PTEN and glioblastoma: We took advantage of the orthotopic, genetic murine GBM model with a native microenvironment, induced by RCAS/N-tva-mediated somatic PDGF gene transfer in Ink4a-Arf−/−;Pten−/− neural stem/progenitor cells (Fig. 7d), followed by tumor transplantation into the new generated Cdh5-CreERT2;Il6fl/fl mice.