5-Fluorouracil incorporated into the tissue RNA of human and rat bladder carcinoma after administration of 1-(2-tetrahydrofuryl)-5-fluorouracil combined with uracil

Int J Clin Oncol. 2008 Apr;13(2):138-43. doi: 10.1007/s10147-007-0734-2. Epub 2008 May 8.

Abstract

Background: UFT is an anticancer agent consisting of 1-(2-tetrahydrofuryl)-5-fluorouracil (5-FU) combined with uracil in a molar ratio of 1: 4. Its mechanisms of action are, presumably, inhibition of deoxyribonucleic acid (DNA) synthesis by thymidylate synthetase (TS) and impairment of ribonucleic acid (RNA) function by the incorporation of 5-fluorouridine-5'-triphosphate into RNA. This study was conducted to examine the TS inhibition rate (TS-IR) and the concentration of 5-FU incorporated in RNA per milligram of tissue treated with UFT (F-RNA).

Methods: We administered UFT to 12 patients with bladder cancer. We also administered UFT to 20 rats bearing bladder tumors induced by N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN), and to 10 BBN-untreated control rats. We then determined the total TS concentration, TS-IR, and F-RNA in the human bladder tumor and normal tissues and in the BBN-treated and BBN-untreated rat organs, including the urinary bladder.

Results: In the bladder cancer patients, the mean F-RNAs in the bladder tumor and normal tissue were 0.133 +/- 0.137 and 0.056 +/- 0.062 ng/mg, respectively, without a significant difference (P < 0.1). The mean TS-IR was 35.3 +/- 19.6% in the tumor tissue and 38.0 +/- 16.6% in the normal bladder tissue, and this difference was also not significant. In the rat bladder cancer model, the total TS concentration and F-RNA in the tumor after the administration of UFT were 15.32 pmol/g and 0.780 ng/mg, respectively, being markedly higher than the corresponding values (1.22 pmol/g and 0.129 ng/mg) in the control normal bladder tissue.

Conclusion: The impairment of RNA metabolism by F-RNA incorporated in RNA did not seem to be the critical mechanism of the antitumor effect of UFT at the usual clinical dose, as neither TS-IR nor F-RNA (as antitumor parameters) seemed to increase significantly after a clinical dose of UFT. However, the inhibition of DNA synthesis and the impairment of RNA were independent mechanisms of the action of high-dose UFT in the experimental rat bladder tumors, as both total is concentration and F-RNA were increased significantly.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Animals
  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use
  • Drug Combinations
  • Female
  • Fluorouracil / metabolism*
  • Humans
  • Male
  • Middle Aged
  • RNA, Neoplasm / metabolism
  • Rats
  • Rats, Inbred F344
  • Tegafur / therapeutic use*
  • Uracil / therapeutic use*
  • Urinary Bladder Neoplasms / drug therapy*
  • Urinary Bladder Neoplasms / metabolism*
  • Xenograft Model Antitumor Assays

Substances

  • Drug Combinations
  • RNA, Neoplasm
  • UFT(R) drug
  • Tegafur
  • Uracil
  • Fluorouracil