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)

Dihydrofolate reductase, purified to homogeneity from a subline of L1210 murine leukemia cells resistant to 10(-6) M Methotrexate, was resolved into two principal forms (1 and 2) by isoelectric focusing. These forms had pI values of 7.4 and 8.2, respectively; both stained for protein and catalytic activity. Form 1 was a single component, comprising ca. 10% of the total protein, but multiple components of 2 were observed by narrowing the pH range in the electrophoretic procedure. Urea-denatured enzyme exhibited two bands of approximately equal intensity upon isoelectric focusing. These results were interpreted to mean that the enzyme consists of a set of conformationally different forms, arising from two primary structures. Inhibition of the native enzyme by Methotrexate was polyphasic, and appreciable activity remained when the drug was present at an equimolar concentration. Various agents (KCl, H+, urea, and SH-modifiers), known to "activate" dihydrofolate reductases, produced a monophasic, stoichiometric inhibition. Activating agents appear to induce a more open (and labile) conformation of the enzyme. This leads to increased affinity for MTX accompanied, in some instances, by increased catalytic activity.
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PMID:L1210 dihydrofolate reductase: activation and enhancement of methotrexate sensitivity. 383 18

Methotrexate(MTX)-resistant human promyelocytic-leukaemia cells (HL-60) derived from MTX-sensitive cells have a 20-fold increase in dihydrofolate reductase (DHFR) activity as compared with the sensitive cells. This increase is not associated with a concomitant increase in DHFR protein as determined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and by immunological methods using mouse anti-DHFR antibody. The rate of DHFR synthesis is similar in both cell lines. Furthermore, both the sensitive and resistant cells have similar amounts of RNA hybridizing to a DHFR complementary-DNA probe, correlating well with the lack of increase in DHFR protein. DHFR-gene dosages were similar in both types of cells. We conclude that the 20-fold increase in DHFR activity present in these MTX-resistant cells is not due to the overproduction of DHFR but due to the expression of a more active form of the enzyme.
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PMID:Increased dihydrofolate reductase activity in methotrexate-resistant human promyelocytic-leukaemia (HL-60) cells. Lack of correlation between increased activity and overproduction. 385 28

Lymphocyte count, lymphocyte subpopulations identified by monoclonal antibodies and mitogen stimulation assays with phytohaemagglutinin, concanavalin A, pokeweed mitogen and staphylococcal protein A, were used to quantitate the effect of methotrexate on the immune response in children with acute lymphatic leukaemia on maintenance therapy. Methotrexate exerted a profound but apparently short-term effect on these parameters as it is prescribed in current maintenance schedules for childhood acute lymphatic leukaemia. A significant drop in lymphocyte count, affecting all subpopulations, was observed 4 h after oral or intramuscular administration of methotrexate which had reverted to pre-methotrexate values one week after the drug was given. Lymphocyte function was markedly affected, with a major decrease in mitogen responsiveness 1 h after methotrexate and a reversion to pre-methotrexate values by 48 h. A selectivity of suppressor T cells to methotrexate is proposed as being responsible for early recovery. Scheduling of methotrexate in current maintenance programmes would therefore appear to allow adequate time for recovery of immunoresponsiveness between doses.
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PMID:Effect of methotrexate on the immune response in children with acute lymphatic leukaemia. 385 20

A new regimen for prevention of acute graft-versus-host disease (GvHD)--OKT3 (murine monoclonal anti-pan-T antibody), prednisone and methotrexate (OKT3-pred-MTX)--was compared with the Minnesota standard regimen--antithymocyte globulin, prednisone and methotrexate (ATG-pred-MTX)--for adverse effects, effect on incidence of acute GvHD, and survival at 1 year post-transplant. Twenty patients (aged 25 +/- 9 years) had bone-marrow transplantation (BMT) from their HLA-MLC identical sibling donors for treatment of aplastic anaemia (four), acute leukaemia in remission (13) or chronic myelogenous leukaemia (three). These 20 patients received (OKT3-pred-MTX) on days 8-22 post-transplant. Results of this group are compared to those of 19 concurrent patients (aged 26 +/- 12 years) who received ATG-pred-MTX on days 8-22 post-transplant. On the first day of treatment, 20/20 OKT3 patients and 18/19 ATG patients were febrile. Within 24 h of the first dose of OKT3, 6/20 patients experienced dyspnoea or chest pain and 3/20 patients developed diarrhoea. No further adverse effects were seen after the second dose of OKT3 and no late adverse effects were attributed to this drug. Time to engraftment (means 25 d) was not statistically significantly different in the two prophylactic groups. Acute GvHD was diagnosed in 14 of 20 patients who received OKT3-pred-MTX and in eight of 19 patients who received ATG-pred-MTX (P = 0.06). The incidence of hepatic or gastrointestinal GVHD (greater than or equal to grade 2) was similar in the two groups: 4/20 OKT3-pred-MTX, 6/19 ATG-pred-MTX. Characteristics of post-transplant infections were also similar for the two prophylactic groups. Survival at 1 year post-transplant was 65% for patients who received OKT3 and 44% for patients who received ATG (P = 0.13). The use of OKT3 with prednisone and methotrexate is relatively safe and is associated with a similar incidence of moderate-severe acute GvHD to that experienced in the use of ATG with prednisone and methotrexate.
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PMID:Graft-versus-host disease prophylaxis with anti-T-cell monoclonal antibody OKT3, prednisone and methotrexate in allogeneic bone-marrow transplantation. 389 Sep 26

