To analyze the effect of HRG on glioma development neonatal Ntv-a Arf-/- mice were intracranially injected with equal numbers of DF-1 RCAS-PDGF-B-eGFP[33] and DF-1 RCAS-HRG or DF-1 RCAS-X (control virus, complete RCAS without inserted exogenous gene). Here, HRG is linked to central nervous system cancer.