PDCD1 and glioblastoma: SRS has been proven to synergize anti-PD-1 therapy in orthotopic mouse GBM models, by leading to an increase in the amount of CD8+ T cells expressing interferon gamma (IFNγ) as well as a decrease of tumor-infiltrating T reg cells, when compared with a single treatment with SRS or anti-PD-1 therapy [92].