Endostatin, a 20-kDa C-terminal proteolytic fragment of collagen XVIII, is an endogenous angiogenesis inhibitor localized in the vascular basement membrane in various organs (http://www.uniprot.org/uniprot/P39060). The biological functions of the Endostatin-network involve SPARC, thrombospondin-1, glycosaminoglycans, collagens, and integrins.