CD248 and glioblastoma: Finally, we show that Tem1/endosialin upregulation occurs in the tumor vasculature of intracranial GBM xenografts and absence of Tem1/endosialin is associated with increased numbers of microvessels within tumors explanted from Tem1/endosialin KO mice, supporting a role for TEM1/endosialin in the migration and maturation of the brain tumor vasculature.