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)

A rapid and convenient tritium release assay for measuring thymidylate (dTMP) synthase activity and its inhibition within intact mammalian cells is described in detail. Short-term incubation of murine leukemia L1210 cells with an appropriately labeled substrate precursor, either deoxyuridine ([5-3H]dUrd) or deoxycytidine ([5-3H]dCyd), allowed for: (1) uptake and intracellular conversion to the substrate deoxyuridylate ([5-3H]dUMP); and (2) the obligatory displacement of tritium from [5-3H]-dUMP during the dTMP synthase catalyzed reaction. Tritium released into the aqueous environment was quantitated after a quick one-step separation of tritiated H2O from other radiolabeled materials and cell debris. The amount of tritium released was evaluated as a function of a number of variables, including the concentration of labeled substrate precursors, cell number, and incubation time. Tritium from [5-3H]dCyd was released significantly faster than from [5-3H]dUrd under a variety of conditions. Both 5-fluorodeoxyuridine (1 microM) and methotrexate (10 microM), which effectively block intracellular dTMP synthesis, completely inhibited the release of tritium from either [5-3H]dCyd or [5-3H]dUrd demonstrating that the release of tritium is mediated exclusively by the dTMP synthase catalyzed reaction. In addition, there was a good correlation between tritium release, cellular uptake, and incorporation of [2-14C]dUrd into DNA. The inhibitory effects of antifolates such as methotrexate were independent of the type of labeled precursor used. In contrast, preferential interference with the release of tritium from [5-3H]-dCyd by dCyd derivatives and from [5-3H]dUrd by dUrd derivatives was observed, suggesting that competition for uptake and/or phosphorylation may contribute to the overall effects of certain nucleoside analogues on cellular dTMP synthase activity measured using the tritium release assay.
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PMID:Rapid determination of thymidylate synthase activity and its inhibition in intact L1210 leukemia cells in vitro. 316 Mar 52

Thymidylate (dTMP) synthase (EC 2.1.1.45) activity was measured in 100,000 x g supernatant fluid with a sensitive, rapid radio assay. The activity in normal rat liver was low (0.098-0.204 nmol/hr/mg protein). dTMP synthase specific activities in rat thymus, spleen, bone marrow, testis, lung, heart, brain, kidney, and small intestine were 6297, 1842, 1500, 788, 215, 76, 61, 39 and 24%, respectively, of that of the liver. The activity in 5-day-old rat liver was 16-fold higher than in adult. dTMP synthase activity increased in rat hepatomas to 7- to 125-fold of that of normal rat liver. There was a significant correlation between the increase in synthase activity and the proliferation rates of the hepatomas. In 8 human colon carcinomas, dTMP synthase activity increased to 2.9- to 8-fold of that of normal human colon mucosa. In leukemic leukocytes from 3 leukemia patients, activity was 8- to 10-fold higher than in normal leukocytes.
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PMID:Increased thymidylate synthase (EC 2.1.1.45) activity in normal and neoplastic proliferation. 322 29

We have utilized an electrophoretic assay of misincorporation to investigate the possibility that ionization of 5-bromouracil (BU) may play a role in its mispairing during DNA synthesis in vitro. We examined the effects of increasing pH on the relative rates of formation of BU.G and T.G mispairs during chain elongation catalyzed by various DNA polymerases. For the Klenow fragment of Escherichia coli DNA polymerase I, increasing pH facilitated BU.G mispair formation (relative to T.G mispairing) when BU was present in the template strand. This effect showed a strong dependence on sequence context. Increasing pH had little effect on the relative rate of misincorporation of BrdUMP versus dTMP (at template G) by the Klenow polymerase. Misincorporation opposite template BU residues catalyzed by Maloney murine leukemia virus DNA polymerase and DNA polymerase beta (Novikoff hepatoma) also increased with pH, but for these two enzymes, there was no apparent dependence on sequence context. With T4 DNA polymerase and E. coli DNA polymerase III holoenzyme, a similar occurrence of BU.G and T.G mispairing during polymerization was observed, whether BU was present in the template or in the incoming nucleotide, and there was little effect of pH. The results reported here are consistent with a mispairing mechanism for template BU wherein the anionic form of the base mispairs with G.
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PMID:Effect of pH on the base-mispairing properties of 5-bromouracil during DNA synthesis. 328 89

