Macrophages are an important type of white blood cells in the dialogue between inflammatory response and cancer. Macrophages can maintain a chronic inflammatory state that predisposes to the development of cancer. In the tumor, macrophages phagocytose and kill cancer cells directly and promote the generation of antitumoral cytotoxic lymphocyte response. Cancer cells, however, often modulate the functions of macrophages in several ways to promote tumor progression. Such protumoral macrophages increase neovascularization, produce molecules promoting the growth and dissemination of cancer cells, and suppress antitumoral immune responses. Hence, abundant macrophage infiltration correlates with poor prognosis in most types of cancer. Many cancer treatments also affect the antitumoral properties of macrophages. New drugs are developed to reduce the accumulation of macrophages into malignant tissue and to re-educate pro-tumoral macrophages to anti-tumoral macrophages and some of these drugs have already entered clinical trials.
