The Complex Role of Neutrophils in Tumor Angiogenesis and Metastasis

Chronic inflammation fosters cancer development and progression and also modulates tumor responses to anticancer therapies. Neutrophils are key effector cells in innate immunity and are known to play a critical role in various inflammatory disorders. However, the functions of neutrophils in cancer pathogenesis have been largely neglected until recently and still remain poorly characterized compared with other immune cells in the tumor microenvironment. We highlight recent findings on the mechanisms by which tumor cells, in cooperation with tumor-associated stromal cells, induce expansion, recruitment, and polarization of neutrophils. We also review the multifaceted roles that neutrophils play in different aspects of cancer development and progression, with an emphasis on tumor angiogenesis and metastasis.