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)

Methotrexate produced the first remission in leukemia and the first cure of a solid tumor, choriocarcinoma. Methotrexate tightly binds to dihydrofolate reductase (DHFR), blocking the reduction of dihydrofolate to tetrahydrofolic acid, the active form of folic acid. Methotrexate also directly inhibits the folate-dependent enzymes of de novo purine and thymidylate synthesis. Resistance to methotrexate may develop as a result of elevated DHFR activity or defective transport of methotrexate into malignant cells. Increased DHFR enzyme levels may also result from amplification of the DHFR gene, which is now clinically significant in selected patients. Methotrexate is an active drug in the first-line treatment of gestational trophoblastic disease (GTD) and in metastatic squamous cell carcinoma of the cervix. Since the introduction of methotrexate chemotherapy for malignant GTD, most hospitals have reported almost 100% cure rates for patients with nonmetastatic disease using single-agent regimens. Patients with low-risk metastatic disease have been treated with methotrexate and folinic acid and over 50% complete remission rates have been reported. Patients with metastatic GTD who had one or more high-risk factors benefited from initial multiagent chemotherapy, rather than waiting for acquisition of drug-resistance to single-agent therapy to start multiagent treatment. Using multiagent combination chemotherapy such as MAC (methotrexate, actinomycin D, cyclophosphamide) or EMA-CO (etoposide, methotrexate, actinomycin D and cyclophosphamide, vincristine), most investigators have reported remission in approximately 60 to 80% of patients with high-risk metastatic GTD. Although the role of chemotherapy in carcinoma of the cervix has been limited for several reasons, trial of combination chemotherapy including methotrexate has been reported. However, it is still impossible to draw definite conclusions as to whether methotrexate combined with another clearly active drug may yield a superior response rate and survival.
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PMID:[Methotrexate in gynecologic oncology]. 897 93

The 4-amino-7-oxo-substituted analogues of 5-deaza-5,6,7, 8-tetrahydrofolic acid (5-DATHF) and 5,10-dideaza-5,6,7, 8-tetrahydrofolic acid (DDATHF) were synthesized as potential antifolates. Treatment of the alpha,beta-unsaturated esters 11a-c, obtained in one synthetic step from commercially available para-substituted methyl benzoates (9a-c) and methyl 2-(bromomethyl)acrylate (10), with malononitrile in NaOMe/MeOH afforded the corresponding pyridones 12a-c. Formation of the pyrido[2,3-d]pyrimidines 13a-c was accomplished upon treatment of 12a-c with guanidine in methanol. After the hydrolysis of the ester group present in 13a-c, the resulting carboxylic acids 14a-c were treated with diethyl cyanophosphonate in Et3N/DMF and coupled with L-glutamic acid dimethyl ester to give 15a-c. Finally, the basic hydrolysis of 15a-c yielded the desired 4-amino-7-oxo-substituted analogues 16a-c in 20-27% overall yield. Compounds 16a-c were tested in vitro against CCRF-CEM leukemia cells. The results obtained indicated that our 4-amino-7-oxo analogues are completely devoid of any activity, the IC50 being higher than 20 microg/mL for all cases except 14c for which a value of 6.7 microg/mL was obtained. These results seem to indicate that 16a-c are inactive precisely due to the presence of the carbonyl group in position C7, the distinctive feature of our synthetic methodology.
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PMID:Synthesis and biological activity of 4-amino-7-oxo-substituted analogues of 5-deaza-5,6,7,8-tetrahydrofolic acid and 5,10-dideaza-5, 6,7,8-tetrahydrofolic acid. 971 7

