RESUMO
Mononuclear macrophages are versatile cells that can have different responses to various microenvironmental signals. Under different stimuli of circumstances, macrophages can be fully polarized into classically activated macrophages (M1) and alternatively activated macrophages (M2), which are the extremes of a continuum of functional states. Nuclear factor-κB, cyclooxygenase 2, anoxia status, proto-oncogene MYC, Toll-like receptor signaling pathway, Notch signaling pathway and cytokines are all closely involved in the transition of tumor-associated macrophages from M1 to M2 phenotype. Macrophages that infiltrate tumor tissues are driven by tumor-derived cytokines to acquire a polarized M2 phenotype. These functionally polarized cells play a key role in the subversion of adaptive immunity and in inflammatory circuits that promote tumor development and progression. Exosomes derived from tumors have the characteristics of tumor cells and could participate in multiple processes of tumorigenesis and development. This review focused on exosomes derived from various cancer cells and discussed the role of the payloads of tumor-derived exosomes in modulating macrophage polarization in the tumor immune microenvironment and the intracellular signal mechanisms involved.