1. An endogenously produced antiangiogenic protein, a proteolytic fragment of collagen XVIII, that inhibits endothelial cell proliferation, angiogenesis and tumor growth, and stimulates endothelial apoptotic cell death. The proapoptoic activity appears to be mediated through tyrosine kinase signaling and a reduction of the antiapoptoic proteins Bcl-2 and Bcl-XL.
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