Thymidine phosphorylase is angiogenic and promotes tumor growth

Abstract

Platelet-derived endothelial cell growth factor was previously identified as the sole angiogenic activity present in platelets; it is now known to be thymidine phosphorylase (TP). The effect of TP on [methyl-3H]thymidine uptake does not arise from de novo DNA synthesis and the molecule is not a growth factor. Despite this, TP is strongly angiogenic in a rat sponge and freeze-injured skin graft model. Neutralizing antibodies and site-directed mutagenesis confirmed that the enzyme activity of TP is a condition for its angiogenic activity. The level of TP was found to be elevated in human breast tumors compared to normal breast tissue (P < 0.001). Overexpression of TP in MCF-7 breast carcinoma ..