The origin and function of tumor-associated macrophages

Tumor-associated macrophages (TAM) have a complex relationship with the neoplastic cells of the tumor. On the one hand, the two cell types produce reciprocal growth factors and may be considered to have a symbiotic relationship. On the other hand, TAM can be activated to inhibit tumor growth and destroy neoplastic cells. Here, Alberto Mantovani and colleagues describe this delicate balance and the prospects for its therapeutic manipulation.