TGFB1 and glioblastoma: Consistent with these data, Li et al. showed that in GBM, microglial cells showed to have a pro-tumor phenotype that is associated with the M2-like phenotype of macrophages due to its expression of specific factors, such as ILs, transforming growth factor beta 1 (TGF-β1), monocyte chemoattractant protein (MCP-1), and prostaglandin E2 (PGE-2) [45].