VEGFA and central nervous system cancer: Subsequently, experiments in a rat glioma model suggested that even angiogenic tumours initially co-opt normal blood vessels after which a host defence response, governed by angiopoietin-2 expression on the co-opted endothelial cells, causes blood vessel regression with concomitant hypoxia and vascular endothelial growth factor (VEGF)-mediated angiogenesis (Holash et al, 1999).