Endostatin is a naturally occurring 20 kDa polypeptide derived from the C-terminal portion of type XVIII collagen. It functions as an anti-angiogenic cytokine that is expressed in various organs, with the highest levels in liver, lung and kidney. Endostatin inhibits angiogenesis by blocking the pro-angiogenic activities of VEGF and FGF-basic. Recombinant Human Endostatin is a 20.2 kDa protein consisting of 184 amino acid residues.