Role of platelet derived endothelial cell growth factor/thymidine phosphorylase in fluoropyrimidine sensitivity and potential role of deoxyribose-1-phosphate

Thymidine phosphorylase (TP) catalyzes the phosphorolytic cleavage of thymidine (TdR) to thymine and deoxyribose-1-phosphate (dR-1-P). TP, which is overexpressed in a wide variety of solid tumors, is involved in the activation and inactivation of fluoropyrimidines. We investigated the role of TP in 5′-deoxy-5-fluorouridine (5′DFUR), 5-fluorouracil (5FU) and trifluorothymidine (TFT) sensitivity. TP had no effect on TFT while it activated 5′DFUR and to a lesser extent 5FU. In order to provide an explanation for this difference in activation of 5′DFUR and 5FU, we studied the role of the 5FU co-substrate, dR-1-P, needed for its activation.