5-10-methylenetetrahydrofolic-acid and Stomach-Neoplasms

Currently, biochemical modulation for 5-fluorouracil (5-FU) by cisplatin (CDDP) is one of the most successful forms of chemotherapy for gastric cancer. Although the mechanism of this modulation is thought to increase intracellular folate levels, it is still unknown how much CDDP is needed to elevate folate levels. The purpose of this study is to determine the appropriate volume of CDDP as a modulator for 5-FU. Either 5, 20, 100 mg/body of CDDP was administered intravenously to advanced gastric cancer patients just before operation. Four hrs later, the stomach was resected and folate levels were measured in the tumor and normal mucosa by thymidylate synthase binding assay. The results showed folate elevation only after administration of 100 mg/body of CDDP, both in the tumor and mucosa (p < 0.01). In conclusion, if CDDP is infused as a bolus, a relatively large amount is needed to modulate the intratumor folate level.

Topics: Adult; Aged; Cisplatin; Female; Folic Acid; Gastric Mucosa; Humans; Male; Middle Aged; Stomach Neoplasms; Tetrahydrofolates

Various factors, including thymidylate synthase, thymidine kinase, 5-fluorouracil phosphorylation and degradation pathways, folate concentrations, and the stability of ternary complex, which influence thymidylate synthase inhibition rate of fluoropyrimidines, were studied in 87 human adenocarcinoma tissues.. The activity of the 5-fluorouracil degradation pathway was not significantly lower than the activity of the 5-fluorouracil phosphorylation pathway. The activity of the catabolism pathway of 5-fluorouracil should be considered in human adenocarcinoma tissue during chemotherapy. On the other hand, the means plus or minus standard deviations (means +/- SD) of the concentration of 5,10-methylenetetrahydrofolate and tetrahydrofolate were 0.69 +/- 0.54 and 1.25 +/- 0.69 nM, respectively, for the adenocarcinoma tissues without previous chemotherapy.. Because the half-life of tritium-labeled ternary complex and folate concentration in cytosol were correlated well, the differences in folate concentration among tumors must influence the dynamic equilibrium of ternary complex formation. Moreover, these results show that the ratio of 5,10-methylenetetrahydrofolate concentration to thymidylate synthase concentration influences the thymidylate synthase inhibition rate in tumor, and that the new synthesis of 5,10-methylenetetrahydrofolate and tetrahydrofolate from other endogenous reduced folates is also important in tumors with high thymidylate synthase concentrations.

Topics: Adenocarcinoma; Colorectal Neoplasms; Culture Techniques; Fluorouracil; Folic Acid; Humans; Leucovorin; Lymph Nodes; Phosphorylation; Stomach Neoplasms; Tetrahydrofolates; Thymidine Kinase; Thymidylate Synthase

Leucovorin (LV) increases the cytotoxic effect of fluorouracil (FUra) and 5-fluoro-2'-deoxyuridine (FdUrd) by enhancing the formation of the fluorodeoxyuridine monophosphate (FdUMP) thymidylate synthase (TS) 5,10-methylenetetrahydrofolate (mTHF) ternary complex. To study the difference in the efficacy of this combination against different tumors, we compared the effect of LV (20 microM) on the cytotoxicity of FUra, FdUrd, and 5-fluorouridine (FUrd) in vitro against cell lines of five colorectal carcinomas (CC), five gastric carcinomas (GC), and four non-small-cell lung carcinomas (NSCLC) using the colony-forming assay. At the concentration used in the experiments, LV alone failed to inhibit colony formation in any of the cell lines tested. The NSCLC cell lines were more resistant to FdUrd than were the CC and GC lines. LV modulated the cytotoxicity of FdUrd in all five CC lines and in three of the five GC lines but failed to do so in any of the NSCLC lines. In addition, following 20 h treatment with 1 microM [3H]-FdUrd, formation of the FdUMP/TS/mTHF ternary complex was enhanced by LV in the LV-sensitized CC and GC cell lines but not in the LV-refractory NSCLC lines. These in vitro data corresponded well to the results of clinical trials. Therefore, the colony-forming assay may be useful for the identification of the sensitivity of tumors according to phenotype.

Topics: Adenocarcinoma; Carcinoma, Non-Small-Cell Lung; Cell Survival; Colony-Forming Units Assay; Colorectal Neoplasms; Drug Synergism; Floxuridine; Fluorodeoxyuridylate; Fluorouracil; Leucovorin; Lung Neoplasms; Stomach Neoplasms; Tetrahydrofolates; Thymidylate Synthase; Tumor Cells, Cultured

Leucovorin and interferon are capable of modulating the cytotoxicity of fluorouracil (5-FU). Preclinical studies demonstrate that d,l-leucovorin is rapidly metabolized in human breast and colon cells into the various one-carbon substituted folate pools and to the polyglutamated state. While increases in intracellular folate pools are proportional to the exposure concentration of leucovorin, relatively large increases in leucovorin concentrations (50- to 100-fold) are required to produce small intracellular changes (twofold). Polyglutamation is favored by prolonged exposures to leucovorin. Polyglutamate forms have a prolonged intracellular retention and a higher affinity for the target enzyme, thymidylate synthase. Ratios of up to 20:1 inactive to active leucovorin stereo-isomers had essentially no effect on the intracellular metabolism of the active isomer. Interferon gamma interacts with 5-FU in H630 colon cancer cells at the level of thymidylate synthase and enhances cytotoxicity of 5-FU by eliminating the 5-FU-induced acute overexpression of the target enzyme. No alterations in the intracellular metabolism or nucleic acid incorporation of 5-FU could be demonstrated with the addition of interferon gamma. A clinical trial combining interferon-alfa-2a (IFN-alpha-2a) (subcutaneous days 1 to 7) with 5-FU and leucovorin (given IV days 2 to 6) demonstrated that these agents could be combined with acceptable toxicity. While the addition of interferon did not allow dose escalation of 5-FU, it resulted in a significant increase in drug exposure (1.5-fold) compared with matched cycles of 5-FU plus leucovorin without interferon. The overall response rate in this pilot study of 13 untreated patients with gastrointestinal adenocarcinoma was 46%, including two complete responses. There were no responses in eight patients who had previously failed therapy with 5-FU.

Topics: Colonic Neoplasms; Colorectal Neoplasms; Drug Administration Schedule; Drug Interactions; Fluorouracil; Humans; Interferon alpha-2; Interferon-alpha; Interferon-gamma; Leucovorin; Neoplasms, Unknown Primary; Pancreatic Neoplasms; Recombinant Proteins; Stomach Neoplasms; Tetrahydrofolates; Tumor Cells, Cultured