VEGFA and neoplasm: Angiopoietin-1 (Ang-1) maintains pericyte/endothelial cell interactions (Hanahan, 1997; Thurston et al, 1999) while Angiopoietin-2 (Ang-2) is a functional antagonist of Ang-1 and leads to marked vessel regression in tumours in the absence of VEGF-A (Holash et al, 1999).