TGFB1 and central nervous system cancer: Recently, Zhu et al. (2016) showed that TGF-β levels were twofold higher in microglia treated with glioma-conditioned medium (G/MCM) when compared to that in glioma-conditioned medium (G/CM), which shows that glioma stimulates microglia to produce high levels of TGF-β (Zhu et al., 2016).