STAT3 and neoplasm: Blocking STAT3 in human tumor cells has been shown to down-regulate Mcl-2 expression and induce tumor cell apoptosis [24], and metformin promoted autophagy and apoptosis in esophageal squamous cell carcinoma by down-regulating STAT3 signaling [25] indicated that active STAT3 contributed to the inhibition of tumor apoptosis.