TGFB1 and glioblastoma: Furthermore, TGF-β is a pleiotropic cytokine associated with poor prognosis in GBM, playing a protumorigenic role by promoting immunosuppression, angiogenesis, metastasis, mesenchymal transition, and fibroblast activation (28, 39–41), and has been proven to promote the progression of GBM via an autocrine signaling loop (42).