Novel 6-substituted uracil analogs as inhibitors of the angiogenic actionsof thymidine phosphorylase

Thymidine phosphorylase (TP) catalyzes the reversible phosphorolysis of thy midine and other pyrimidine 2'-deoxyribonucleosides. In addition, TP has be en shown to possess angiogenic activity in a number of in vitro and in vivo assays, and its angiogenic activity has been linked to its catalytic activ ity. A series of 5- and 6-substituted uracil derivatives were synthesized a nd evaluated for their abilities to inhibit TP activity. Among the most act ive compounds was a 6-amino-substituted uracil analog, 6-(2-aminoethyl)amin o-5-chlorouracil (AEAC), which was a competitive inhibitor with a K-i of 16 5 nM. The inhibitory activity of AEAC was selective for TP, as it did not i nhibit purine nucleoside phosphorylase or uridine phosphorylase at concentr ations up to 1 mM. Human recombinant TP induced human umbilical vein endoth elial cell (HUVEC) migration in a modified Boyden chamber assay in vitro, a nd this action could be abrogated by the TP inhibitors. The actions of the inhibitors were specific for TP, as they had no effect on the chemotactic a ctions of vascular endothelial growth factor (VEGF). HUVEC migration was al so induced when TP-transfected human colon and breast carcinoma cells were co-cultured in the Boyden chamber assay in place of the purified angiogenic factors, and a TP inhibitor blocked the tumor cell-mediated migration almo st completely. These studies suggest that inhibitors of TP may be useful in pathological conditions that are dependent upon TP-driven angiogenesis. (C ) 2001 Elsevier Science Inc. All rights reserved.