The Function of ß2-glycoprotein I in Angiogenesis and Its in Vivo Distribution in Tumor Xenografts.

Intact ß2-glycoprotein I (iß2GPI) is a glycoprotein that regulates coagulation and fibrinolysis. Nicked ß2GPI (nß2GPI) possesses an angiogenic property at a relatively low concentration, and an antiangiogenic property at a high concentration. Here we investigated the functions of ßi 2GPI and nß2GPI in vascular endothelial growth factor (VEGF)-A-induced endothelial cell proliferation and tube formation. We used noninvasive PET imaging to analyze the ｉｎ　ｖｉｖｏ distribution of intravenously injected ß2GPI variants in tumor lesions in mice. iß2GPI was incubated with plasmin to obtain nß2GPI, and its N-terminal sequence was analyzed. nß2GPI had at least one other cleavage site upstream of the ß2GPI's domain V, whereas the former plasmin-cleavage site locates between K317 and T318. Both of intact and nicked ß2GPI significantly inhibited the VEGF-A-induced cell proliferation and the tube formation of human umbilical vein endothelial cells (HUVECs). PET imaging visualized considerably distributed intensities of all tested ß2GPI variants in tumor lesions of pancreatic tumor cell-xenografts. These results indicate that ß2GPI may be physiologically and pathophysiologically important in the regulation of not only coagulation and fibrinolysis, but also angiogenesis.