STAT3 and neoplasm: 122 Based on cytokines, macrophages are divided into two subgroups: classical activation (M1) and alternative activation (M2). Macrophages are crucial in eliminating tumor cells; nevertheless, several immunosuppressive signals inhibit their action in solid tumors, thus contributing to tumor growth and metastasis. 123,124 Moreover, TAMs suppress immune cell function by expressing multiple receptors or ligands of the inhibitory receptors (PD-L1, PD-L2, B7-1) 125 by secreting IFN-c through the Janus kinase-STAT3 and phosphoinositide 3-kinase-AKT signaling pathways.