Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Four cell lines, SK-N-SH, SK-N-MC, SK-N-BE(2), and IMR-32, established in vitro from tumor tissue of patients with neuroblastoma were analyzed by trypsin-Giemsa banding methods. In two of the lines a large, abnormally staining chromosome region was observed. This "homogeneously staining region" (HSR) was considerably longer than any of the bands present in normal human cells and, as revealed by both G- and Q-banding, stained with an intermediate intensity. It was located on chromosomes No 6, 10, 17, or 19 of the SK-N-BE(2) cell line and on chromosome No 1 of the IMR-32 line. In concurrent studies, long HSR's were also observed in Chinese hamster sublines that had been exposed to and had developed high levels of resistance to methotrexate or methasquin and high levels of activity of target enzyme dihydrofolate reductase. For several sublines with the highest levels of enzyme activity, approximately 2% of the total cell protein was dihydrofolate reductase. Of 13 independently derived sublines with acquired resistance to antifolate, only those 7 with greater than 100-fold increases in enzyme activity consistently exhibited HSR's. These regions comprised 2-5% of the total length of the chromosome complement and were specifically localized, as demonstrated by G-banding. Analysis of chromosome replication patterns of the HSR in human neuroblastoma and in drug-resistant Chinese hamster cells by tritiated thymidine radioautography indicated that the long, abnormally staining region replicated relatively rapidly and synchronously and terminated replication before the midpoint of the S phase. The HSR thus appeared to represent a novel chromosome abnormality that may be present in cells with specialized functions. Drug-resistant Chinese hamster cells were characterized by overproduction of target enzyme, whereas human neuroblastoma cells had phenotypes of normal neuronal cells. Whether the HSR is transcriptionally active was not elucidated.
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PMID:A novel chromosome abnormality in human neuroblastoma and antifolate-resistant Chinese hamster cell lives in culture. 6 55

In the experiments on enzymic systems functioning in the metabolism of folic acid and on transplantable tumors in animals the preparation thomizine (chlorohydrate 4-methoxy-6-aminopyrimido (4,5-b) (1,4) thiazine) was worked out. Thomizine, as well as the known antimetabolite of folic acid-methotrexate, suppresses the activity of dihydrofolate reductase, but contrary to it suppresses FAP enzymic system, inhibiting aminopterin in the organism. Thomizine differes from methotrexate by another spectrum of antitumor effect, selective suppression of the tumor tissue growth, compared with the normal in vitro, it does not inhibit leucopoiesis, shows less toxicity and insignificant cumulative properties.
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PMID:[Tomizine--a new inhibitor of folate metabolism enzymes possessing an antitumor activity]. 17 6

BOT-2 cells (human breast tumor origin) have an impaired ability to utilize exogenous thymidine. Previous studies revealed this deficiency to be the permeation event rather than phosphorylation, since the cells have active thymidine kinase. Chromosome-mediated gene transfer was used to transfer genetic information in the form of metaphase chromosomes, from HeLa-65 cells to the BOT-2 cells, correcting the permease deficiency. Poly-L-ornithine or lipochromes were used for facilitation of chromosome uptake. After selection on HAT medium, transferant clones were isolated at a frequency of 4 x 10(-5) and 1 x 10(-5), respectively. Transferants MGP-1 and MGL-1 are stable after 18 months and have been characterized on the bases of purine and pyrimidine nucleoside uptake, relative thymidine kinase activities, alkaline phosphatase activities, and hydrocortisone-induced alkaline phosphatase activity. MGP-1 demonstrates positive thymidine uptake and incorporates radiolabeled thymidine into DNA. MGL-1 remains thymidine transport-deficient and surveys on HAT by increasing endogenous dihydrofolate reductase activity. Alkaline phosphatase activity in MGL-1 is similar to HeLa-65, 2% of that in BOT-2, and in addition, is inducible 25-30-fold by 3 micro M hydrocortisone. We have separated, genetically, a thymidine permease function from phosphorylation in cells of human origin and have transferred genetic information for the regulation of alkaline phosphatase.
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PMID:Alteration of human breast tumor cell membrane functions by chromosome-mediated gene transfer. 23 36

