Initial studies in VCO hypothesized that cancer cells could arise or metastasize to highly vascularized tissues and co-opt the preexisting vasculature to enhance angiogenesis through a balance between VEGF and Angpt-2 [109], such studies also observed that VCO was followed by vessel regression, tumor hypoxia and the induction of angiogenesis by Angpt-1 and -2 and also VEGF [109]. Here, VEGFA is linked to cancer.