PTEN and glioblastoma: Notably, the Cre-LoxP system is a conditional gene targeting strategy that has been used to assess the role of p53 and PTEN function in glial fibrillary acidic protein (GFAP) positive GBM and has also been hugely beneficial in trialling immunotherapies [42] A significant advantage of GEMMS is their ability to model GBM in immunocompetent mice, therefore permitting crucial in-vivo investigations of immunotherapies.