PECAM1 and glioblastoma: Functionally, the isolated CD146+CD31–CD45– pericytes were well stretched over vascular tubules formed by human brain microvascular endothelial cells (HBMECs), and the proportion of stretched cells from pericytes (82.2% ± 2.2%) was significantly higher than that from control GBM cells (14.3% ± 1.6%) (Fig. 3c, d).