Tumor-Induced NETosis as a Risk Factor for Metastasis and Organ Failure

A large proportion of cancer-related deaths are caused by thrombosis and general organ failure. One example is acute renal failure, a major cause of morbidity and mortality in cancer patients. Surprisingly, however, little is known about the situation in organs that are not targets for metastasis or affected by the primary tumor. Recently, neutrophil extracellular traps (NET) were implicated in tumor-induced effects on distant organs unaffected by the actual tumor cells. Formation of NETs (NETosis) was identified a decade ago as amechanismby which the innate immune system protects us from infections, especially in situations with sepsis. NETs are formed when neutrophils externalize their nuclear DNA together with antimicrobial granule proteins and form a web-like structure that can trap and kill microbes. It is now becoming increasingly clear that NETs also form under noninfectious inflammatory conditions like cancer, thrombosis, autoimmunity, and diabetes and significantly contribute to disease development. The existence of NET-dissolving drugs like heparin and DNase I, already in clinical use, and recent development of specific inhibitors of proteinarginine deiminase 4 (PAD4), an enzyme required for NET formation, should enable clinical targeting of NETosis. Preventing NETosis in cancer could provide a strategy to counteract tumor-induced thrombosis and organ failure as well as to suppress metastasis. (C) 2016 AACR.