Combination chemotherapy using the water-soluble nitrosourea MCNU with various anti-cancer agents was studied using L1210 leukemia and P388 leukemia. In titration experiments MCNU showed remarkable antitumor effects at doses from 5 mg/kg to 80 mg/kg, producing numbers of 60-day survivors with L1210 leukemia. In L1210 leukemia, respective combinations of MCNU with the antimetabolites, MTX, 6-MP, 6-TG, MCNU, 5-FU and Cyclo-C showed enhanced antitumor effects. MCNU combined with each of ADR, MMC and CPM also showed marked anti-tumor effects with 60-day survivors. In P388 leukemia MCNU combined with each of ADR, MMC, VDS and CPM produced strong anti-tumor effects with numbers of 60-day survivors. In the results of these combinations, especially the combinations of MCNU + 5-FU in L1210 leukemia and MCNU + CPM in both L1210 and P388 leukemia, a significant increase in mean survival time was achieved. These combinations also produced many 60-day survivors which were considered to be due to the synergistic antitumor effects of the combined drugs.
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PMID:[Effects of combination chemotherapy of MCNU with various anti-cancer agents]. 391 6

Methotrexate-thymidine synchronization increased mitotic yield and the numbers of cells with longer chromosomes when compared with direct and day culture (24 hr) techniques. The longer chromosomes overlapped more than shorter ones, but this adverse effect of cell synchronization was outweighed by the substantial gains from increased band number of metaphase cells. A critical feature of the synchronization technique that determines chromosome length is the period of cell culture following thymidine release. This will depend on cell cycle time. Variable results obtained with the synchronization technique probably occur because the cell cycle time of leukemic cells differs from that of normal hematologic cells and normal lymphocytes. It may also differ between patients and between acute and chronic forms of leukemia.
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PMID:An evaluation of high resolution chromosome banding of hematologic cells by methotrexate synchronization and thymidine release. 396 8

Methotrexate (MTX) analogues 27a-c bearing 2, omega-diaminoalkanoic acids (ornithine and its two lower homologues) in place of glutamic acid were synthesized by routes proceeding through N2-[4-(methylamino)benzoyl]-N omega-[(1,1-dimethylethoxy)carbonyl]-2, omega-diaminoalkanoic acid ethyl esters and N2-[4-(methylamino)benzoyl]-N5-[(1,1-dimethylethoxy)carbonyl]-2, 5-diaminopentanoic acid followed by alkylation with 6-(bromomethyl)-2, 4-pteridinediamine hydrobromide. Reactions at the terminal amino group of 27-type analogues or of appropriate precursors led to other MTX derivatives whose side chains terminate in ureido, methylureido, N-methyl-N-nitrosoureido, N-(2-chloroethyl)-N-nitrosoureido, and 4-chlorobenzamido groups. Also prepared were unsymmetrically disubstituted ureido types resulting from addition of ethyl isocyanatoacetate and diethyl 2-isocyanatoglutarate to the ethyl esters of 27a,b. Of these ureido adducts (32a,b and 33a,b, respectively), only 33a was successfully hydrolyzed to the corresponding pure acid, in this instance the tricarboxylic acid 34, a pseudo-peptide analogue of the MTX metabolite MTX-gamma-Glu. Biological evaluations of the prepared compounds affirmed previous findings that the gamma-carboxyl is not required for tight binding to dihydrofolate reductase (DHFR) but is operative in the carrier-mediated transport of classical antifolates through cell membranes. High tolerance levels observed in studies against L1210 leukemia in mice suggest the reduced potency may be due not only to lower transport efficacy but also to loss of the function of intracellular gamma-polyglutamylation. The N-nitrosoureas 30 and 31 showed appreciable activity in vivo vs. L1210, but the activity did not appear to be due to antifolate action as evidenced by their poor inhibition of both L1210 DHFR and cell growth in vitro.
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PMID:Syntheses and evaluation as antifolates of MTX analogues derived from 2, omega-diaminoalkanoic acids. 402 Aug 24

