ABSTRACT
Innate immune cells are highly represented in the tumor microenvironment,and among the most abundant of these are macrophages.However,macrophages are broadly categorized as"classically activated"pro-inflammatory M1 macrophages and"alter-natively activated"anti-inflammatory M2 macrophages,which might be too simplified to describe the various phenotypes and func-tions of tumor-associated macrophages(TAMs).Most TAMs are now reclassified into CD68+TAM,CD163+TAM,CD204+TAM,CD169+TAM,and CCL18+TAM,among others,according to the different expression of surface proteins.These surface proteins have different types of ligands and regulate different signaling pathways and cytokines.Therefore,even if these subtypes of TAMs have similar ef-fects of promoting or inhibiting tumors,the mechanisms involved and the induced clinical manifestations are different.In this paper, the effects of various phenotypes of TAMs on tumor growth,metastasis,prognosis,and clinical relevance are reviewed.