Figure 1.

Glioblastoma (GB) microenvironment. (A) GB cells secret TGF-β, PGE₂, CCL2 and CCL22 for recruiting Treg cells which contribute to the tumor progression by blocking CTLs’ cytotoxic activity. Additionally, GB cells also produce VEGF, PGE₂, TGF-β and IL-10 for suppressing CTLs′ response and proliferation. (B) Liberation of TGF-β, IL-4, IL-10 and IL-13 promote the microglial cell transition to macrophage M2-like phenotype. In exchange, microglial cells secrete VEGF, TGF-β, EGF, IL-6 and MMPs to stimulate the tumor growth. (C) Astrocytes release IL-8 and IL-6 to stimulate VEGF expression in GB cells. (D) TAMs are recruited by gradient of chemokines (CXCL3 and CCL5). They participate in the angiogenesis and tumor expansion by producing VEGF, TGF-β, EGF, IL-6 and MMPs. (E) Interaction of (PDGF)-DD ligand, expressed in GB cells, with PDGFRβ receptor of platelets surface promotes tumor proliferation.