PTT.119 [p-F-Phe-m-bis-(2-chloroethyl)amino-L-Phe-Met ethoxy HCl], a new synthetic tripeptide, was highly effective against the L-phenylalanine mustard (L-PAM) resistant (L1210/L-PAM and P388/L-PAM) tumor lines, as well as the sensitive L1210 leukemia. Cytolytic activity of PTT.119 against all three leukemias was significantly greater than equimolar doses of L-PAM. These in vitro results paralleled the significant increases in mean survival times of hosts and, in some cases, abrogations of tumor formation observed in the in vivo bioassays of PTT.119-treated L1210 and L1210/L-PAM cells. Dose-response studies failed to demonstrate cross-resistance to the tripeptide by L-PAM resistant cells. Doses of PTT.119 required to reduce the viable fraction by 50% (tissue culture dose 50, TCD50) or 100% (TCD100) were 1.3- to 3-fold lower for the L-PAM resistant cells than for the L1210 leukemia. In comparison, L-PAM was unable to completely eliminate cell survival; 0.2 to 3% of the cells in all three leukemias remained viable even at doses of 75 and 163 microM. In similar studies, L1210 leukemia cells made resistant to methotrexate (L1210 MTX) and cisplatin (L1210DDP) were also completely susceptible to PTT.119; TCD50 values of the two resistant lines were 1.94 microM for L1210 MTX and 0.525 microM for L1210DDP compared to 2.38 microM for the susceptible parent L1210S leukemia. Continuous low-dose PTT.119 treatment of MJY-alpha mammary tumor cells for 8 months and exposure of L1210 leukemia to escalating levels of tripeptide for over 100 passages failed to select or induce drug-resistant phenotypes in either cell line. PTT.119 appears to be a poor mutagen and is unlikely to readily increase the probability of drug-resistant mutants in the tumor cell populations.
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PMID:PTT.119, p-F-Phe-m-bis-(2-chloroethyl)amino-L-Phe-Met ethoxy HCl, a new chemotherapeutic agent active against drug-resistant tumor cell lines. 404 Mar 66

Dihydrofolate reductase, purified to homogeneity (as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis), from a subline of L1210 murine leukemia cells resistant to 10(-6) M methotrexate, was resolved into two principal forms (1 and 2) by polyacrylamide gel electrophoresis at pH 8.3 or isoelectric focusing. In the latter procedure, these forms had pI values of 7.4 and 8.2, respectively; both stained for protein and catalytic activity. Form 1 appears to be a single component, comprising ca. 10% of the total protein and at least 20% of the total catalytic activity. It is also more sensitive to inhibition by MTX, more heat-stable, and less susceptible to activation than form 2. Multiple components of 2 were observed by narrowing the pH range in isoelectric focusing, and further resolution was achieved by urea denaturation. Substrate and inhibitor complexes of 1 and 2, differentiated by polyacrylamide gel electrophoresis or isoelectric focusing, provided information about the ability of the enzyme to undergo conformational changes. Interconversion of 1 with one of the components of 2 may also involve conformational isomerism. These conclusions are consistent with the well-known ability of eukaryotic dihydrofolate reductases to exhibit increased catalytic activity (attributed to transformations to more open conformations) when treated with salts, chaotropes, or cysteine-modifying agents. Treatment of the L1210/R6 enzyme preparation with one of these activating agents, 5,5'-dithiobis(2-nitrobenzoic acid), derivatized both 1 and 2 (changing their pI values to 7.3 and 6.9, respectively) and altered the enzyme such that stoichiometric inhibition for MTX was observed.
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PMID:Polymorphism of dihydrofolate reductase from a methotrexate-resistant subline of L1210 cells. 407 99

Folate (pteroylglutamate) and methotrexate rapid (seconds) uptake by the trophoblast was investigated from either the maternal or fetal circulations of the isolated dually-perfused guinea-pig placenta. Tissue uptake was measured by using a single-circulation paired-tracer (3H-test and 14C-extracellular marker) technique. [3H]Folate uptakes were 80 and 52% (mean) in perfusates without unlabelled folate, on maternal and fetal sides, respectively. There was negligible 3H-tracer backflux into the circulation up to 6 min probably due to metabolic sequestration. [3H]Methotrexate uptakes were about 85 and 22% on maternal and fetal sides, respectively; however these uptakes were followed by rapid and complete backflux of the label. Specific transplacental transfer of [3H]folate or [3H]methotrexate in either direction was not detectable within 5-6 min. At the brush-border side (maternal) uptake of [3H]folate was highly inhibited by 100 nM unlabelled folate or its reduced form, methyltetrahydrofolate (the main form in plasma); however, equimolar methotrexate (an antifolate chemotherapeutic agent) failed to produce any inhibition of folate uptake. Our findings demonstrate that on both sides of the placenta a high-affinity transport system exists for trophoblast uptake of folate compounds. For methotrexate, either a separate transport system may exist or methotrexate may have a very low affinity for the folate system. These results are distinct from the findings reported in mouse L1210 leukemia cells.
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PMID:Transport of folates at maternal and fetal sides of the placenta: lack of inhibition by methotrexate. 407 42


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