STAT3 and cancer: In fact, in some types of cancer, pro-inflammatory mediators such as IL-22, TNF-α, MIP-3α, CXCL2, CXCL3 and other CXCR2 ligands indirectly contribute to tumor growth through the proliferation of epithelial cells (e.g. STAT3, NF-κB) (47–49).