A Novel Peptide Derived from Tissue-Type Plasminogen Activator Potently Inhibits Angiogenesis and Corneal Neovascularization.

The recombinant protein TK1-2, which consists of two kringle domains of tissue-type plasminogen activator (t-PA), inhibits angiogenesis and tumor growth. ɪn this study, we examined the anti-angiogenic activities of peptides derived from kringle 2 domain of t-PA to identify the functional core sequence. Seven peptides were constructed from the kringle 2 sequence, based on the structure and characteristics of amino acid residues, and were analyzed for their inhibitory effects on endothelial cells (ECs). Among them, TP-7 (derived from a β-sheet motif) potently inhibited proliferation, tube formation, and migration of ECs in a dose-dependent manner, whereas truncation of 3–9 amino acid residues from either N or C terminus of TP-7 abrogated its inhibitory effects on ECs. TP-7 also potently inhibited angiogenesis in a Matrigel plug assay in vivo. Moreover, TP-7 dose-dependently suppressed corneal neovascularization induced by an acute chemical burn in a rat model. At the molecular level, TP-7 inhibited VEGF- or bFGF-induced phosphorylation of FAK and ERK1/2 and drastically disrupted VEGF- or bFGF-induced formation of stress fibers and focal adhesion complexes. In addition, TP-7 markedly suppressed attachment and spreading of ECs on a collagen type I or fibronectin matrix. Adhesion of ECs to immobilized TP-7 increased dose-dependently, which was disrupted strongly by pretreatment with soluble TP-7 and slightly by an integrin α2β1-blocking antibody. These results suggest that TP-7 is a potent anti-angiogenic peptide in part affecting the integrin α2β1-dependent pathway and that it can be used for treatment of corneal neovascularization by targeting VEGF and non-VEGF pathways. J. Cell. Biochem. 118: 1132–1143, 2017. © 2016 Wiley Periodicals, Inc.