Methotrexate uptake by murine Lewis lung tumor was measured in vivo over a wide dose range. The data were analyzed according to a model previously developed for tissues in which methotrexate uptake is rate limited by transport across the cell membrane. Methotrexate transport in this tumor followed Michaelis-Menten kinetics with a rate constant for permeability (k/K) of 0.012 min-1. The methotrexate binding capacity of dihydrofolate reductase in the tumor was not exceeded at any dose studied. A low membrane permeability in conjunction with a high dihydrofolate reductase level explains the resistance of this tumor to methotrexate.
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PMID:In vivo methotrexate transport in murine Lewis lung tumor. 48 Jan 71

Blood levels of three aryldihydro-s-triazines in rats were followed: 4,6-diamino-1,2-dihydro-2,2-dimethyl-1-phenyl-s-triazine (I), the prototype of the series; 4,6-diamino-1-(3,4-dichlorophenyl)-1,2-dihydro-2,2-dimethyl-s-triazine (II); and N-(m-tolyl)-p-(4,6-diamino-1,2-dihydro-2,2-dimethyl-s-triazin-1-yl)hydrocinnamide (III). The blood profiles obtained provide substantial evidence that III, but not II, was precipitated in the peritoneal cavity where it was injected. Precipitation after intraperitoneal injection may explain why III and similar triazines with long nonpolar chains have been reported to be more active against intraperitoneal Walker 256 tumor than is II, even though the latter compound is a far more potent inhibitor of Walker 256 dihydrofolate reductase and of tumor cell cultures in vitro. Precipitation in the peritoneal cavity also may be involved in the difficulty of obtaining the toxicity-free antineoplastic activity expected from certain aryldihydrotriazines selectively inhibiting neoplastic dihydrofolate reductase.
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PMID:Pharmacokinetics of Aryldihydro-s-triazines with antifolate activity II: Blood levels and their relevance to antineoplastic activity in rats. 64 13

Triazinate (TZT), a potent inhibitor of dihydrofolate reductase, was selected for detailed investigation to determine its mechanism of selective action as well as its metabolic fate in mice, rats, dogs, and monkeys. The serum disappearance of TZT in normal and tumor-bearing mice was similar, with a rapid tissue equilibration phase and a slower elimination phase. Serum disappearance in normal and tumor-bearing rats was 1.5 to 2.2 hr. Serum disappearance in dogs and monkeys was similar, with half-lives of 3 to 4 and 2 to 4 hr, respectively. Urinary excretion of TZT at 24 hr was only 5 to 6% of the injected dose in mice and rats; in contrast, the dogs excreted 60% of the injected dose in 8 hr. TZT accumulated to comparable degrees in the organs of rats and mice, with progressively lesser concentrations in liver, kidney, spleen, and brain. Dihydrofolate reductase activity became almost undectectable in all tissues studied within 15 min after drug adminsitration. An important difference in drug accumulation was in the ascites cells of tumor-bearing animals: in mice, the drug level was consistently lower in the L1210 cells than in the ascites fluid; in contrast, by 30 min after treatment with TZT the drug level in Walker 256 cells was 10-fold higher than the level in the ascites fluid. No evidence for drug metabolism was found in extracts of urine, feces, or organ tissues from either mice or rats. TZT and two related triazines were studied for their ability to accumulate in the cerbrospinal fluid of dogs after i.v. administration. TZT achieved a cerebrospinal fluid level of approximately 15% of the serum concentration at 1 hr; in contrast, the other two triazines reached maximum cerebrospinal fluid values of 1% at 1 hr.
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PMID:Pharmacology of a new triazine antifolate in mice, rats, dogs, and monkeys. 80 54

