Angiostatin is a 38 ku circulating angiogenesis inhibitor purified from the
serum and urine of mice bearing a murine Lewis lung carcinoma. It is regar
ded as an internal fragment of plasminogen containing tile first 4 Kringle
structures. In vitro, angiostatin specifically inhibits endothelial cell pr
oliferation. In vivo, it inhibits angiogenesis and suppresses the growth of
such primary tumors as Lewis lung carcinoma and hemangioendotheliolma in m
ice.