STAT3 and neoplasm: Within the tumor microenvironment, the immunosuppressive effects of Tregs may prevent the initiation of antitumor immune responses by interferon-γ-producing CD4+ Th1 and CD8+ T cells; however, these effects may not be capable of overcoming the already established cycle of IL-6- and signal transducer and activator of transcription 3-mediated inflammation (21).