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


CONCLUSIONS
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.
Tsujimoto
Shigehiro
S
Department of Urology, Takanohara Central Hospital, 3-3 Ukyo 1-chome, Nara, Nara, 634-8522, Japan. tsujimoto@takanohara-ch.or.jp
Fujimoto
Kiyohide
K
Okajima
Eijiro
E
Ozono
Seiichiro
S
Okajima
Eigoro
E
Hirao
Yoshihiko
Y
D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D004338:Drug Combinations; D005260:Female; D005472:Fluorouracil / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012334:RNA, Neoplasm / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D005641:Tegafur / Q000627:therapeutic use*; D014498:Uracil / Q000627:therapeutic use*; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy* / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
D004338:Drug Combinations; D012334:RNA, Neoplasm; C096910:UFT(R) drug; D005641:Tegafur; D014498:Uracil; D005472:Fluorouracil