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 classic inhibitor of dihydrofolate reductase (DHFR), methotrexate (MTX), has been shown to be an effective inducer of the differentiation of HL-60 promyelocytic leukemia cells (Bodner A.J. et al.; J. Natl. Cancer Inst. 67:1025-1030; 1981). We have obtained evidence that induction of the differentiation of these cells by MTX, as well as by other folic acid antagonists, is the result of the effects of these agents on purine and thymine nucleotide biosynthesis. Thymidine (10 microM) completely blocked both the cytotoxicity and induction of differentiation produced by the specific inhibitor of thymidylate synthase (TS), N10-propargyl-5,8-dideazafolic acid (CB-3717). Thymidine also blocked the acute cytotoxicity caused by MTX and trimetrexate (TMQ); the induction of differentiation and the loss of proliferative capacity, however, were only partially prevented by thymidine. Hypoxanthine (100 microM), which completely restored antifolate-depleted purine nucleotide levels, had no effect on either the cytotoxicity or the induction of maturation produced by these agents. The growth inhibitory effects and the induction of differentiation caused by dideazatetrahydrofolic acid (DDATHF), which acts on de novo purine nucleotide biosynthesis rather than on DHFR or TS, was completely prevented by hypoxanthine. Hypoxanthine also completely prevented the inhibition of cellular replication and induction of differentiation by MTX and TMQ when combined with thymidine. The findings suggest that the depletion of intracellular thymine nucleotide levels by the antifolates, MTX, TMQ, and CB-3717 is the primary event involved in the maturation of HL-60 leukemia cells produced by these agents and that maturation occurs concomitantly with a high level of cytotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mechanism of the induction of the differentiation of HL-60 leukemia cells by antifolates. 270 Sep 13

Three new 5,8-dideaza analogues of folic acid devoid of an amino group at position 2 have been prepared by using synthetic routes patterned after earlier methodologies. They were 2-desamino-5,8-dideazaisofolic acid, 2b, 2-desamino-10-thia-5,8-dideazafolic acid, 2c, and 2-desamino-10-oxa-5,8-dideazafolic acid, 2d. These compounds were found to be 4-6-fold more cytoxic toward L1210 leukemia cells than their 2-NH2 counterparts and to be poor inhibitors of mammalian thymidylate synthase. However, they were only 1.5-3-fold less inhibitory toward dihydrofolate reductase than the analogous compounds containing a 2-NH2 group. The known thymidylate synthase inhibitors 2-desamino-10-propargyl-5,8-dideazafolic acid and 10-propargyl-5,8-dideazafolic acid were included in this study for purposes of comparison.
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PMID:Comparison of the biological effects of selected 5,8-dideazafolate analogues with their 2-desamino counterparts. 270 31

Exponentially growing human lymphoblasts (culture LS-2) were separated by cell sorting (FACS II, Becton Dickinson) according to their deoxyribonucleic acid (DNA) content, designating them at particular phases of the cell cycle. Prior to cell sorting the DNA has been fluorochrome-labeled with the Hoechst stain H 33342. Maximum cell enrichments of 94% for G0 + G1 cells, 96% for S cells and 74% for G2 + M cells could be achieved. The enzyme activities of thymidine kinase (TK), thymidylate synthase (TS), DNA polymerase (DNA-P), dihydrofolate reductase (FH2-R), methionine synthase (MS), and hexokinase (HK) were determined in the obtained cell fractions. Although incorporation of 3H-thymidine (3H-dTR) and the 3H-dTR labeling index were significantly inhibited by the dye, no evidence of cell staining's having a significant effect on the enzyme activities was found. The enzyme activities for approximately 100% pure G0 + G1, S, and G2 + M cells were computed. With exception of TK, all the enzymes under study were shown to exhibit activities--although of differing degree--in the G0 + G1, S, and G2 + M cells. No TK activity was shown in G0 and G1 cells; its activity, however, was approximately the same in S and G2 + M cells. This applies likewise for TS which, in contrast to TK, exhibits minor activity in G0 + G1 cells. DNA-P was highly active in G0 + G1 cells, but maximum activity was in S cells. FH2-R exhibited maximum activity in S cells, although the difference in activity between S and G2 + M cells was not significant. None of the observed differences in MS activity was significant, indicating equally high activity in cells of all cell cycle phases. HK activity is approximately twice as high in G2 + M cells as in G0 + G1 cells.
Leukemia 1989 May
PMID:Relation between cell cycle stage and the activity of DNA-synthesizing enzymes in cultured human lymphoblasts: investigations on cells separated according to DNA content by way of a cell sorter. 271 50

