Dual role of macrophage in tumor immunity

Macrophages are significant in immune responses, assuming a defensive role. In contrast, macrophages often cause undesirable changes. These reactions are processes by which macrophages express different functional programs in response to microenvironmental signals, defined as M1/M2 polarization. Tumor immunity has been acknowledged for contributing to the elucidation of the mechanism and clinical application in cancer therapy. One of the mechanisms for the refractoriness to cancer immunotherapy is the production of inhibitory cytokines by tumor cells or macrophages. Therefore, therapeutic strategy targeting macrophage or macrophage-derived cytokines may be effective and attractive. This review aims to investigate macrophage-associated pathophysiology and biological behavior in cancers, especially related to microenvironment, such as hypoxia, and current topics regarding some therapies involving macrophages.