Tumor-associated macrophages and the related myeloid-derived suppressor cells as a paradigm of the diversity of macrophage activation.

Macrophages undergo a wide spectrum of polarized activation states, and have the potential both to elicit tumor and tissue destructive reactions and to promote tumor progression (macrophage balance). In general, tumor-associated macrophages (TAM) from established tumors and the related myeloid-derived suppressor cells are diverse and have properties of M2-activated cells. As such, they help cancer progression and metastasis. Therefore, TAM are a key component of pathways connecting inflammation and cancer.