Expression of thymidylate synthase in primary colorectal adenocarcinoma.

Thymidylate synthase (TS) is a key regulatory enzyme in the cellular pathway of de novo pyrimidine synthesis and a target enzyme for 5-fluorouracil (5-FU). Most clinical studies have shown that high levels of TS in tumors are associated with decreased sensitivity to 5-FU treatment. In this study TS expression was assessed at DNA, RNA, and protein levels.