5-methyltetrahydrofolate and Neoplasms

Normal cells can synthesize sufficient methionine for growth requirements from homocysteine and 5-methyltetrahydrofolate and vitamin B12. However, many cancer-cell types require exogenous methionine for survival and therefore methionine restriction is a promising avenue for treatment. While the lack of the methionine salvage enzyme methylthioadenosine phosphorylase (MTAP) deficiency is associated with methionine dependence in cancer cells, there are other causes for tumors to require exogenous methionine. In this review we describe studies that show restricting methionine to certain cancers by diet or by enzyme depletion, alone or in combination with certain chemotherapeutics is a promising antitumor strategy. The basis for methionine dependence in tumor cells is also briefly reviewed.

Topics: Animals; Antineoplastic Agents; Clinical Trials as Topic; Humans; Methionine; Neoplasms; Purine-Nucleoside Phosphorylase; Tetrahydrofolates; Treatment Outcome; Tumor Cells, Cultured

The phase I development program of tegafur and uracil (UFT) in the United States has included evaluation of the drug as a single agent and subsequent studies of its biochemical modulation by oral leucovorin. Phase I trials of single-agent UFT examined both a 5-day schedule repeated every 21 days and a 28-day schedule repeated every 35 days. In all of the trials the total dose was divided by three and administered three times daily at 8-hour intervals. Like intravenous schedules of fluorouracil (5-FU), UFT has schedule-dependent toxicity, with granulocytopenia being the dose-limiting toxicity for the 5-day regimen and diarrhea being the dose-limiting toxicity for the 28-day regimen. The suggested phase II doses for UFT administered without leucovorin were 800 mg/m2/day for the 5-day schedule and 360 mg/m2/day for the 28-day schedule. Subsequent phase I studies combining UFT with oral leucovorin used a 28-day schedule repeated every 35 days. Diarrhea was the dose-limiting toxicity, and the recommended phase II dose was UFT, 300 mg/m2/day, plus leucovorin, 90 mg/day. Pharmacokinetic evaluation showed that single-dose UFT results in maximum plasma levels and an area under the concentration-time curve that increased with escalating UFT doses. In addition, 5-FU levels were detectable throughout the 28-day dosing period; however, there was no evidence of significant accumulation of uracil, tegafur, or 5-FU. The administration of leucovorin in this trial provided continuous exposure of d,l-leucovorin and 5-methyltetrahydrofolate with little variation between doses or days.

Topics: Administration, Oral; Antidotes; Antineoplastic Combined Chemotherapy Protocols; Clinical Trials, Phase I as Topic; Drug Combinations; Fluorouracil; Humans; Leucovorin; Neoplasms; Tegafur; Tetrahydrofolates; Uracil

Because of the synergy seen in adult trials when 5-fluorouracil is combined with leucovorin, we initiated a Phase I trial of this combination in children's refractory cancer. Leucovorin, an equal mixture of the (6R,S)-diastereoisomers, was administered p.o. for 6 consecutive days as 4 equal doses at 0, 1, 2, and 3 h totaling 500 mg/m2/day. 5-Fluorouracil was given daily on days 2 to 6 as an i.v. bolus immediately following the last dose of leucovorin. The leucovorin dose was held constant while the 5-fluorouracil dose was escalated in cohorts of patients from 300 mg/m2/day to its maximally tolerated dose. Thirty-five patients (19 with acute leukemia and 16 with solid tumors) were evaluable for toxicity. The maximally tolerated dose of FUra was 450 mg/m2/day for 5 treatments for patients with solid tumors and 650 mg/m2/day for 5 treatments for the children with leukemia. The dose-limiting toxicities were myelosuppression and stomatitis. Other side effects included transient, mild elevations of serum transaminases, mild nausea, vomiting, and diarrhea. The pharmacokinetics of high-dose p.o. leucovorin was studied in 23 children. There was considerable interpatient variability in the plasma concentrations of total bioactive folates (TBAF), (6S)-leucovorin, and (6S)-5-methyltetrahydrofolic acid. The maximum plasma concentration (Cmax) of TBAF was 821 +/- 97 (SE) nM, occurring at a median of 8 h; the Cmax of (6S)-leucovorin was 77 +/- 11 nM, occurring at 4 h. The TBAF concentration fell to 146 +/- 42 nM by 24 h. (6S)-5-Methyltetrahydrofolic acid accounted for 90 +/- 7% of the TBAF at the Cmax. The plasma concentration of (6R)-leucovorin, the unnatural isomer, was equal to that of TBAF. Thus, p.o. leucovorin reduced the 5-fold excess of (6R)-leucovorin over TBAF seen after i.v. doses. The relative amounts of the three major plasma species were approximately the same as in adults, even though the Cmax of each compound was lower.

