INHIBITION OF RECEPTOR-BINDING BY HIGH-AFFINITY RNA LIGANDS TO VASCULAR ENDOTHELIAL GROWTH-FACTOR

The proliferation of new blood vessels (angiogenesis) is a process tha t accompanies many pathological conditions including rheumatoid arthri tis and solid tumor growth. Among angiogenic cytokines that have been identified to date, vascular endothelial growth factor (VEGF) is one o f the most potent. We used SELEX [systematic evolution of ligands by e xponential enrichment; Tuerk, C., and Gold, L. (1990) Science 249, 505 -510] to identify RNA ligands that bind to VEGF in a specific manner w ith affinities in the low nanomolar range. Ligands were selected from a starting pool of about 10(14) RNA molecules containing 30 randomized positions. Isolates from the affinity-enriched pool were grouped into six distinct families on the basis of primary and secondary structure similarities. Minimal sequence information required for high-affinity binding to VEGF is contained in 29-36-nucleotide motifs. Binding of t runcated (minimal) high-affinity ligands to VEGF is competitive with t hat of other truncated ligands and heparin. Furthermore, truncated lig ands from the six ligand families inhibit binding of [I-125]VEGF to it s cell-surface receptors. Oligonucleotide ligands described here repre sent an initial set of lead compounds in our ongoing effort toward the development of potent and specific VEGF antagonists.