To determine whether the inhibition of tumor cell differentiation is unique in c-Myc-induced GBM, we performed immunohistochemical staining with antibodies that were specific for glial cell differentiation markers containing GFAP and Nestin and found that the resultant tumor cells expressed both Nestin and GFAP in kRas/Akt3/c-Myc- and kRas/Akt3/Cdc20-induced GBM (Figure 5A). This evidence concerns the gene KRAS and glioblastoma.