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 pathway for de novo biosynthesis of purine nucleotides contains two one-carbon transfer reactions catalyzed by glycinamide ribotide (GAR) and 5-aminoimidazole-4-carboxamide ribotide (AICAR) transformylases in which N10-formyltetrahydrofolate is the one-carbon donor. We have found that the antifolates methotrexate (MTX) and piritrexim (PTX) completely block the de novo purine pathway in mouse L1210 leukemia cells growing in culture but with only minor accumulations of GAR and AICAR to less than 5% of the polyphosphate derivatives of N-formylglycinamide ribotide (FGAR) which accumulate when the pathway is blocked completely by azaserine. This azaserine-induced accumulation of FGAR polyphosphates is completely abolished by MTX, indicating that inhibition of the pathway is at or before GAR transformylase (reaction 3; Lyons, S. D., and Christopherson, R. I. (1991) Biochem. Int. 24, 187-197). Three h after the addition of MTX (0.1 microM), cellular 5-phosphoribosyl-1-pyrophosphate has accumulated 3.4-fold while 6-methyl-mercaptopurine riboside (25 microM) induces a 6.3-fold accumulation. These data suggest that amido phosphoribosyltransferase catalyzing reaction 1 of the pathway is the primary site of inhibition. In support of this conclusion, we have found that dihydrofolate-Glu5, which accumulates in MTX-treated cells, is a noncompetitive inhibitor of amido phosphoribosyltransferase with a dissociation constant of 3.41 +/- 0.08 microM for interaction with the enzyme-glutamine complex in vitro. Folate-Glu5, MTX-Glu5, PTX, dihydrotriazine benzenesulfonyl fluoride, and AICAR also inhibit amido phosphoribosyltransferase.
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PMID:Antifolates induce inhibition of amido phosphoribosyltransferase in leukemia cells. 159 45

5,10-Dideazatetrahydrofolic acid (DDATHF) is a new potent antitumor agent that specifically inhibits purine biosynthesis, primarily through inhibition of glycinamide ribonucleotide transformylase, the first of the tetrahydrofolate-requiring enzymes in the de novo synthesis pathway. DDATHF has been shown to be an excellent substrate for mouse liver folylpolyglutamate synthetase in vitro, suggesting that intracellular conversion to polyglutamates could play an important role in the action of this antifolate. In this report, metabolic studies of the 6R-diastereomer of DDATHF in the cultured human leukemia cell lines CCRF-CEM and HL-60 are presented. At both 1 and 10 microM (6R)-DDATHF was rapidly converted to polyglutamates in both cell lines. DDATHF(Glu)5 and DDATHF(Glu)6 were the main intracellular metabolites. After incubation in drug-free medium, (6R)-DDATHF polyglutamates were better retained intracellularly with increasing glutamate chain length. (6R)-DDATHF showed reduced cytotoxicity toward a folylpolyglutamate synthetase-deficient cell line, CCRF-CEM30/6 related to a dramatically diminished accumulation of polyglutamates. The activity of (6R)-DDATHF in CCRF-CEM30/6 cells was decreased after both short and prolonged exposures. These results suggest that polyglutamylation of (6R)-DDATHF not only represents a mechanism for trapping the drug inside the cells but also produces a more potent inhibitor of the target enzyme.
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PMID:Intracellular metabolism of 5,10-dideazatetrahydrofolic acid in human leukemia cell lines. 170 76

