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)

Exponentially growing K562 cells incubated with 1-beta-D-arabinofuranosylcytosine (ara-C) accumulate ara-C triphosphate (ara-CTP) at a higher rate and to a greater concentration after pretreatment with 9-beta-D-arabinofuranosyl-2-fluoroadenine (F-ara-A) than do cells treated with ara-C alone. Potentiation of ara-C metabolism is due in part to an indirect effect of F-ara-A triphosphate (F-ara-ATP)-mediated reduction in deoxynucleotide pools and consequent activation of deoxycytidine kinase. Because the levels of deoxynucleotide pools and the activity of deoxycytidine kinase are cell cycle-specific, we investigated the effect of cell cycle phases on the accumulation of ara-CTP and the influence of F-ara-A pretreatment on such accumulation. Exponentially growing K562 cells were fractionated into G1, S, and G2+M phase-enriched subpopulations (each enriched by > 60%) by centrifugal elutriation. The rate of ara-CTP accumulation was 22, 25, and 14 microM/h and the rate of F-ara-ATP accumulation was 38, 47, and 33 microM/h in the G1, S, and G2+M subpopulations, respectively. The rate of elimination of arabinosyl triphosphates was similar among the different phases of the cell cycle. After pretreatment with F-ara-A, the rate of ara-CTP accumulation in the G1, S, and G2+M phase-enriched subpopulations was 43, 37, and 26 microM/h, indicating a 1.7-, 1.5-, and 1.9-fold increase, respectively. These results suggest that a combination of F-ara-A and ara-C may effectively potentiate ara-CTP accumulation in all phases of the cell cycle. This observation is consistent with the results of studies on the modulation of ara-C metabolism by F-ara-A in lymphocytes and leukemia blasts obtained from patients with chronic lymphocytic leukemia and acute myelogenous leukemia, respectively.
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PMID:Cell cycle-specific metabolism of arabinosyl nucleosides in K562 human leukemia cells. 145 54

The accumulation of cytosine arabinoside-5'-triphosphate (ara-CTP), the activities of nucleotide-metabolizing enzymes and the nucleoside transport capacity were examined in eleven human leukemic cell lines differing in phenotype. The highest amount of ara-CTP was accumulated in T-acute lymphoblastic leukemia cells (T-ALL), followed by myeloid leukemia cell lines (AML), and the least accumulation was observed in common acute lymphoblastic leukemia (c-ALL) and B-acute lymphoblastic leukemia cells (B-ALL). The levels of enzymes involved in ara-C metabolism (deoxycytidine kinase, pyrimidine monophosphate kinase and deoxycytidylate deaminase) did not correlate with ara-CTP accumulation. The sensitivity of the leukemic cell lines to ara-C, which was measured in terms of decrease of clonogenic survival, correlated with the amount of ara-CTP formed. Moreover, the nucleoside transport capacity, estimated from the binding of the radiolabeled nucleoside analogue, [3H]nitrobenzylthioinosine, showed a good correlation with ara-CTP accumulation. The mean numbers of nucleoside-binding sites in T-ALL cells were significantly greater than in B-ALL cells. We conclude that the cellular nucleoside transport capacity is the most important factor for the formation and accumulation of ara-CTP in the cells.
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PMID:Formation of cytosine arabinoside-5'-triphosphate in cultured human leukemic cell lines correlates with nucleoside transport capacity. 311 33

The activities of the enzymes cytidine deaminase (CDD), deoxycytidine kinase (dCK), adenosine deaminase (ADA), and purine nucleoside phosphorylase (PNP), have been investigated in the promyelocytic leukemia cell line HL60. The activities of the enzymes corresponded well with that seen in acute myeloid leukemia cells except, that the CDD activity was very low in the HL60 cells. Induction of differentiation in HL60 cells by 1,25 dihydroxy D3 resulted in an increase in CDD from 12 to 247 nmol/h/mg and a decrease in ADA from 1326 to 896 nmol/h/mg, while the activities of dCK, and PNP were unchanged. Retinoic acid, another used inducer of differentiation, gave no changes of the enzyme activities. The increase in CDD activity induced by 1,25 dihydroxy D3 was prevented by inhibition of protein synthesis, whereas inhibition of proliferation of the cells did not abolish the increase of CDD. The changes correspond well with the differences seen between immature and mature myeloid cells. The results may have consequences for the interpretation of results obtained with cytostatics, which are metabolized by the enzymes.
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PMID:Changes in the activities of cytidine deaminase during differentiation of HL60 cells induced by 1,25 dihydroxy D3. 316 86

