The metastasis-promoting roles of tumor-associated macrophages

Under the stimulation of different cytokines,tumor-associated macrophages(TAM) immersed into the tumor microenvironment can be differentiated into M1 macrophage with anti-tumor function and M2 macrophage with tumor-promoting function.M2 macrophage is the major type of TAM in the majority of tumors.It is involved in the multiple metastasis-related processes,such as tumor angiogenesis,breakdown of the basement membrane,remodeling of the extracellular matrix and tumor cell's epithelial-mesenchymal transition.So that TAM has become an important target for tumor targeting therapy.This article mainly discusses the interaction between TAM and tumor cells and its underlying molecular mechanisms in promoting tumor metastasis.