TGFB1 and glioblastoma: We (Lu-Emerson et al., 2013; Cui et al., 2018) and others (Thomas et al., 2012) recently demonstrated that GBM secrete immunosuppressive factors including transforming growth factor-β1 (TGF-β1), and colony-stimulating factor-1 (CSF-1) polarizing monocytes toward an immunosuppressive ‘M2-like’ phenotype.