TGFB1 and glioblastoma: For example, GBM cells express high levels of immunosuppressive checkpoints such as programmed cell death 1-ligand 1 [14]; GBM microenvironment possesses a paucity of infiltrating T cells, especially anti-tumor T cells [15]; tumor-associated macrophages, which account for up to 30–50% of the total tumor composition, are the most abundant non-neoplastic cell types in GBM microenvironment, they can secrete immunosuppressive cytokines such as transforming growth factor-β1 (TGF-β1) and interleukin 10 (IL-10), and then further reduce the local myeloid and lymphoid immune cells [16, 17].