The in vivo development of an ara-C-resistant leukemic cell line is reported in a rat leukemia model (BNML) that is generally accepted as a relevant model for human acute myelocytic leukemia. It took 32 continuous leukemia transplant generations, performed over 20 months, and a total dose of 28.5 g ara-C/kg to induce complete resistance. Preliminary data indicate that the development of ara-C resistance is related with decreased intracellular levels of deoxycytidine kinase. Deoxycytidine deaminase levels were not increased. Thus this enzyme does not seem to be involved with induction of resistance. This preclinical rat model for human AML provides a solid basis for studies in depth on the mechanism(s) and possible prevention and effective treatment of resistance to ara-C.
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PMID:In vivo development of cytosine arabinoside resistance in the BN acute myelocytic leukemia. 347 77

Cytosine arabinoside (araC) has proven efficacy in acute myeloid leukemia (AML), but its place in the treatment of acute lymphoblastic leukemia (ALL) and T lymphoblastic lymphoma is uncertain. The therapeutic potential of araC has been assessed in patients with AML, ALL, and T lymphoblastic lymphoma by measuring the conversion of araC to its active metabolite, the 5'-triphosphate of araC (araCTP), in purified blasts from patients as well as in normal polymorphs and lymphocytes. In all leukemias, araCTP was the major intracellular metabolite of araC. The highest araCTP formation was in blasts from T lymphoblastic lymphoma, which formed threefold more nucleotide than myeloblasts, and in turn myeloblasts formed twofold more araCTP than lymphoblasts from ALL. The mean araCTP formation in myeloblasts was sixfold greater than polymorphs, but in contrast, lymphoblasts and lymphocytes formed low and similar amounts of this nucleotide. Reasons for the sixfold range in araCTP accumulation in the various leukemic blasts were studied. The mean size of myeloblasts was 35-70% larger than lymphoblasts when compared on the basis of protein or intracellular water content, but T lymphoblastic lymphoma blasts and lymphoblasts were the same size. Activities of deoxycytidine kinase, deoxycytidylate deaminase, and pyrimidine nucleoside monophosphate kinase were not different between any of the leukemic cell types. The number of nucleoside transport sites on blasts was estimated by measuring the equilibrium binding of [3H]nitrobenzylthioinosine (NBMPR), which binds with high affinity to the transporter. Scatchard analysis yielded mean values of 27,500 sites/cell for T lymphoblastic lymphoma blasts, 10,000 sites/cell for myeloblasts, and 2,300 sites/cell for lymphoblasts. Our previous work has shown that araC influx correlates with the maximum number of 3H-NBMPR binding sites in leukemic and normal white cells. A strong correlation was observed between the number of nucleoside transport sites per leukemic blast cell and the accumulation of intracellular araCTP from extracellular araC at 1 microM. Membrane transport of araC at the low concentrations (approximately 1 microM), which are achieved therapeutically, is a major rate-limiting step in its conversion to araCTP by leukemic blast cells. Myeloblasts form more araCTP than lymphoblasts because of both higher nucleoside transport capacity and larger cell size. The highest nucleoside transport capacity and largest conversion of araC to araCTP is in T lymphoblastic lymphoma, which suggests that araC may be effective in the treatment of this disease.
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PMID:Cytosine arabinoside transport and metabolism in acute leukemias and T cell lymphoblastic lymphoma. 387 94

