UFT: mechanism of drug action.

The mechanism of action of fluorouracil (5-FU) and the oral fluoropyrimidines and the importance of biochemical modulation and inhibition of dihydropyrimidine dehydrogenase for oral application of the prodrugs of 5-FU are discussed. The regulation of thymidylate synthase, as well as its roles as a target for antineoplastic activity and in drug resistance, are also mentioned. The more downstream events of 5-FU action and their implication in 5-FU resistance, with the possible involvement of the Fas/FasL system and the proteins associated with apoptosis regulation, are highlighted. Also discussed is the suggestion that the oral 5-FU prodrug tegafur and uracil (UFT) and its metabolites function as an angiogenesis inhibitor.