5,10-Dideazatetrahydrofolic acid (DDATHF) is a folate antimetabolite that shows activity against glycinamide ribonucleotide (GAR) transformylase, a folate-requiring enzyme in the de novo purine nucleotide biosynthetic pathway. Previous studies from our laboratory have shown that DDATHF is an effective inducer of the maturation of HL-60 promyelocytic leukemia. In solution, DDATHF is a mixture of two diastereomers due to an asymmetric configuration at carbon 6. Incubation of HL-60 cells with 1 microM of each diastereomer resulted in an inhibition of cellular proliferation after 48 h that preceded an increase in the number of differentiated myeloid cells, as determined by the ability of cells to reduce nitroblue tetrazolium (NBT) and by the binding of the myeloid-specific antibody Mo 1. Several analogs of DDATHF were also tested as inducers of the differentiation of HL-60 cells. With the exception of the 10-acetyl analog of 5-deazatetrahydrofolic acid, all compounds displayed similar activities as inducers of maturation. The finding that both stereoisomers of DDATHF, as well as the analogs tested, could selectively reduce intracellular purine nucleotide levels suggested that these compounds inhibited purine nucleotide biosynthesis de novo. This possibility was confirmed by the finding that hypoxanthine completely prevented the reduction of intracellular purine nucleotide levels, as well as the induction of differentiation and the inhibition of cellular growth, by these folate analogs. The results suggest that GAR transformylase is a target for a series of compounds whose structures resemble that of tetrahydrofolate and indicate that the inhibition of GAR transformylase by these compounds is sufficient to induce the maturation of HL-60 leukemia cells.
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PMID:Induction of HL-60 leukemia cell differentiation by tetrahydrofolate inhibitors of de novo purine nucleotide biosynthesis. 204 32

5,10-Dideazatetrahydrofolic acid (DDATHF) is a potent inhibitor of glycinamide ribonucleotide transformylase, one of the folate-dependent key enzymes in de novo purine biosynthesis. The present report demonstrates that multiple membrane-transport routes may be involved in the cellular uptake of DDATHF. These routes include the classic reduced folate carrier and a membrane-associated folate-binding protein (mFBP). The role of an mFBP in the uptake of DDATHF was suggested from observations that (a) the mFBP showed a very high binding affinity for DDATHF, (b) murine and human leukemia cells expressing an mFBP were highly sensitive to growth inhibition by DDATHF, and (c) protection against this growth inhibition could be achieved using folic acid rather than reduced folate compounds.
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PMID:Growth-inhibitory effects of 5,10-dideazatetrahydrofolic acid on variant murine L1210 and human CCRF-CEM leukemia cells with different membrane-transport characteristics for (anti)folate compounds. 206 81

The synthesis and biological evaluation of N-[4-[[3-(2,4-diamino-1,6-dihydro-6-oxo-5-pyrimidinyl)propyl]amino]- benzoyl]-L-glutamic acid (1) (5-DACTHF, 543U76), an acyclic analogue of 5,6,7,8-tetrahydrofolic acid (THFA), are described. The key intermediate, hemiaminal 8, was prepared in four stages from 3-chloropropionaldehyde diethyl acetal. Reaction of 8 with dimethyl N-(4-aminobenzoyl)-L-glutamate gave the 2,4-bis(acetylamino) derivative 11, which was hydrolyzed with 1 N sodium hydroxide to give 1; the glycine analogue 16 was prepared in a similar manner. The N-methyl analogue 2 and N-formyl analogue 3 were prepared from 11 and 1, respectively. Compounds 1-3 inhibited growth of Detroit 98 and L cells in cell culture, with IC50s ranging from 2 to 0.018 microM. Cell culture toxicity reversal studies and enzyme inhibition tests showed that 1 was cytotoxic but not by the mechanism of the dihydrofolate reductase inhibitor aminopterin. Compound 1 and its polyglutamylated homologues inhibited glycinamide ribonucleotide transformylase (GAR-TFase) and aminoimidazole ribonucleotide transformylase (AICAR-TFase), the folate-dependent enzymes in de novo purine biosynthesis; and 1 was an effective substrate for mammalian folyl-polyglutamate synthetase. The compound inhibited (IC50 = 20 nM) the conversion of [14C]formate to [14C]-formylglycinamide ribonucleotide by MOLT-4 cells in culture. These data suggest that the site of action of 1 is inhibition of purine de novo biosynthesis. Moderate activity was observed against P388 leukemia in vivo.
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PMID:Synthesis and biological activity of an acyclic analogue of 5,6,7,8-tetrahydrofolic acid, N-[4-[[3-(2,4-diamino-1,6-dihydro-6-oxo-5- pyrimidinyl)propyl]amino]-benzoyl]-L-glutamic acid. 229 24