alpha-Monoamides of methotrexate were evaluated for their potential as prodrugs. Studies on 11 alpha-monoamides and 5 gamma-monoamides of methotrexate showed that the gamma-monoamides were about as strong inhibitors of Lactobacillus casei dihydrofolate reductase as methotrexate, while I50 of the alpha-monoamides were 1-2 orders higher. The concentration for growth inhibition of murine L1210 cells for methotrexate gamma-propylamide and alpha-propylamide were respectively 1-2 and 2-3 orders higher than that of methotrexate. In contrast, only alpha-monoamides caused significant increase in life span of mice with transplanted L1210 leukaemia, the highest effect being given by the alpha-propyl and the alpha-butylamide. The possibility that the in vivo activity of the alpha-monoamides might be related to in vivo transformation to methotrexate was studied by HPLC analysis of mice serum after administration of the alpha- and gamma-propylamides.
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PMID:Alpha-monoamides of methotrexate as potential prodrugs. 271 39

This report examines the intracellular activity of dihydrofolate reductase using an in situ assay designed to measure enzymatic activity in intact cells. The rate of uptake of folic acid exceeded the rate of in situ dihydrofolate reductase activity suggesting that the reduction of folate to dihydrofolate, rather than transport, was the rate limiting step. In situ dihydrofolate reductase activity varied linearly with cell number. A comparison of the in situ activity revealed that a squamous cell carcinoma selected for methotrexate (MTX) resistant (SCC-15R) had 100 times greater dihydrofolate reductase (DHFR) activity than L1210 leukemia. In agreement with this finding, the in situ DHFR activity in SCC-15R cells was 50-fold less sensitive to the inhibitory effects of MTX than the L1210 in situ DHFR activity (IC50 = 1.1 x 10(-5) M and 2.4 x 10.7(-7) M respectively). The inhibition of in situ dihydrofolate reductase activity by MTX was found to correlate with the inhibition of growth, DNA synthesis (CdR incorporation) and in situ thymidylate synthase activity.
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PMID:A comparison of dihydrofolate reductase activity in intact leukemia cells and squamous cell carcinoma. 275 54

The novel tetrahydrofolate, 5,10-dideazatetrahydrofolic acid (DDATHF), was designed as an inhibitor of folate metabolism at a site other than dihydrofolate reductase. DDATHF has been shown to inhibit glycinamide ribonucleotide transformylase, a folate-requiring enzyme that catalyzes the first of two one-carbon transfer reactions in the de novo purine nucleotide biosynthetic pathway. Incubation of HL-60 promyelocytic leukemia cells with 5 x 10(-8) to 10(-5) M DDATHF resulted in a marked inhibition of growth after 48 h, with a complete cessation of cellular replication by day 4. Cell cycle analyses of DDATHF-treated HL-60 cells demonstrated an initial block in early S phase by day 3 followed by an accumulation of cells in the G1 and G2 + M phases of the cell cycle. Inhibition of growth was accompanied by a concentration-dependent increase in the percentage of mature myeloid cells that expressed nitroblue tetrazolium positivity, and a small increase in nonspecific esterase activity. Induction of differentiation and inhibition of growth by DDATHF were completely prevented by hypoxanthine and 5(4)-amino-4(5)-imidazole carboxamide, suggesting that depletion of intracellular purine nucleotide pools has an important role in the biological effects of this inhibitor. This possibility was confirmed by the finding that DDATHF caused a pronounced reduction in intracellular GTP and ATP levels within 2 h, with maximum decreases being observed by 24 h, a time interval which preceded the inhibition of cellular proliferation by this agent. Pyrimidine nucleoside triphosphate levels were markedly increased under these conditions. The findings indicate the importance of purine nucleotides to both the inhibition of growth and the induction of differentiation of HL-60 leukemia cells by DDATHF.
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PMID:Induction of HL-60 leukemia cell differentiation by the novel antifolate 5,10-dideazatetrahydrofolic acid. 275 15

A selected number of 1,3-diaminobenzo[f]quinazolines and 1,3-diamino-5,6-dihydrobenzo[f]quinazolines, which may be viewed as tricyclic analogues of the lipid-soluble antifolates pyrimethamine (PM), metoprine (DDMP), and etoprine (DDEP), were tested as inhibitors of purified dihydrofolate reductase (DHFR) from WI-L2 lymphoblasts, and as inhibitors of the growth of Streptococcus faecium ATCC 8043 and L1210 murine leukemia cells in culture. In addition, these tricyclic compounds were tested for antimalarial activity against Plasmodium berghei in mice, and for the ability to inhibit the growth of Pneumocystis carinii trophozoites in WI-38 human lung fibroblast cultures in the presence of leucovorin (LV). The most potent analogues were those with chlorine substitution in the ring distal to the 2,4-diaminopyrimidine moiety. Fully aromatic compounds tended to be more active than those in which the 5,6-bond was reduced, suggesting that planarity favors binding to the DHFR active site and may be favorable for cellular uptake. Several of the 2,4-diaminopyrimidine analogues showed greater potency than PM, DDMP or DDEP, and were more nearly comparable to the bicyclic 2,4-diaminopyrimidine antifolates trimetrexate (TMQ) or piritrexim (BW301U), which are known to be selectively toxic to P. carinii in the presence of LV. Two of the tricyclic compounds, 1,3-diamino-8-chlorobenzo[f]quinazoline and 1,3-diamino-9-chlorobenzo[f]quinazoline, proved to have activity similar to TMQ and BW301U in this system.
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PMID:Tricyclic 2,4-diaminopyrimidines with broad antifolate activity and the ability to inhibit Pneumocystis carinii growth in cultured human lung fibroblasts in the presence of leucovorin. 278 20