Chemical mutagenesis with N-methyl-N-nitrosourea was employed to study the pattern of mutations in the reduced folate carrier (RFC1) that results in transport-related methotrexate resistance and to identify amino acid residues that are critical to carrier structure and/or function. Thirty-four methotrexate transport-defective L1210 leukemia cell lines were isolated with folic acid as the sole folate source under antifolate selective pressure. The RFC1 mRNA levels were comparable with, or not substantially decreased, in most of these cell lines relative to wild-type L1210 cells. The molecular basis for the transport defects was investigated by sequencing multiple RFC1 cDNA clones isolated from these mutants by reverse transcription-polymerase chain reaction, which encompassed the entire coding region. The mutations identified were further confirmed either by direct sequencing or, when applicable, by restriction analysis of total reverse transcription-polymerase chain reaction products. The majority of mutations (21) led to single amino acid substitutions that were in, or near, 9 of 12 predicted transmembrane domains, with the highest frequencies in the first, fifth, and eighth. There were no mutations in the sixth, ninth, and twelfth transmembrane domains. Glycine, serine, and arginine were the most frequently mutated residues. These data suggest that several transmembrane domains, rather than the amino- and carboxyl-termini, and the large intracellular loop between the sixth and seventh transmembrane domains play key roles as sites for RFC1 inactivation because of single point mutations. This panel of mutated cell lines offers an important resource for studies on RFC1 structure-function and for the evaluation of transport-related cross-resistance patterns with new-generation antifolate inhibitors of tetrahydrofolate cofactor-dependent enzymes.
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PMID:Pattern of mutations that results in loss of reduced folate carrier function under antifolate selective pressure augmented by chemical mutagenesis. 1038 85

The bioactivity of 10-formyl-7,8-dihydrofolic acid and 10-formyl-folic acid was determined in human leukemia (CCRF-CEM) cells grown in a folate-depleted medium containing methotrexate. Excess 10-formyl-7,8-dihydrofolic acid, (but not 10-formyl folic acid) supported the growth of these cells, but it was less potent than5-formyl-5,6,7,8-tetrahydrofolic acid (a control). 10-formyl-7, 8-dihydrofolic acid (not 10-formyl folic acid) was active as substrate for aminoimidazole carboxamide ribotide transformylase and dihydrofolate reductase. This is the first experimental evidence that 10-formyl-7,8-dihydrofolic acid is a bioactive folate in mammalian cells. These experiments and several other lines of evidence in the literature suggest that 10-formyl-folic acid must be metabolized to bioactive folate by enteric bacteria before it can be utilized by the vertebrate host.
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PMID:10-Formyl-dihydrofolic acid is bioactive in human leukemia cells. 1039 92

The chemotherapeutic agent methotrexate is widely used in tumor therapy for different forms of leukemia and for the therapy of arthritis. Methotrexate is eliminated from systemic blood circulation by the liver and its transport into hepatocytes is therefore described in detail in this paper. Methotrexate uptake is energy- and sodium-dependent. The Km and the Vmax are 23 microM and 36 pmol/mg protein min, respectively. The apparent activation energy (E(app)) of methotrexate uptake (5 microM [3H]methotrexate) is 53.73 kJ/mol, which indicates an energy-dependent carrier-mediated process. Although methotrexate is a folate derivative, folate itself does not inhibit methotrexate uptake, whereas the reduced folates, dihydrofolate and tetrahydrofolate are weak uncompetitive inhibitors. In contrast, the bile acids taurocholate and cholate are effective competitive inhibitors of methotrexate uptake into hepatocytes. Further strong inhibitors are the loop diuretic bumetanide, the mycotoxin ochratoxin A and bromosulfophthalein. Because tumor patients develop drug resistance during methotrexate therapy, the uptake of methotrexate was tested in different hepatoma cell lines. In HepG2-cells and Reuber hepatoma Fao-cells the transport was non-existent or very small. However, the hepatocytoma fusion cell line HPCT-1E3, a hybrid cell line between primary rat hepatocytes and rat Reuber Fao-cells, shows an intermediate transport activity with a threefold increase of the methotrexate uptake. These results indicate the presence of a bile acid sensitive methotrexate carrier in hepatocytes which is absent in dedifferentiated hepatoma cells. The carrier differs from previously described transporters for the uptake of organic anions.
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PMID:Characterization of the bile acid sensitive methotrexate carrier of rat liver cells. 1049 92

