M2 tumor-associated macrophage (M2 TAM)

M2 tumor-associated macrophages (M2 TAMs) are a distinct population of immune cells within the tumor microenvironment that have been alternatively activated to support tumor growth rather than eliminate it. Unlike the pro-inflammatory M1 phenotype, M2 TAMs exhibit anti-inflammatory properties and are characterized by the secretion of immunosuppressive cytokines such as IL-10 and TGF-beta, which dampen the activity of cytotoxic T cells and natural killer cells [1.1.1, 1.3.1]. They play a critical role in promoting tumor progression by stimulating angiogenesis, facilitating extracellular matrix remodeling, and enhancing cancer cell invasion and metastasis [1.3.2, 1.4.1]. M2 TAMs are typically recruited to the tumor site via the CCL2/CCR2 axis and are maintained by factors like colony-stimulating factor 1 (CSF-1) [1.1.3, 1.2.2]. Because their high density in tumors is strongly associated with poor clinical outcomes and resistance to therapies like chemotherapy and checkpoint inhibitors, they are a major target for novel cancer immunotherapies [1.1.4, 1.4.2]. Current therapeutic approaches focus on depleting these cells using CSF1R inhibitors, blocking their recruitment, or reprogramming them into the tumor-killing M1 phenotype using TLR agonists or metabolic modulators [1.2.3, 1.2.5].

Other names

Alternatively activated macrophageM2-like macrophageM2-polarized macrophageTumor-associated macrophage (M2 type)

Therapeutic strategies targeting M2 tumor-associated macrophages primarily involve the depletion of the macrophage population, inhibition of their recruitment to the tumor site, or the repolarization of the cells from a pro-tumoral M2 phenotype to an anti-tumoral M1 phenotype.