[New insights into the role of macrophages in tumor immunotherapy]

Macrophages are the main components of the innate immunity system, derived mainly from blood monocytes, and help the host to defend itself against many pathogens and cancers. Most established tumors can educate macrophages into tumor-associated macrophages (TAMs), which contribute to tumor growth, invasion and metastasis, as well as resistance to chemotherapeutic agents and immune checkpoint inhibitors. However, when appropriately activated, macrophages can also exert anti-tumor effects through enhanced phagocytosis and cytotoxicity against tumor cells. In addition, TAMs are associated with poor prognosis and drug resistance, including immunotherapies, suggesting that macrophages are attractive targets as part of combination therapy in cancer treatment. Herein, we review the recent findings on the role of macrophages in tumor development, metastasis and immunotherapy. We focus mainly on macrophage-centered therapy, including strategies to reduce and reshape TAMs, to represent potential targets for tumor immunotherapy.