TGFB1 and glioma: Possible mechanisms involve glioma-associated microglia and macrophages (GAMs) releasing pro-tumorigenic cytokines such as TGFβ, EGF, Il-6, and IL-1β (57) (59) while microglia alone may upregulate platelet-derived growth factor receptor (PDGFR) in both murine and human low- and high-grade glioma (57), (60).