STAT3 and cancer: IL-6 is expressed by GBMs[19] and has been associated with the accumulation of MDSCs in human cancers and in animal models.[38–40] IL-6 is also a potent activator of STAT3 which, in turn, is associated with MDSC mediated immunosuppression.[41] Similarly, IL-8 expression by GBM’s may be important in trafficking MDSCs into the tumor environment by acting on the CXCR2 receptor [42] (which can also serve as a receptor for MIF [43]).