Triazinate (TZT), a triazine folate antagonist, is a potent inhibitor of dihydrofolate reductase from mammalian cells. Because antitumor activity of triazinate in experimental tumors correlated closely with the in vitro inhibition of DNA synthesis in tumor cells derived from these tumors, we studied cells from patients with leukemia, solid tumor effusions, and cells from normal marrow to determine their in vitro sensitivity to TZT. DNA synthesis in cells from patients with acute leukemia was less sensitive to TZT than it was to methotrexate (MTX) at 2 X 10(-6) M concentration of the inhibitor, whereas the sensitivity was similar at 10(-5) M. This could be accounted for by the known greater sensitivity of dihydrofolate reductase to MTX than to TZT, and the observation that, whereas intracellular drug levels were similar at low (2 X 10(-6) M) extracellular concentrations of TZT or MTX, at the higher (10(-5) M) extracellular drug concentration intracellular TZT was greater than 3 times intracellular MTX. In vitro inhibition of DNA synthesis in cells obtained after patients were treated with TZT was correlated with drug serum concentration and with leukemia cell kill. The sensitivity of cells from solid tumor effusions to TZT was similar to the sensitivity to MTX. Since patients can tolerate doses of TZT five times higher than MTX with less toxicity, there may be advantage to the clinical use of TZT in some tumor cell types.
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PMID:Inhibition of DNA synthesis in normal and malignant human cells by triazinate (Baker's antifol) and methotrexate. 95 90

The administration of calcium leucovorin, either concurrently or after high dosages of methotrexate in L1210 leukemic mice, has both pharmacokinetic and biochemical effects in tumor cells and drug-limiting proliferative normal tissue in small intestine. A reduction in the maximal level of accumulation and retention of exchangeable drug (unbound to dihydrofolate reductase) in tissue could be demonstrated when calcium leucovorin was given simultaneously with methotrexate at equal or greater dosages than the latter. The dose dependence for calcium leucovorin-introduced drug loss is similar in both tissues and showed the expected variation when the time interval between methotrexate and calcium leucovorin doses was increased. With 400 mg methotrexate per kg, greater than 96 mg calcium leucovorin per kg were required maximally to affect overall drug retention in tissue 2 hr after drug, whereas only 24 mg calcium leucovorin per kg were required 16 hr after drug. Calcium leucovorin, given after methotrexate, induced synchronous recovery of DNA synthesis (measured by labeled deoxyruridine incorporation) in both small intestine and L1210 cells. An initial cycle of synthesis was induced in the presence of exchangeable levels of drug. Two hr after methotrexate, 12 mg/kg, calcium leucovorin induced an immediate but only partial (20 to 25% of control rate) recovery of synthesis with dose dependence from 3 to 12 mg calcium leucovorin per kg. Less synthesis was induced after 96 mg/kg and almost none after methotrexate, 400 mg/kg. With calcium leucovorin, 24 mg/kg, given 2 hr after methotrexate, 12 or 96 mg/kg, a major cycle of synthesis occurred when total drug levels approached the equivalence of the dihydrofolate reductase content. The magnitude of this cycle of synthesis in both L1210 cells and small intestine was the same as that seen in animals recovering from methotrexate alone. However, this is based on the assumption that an approximately equivalent relationship between DNA synthesis and labeled doexyuridine incorporation in each tissue during the period of maximal incorporation within the cycle. The major effect of calcium leucovorin, then, was to induce an earlier resumption of DNA synthesis as a consequence of the pharmacokinetic effect in each tissue. With calcium leucovorin, 24 or 400 mg/kg, given 16 hr after methotrexate, an identical effect on drug retention was observed in both L1210 cells and small intestine. Although there was a difference in the time course for recovery in small intestine at each dosage of calcium leucovorin, the recovery of DNA synthesis as drug levels approached the dihydrofolate reductase content was similar in magnitude. In L1210 cells, however, substantial recovery of synthesis to a comparable level and with a similar time-course occurred only after leucovorin, 400 mg/kg. Little or no recovery of DNA synthesis was observed after calcium leucovorin, 24 mg/kg, during the same time period. This dosage schedule (methotrexate, 400 mg/kg, s.c...
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PMID:Biochemical and pharmacokinetic effects of leucovorin after high-dose methotrexate in a murine leukemia model. 108 82