Topics: Administration, Oral; Adolescent; Adult; Child; Child, Preschool; Drug Administration Schedule; Drug Evaluation; Drug Synergism; Drug Therapy, Combination; Female; Fluorouracil; Humans; Infant; Leucovorin; Male; Neoplasms; Stereoisomerism; Tetrahydrofolates

Folate supplementation may be associated with an increased risk of developing several types of cancer and a derangement of immune function. Among the latter, Natural killer (NK) cells are involved in non-MHC-restricted natural immunity against malignant target cells. Abnormalities in NK cell number or function have been associated with a higher cancer risk. The aim of this study was to study in vitro the possible effect of different concentrations of 5-methyltetrahydrofolic acid (5-MTHF) or folic acid on NK cell cytotoxic function, and expression of the stimulatory and inhibitory receptors KIRDL4, KIRDL3, and NKG2D.. Volunteer-derived peripheral mononuclear cells (PBMC) and highly enriched NK cells (95% CD56+ CD16+) were grown in folic acid free-RPMI 1640, supplemented either with folic acid or 5-MTHF (15-100 nM) during 72 h to 96 h.. No differences in the cytolytic activity of PBMC and enriched NK cells were observed. After 96 h of in vitro culture without folate or supplemented with FA or 5-MTHF (30 or 100 nM), there were no changes in the percentage of HPNK receptor-positive cells.. Our data indicate that a high dose of 5-MTHF or folic acid does not influence NK cell function in vitro.

Topics: CD56 Antigen; Cytotoxicity, Immunologic; Dietary Supplements; Female; Folic Acid; Humans; Killer Cells, Natural; Leukocytes, Mononuclear; Male; Neoplasms; Receptors, IgG; Receptors, Natural Killer Cell; Tetrahydrofolates; Vitamin B Complex

The folate receptor (FR) is frequently overexpressed in tumors and can be targeted with folate-based (radio)pharmaceuticals. However, significant accumulation of radiofolates in FR-positive kidneys represents a drawback. We have shown that preadministration of the antifolate pemetrexed (PMX) significantly improved the tumor-to-kidney ratio of radiofolates in mice. The aim of this study was to investigate the dose dependence of these effects and whether the same results could be achieved with folic acid (FA) or 5-methyl-tetrahydrofolate (5-Me-THF).. Biodistribution was assessed 4 h postinjection of the organometallic (99m)Tc-picolylamine monoacetic acid folate in nude mice bearing FR-positive KB tumor xenografts. PMX (50-400 microg/mouse) was injected 1 h previous to radioactivity. The effects of FA and 5-Me-THF (0.5-50 microg/mouse) were investigated likewise. Tissues and organs were collected and counted for radioactivity and the values tabulated as percentage of injected dose per gram tissue (% ID/g).. PMX administration reduced renal retention (<1.6% ID/g vs. control: >10% ID/g), while the tumor uptake (average 1.35%+/-0.40% ID/g vs. control: 1.79%+/-0.49% ID/g) was only slightly affected independent of the PMX dose. Replacement of PMX by FA or 5-Me-THF (50 microg/mouse) resulted in a significant renal blockade (<0.1% ID/g) but at the same time in an undesired reduction of tumor uptake (<0.2% ID/g).. Selective reduction of radiofolate uptake in kidneys under retention of high tumor accumulation could be achieved in combination with PMX over a broad dose range but not with FA or 5-Me-THF.

Topics: Animals; Dose-Response Relationship, Drug; Female; Folic Acid; Folic Acid Antagonists; Humans; KB Cells; Kidney; Mice; Mice, Nude; Neoplasm Transplantation; Neoplasms; Organotechnetium Compounds; Radiopharmaceuticals; Tetrahydrofolates; Tissue Distribution

Topics: Chromatography, High Pressure Liquid; Drug Monitoring; Folic Acid Antagonists; Humans; Leucovorin; Methotrexate; Neoplasms; Tetrahydrofolates

Topics: Colorectal Neoplasms; DNA; DNA Repair; Folic Acid; Genotype; Humans; Methylenetetrahydrofolate Reductase (NADPH2); Neoplasms; Nutritional Physiological Phenomena; Oxidoreductases Acting on CH-NH Group Donors; Polymorphism, Genetic; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Risk Factors; Tetrahydrofolates; Thymidine; Uridine

