SUPPRESSION OF TUMOR-GROWTH WITH RECOMBINANT MURINE ANGIOSTATIN

Angiostatin, a 38 kDa internal fragment of plasminogen, is an antiangi ogenic endothelial cell inhibitor. It regresses several primary and me tastatic tumors in mice. To produce recombinant angiostatin for furthe r structural and functional studies, the mouse angiostatin gene preced ed by a sequence including a signal peptide of plasminogen was introdu ced into baculovirus. Recombinant murine angiostatin was purified from the culture medium of angiostatin baculovirus-infected insect cells ( yield = 1 mg/liter) with a single-step of lysine-Sepharose chromatogra phy. The angiostatin baculovirus-infected insect cells expressed and s ecreted a 52 kDa polypeptide that demonstrated all of the biological a ctivities of angiostatin. A partial amino acid sequence of the NH2-ter minus of the secreted protein revealed that the signal peptide was rec ognized and properly cleaved in insect cells. The recombinant murine a ngiostatin potently inhibited the proliferation of bovine capillary en dothelial cells in vitro (half maximal inhibition = 50 ng/ml) and supp ressed the growth of primary Lewis lung carcinoma in vivo (6 mg/ kg/da y, T/C = 0.08). (C) 1997 Academic Press.