We conducted a randomized, double-blind, placebo-controlled study to evaluate the efficacy of oral trimethoprim/sulfamethoxazole (TMP/SMX) in the prevention of bacterial infections in children with cancer. Sixty-three patients with acute leukemia were studied during the induction phase of chemotherapy; 28 patients with solid tumors who were starting intensive chemotherapy were also enrolled and treated for 2 months. There was no significant difference in the frequency of febrile episodes between the 43 children receiving trimethoprim/sulfamethoxazole and the 48 receiving placebo. However, when the group of 74 children who experienced granulocytopenia (absolute granulocyte count less than 500/microL) was analyzed separately, significant reductions in the frequencies of confirmed bacteremia (2.6% v 20.0%, P = .02) and febrile episodes (35.9% v 65.7%, P = .01) were observed in the trimethoprim/sulfamethoxazole group. Furthermore, life table analysis showed that children with leukemia receiving trimethoprim/sulfamethoxazole had significantly more days without fever and without bacteremia. No benefits from prophylaxis were recognized in the subgroup with solid tumors. Although the frequency of oral thrush was greater (P = .02) in the trimethoprim/sulfamethoxazole group (25.6%) than in the placebo group (6.3%), invasive fungal infection did not occur. Although the mean duration of granulocytopenia was greater among those receiving trimethoprim/sulfamethoxazole (13.7 v 9.0 days, P = .05), this did not appear to increase the overall risk for bacterial infection. These data suggest that trimethoprim/sulfamethoxazole reduces the frequency of bacteremia and febrile episodes in granulocytopenic children undergoing induction chemotherapy for acute leukemia.
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PMID:Oral trimethoprim/sulfamethoxazole for prevention of bacterial infection during the induction phase of cancer chemotherapy in children. 390 47

The carbocyclic analogue of 5-nitro-2'-deoxyuridine (NO2dUrd), in which the sugar moiety is replaced by a cyclopentane ring and which was designated C-NO2dUrd, has been evaluated for its cytostatic, antimetabolic, and antitumor properties. The following findings are noted. C-NO2dUrd is about 500- to 2000-fold less inhibitory to tumor cell proliferation in vitro than NO2dUrd. Phosphorolysis of C-NO2dUrd by rabbit liver extracts was not observed under conditions where NO2dUrd was readily converted to 5-nitrouracil (NO2Ura). Also, C-NO2dUrd is converted to its 5'-monophosphate (C-NO2dUMP) by dThd kinase nearly as efficiently as the true nucleoside NO2dUrd. This metabolic conversion is necessary for the inhibitory effect of C-NO2dUrd on tumor cell proliferation in cell culture. The principal target enzyme for the cytostatic action of C-NO2dUrd is 2'-deoxythymidylate (dTMP) synthetase. C-NO2dUMP, the active metabolite of C-NO2dUrd, has a much lower affinity for dTMP synthetase than does NO2dUMP. This is the first demonstration of the interaction of a carbocyclic pyrimidine nucleotide analogue with dTMP synthetase. Neither NO2dUrd nor C-NO2dUrd exerts any significant antitumor activity in mice bearing L1210 or P388 leukemia; for NO2dUrd, this failure may be related to a rapid degradation to its inactive metabolite, NO2Ura; for C-NO2dUrd, it is most likely due to a decreased affinity of C-NO2dUMP for its target enzyme, dTMP synthetase.
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PMID:Role of thymidine kinase and thymidylate synthetase in the cytostatic, antimetabolic, and antitumor effects of the carbocyclic analogue of 5-nitro-2'-deoxyuridine. A comparison with 5-nitro-2'-deoxyuridine. 399 Jun 80

JLS-V9 mouse bone marrow cells were readily adapted to suspension culture, chronically infected with Rauscher leukemia virus (RLV), and subsequently grown in 7.5- and 14-liter New Brunswick fermentors. The suspension-type cell system can be modified to produce virus with clearly defined properties, such as high ribonucleic acid-dependent deoxyribonucleic acid polymerase (RDDP) activity, high particle count, and high infectious particle count. Biological and biophysical properties of suspension-produced RLV were not affected by concentration and purification employing continuous-flow and rate-zonal centrifugation procedures. The RDDP assay was standardized and showed a linear incorporation of (3)H-thymidine 5'-monophosphate ((3)H-TMP) up to 30 min. Further characterization indicated that a high percentage of (3)H-TMP incorporation was due to RDDP.
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PMID:Adaptation and infection of mouse bone marrow (JLS-V9) cells in suspension culture for production of Rauscher leukemia virus. 412 75

In an attempt to reduce the incidence of fever and infection, we randomized patients with cancer to receive trimethoprim/sulfamethoxazole plus erythromycin (TMP/SMX + E) versus placebos after each cycle of chemotherapy (no crossover) and to continue until granulocytopenia (polymorphonuclear leukocytes less than 500/mm3) resolved or the patient became febrile. We evaluated 541 episodes (150 patients); 249 episodes (77 patients) with TMP/SMX + E and 292 episodes (73 patients) with placebos. The patients' median age was 17 years. Thirty percent of the patients had leukemia, 23% had lymphoma, and 47% had solid tumors. Compliance with prescribed medication was prospectively rated as excellent in 60.6%, good in 11.7%, poor in 11.1%, and unknown in 16.6%; compliance was better for the placebo group (P = 0.001). The overall incidence of fever or infection was 22.1% for the TMP/SMX + E group versus 26.9% for the placebo group. When only episodes with excellent compliance in which granulocytopenia was documented were compared, the incidence of fever or infection was 18.1% for the TMP/SMX + E group vs 32.2% for the placebo group (P = 0.009), with bacterial infection occurring in 3.8% of the TMP/SMX + E group vs 11.9% of the placebo group (P = 0.019), and unexplained fever in 10.5% of the TMP/SMX + E group vs 19.6% of the placebo group (P = 0.037). Patients with good or poor compliance showed no significant benefit from the TMP/SMX + E, and patients with excellent compliance did best, regardless of whether they were receiving antibiotics or placebos, suggesting that patient compliance is an important independent variable. The incidence of fever or infection was significantly lower for patients with leukemia with excellent compliance who received antibiotics (P = 0.037) than for patients with lymphomas or solid tumors. Oral antibiotic prophylaxis reduced the incidence of fever and infection in some granulocytopenic patients, but the benefit was limited and restricted to patients whose compliance was complete.
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PMID:Oral antibiotic prophylaxis in patients with cancer: a double-blind randomized placebo-controlled trial. 633 81

