STAT3 and neoplasm: In addition, both GBM tumor cells and infiltrating immune cells induce constitutive activation of signal transducer and activator of transcription 3 (STAT3), which drives multiple pro-oncogenic pathways and dampens the anti-tumor immune response through recruitment and expansion of Treg cells and MDSCs, induction of T cell tolerance through STAT3 hyper-activation in APCs, and regulation of immunosuppressive cytokines [50].