Abstract 161: Effects of Radiation Dose on Gene Expression in Cultured Murine Brain Endothelial Cells

Abstract

Brain arteriovenous malformations (AVMs) are direct connections between arteries and veins that allow high pressure arterial blood to flow into fragile cerebral veins. AVMs are the leading cause of hemorrhagic stroke in children and young adults. Treatment of large and deep AVMs is challenging; new treatment methods are required. It is proposed that stereotactic radiosurgery could be used to selectively alter the AVM endothelial cell phenotype, allowing targeted molecular therapies which stimulate thrombosis. We have previously shown that irradiation of endothelial cell cultures with 25Gy results in up-regulation of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). In this study we hypothesise that a lower dose of radiation is similarly effective at causing up-regulation in ICAM-1 and VCAM-1 expression. Murine brain endothelial cell cultures were irradiated with 15Gy (n = 4) or 25Gy (n = 4) using a linear accelerator; non-irradiated cells were used as controls (n = 4). The relative gene expression at 96, 120, 144 and 168h after radiation was measured by quantitative real-time PCR. Genes encoding for ICAM-1 and VCAM-1 were found to be significantly up-regulated post-radiation with either 15Gy or 25Gy (p <0.001). Maximum gene expression of ICAM-1 and VCAM-1 was observed at 144h (7-fold) and at 120h (23-fold), respectively. There was no significant difference between the two doses. These results support the hypothesis that a 15Gy dose is as effective as a 25Gy dose. Therefore a lower dose of radiation might be equally effective at causing changes in endothelial cell phenotype. This is important from a clinical perspective because lower doses of radiation will be safer for the treatment of large AVMs.