The effect of low methotrexate levels on methylenetetrahydrofolate and four other reduced folate pools in cultured L1210 cells has been examined over a 48-h period. Media folate levels and methotrexate were used to alter intracellular levels of reduced folates, and the distribution among individual reduced folates, so that they could be evaluated in terms of their effects on thymidylate synthes...

The behavior of the activities of thymidine metabolizing enzymes, dihydrothymine dehydrogenase (EC 1.3.1.2) and thymidine phosphorylase (EC 2.4.2.4) for thymidine degradation, thymidine kinase (EC 2.7.1.75) and thymidylate synthase (EC 2.1.1.45) for DNA synthesis, was elucidated in cytosolic extracts from normal human lymphocytes and 13 human leukemia-lymphoma cell lines. In the normal human ly...

This paper describes two SlipChip-based approaches to protein crystallization: a SlipChip-based free interface diffusion (FID) method and a SlipChip-based composite method that simultaneously performs microbatch and FID crystallization methods in a single device. The FID SlipChip was designed to screen multiple reagents, each at multiple diffusion equilibration times, and was validated by scree...

The growth-inhibitory effect of fluoropyrimidines combined with a short-term exposure to leucovorin and the pattern of polyglutamylation of folates were compared between parental CCRF-CEM cells and a cell line with impaired ability to form polyglutamates (CCRF-CEM/P). The combination of leucovorin with 5-fluorouracil or 5-fluorodeoxyuridine increased the growth inhibition of CCRF-CEM cells comp...

The tritium release assay for the demonstration of thymidylate synthetase activity has been applied to the measurement of enzyme activity in the bone marrow of four patients with pernicious anemia and nine normal subjects. On the average, an approximately ninefold increase in enzyme activity was observed in patients with pernicious anemia. In the absence of 5, 10-methylene-tetrahydrofolate, enz...

Thymidylate synthase (TS) is a major target in the chemotherapy of colorectal cancer and some other neoplasms. The emergence of resistance to the treatment is often related to the increased levels of TS in cancer cells, which have been linked to the elimination of TS binding to its own mRNA upon drug binding, a feedback regulatory mechanism, and/or to the increased stability to intracellular de...

Depression of thymidylate synthetase activity by cytosine arabinoside in CCRF-CEM cells was correlated with a blocking of precursor incorporation into RNA and with cell lysis. With increasing concentrations of cytosine arabinoside in the culture media, a proportional decrease of uridine incorporation into RNA and decrease in thymidylate synthetase activity occurred and was accompanied by lysis ...

L1210 mouse leukemia cells were synchronized by isoleucine deprivation followed by hydroxyurea treatment. Changes of thymidylate synthetase activity both in cell extracts and in the intact cells (in situ) were followed throughout the cell cycle. The enzyme activity assayed in situ, by measuring tritium released from [5-3H]deoxyuridine, changed markedly in relation to the DNA synthesis pattern, ...

PURPOSE This dose-escalating study investigated the toxicity, pharmacokinetics, and efficacy of the novel direct-acting antifolate ZD9331, given as a 5-day i.v. infusion every 3 weeks. EXPERIMENTAL DESIGN Forty-five patients with refractory solid malignancies received ZD9331, which was escalated from 0.125 mg/m(2)/day. RESULTS Dose-limiting grade 4 thrombocytopenia occurred in 3 of 6 patien...

PURPOSE Folate deficiency and reduced DNA repair capacity are established risk factors for squamous cell carcinoma of the head and neck (SCCHN). We hypothesized that polymorphisms of the thymidylate synthase (TYMS) gene, which regulates a key enzyme in folate metabolism required for DNA synthesis and repair, are associated with SCCHN risk. EXPERIMENTAL DESIGN In a hospital-based case-control ...