Four L1210 murine leukemia cell lines resistant to 5, 10-dideazatetrahydrofolate (DDATHF) and other folate analogs, but sensitive to continuous exposure to methotrexate, were developed by chemical mutagenesis followed by DDATHF selective pressure. Endogenous folate pools were modestly reduced but polyglutamate derivatives of DDATHF and ALIMTA (LY231514, MTA) were markedly decreased in these mutant cell lines. Membrane transport was not a factor in drug resistance; rather, folypolyglutamate synthetase (FPGS) activity was decreased by >98%. In each cell line, FPGS mRNA expression was unchanged but both alleles of the FPGS gene bore a point mutation in highly conserved domains of the coding region. Four mutations were in the predicted ATP-, folate-, and/or glutamate-binding sites of FPGS, and two others were clustered in a peptide predicted to be beta sheet 5, based on the crystal structure of the Lactobacillus casei enzyme. Transfection of cDNAs for three mutant enzymes into FPGS-null Chinese hamster ovary cells restored a reduced level of clonal growth, whereas a T339I mutant supported growth at a level comparable to that of the wild-type enzyme. The two mutations predicted to be in beta sheet 5, and one in the loop between NH(2)- and COOH-terminal domains did not support cell growth. When sets of mutated cDNAs were co-transfected into FPGS-null cells to mimic the genotype of drug-selected resistant cells, clonal growth was restored. These results demonstrate for the first time that single amino acid substitutions in several critical regions of FPGS can cause marked resistance to tetrahydrofolate antimetabolites, while still allowing cell survival.
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PMID:Molecular analysis of murine leukemia cell lines resistant to 5, 10-dideazatetrahydrofolate identifies several amino acids critical to the function of folylpolyglutamate synthetase. 1085 98

A set of 16 new simplified analogues of acetogenins has been designed based on: (i) the replacement of the bis THF moiety of these natural products by an ethylene glycol bis ether unit; (ii) the introduction of different lipophilic side chains (alkyl, aryl, dialkylamino, O-cholesteryl); (iii) the presence of the same terminal isolactone. In vitro cytotoxic activity against L1210 leukemia is reported.
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PMID:Synthesis and cytotoxic activity of acetogenin analogues. 1089 Jan 67

A murine leukemia cell line was identified that is highly resistant to methotrexate (MTX), due to impaired transport, but fully sensitive to 5,10-dideazatetrahydrofolate (DDATHF). A valine-to-methionine substitution at amino acid 104 in the reduced folate carrier (RFC1) explains this disparity in drug resistance. Transfection of the V104M cDNA into an RFC1-deficient cell line markedly increased DDATHF influx (32x) but only modestly increased influx of MTX and 5-formyltetrahydrofolate (4- and 6-fold, respectively). The growth inhibition or growth requirements for these folates fell by factors of 18, 2, and 4, respectively, in the transfectant. Preservation of DDATHF influx in cells with V104M RFC1 resulted in even greater preservation (60%) of the exchangeable drug level. Another major element in the preservation of DDATHF activity was the impact of the mutated carrier on cellular folate pools. For folic acid, folate pools were essentially unchanged but DDATHF polyglutamate levels decreased in lines that express the V104M carrier. However, with 5-formyltetrahydrofolate as the growth source, there was a marked decrease in folate pools in the lines carrying the mutated carrier, and DDATHF polyglutamate levels were unchanged. Hence, DDATHF activity was preserved in cells with V104M RFC1 due to (a) relative conservation of DDATHF transport, and (b) depletion of cellular THF cofactors with diminishing folate cofactor competition at folylpolyglutamate synthetase and possibly glycinamide ribonucleotide formyltransferase. Hence, resistance to one antifolate, in this case MTX, because of a loss of RFC1 transport activity need not exclude the subsequent utility of another antifolate that uses the same carrier.
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PMID:Sensitivity to 5,10-dideazatetrahydrofolate is fully conserved in a murine leukemia cell line highly resistant to methotrexate due to impaired transport mediated by the reduced folate carrier. 1095 17

