fig2

Figure 2. 5-FU Resistance develops from processes that increase thymidylate synthase (TS) activity in cancer cells. Increased TS activity can result from multiple processes including gene amplification, increased transcription, TSER*3R polymorphism, increased TS nuclear localization, and decreased TS protein degradation, which are indicated by red arrows. Increased TS activity renders cells 5-FU-resistant because FdUMP levels are insufficient to inhibit all the TS available. 5-FU: 5-Fluorouracil; FdUMP: 5-Fluoro-2’-deoxyuridine-5’-O-monophosphate; FOXM1: forkhead box M1.