To identify the defect in cobalamin metabolism in the human melanoma cell line MeWoLC1, and to determine how frequent this defect is in other methionine-dependent tumour cell lines.. Biochemical and somatic cell genetics study.. Aspects of cobalamin metabolism were measured in a panel of 14 human tumour cell lines that were unable to proliferate normally in medium in which methionine had been replaced by its metabolic precursor homocysteine (methionine-dependent cell lines).. The human melanoma cell line MeWoLC1 was unique among these cell lines, in that it was characterized by decreased uptake of cobalamin, decreased synthesis of coenzyme derivatives, and decreased functional activity of the cobalamin-dependent enzymes methionine synthase and methylmalonylCoA mutase. This phenotype was identical to that observed in fibroblasts from patients with the cblC and cblD inborn errors of cobalamin metabolism. The defect in cobalamin metabolism in MeWoLC1 was complemented in somatic cell complementation analysis by cblA, cblB, cblD, cblE and cblG fibroblasts, but not by cblC fibroblasts, strongly suggesting that the defect in this cell line affects the cblC locus. Similar changes in cellular cobalamin metabolism were not seen in any other methionine-dependent cell line in the panel, suggesting that there may be multiple causes of methionine dependence, and that inactivation of the cblC locus may not be a common cause of this phenotype in transformed cells.. The defect underlying methionine dependence in MeWoLC1 appears to involve the locus that is affected in patients with the cblC inborn error of metabolism. This defect does not seem to be common among other methionine-dependent cell lines.

Topics: Carbon Radioisotopes; Culture Media; Humans; Leukemia; Melanoma; Methionine; Neoplasms; Propionates; Tetrahydrofolates; Tumor Cells, Cultured; Vitamin B 12

We have studied the molecular effects of a LFD in a murine model in order to better define the biochemical changes associated with folate deficiency. In addition, we have demonstrated the effect of a LFD on the pharmacokinetic profile and therapeutic activity and toxicity of lometrexol. These studies showed increased density of FR in tumors implanted in LFD mice and a decrease in the affinity of these receptors for folic acid. The results suggest that tumors can compensate for low folate bioavailability by up-regulation of a second FR with slightly lower affinity for folic acid. The higher density of this FR would provide greater capacity for garnering serum folate. FPGS activity increased in several tumors and liver and kidney of LFD mice. The increase in this enzyme activity would result in enhanced polyglutamation of folates and classical antifolates and thus increased cellular retention. Consistent with these changes in liver FPGS, mice injected i.v. with a single dose of lometrexol accumulated significantly more drug in liver and tumors of LFD animals compared to SD mice. Also, higher liver concentrations of lometrexol persisted longer in LFD mice. Polyglutamate analysis showed that longer polyglutamate forms appeared earlier in liver of LFD mice. After 7 days, longer polyglutamyl forms were recovered from liver of LFD mice (octa- and hepta-glutamyl lometrexol) compared to those on SD. A comparison of the efficacy and toxicity of lometrexol in C3H mammary tumor-bearing mice showed that in mice on LFD, lometrexol treatment produced a delayed toxicity with an LD50 of 0.1-0.3 mg/kg, a 3000-fold increase in lethality compared to SD mice. Supplementation of mice with folic acid restored anti-tumor activity and increased the therapeutic dose-range over which efficacy could be assessed. These studies support the use of folic acid supplementation for cancer patients treated with antifolate therapy in order to prevent the biochemical changes in FR and FPGS associated with folate deficiency, prevent delayed toxicity to GARFT inhibitors and enhance the therapeutic potential of this class of drugs.

Topics: Acyltransferases; Animals; Carrier Proteins; Diet; Enzyme Inhibitors; Folate Receptors, GPI-Anchored; Folic Acid; Hydroxymethyl and Formyl Transferases; Kidney; Liver; Mice; Neoplasms; Peptide Synthases; Phosphoribosylglycinamide Formyltransferase; Polyglutamic Acid; Protein Binding; Receptors, Cell Surface; Tetrahydrofolates; Tumor Cells, Cultured

