The majority of GEMMs of GBM have used combinations of tumor suppressors p53 and/or Rb inactivation (directly or through Cdkn2a deletion), and the activation of pro-survival RTK and Ras signaling (through Pten and Nf1 deletion or RTK/Ras activation) [6, 48–50]. The gene discussed is RB1; the disease is glioblastoma.