TGFB1 and central nervous system cancer: In glioma stem cells (GSCs), STAT3 activation leads to increased secretion of macrophage inhibitory cytokine-1 (MIC-1), IL-10, IL-4, and transforming growth factor β (TGF-β), which inhibit the phagocytic activity of macrophages and induce them to become immunosuppressive [34,35,36,37].