STAT3 and cancer: On the one hand, phosphorylated STAT3 regulates the expression of its downstream target genes and directly promotes the proliferation, invasion, and apoptosis of cancer cells; on the other hand, STAT3 can induce overexpression of a variety of cytokines and chemokines associated with cancer progression in TME, thus acting as a link between tumor and inflammation and tumor and immune cells [2,4].