The current study was undertaken to determine the relevance of leukemic blast cell proliferative activity, cellular parameters of Ara-C metabolism and the in vitro sensitivity to GM-CSF in association with the clinical response to TAD-9 induction therapy in 66 patients with de novo acute myeloid leukemia (AML). Proliferative activity was assessed by 3H-thymidine (3H-TdR) incorporation and thymidine kinase (TK) activity, parameters of Ara-C metabolism comprised the activities of deoxycytidine kinase (DCK) and DNA polymerase alpha (poly alpha) as well as Ara-CTP concentrations and 3H-Ara-C uptake into DNA. GM-CSF sensitivity was determined by in vitro incubation of blasts for 48 h with or without GM-CSF (100 U/ml) followed by an additional 4 h concurrent exposure to GM-CSF and 3H-TdR (0.5 microCi/ml). The following results were obtained as expressed by median values and ranges: 3H-TdR incorporation: 1.07 pmol/10(5) cells (0.0-10.1), TK: 7.3 pmol/min/mg protein (1.3-56.0), DCK: 9.3 pmol/min/mg protein (0.77-47.1), poly alpha: 1.7 pmol/min/mg protein (0.00-28.9), Ara-CTP: 53.3 ng/10(7) cells (13.3-211.0), 3H-Ara-C uptake: 0.06 pmol/10(5) cells (0.0-0.57). 3H-Ara-C uptake was correlated with 3H-TdR incorporation (r = 0.74) and with the (S-phase dependent) activities of TK (r = 0.73) and poly alpha (r = 0.71, but not with DCK activity or intracellular Ara-CTP content. Blast cells of 37 from 55 analyzed patients were found to be sensitive to GM-CSF stimulation as defined by an increase in 3H-TdR incorporation > or = 1.5-fold over control values after the 48 h GM-CSF exposure. In vitro data were related with clinical response to TAD-9 induction therapy in 43 patients with newly diagnosed AML, taking the blast cell reduction at day 10 or 16 to < 5% or > or = 5% residual blasts as early parameter for adequate or inadequate response, respectively. While neither 3H-Ara-C uptake, nor intracellular Ara-CTP concentration, TK nor DCK activity were predictive for response, a high 3H-TdR incorporation and a high poly alpha activity were associated with adequate blast cell reduction. Median values of 3H-TdR incorporation were 2.26 pmol/10(5) cells for patients with adequate blast cell clearance and 0.80 pmol/10(5) cells for patients with inadequate blast cell clearance (P = 0.11), the respective values for poly alpha were 3.22 pmol/min/mg protein for responders and 1.1 pmol/min/mg protein for non-responders (P = 0.0085).(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Blast cell proliferative activity and sensitivity to GM-CSF in vitro are associated with early response to TAD-9 induction therapy in acute myeloid leukemia. 747 75

Deficiency of deoxycytidine kinase (dCK) activity represents one possible cause of resistance to cytosine arabinoside (ara-C). Mutations of the dCK gene have recently been shown to be responsible for dCK deficiency and increased resistance in vitro. In order to define the relevance of this mechanism in vivo, we analyzed the dCK gene in 16 adult patients with relapsed/refractory acute myeloid leukemia (AML) and clinical resistance to standard-dose and/or high-dose ara-C. Southern blot analysis using genomic DNA from peripheral blood or bone marrow samples containing > or = 70% leukemic blasts and agarose gel electrophoresis of cDNA obtained by RT-PCR did not reveal gross rearrangements of the dCK gene. Sequencing of the dCK coding region showed point mutations in seven patients. Besides two silent mutations (or RFLPs) in codon 42 and 86, base pair mutations resulting in amino acid replacements were found in five patients affecting codon 20, 93, 98, 99, and 154, respectively. dCK cDNA clones from three patients with > or = 50% of sequenced clones revealing the specific base pair alteration were bacterially expressed in E. coli and analyzed for dCK activity. Normal enzyme activity was found in two patients (codon 20 and 98), and a complete loss of activity in one patient (codon 99). We conclude that structural alteration of the coding region of the dCK gene represents one possible mechanism for ara-C resistance in vivo, but, considering the frequency of this event, other mechanisms may play a more important role for clinical resistance to ara-C in patients with AML.
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PMID:Structural analysis of the deoxycytidine kinase gene in patients with acute myeloid leukemia and resistance to cytosine arabinoside. 1136 49

