Radiation-induced expression of platelet endothelial cell adhesion molecule-1 in cerebral endothelial cells

Background: Radiationinduced molecular changes on the endothelial surface of brain arteriovenous malformations (AVM) may be used as markers for specific vascular targeting agents. In this study, we examined the level of expression of platelet endothelial cell adhesion molecule1 (PECAM-1) on brain endothelial cell surface after radiation treatment, with the aim of targeting the radiationinduced PECAM-1 on the AVM endothelium with prothrombotic agents to selectively occlude AVM vessels. Materials and Methods: Mouse cerebral endothelial cells (bEnd.3) were irradiated with 5, 15, or 25 Gy. Realtime quantitative polymerase chain reaction (PCR) and incell enzymelinked immunosorbent assay (ELISA) were performed to quantify the temporal gene and surface PECAM-1 protein expression up to 168 hours postirradiation. Twotailed unpaired ttests were used to determine statistical significance. Results: PECAM-1 gene expression was found to be significantly elevated postirradiation in realtime quantitative PCR, with the maximum level of gene expression being evident at 120 hours postirradiation representing an 11-fold increase in comparison to nonirradiated controls (p 0.001). Incell ELISA detected a similar upregulation for protein expression on the cell surface with delayed peak time. Conclusion: Ionising radiation can induce the upregulation of PECAM-1 on brain endothelial cell surface. This protein may be a potential candidate for facilitating selective AVM vessel occlusion through the application of radiosurgery followed by vascular targeting.