PECAM1 and cancer: Moreover, overexpression of ANG2 resulted in the upregulation of CD31, which is a platelet endothelial cell adhesion molecule, an angiogenesis marker and functions as a bridge that links tumor cells and vascular endothelial cells and promotes the metastasis of malignant tumors.17 These results indicated that ANG2-induced abnormal angiogenesis promoted tumor progression.