Clinical studies on cancer and psoriasis patients have shown that plasma and urinary homocysteine (Hcy) responds to methotrexate (MTX) therapy, indicating that Hcy in extracellular fluids may be an indicator of the antifolate effect. However, the clinical data indicate that the burden of proliferating cells, cytotoxicity and the folate status are also determinants of extracellular Hcy. To evaluate this further, we investigated the modulation of cellular Hcy egress by MTX, rescue agents, cell proliferation and cytotoxicity. Nontransformed and chemically transformed fibroblasts and murine lymphoma cells, which are characterized by different growth behavior and MTX response, were used. The Hcy export rate was correlated positively with the proliferation rate in all cell types. 5-Formyltetrahydrofolate or 5-methyltetrahydrofolate added to fibroblasts not exposed to MTX reduced the Hcy export rate, whereas the export from the lymphoma cells was not affected. All cells types exposed to MTX were rescued by thymidine + hypoxanthine, and this allowed the assessment of Hcy export during MTX exposure without interference from cytotoxicity. In the fibroblasts, MTX with thymidine + hypoxanthine rescue induced a marked increase in Hcy export, and the dose-response paralleled the cytotoxicity curves obtained for MTX without rescue. Nontoxic concentrations of MTX without rescue enhanced the Hcy export. When MTX concentration was increased further, Hcy export was stimulated initially, and then declined rapidly as cell death ensued. MTX did not enhance the Hcy export from the lymphoma cells and, in the absence of rescue, the Hcy export from these cells declined in proportion to inhibition of cell growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Cell Division; Cell Survival; Cells, Cultured; Dose-Response Relationship, Drug; Homocysteine; Methotrexate; Mice; Neoplasms; Tetrahydrofolates; Thymidine

Topics: Antineoplastic Combined Chemotherapy Protocols; Drug Administration Schedule; Drug Evaluation; Fluorouracil; Humans; Infusions, Intravenous; Leucovorin; Neoplasms; Stereoisomerism; Tetrahydrofolates

A reversed-phase HPLC method is described for the simultaneous determination of folinic acid, MTX, and their plasma metabolites 5-CH3-FH4 and 7-OH-MTX respectively. In addition, this technique allows the separation of FA another naturally occurring folate, and of AMT, used as internal standard. Separation of these compounds was achieved on a Waters Spherical C18 column at a flow rate of 0.8 ml.min-1. Elution was carried out with 0.1 M sodium acetate buffer (pH 5.5) as solvent A and 7.5% acetonitrile 92.5% bidistilled water as solvent B. UV detection was performed at 280 nm. This method was applied in a pharmacokinetic study of folinic acid and its plasma metabolite 5-CH3-FH4 following two different protocols: (1) i.v. bolus injection of 50 mg calcium folinate in six healthy volunteers and (2) simultaneous i.v. bolus injections of 50 mg/m2 MTX and 50 mg/m2 folinic acid in four cancer patients. Mean apparent half-life values for folinic acid and its metabolite were 7.02 +/- 1.81 h and 3.90 +/- 0.86 respectively in the first protocol, 4.80 +/- 1.48 h and 4.74 +/- 1.47 h in the second protocol. MTX and 7-OH-MTX were also quantified in the second protocol and were found not to affect the pharmacokinetics of folinic acid and 5-CH3-FH4. Since in vitro studies on metabolism of folinic acid might be of great interest in trying to assess the mechanism of action of the folates and the potential interaction of MTX and 7-OH-MTX in this mechanism via the metabolism, the chromatographic method we describe here has been adapted for the separation of all the potential intracellular monoglutamyl metabolites of folinic acid.

Topics: Adult; Aged; Chromatography, High Pressure Liquid; Female; Half-Life; Humans; Kinetics; Leucovorin; Male; Methotrexate; Middle Aged; Neoplasms; Tetrahydrofolates

Topics: Animals; Chemical Phenomena; Chemistry; Goats; Haptens; Humans; Leucovorin; Methotrexate; Neoplasms; Rabbits; Radioimmunoassay; Sheep; Tetrahydrofolates

The metabolism of [2-14C]+[3', 5', 7, 9-3H] folic acid and [214C]+[3', 5', 7, 9-3H] 10-formylfolate was studied in hospital inpatients. Metabolites detected in the urine after folic acid feeding included the unchanged compound, other folates and a number of breakdown products, such as p-acetamidobenzoyl-L-glutamate and p-acetamidobenzoate. This confirms the existence of a folate catabolic pathway in man. Patients with malignant disease excreted less of the dose in urine, incorporated more into the reduced folate pool, and showed decreased catabolism of folate, when compared to controls. 10-Formylfolate was excreted largely unchanged, and appears not to be reduced by man. Also 10-formylfolate interfered with the reduction of folic acid given simultaneously.

Topics: 4-Aminobenzoic Acid; Adolescent; Aged; Feces; Female; Folic Acid; Glutamates; Humans; Male; Middle Aged; Neoplasms; para-Aminobenzoates; Tetrahydrofolates