IFNG and neoplasm: Radiotherapy has been proven to improve immunosuppression in the tumor microenvironment, increase the permeability of the blood–brain barrier, promote T-cell activation by stimulating IFN-γ production and increasing MHC Class I, promote tumor antigen presentation, upregulate PD-L1 expression on the surface of tumor cells, and increase the efficacy of immune checkpoint inhibitors (47–51).