In addition, prior work in medulloblastoma and adult glioblastoma have shown that inhibition of endothelial Wnt-signaling, by either expression of secreted Wnt-antagonists such as Dkk1 and Wif1 [14, 16], or genetic deletion of Wnt signaling components in endothelial cells [17], results in tumor vascular abnormalities and blood–brain barrier dysfunction. Here, DKK1 is linked to glioblastoma.