Sixty-three patients with acute nonlymphoid leukemia (ANLL) under cytostatic treatment were investigated in a randomized trial to determine whether oral administration of cotrimoxazole (TMP/STX) would reduce the rate of infection. Four significant differences were observed between the group given TMP/STX (30 patients) and the control group (33 patients): 1) the mean duration of severe granulocytopenia (less than or equal to 500 PMN/mm3) before the first febrile episode was longer in prophylaxis group, 14.26 days versus four in the control group (p less than 0.001); 2) the number of febrile episodes was 37 in TMP/STX group and 69 in control group (p less than 0.01); 3) 23 patients on prophylaxis presented at least one febrile episode versus 33 in the control group (p less than 0.01); 4) deaths due to infection were two in the TMP/STX group versus 11 in control group (p less than 0.05). Prophylaxis with TMP/STX appears to be useful since by reducing the number of febrile episodes and deaths due to infection, it increases the survival of leukemia patients under cytostatic drugs. Nevertheless, further studies on a larger number of patients are necessary in order to confirm the true efficacy of the drug in the reduction of sepsis and death due to infection.
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PMID:Cotrimoxazole prophylaxis in patients with leukemia and prolonged granulocytopenia. 637 70

Thymidine kinase (TK) isoenzymes and thymidine phosphorylase (TP) activities have been measured in peripheral mononuclear cells of patients with acute lymphoblastic and monoblastic leukaemia or B-chronic lymphocytic leukaemia, as well as in normal subjects, and also in lymph node cells from patients with non-Hodgkin's lymphoma, with Hodgkin's disease and with benign adenopathies. TK1 isoenzyme activity was highest in acute lymphoblastic leukaemia and in centroblastic lymphoma. Then in progressively decreasing order appeared the Hodgkin's disease values, the centroblastic centrocytic lymphoma values and the benign reactive lymph node cell values. When compared to normal blood mononuclear cells, TP was greatly decreased in acute lymphoblastic leukaemia and slightly but significantly decreased in chronic leukaemia. Monoblastic cells exhibited a unique enzyme pattern; moderately increased TK1 activity and high TP activity. Our results suggest that both enzymes are indicative of the maturation status of leukaemic cells from B lineage. They demonstrate that in lymph node cells, TK1 reflects the proliferative status of both malignant and non-malignant cells and that in monoblastic cells the synthesis of dTMP through de novo synthesis is favoured.
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PMID:Thymidine kinase and thymidine phosphorylase activities in various types of leukaemia and lymphoma. 653

Two strategies have been pursued to monitor the inhibition of thymidylate (dTMP) synthase (5,10-methylenetetrahydrofolate:dUMP C-methyltransferase, EC 2.1.1.45) by thymidine (dThd) analogs in intact murine leukemia L1210 cells. The first method was based on the determination of tritium release from 2'-deoxy[5-3H]uridine [( 5-3H]dUrd) or 2'-deoxy[5-3H]cytidine [( 5-3H]dCyd); the second method was based on an estimation of the amount of dCyd incorporated into DNA as dTMP. The validity of these procedures was assessed by evaluating the inhibition of thymidylate synthase in murine leukemia L1210 cells by a series of 18 dThd analogs. There was a strong correlation between the inhibitory effects of the dThd analogs on the proliferation of L1210 cells on the one hand, and (i) their inhibitory effects on tritium release from [5-3H]dCyd (r = 0.926) and (ii) their inhibitory effects on the incorporation of dCyd into DNA dTMP (r = 0.921), on the other hand. Evaluation of tritium release from [5-3H]dCyd proved to be the most convenient method that has been described so far to measure thymidylate synthase activity and to follow the inhibitory effects of thymidylate synthase inhibitors in intact L1210 cells, since this method is rapid and very sensitive, and since it proved superior to the evaluation of tritium release from [5-3H]dUrd because it circumvents possible interactions of the inhibitors with thymidine kinase activity.
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PMID:Strategies for the measurement of the inhibitory effects of thymidine analogs on the activity of thymidylate synthase in intact murine leukemia L1210 cells. 669 20


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