A novel vascular endothelial growth factor heparin-binding domain substructure binds to glycosaminoglycans in vivo and localizes to tumor microvascular endothelium.

Vascular endothelial growth factor has an exon 7-encoded heparin-binding domain. To explore the expression of complementary ligands on endothelial surfaces in vivo and to assess potential for localization within the vascular tree, we introduced a truncated version of this domain (HBDt) into a modified M13 phage. Despite the small size and trace-level expression, this HBDt endowed the phage with affinity for heparin to which it bound in vitro. It also preferentially and selectively localized the phage in vivo to vascular endothelial surfaces, especially of tumors. Competition assays demonstrated that accumulation and localization of this phage was attributable to expression of the HBDt on the phage surface and sequence comparison suggests its novelty. We propose to use this novel HBDt structure to explore the expression of the ligand glycosaminoglycans within the vascular tree. This structure may facilitate directed delivery of therapeutic molecules.