Neutrophil Extracellular Traps (NETs) in Cancer Metastasis

SIMPLE SUMMARY: Neutrophil Extracellular Traps (NETs) are formed following the activation of neutrophils and play an important role in the development of cancer, especially metastatic disease. In this review, we will portray the role of Neutrophils/NETs in the tumor microenvironment and circulation. We will furthermore discuss the role of neutrophil reverse migration, NET-mediated pre-metastatic niche formation, and possible treatment strategies to decrease metastatic cascade. ABSTRACT: Metastasis is the leading cause of cancer related morbidity and mortality. The metastatic process involves several identifiable biological stages, including tumor cell dissemination, intravasation, and the extravasation of circulating cancer cells to facilitate colonization at a distant site. Immune cell infiltration and inflammation within the tumor microenvironment coincide with tumor progression and metastatic spread and are thought to be the key mediators of this complex process. Amongst many infiltrating cells, neutrophils have recently emerged as an important player in fueling tumor progression, both in animal models and cancer patients. The production of Neutrophil Extracellular Traps (NETs) is particularly important in the pathogenesis of the metastatic cascade. NETs are composed of web-like DNA structures with entangled proteins that are released in response to inflammatory cues in the environment. NETs play an important role in driving tumor progression both in experimental and clinical models. In this review, we aim to summarize the current advances in understanding the role of NETs in cancer, with a specific focus on their role in promoting premetastatic niche formation, interaction with circulating cancer cells, and in epithelial to mesenchymal transition during cancer metastasis. We will furthermore discuss the possible role and different treatment options for targeting NETs to prevent tumor progression.