In order to study the mutational inactivation of deoxycytidine kinase (Dck) in a rat model for acute myeloid leukemia we have cloned the complete coding region of the rat Dck gene. Using primers chosen from the human Dck cDNA sequence, we obtained a rat-specific probe via PCR and used it to isolate two clones from a rat lymphocyte cDNA library. The ORF showed 89.7 and 92.2% nucleotide identity with the human and mouse Dck, respectively, and encodes a 260-amino-acid protein, that is 91.9 and 94.6% homologous to human and mouse Dck, respectively. Northern blot analysis of rat tissues revealed high expression of a 4.1-kb Dck transcript in the thymus, whereas spleen, liver and lung samples showed weak expression of the gene. This tissue-specific expression pattern was confirmed by cDNA-PCR analysis.
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PMID:Cloning of the Dck gene encoding rat deoxycytidine kinase. 782 5

Fludarabine is a prodrug that must enter cells and be phosphorylated to the nucleoside triphosphate, F-ara-ATP, to elicit biological activity. F-ara-ATP serves as an inhibitory alternative substrate in several key processes involved in DNA synthesis. The enzymes required in DNA synthesis and affected by F-ara-ATP are ribonucleotide reductase, DNA primase, DNA polymerases, 3'-5' exonuclease activity of DNA polymerases delta and epsilon, and DNA ligase I. The action of fludarabine on DNA replication provides a compelling rationale to use this agent for leukemias where target cells are actively synthesizing DNA, for example acute myelogenous leukemia. Additionally, the role of F-ara-ATP to potentiate the activity of deoxycytidine kinase makes it an appropriate candidate to use in combination with other nucleoside analogs which require deoxycytidine kinase for their activation. The present article reviews the effect of fludarabine on enzymes involved in DNA synthesis and the role of fludarabine in combination with arabinosylcytosine for the treatment of diseases other than indolent leukemias.
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PMID:Fludarabine inhibits DNA replication: a rationale for its use in the treatment of acute leukemias. 788 48

The current study investigated the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on the intracellular metabolism and cytotoxicity of 1-beta-D-arabinofuranosylcytosine (araC) in leukemic cells of 45 patients with acute myeloid leukemia (AML). AML blasts from bone marrow (BM) (n = 39) and peripheral blood (PB) (n = 17) were incubated for 48 h with or without GM-CSF (100 U/ml) followed by a concurrent treatment with increasing concentrations of araC (0.06-100 microM) for an additional 24 h. After GM-CSF a 1.5-8.4-fold (median 2.3) increase in 3H-araC incorporation into the DNA was observed in ten of 14 peripheral blast specimens and in 23 of 28 bone marrow samples, 18 of whom also showed an enhanced 3H-TdR incorporation (1.5-8.5-fold, median 2.0-fold). Four different types of response were identified when analyzing 3H-araC incorporation into the DNA of bone marrow samples in relation to the applied araC dose: (i) 8/28 cases had increases of the araC incorporation at all araC dose levels applied (0.06-100 microM), (ii) 12/28 at low araC concentrations only (0.06-1.0 microM), (iii) 3/28 at high araC concentrations only (10-100 microM), and (iv) 5/28 showed no increase at any dose level given. Hence, 20 of the 23 responding patients revealed a GM-CSF induced enhancement of araC incorporation at low or conventional doses of araC (0.06-1.0 microM). Fourteen of the 18 cases with concomitant rises of 3H-TdR and 3H-araC incorporation into the DNA after GM-CSF had elevated DNA polymerase alpha activity (16-531%, median 72%) and in ten cases overall DNA polymerase activity was enhanced (10-70%, median 22.5%). In contrast, thymidine kinase (TK) and deoxycytidine kinase (dCK) activity were elevated after GM-CSF in only ten and five patients, respectively. An increase in the fraction of cells in S phase was found in 11/21 bone marrow specimens and in 5/9 peripheral blast samples. However, no correlation was observed between increases in the proportion of cells in S phase and enhancements in enzyme activities. In 13 cases the cytotoxicity of araC with and without GM-CSF was assessed by means of a blast cell colony assay. Preincubation with GM-CSF increased the araC mediated cytotoxicity in ten of 13 patients by a median of 3.2-fold (range 2.2-229-fold). The respective LD50 values for araC were reduced from 0.45 to 0.19 microM on average.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Modulation of intracellular metabolism of cytosine arabinoside in acute myeloid leukemia by granulocyte-macrophage colony-stimulating factor. 830 45


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