STAT3 and central nervous system cancer: Cytokines secreted by glioma can activate the STAT3 signaling in macrophages, down-regulate the surface antigens required for the antigen presentation, and up-regulate M2 macrophages-specific antigens like epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), and matrix metallopeptidase (MMPs), which in turn promote the tumor growth and invasion (29–31).