Thymidine phosphorylase (TP) is a platelet-derived endothelial cell growth factor (PD-ECGF) that catalyzes the formation of thymine and 2-deoxy-D-ribose-1-phosphate from thymidine and orthophosphate (1). This intracellular enzyme is capable of both promoting angiogenesis and inhibiting apoptosis. Thymidine phosphorylase catalytic activity is required for its angiogenic function (2,3). Increased expression of TP/PD-ECGF is seen in a wide variety of different solid tumors and inflammatory diseases and is often associated with poor prognosis (4,5). Alternatively, TP can activate fluorouracil derivative (DFUR) prodrugs and increase the antitumor activity of the related treatment (1,5). The use of thymidine phosphorylase as a cancer therapeutic target has been studied extensively, with emphasis on either inhibiting TP enzymatic activity or increasing enzyme induction with concomitant DFUR treatment (1,5).