A greater persistence of unbound (exchangeable) drug in tumor cells versus drug-limiting normal tissue (proliferating epithelium of small intestine) correlates with the therapeutic effects of various antifolates against a group of murine tumors. After approsimate equimolar doses (3 mg/kg i.p.) of methotrexate (MTX) methasquin (MQ), aminopterin, and N-([2,4-diamino-5-chloro-6-quinazolinyl) methyl]-amino)benzol)-L-glutamate (5-Cl-deaza-AM), total accumulation in small intestine was vie- to eight-fold greater than the dihydrofolate reductase content. Free drug persisted for less than 4 hr (MTX), 16 hr (MQ), 30 hr (aminopterin),and 48 hr (5-Cl-deaza-AM). Overall drug accumulation in L121O cells was greater (12- to 40-fold enzyme level), and drug persistence above enzyme level was more prolonged in the case of MTX (24 hr),MQ (32 hr), and 5-Cl-deaza-AM (greater than 48 hr). Persistence of aminopterin was similar to that seen in small intestine. After the same dose of each drug s.c., the results were similar in small intestine. In L121o cells, however, the total drug accumulation was much lower, but the relative persistence of each was similar to that seen after an i.p. dose. After a single optimal therapeutic dose (3, 0.75, 0.3, and 0.1 mg/kg i.p. for MTX, MQ, aminopterin, and 5-Cl-deaza-AM every other day), accumulation of each drug in for no more than 4 hr. In L121O cells, maximal accumulation of each drug also varied, but persistence differed in accordance with the relative therapeutic effectiveness of each (9 hr for 5-Cl-deaza-AM, 12 hr for aminopterin, and more than 20 hr for MTX amd MQ).
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PMID:Further evidence for a basis of selective activity and relative responsiveness during antifolate therapy of murine tumors. 116 15

Biochemical and biological studies have been carried out with 2-desamino-2-methylaminopterin (dmAMT), which inhibits tumor cell growth in culture but is only a weak inhibitor of dihydrofolate reductase (DHFR). Since it was possible that the species responsible for growth inhibition are polyglutamylated metabolites, the di-, tri-, and tetraglutamates of dmAMT were synthesized and tested as inhibitors of purified recombinant human DHFR, murine L1210 leukemia thymidylate synthase (TS), chicken liver glycinamide ribonucleotide formyltransferase (GARFT), and murine L1210 leukemia aminoimidazolecarboxamide ribonucleotide formyltransferase (AICARFT). The compounds with three and four gamma-glutamyl residues were found to bind two orders of magnitude better than dmAMT itself to DHFR, TS, and AICARFT, with 50% inhibitory concentration values in the 200 to 300 nM range against all three enzymes. In contrast, at a concentration of 10 microM, dmAMT polyglutamates had no appreciable effect on GARFT activity. These findings support the hypothesis that dmAMT requires intracellular polyglutamylation for activity and indicate that replacement of the 2-amino group by 2-methyl is as acceptable a structural modification in antifolates targeted against DHFR as it is in antifolates targeted against TS. In growth assays against methotrexate (MTX)-sensitive H35 rat hepatoma cells and MTX-resistant H35 sublines with a transport defect, dmAMT was highly cross-resistant with MTX, but not with the TS inhibitors N10-propargyl-5,8-dideazafolic acid and N-(5-[N-(3,4-dihydro-2-methyl-4-ox-oquinazolin-6-yl)-N- methylamino]thenoyl)-L-glutamic acid, implicating DHFR rather than TS as the principal target for dmAMT polyglutamates in intact cells. On the other hand, an H35 subline resistant to 2'-deoxy-5-fluorouridine by virtue of increased TS activity was highly cross-resistant to N10-propargyl-5,8-dideazafolic acid and not cross-resistant to MTX, but showed partial cross-resistance to dmAMT. Both thymidine and hypoxanthine were required to protect H35 cells treated with concentrations of dmAMT and MTX that inhibited growth by greater than 90% relative to unprotected controls. In contrast, N10-propargyl-5,8-dideazafolic acid and N-(5-[N-(3,4-dihydro-2-methyl-4-oxoquinazolin-6-yl)-N-methylamino] thenoyl)- L-glutamic acid required only thymidine for protection. Like MTX, therefore, dmAMT appears to inhibit purine as well as pyrimidine de novo synthesis, and its effect on cell growth probably reflects the ability of dmAMT polyglutamates to not only block dihydrofolate reduction but also interfere with other steps of folate metabolism, either directly or indirectly via alteration of reduced folate pools.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Biochemical and biological studies on 2-desamino-2-methylaminopterin, an antifolate the polyglutamates of which are more potent than the monoglutamate against three key enzymes of folate metabolism. 131 37


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