The Boon-Leigh procedure, involving condensation of a 6-chloro-5-nitropyrimidine (22) with an alpha-amino ketone (20 or 21) followed by reduction of the nitro group, cyclization, and L-glutamylation, led to the formation of 11-deazahomofolate (29) and its 10-methyl derivative (30). The corresponding (6R,S)-5,6,7,8-tetrahydro (4, 5) and 7,8-dihydro (31, 32) derivatives were prepared by catalytic hydrogenation. (6S)-11-Deazatetrahydrohomofolate was prepared from 29 by enzymatic reduction. Compounds 29 and 30 had little effect (IC50 greater than 2 x 10(-5) M) on Lactobacillus casei glycinamide ribonucleotide (GAR) formyltransferase but (6R,S)-11-deazatetrahydrohomofolate (4) is a potent inhibitor of this enzyme (IC50 = 5 x 10(-8) M). It is at least 100 times more inhibitory than 33, the 6S compound, indicating that the 6R component of the mixture having the unnatural configuration at C6 (34) is responsible for the potent inhibition. Compound 4 is a much weaker inhibitor of murine (L1210) and human (MOLT-4) leukemia cell GAR formyltransferases (IC50 greater than 1 x 10(-5) M). (6R,S)-11-Deaza-10-methyltetrahydrohomofolate (5) (IC50 = 1.1 x 10(-5) is 200 times weaker than 4 against L. casei GAR formyltransferase. However, 11-deaza-10-methyldihydrohomofolate (32) is more inhibitory (IC50 = 5.5 x 10(-7) M) than 5 or 30. None of the compounds showed inhibition of L. casei aminoimidazolecarboxamide ribonucleotide (AICAR) formyltransferase, dihydrofolate reductase, or thymidylate synthase. The dihydro derivatives 31 and 32 are 5% as active as dihydrofolate as substrates for L. casei dihydrofolate reductase. Compound 4 showed moderate inhibition of the growth of L. casei, Streptococcus faecium, MOLT-4 cells, and MCF-7 human breast adenocarcinoma cells.
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PMID:Folate analogues. 31. Synthesis of the reduced derivatives of 11-deazahomofolic acid, 10-methyl-11-deazahomofolic acid, and their evaluation as inhibitors of glycinamide ribonucleotide formyltransferase. 249 18

The diasteromers of 5,10-dideaza-5,6,7,8-tetrahydrofolate (DDATHF) differing in chirality about carbon 6 were resolved and studied as inhibitors of folate-dependent processes in mouse leukemia cells. Both diastereomers of DDATHF were found to be potent inhibitors of leukemia cell growth due to effects on de novo purine synthesis. Cell growth inhibition by these compounds was prevented by 5-formyltetrahydrofolate in a dose-dependent manner. This indicated that the effects of the DDATHF diastereomers were due to inhibition of folate-dependent processes. Metabolite reversal experiments indicated that 5'-phosphoribosylglycinamide formyltransferase was the major site of action of these compounds in mouse cells. Another site in de novo purine synthesis was affected at higher concentrations of diastereomer B in L1210 cells. Low concentrations of both diastereomers were found to inhibit pure L1210 5'-phosphoribosylglycinamide formyltransferase competitively with the folate substrate. The two diastereomers were also efficient substrates for mouse liver folylpolyglutamate synthetase. We conclude that the 6R- and 6S-diastereomers of DDATHF are remarkably similar and equiactive antimetabolites inhibitory to de novo purine synthesis and that the biochemical processes involved in their cytotoxicity display little stereochemical specificity.
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PMID:The 6S- and 6R-diastereomers of 5, 10-dideaza-5, 6, 7, 8-tetrahydrofolate are equiactive inhibitors of de novo purine synthesis. 259 65

