UGT1A1 predicts outcome in colorectal cancer treated with irinotecan and fluorouracil

Figure 1 Schematic diagram of UDP-glucuronosyltransferase1A1 and thymidylate synthetase. A: UDP-glucuronosyltransferase1A1 (UGT1A1) is the main enzyme involved in the glucuronidation of SN-38 (SN-38G). Single-nucleotide polymorphisms (SNPs) of UGT1A1 are the key factor in irinotecan metabolism; B: Thymidylate synthetase (TS) is the main target of 5-fluorouracil (5-FU). The ternary complex of TS, active metabolite of 5-FU (FdUMP) and methyl-tetra-hydrofolic acid (MTHF) inhibits DNA synthesis. SNP of TS affects the expression of enzyme and 5-FU efficacy. CES: Carboxylesterases; TOP1: Topoisomerase-1.