To characterize VEGFR-2 expression in tumor-associated ECs in vivo, we took advantage of a genetically engineered murine glioma model, induced by RCAS/N-tva-mediated somatic Pdgf gene transfer in Ink4a-Arf−/−;Pten−/− neural stem/progenitor cells (Fig. 1d). Here, PTEN is linked to glioma.