Human glioma cell BT325 expresses a proteinase that converts human plasminogen to kringle 1-5-containing fragments

Angiostatin, a specific angiogenesis inhibitor, is an internal fragment of plasminogen, and can be generated in many systems mediated by different enz ymes in vitro. The mechanism of angiostatin generation in vivo has not been well defined. Here we demonstrated that human glioma cell line BT325 can e xpress an enzyme that can convert purified plasminogen to angiostatin-like fragments with molecular masses of 65, 60, and 58 kDa, respectively. These fragments have an identical N-terminal as KVYLS, which starts from Lys(98) Of the plasminogen precusor. According to their molecular mass, the three f ragments should comprise kringle domain 1 to kringle domain 5 (kringle 1-5) . The proteolytic fragments obtained as above can inhibit the growth of bov ine aortic endothelial (BAE) cells specifically, The proteolysis process ca n be completely inhibited by serine proteinase inhibitors, and partially in hibited by EDTA. The molecular weight of the peptide, which contains an enz ymatic activity responsible for the proteolysis, was 13 kD determined by ge l filtration and SDS-PAGE. The present data suggest that glioma cell BT325 can produce a novel proteinase to generate kringle 1-5 of plasminogen as an angiogenesis inhibitor, (C) 2000 Academic Press.