Endostatin/COL18A1 is the alpha chain of type XVIII collagen. Members of the MULTIPLEXIN subgroup contain polypeptides with multiple triple-helical domains separated and flanked by nontriple-helical regions. Proteolytic processing at several endogenous cleavage sites in the C-terminal domain results in production of endostatin, a potent antiangiogenic protein that is able to inhibit angiogenesis and tumor growth.
