STAT3 and cancer: STAT3 acts as an inhibitor of such signaling [18] and also functions to promote cell viability and proliferation; STAT3 has been implicated in many types of human cancer, where it is found at elevated active levels, caused by induced signaling (e.g., via cytokine dysregulation) and/or activating mutations that promote the phosphorylated form of STAT3 [19–23].