We recently described the syntheses of 12a-c, 4-amino-7-oxo substituted analogues of 5-deaza-5,6,7,8-tetrahydrofolic acid (5-DATHF), and 5,10-dideaza-5,6,7,8-tetrahydrofolic acid (DDATHF), in six steps from commercially available p-substituted methyl benzoates in 20-27% overall yields. Such analogues were tested in vitro against CCRF-CEM leukemia cells and showed that they are completely devoid of any activity, the IC(50) being higher than 20 microg/mL for all cases. To clarify if the presence of the carbonyl group in position C7, the distinctive feature of our synthetic methodology, is the reason for this lack of activity, we have now obtained the 7-oxo substituted analogues of 5-DATHF and DDATHF, 18a-c, in 10-30% overall yield. Testing of 18a-c in vitro against CCRF-CEM leukemia cells revealed that these compounds are totally inactive. A molecular modeling study of 18b inside the active site of the complex E. coliGARTFase-5-DATHF-GAR pointed to an electronic repulsion between the atoms of the 7-oxo group and the carbonyl group of Arg90 as a possible explanation for the inactivity of 18a-c.
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PMID:Synthesis and biological activity of 7-oxo substituted analogues of 5-deaza-5,6,7,8-tetrahydrofolic acid (5-DATHF) and 5,10-dideaza-5,6,7,8-tetrahydrofolic acid (DDATHF). 1142 31

The presence of sequence variants in the human reduced folate carrier (hRFC) was assessed in leukemia blasts from children with acute lymphoblastic leukemia (ALL) and in normal peripheral blood specimens. A CATG frame shift insertion at position 191 was detected in 10-60% of hRFC transcripts from 10 of 16 ALL specimens, by RFLP analysis and direct sequencing of hRFC cDNAs. In genomic DNAs prepared from 105 leukemia (n = 54) and non-leukemia (n = 51) specimens, PCR amplifications and direct sequencing of exon 3 identified a high-frequency G to A single nucleotide polymorphism at position 80 that resulted in a change of arginine-27 to histidine-27. The allelic frequencies of G/A80 were nearly identical for the non-leukemia (42.2% CGC and 57.8% CAC) and leukemia (40.7% CGC and 59.3% CAC) genomic DNAs. In cDNAs prepared from 10 of these ALL patients, identical allelic frequencies (40 and 60%, respectively) were recorded. In up to 62 genomic DNAs, hRFC-coding exons 4-7 were PCR-amplified and sequenced. A high-abundance C/T696 polymorphism was detected with nearly identical frequencies for both alleles, and a heterozygous C/A1242 sequence variant was identified in two ALL specimens. Both C/T696 and C/A1242 were phenotypically silent. In transport assays with [(3)H]methotrexate and [(3)H]5-formyl tetrahydrofolate, nearly identical uptake rates were measured for the arginine-27- and histidine-27-hRFC proteins expressed in transport-impaired K562 cells. Although there were no significant differences between the kinetic parameters for methotrexate transport for the hRFC forms, minor (approximately 2-fold) differences were measured in the K(i)s for other substrates including Tomudex, 5,10-dideazatetrahydrofolate, GW1843U89, and 10-ethyl-10-deazaaminopterin and for 5-formyl tetrahydrofolate.
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PMID:Single nucleotide polymorphisms in the human reduced folate carrier: characterization of a high-frequency G/A variant at position 80 and transport properties of the His(27) and Arg(27) carriers. 1170 57


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