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

5,10-dideaza-5,6,7,8-terrahydrofolic acid (DDATHF) is a potent antiproliferative agent in cell culture systems and in vivo in a number of murine and human xenograft tumors. In contrast to classical antifolates, which are dihydrofolate reductase inhibitors, DDATHF primarily inhibits GAR transformylase, the first folate-dependent enzyme along the pathway of de novo purine biosynthesis. The (6R) diastereomer of DDATHF (Lometrexol), currently undergoing clinical investigation, was used to develop CCRF-CEM human leukemia sublines resistant to increasing concentrations of the drug. Three cell lines were selected for ability to grow in medium containing 0.1 microM, 1.0 microM, and 10 microM of (6R)DDATHF, respectively. Impaired polyglutamylation was identified as a common mechanism of resistance in all three cell lines. A progressive decrease in the level of polyglutamylation was associated with diminished folylpolyglutamate synthetase activity and paralleled increasing levels of resistance to the drug. However, the expression of folylpolyglutamate synthetase RNA was not altered in the resistant cell lines compared to the parent cells. The most resistant cell subline also displayed an increased activity of gamma-glutamyl hydrolase. The sublines were scrutinized for other possible mechanisms of resistance. No alterations in drug transport or in purine economy were found. Modest increases were found in the activity of methylene tetrahydrofolate dehydrogenase but no alterations of other folate-dependent enzymes were observed. Increases in accumulation and conversion of folic acid to reduced forms, particularly 10-formyltetrahydrofolate, was also seen. The resistant cell lines were sensitive to dihydrofolate reductase inhibitors, methotrexate and trimetrexate, for a 72-h exposure period but showed cross-resistance to methotrexate for 4 and 24 h exposures. Cross-resistance was also shown toward other deazafolate analogues for both short- and long-term exposures.
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PMID:Multifactorial resistance to 5,10-dideazatetrahydrofolic acid in cell lines derived from human lymphoblastic leukemia CCRF-CEM. 783 26

10-Formyl-7,8-dihydrofolic acid (10-HCO-H2folate) was prepared by controlled air oxidation of 10-formyl-5,6,7,8-tetrahydrofolic acid (10-HCO-H4folate). The UV spectra of the 10-HCO-H2folate preparation has lambda max. 234, 333 nm and lambda min. 301 nm at pH 7.4, and lambda max. 257, 328 nm and lambda min. 229, 307 nm at pH 1. 1H-NMR spectroscopy of 10-HCO-H2folate (in 2H2O; 300 MHz) suggested a pure compound and gave resonances for one formyl group proton, two protons on C-7 and C-9, and no evidence for a C-6 proton, which is consistent with the structure proposed. The spectral properties indicated that the 10-HCO-H2folate preparation is not appreciably contaminated with 10-HCO-H4folate, 5,10-methenyltetrahydrofolic acid (5,10-CH = H4folate) or 10-formylfolic acid (10-HCO-folate). The above data establish that the 10-HCO-H2folate prepared here is authentic. In contrast, a folate with a UV spectrum having lambda max. 272 nm and lambda min. 256 nm at pH 7, which was prepared by 2,6-dichloro-indophenol oxidation of 10-HCO-H4folate and reported to be 97% pure [Baram, Chabner, Drake, Fitzhugh, Sholar and Allegra (1988) J. Biol. Chem. 263, 7105-7111], is apparently not 10-HCO-H2folate. 10-HCO-H2folate is utilized by Jurkat-cell (human T-cell leukaemia) and chicken liver aminoimidazolecarboxamide ribonucleotide transformylase (AICAR T'ase; EC 2.1.2.3) in the presence of excess 5-amino-imidazole-4-carboxamide ribotide (AICAR) resulting in the appearance of approximately 1 mol of H2folate product for each mol of AICAR formylated. The present 10-HCO-H2folate preparation had a kinetic advantage over 10-HCO-H4folate resulting from a difference of approx. 5-fold in K(m) values when both folates were used as cofactors for Jurkat-cell and rat bone marrow AICAR T'ase. No substantial kinetic advantage was observed using chicken liver AICAR T'ase. 10-HCO-H2folate had little or no activity with Jurkat-cell or chicken liver glycinamide ribonucleotide transformylase (GAR T'ase, EC 2.1.2.2). The existence in vivo of 10-HCO-H2folate is suggested in mammals by several reports of detectable amounts of radiolabelled 10-HCO-folate in bile and urine after administration of radiolabelled folic acid.
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PMID:Cofactor role for 10-formyldihydrofolic acid. 894 66


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