9-(2-phosphonylmethoxyethyl)adenine. Strikingly, 2-derived dTTP accumulated to a much higher extent (i.e. 16-40-fold) in the soluble dTTP pool upon 9-(2-phosphonylmethoxyethyl)adenine treatment. In keeping with this finding, a markedly increased thymidine kinase activity could be demonstrated in extracts of 9-(2-phosphonylmethoxyethyl)adenine-treated K562 cell cultures. Also, in the presence of 200 microM 9-(2-phosphonylmethoxyethyl)adenine, 14-fold less thymidylate synthase-derived but only 3-fold less thymidine kinase-derived dTTP was incorporated into the DNA of the K562 cells. These data show that thymidine incorporation may be inappropriate as a cell proliferation marker in the presence of DNA synthesis inhibitors such as 9-(2-phosphonylmethoxyethyl)adenine. Our findings indicate that 9-(2-phosphonylmethoxyethyl)adenine causes a peculiar pattern of (deoxy)ribonucleotide metabolism deregulation in drug-treated tumor cells, as a result of the metabolic block imposed by the drug on the S phase of the cell cycle.
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PMID:Impact of 9-(2-phosphonylmethoxyethyl)adenine on (deoxy)ribonucleotide metabolism and nucleic acid synthesis in tumor cells. 1006 80


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