CD8A and glioblastoma: Further, GAMs release TGF-β, a key signal that inhibits the anti-tumoral effects of T-cells [92], downregulating the expression of the proteins responsible for lymphocyte cytotoxicity, such as perforin, granzyme, and interferon (IFN)-γ; consistently, in vivo studies in GBM-bearing mice have shown that the neutralization of TGF-β upregulates the expression of these genes in CD8+ T-cells [92].