The penetrance of gliomas due to Rosa26-SB11 mobilization of T2/onc was previously found to be greater on a p19Arf+/− background, so a cohort of p19Arf+/−; GFAP-SB11; T2/onc mice as well as controls (p19Arf+/−; GFAP-SB11 and p19Arf+/−; T2/onc) were generated. The gene discussed is GFAP; the disease is central nervous system cancer.