[Potentiation of the antitumor activity of 5-fluorouracil by biochemical modulators]

About 30 kinds of biochemical modulators of 5-fluorouracil (5-FU) are described. They modify the metabolism and cytotoxic action of 5-FU through an alteration in (1) intracellular concentration of 5-FU or its metabolites, (2) intracellular pool of co-substrates essential for 5-FU metabolism, and (3) intracellular pool of normal substrates which compete with 5-FU metabolism. As a result, they affect either its inhibitory effect on thymidylate synthase or incorporation into RNA, or both. Thus, some of these modulators can improve antitumor activity of 5-FU by potentiating its tumor-selective toxicity or reducing its host toxicity selectively. From such various points of view, a variety of biochemical modulators of 5-FU are reviewed.