GBM cells produce the glioblastoma-derived T-cell suppressor factor (G-TsF), a member of the TGF-β family re-named as TGF-β2, which induces immunosuppression by: (i) blocking T-cells activation and proliferation; (ii) downregulating MHC class II expression on CD4+ T-cells; (iii) inhibiting IL-2 production; (iv) suppressing NK-cells activity; and (v) promoting the activation of FoxP3+ regulatory T-cells (Tregs) [33,37,38]. This evidence concerns the gene TGFB1 and glioblastoma.