In order to explore the potential of retrovirus vectors for efficiently transferring foreign genes into mouse embryos, a replication-competent recombinant Moloney murine leukemia virus (Mo-MLV) vector carrying a mutant dihydrofolate reductase (DHFR) cDNA insert in the U3 region of the viral long terminal repeat was used to infect pre- and postimplantation embryos. When preimplantation mouse embryos were infected with the vector, as expected, the provirus integrated into the embryos and the germ line with the same efficiency as that observed with wild-type Mo-MLV, leading to inactivation of the recombinant virus. In contrast, when postimplantation mouse embryos were microinjected with virus-producing cells, between 90 to 100% of the surviving animals proved to be infected with the virus. The recombinant virus spread as efficiently as wild-type Mo-MLV in the infected embryos, resulting in up to three to five proviral copies per genome in heart, thymus, and brain tissues. Substantial expression of mutant DHFR*-coding viral message was found in all somatic tissues analyzed, the amounts correlating with the proviral copy number in the respective organ. These results suggest that replication-competent vectors are useful for efficient transfer and expression of foreign genes into tissues or whole animals when virus spread is needed.
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PMID:Transfer of a mutant dihydrofolate reductase gene into pre- and postimplantation mouse embryos by a replication-competent retrovirus vector. 279 20

A full-length human c-myb cDNA clone has been isolated from a CCRF-CEM leukemia cell cDNA library. The plasmid vector contains simian virus 40-derived promotor, splice, and polyadenylation sequences as well as a transcription unit for a dihydrofolate reductase cDNA. We have introduced this construct into Friend erythroleukemia (F-MEL) cells and have isolated a number of clones which contain intact and transcriptionally active human c-myb sequences. F-MEL clones expressing the highest levels of the human c-myb mRNA differentiate poorly in response to dimethyl sulfoxide. Two clones which initially expressed low levels of human c-myb transcripts and which differentiated normally were subsequently inhibited in their ability to differentiate when grown in successively higher concentrations of methotrexate, due to amplification and enhanced expression of plasmid sequences. The inhibitory effect on F-MEL differentiation appeared to be independent of the early decline in c-myc transcripts which were normally regulated in all cases examined. Our results indicate that constitutive expression of a nontruncated human c-myb cDNA can exert profound effects on erythroid differentiation and argue for a causal role of c-myb in the F-MEL differentiation process.
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PMID:Constitutive expression of a c-myb cDNA blocks Friend murine erythroleukemia cell differentiation. 283 42

Properties of the methotrexate (MTX) transport carrier were examined in a stable single-step 16-fold MTX-resistant L1210 murine leukemia cell line with unchanged dihydrofolate reductase gene copy and thymidylate synthase and dihydrofolate reductase levels and activities. MTX influx was markedly depressed due to a decrease in Vmax without a change in Km. From this cell line a clonal variant with greater resistance to MTX was identified due solely to a further decrease in influx Vmax. Trans-stimulation of MTX influx by 5-formyltetrahydrofolate was induced in parental but not resistant cells. Analysis of specific MTX surface binding demonstrated a small increase in the number of carriers in the first- and second-step resistant lines. Affinity labeling of cells with an N-hydroxysuccinimide ester derivative of [3H]MTX demonstrated carriers with comparable molecular weights in the parent and second-step transport defective lines. In two partial revertants with increased MTX sensitivity isolated from the second-step resistant lines, MTX influx was increased but surface membrane-binding sites were unchanged suggesting that recovery of transport was due to normalization of carrier function rather than an increase in the number of carriers. These studies suggest that impaired MTX transport in these lines is not due to an alteration in the association of the transport carrier with its substrate at the cell surface. Rather, resistance may be due to an alteration in the mobility of the carrier possibly associated with a protein change in the carrier itself or the cell membrane that surrounds it.
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PMID:Evidence for a functional defect in the translocation of the methotrexate transport carrier in a methotrexate-resistant murine L1210 leukemia cell line. 283 83


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