Thymidine phosphorylase (TP) is an enzyme, which catalyses the reversible conversion of thymidine to thymine and deoxy ribose-1-phosphate. TP is identical to PD-ECGF (platelet derived endothelial cell growth factor) and has angiogenic activity. TP expression in tumors influences the prognosis of patients with colorectal and renal cell carcinomas. We recently found that cells transfected with TP cDNA are resistant to hypoxia-induced apoptosis and more invasive and metastatic than parental cells. TPI, a newly synthesized inhibitor of TP, inhibits the growth, metastasis and invasiveness of cells expressing TP.

We review the roles of TP in cancer progression and discuss TP as a new molecular target for anti-cancer therapy.