PROJECT SUMMARY Colorectal cancer is a devastating cause of mortality worldwide, with the majority of patients dying as a result of hepatic metastasis. When feasible, resection of hepatic metastases provides improved overall and disease- free survival; however, hepatic recurrence after surgical resection occurs in 50-60% of patients and is the major cause of treatment failure. Surgery-induced inflammation has long been suggested to enhance the risk of tumor recurrence; however the exact mechanisms remain poorly understood. Activation of the immune response following surgery is fundamental for reparative processes but evidence suggests that the inflammatory response may also evoke alternations in the tumor environment to promote disease recurrence and systemic metastases. This proposal focuses on key factors and mechanisms that contribute to surgery- induced metastasis formation. Our laboratory previously revealed the novel finding that neutrophils, the principal cells in the immune response to surgery, can form neutrophil extracellular traps (NETs) after surgical stress to the liver; and, targeting NETs ameliorates the hepatic as well as systemic inflammation in mice. In addition, our latest exciting results demonstrate that increased NET formation following surgical stress of the liver advances the acceleration of both the development and progression of metastatic colorectal disease. Thus, the overall objective of this grant proposal is to determine the mechanisms by which NETs, formed in the liver following surgical stress, promote the invasiveness of circulating tumor cells and the growth of existing micro-metastatic disease to facilitate disease progression. We will also validate these mechanisms in clinical outcomes of patients undergoing liver surgery for metastatic colorectal cancer. In Aim 1, we will determine the role of NETs in capturing circulating tumor cells released during surgery. Aim 2 will identify the role of surgery induced NETs in maintaining a pro-inflammatory microenvironment to promote metastatic growth. The focus of Aim 3 will be to establish the role of mitochondrial biogenesis in the process of NET-mediated intrahepatic tumor progression. These studies will greatly enhance our knowledge of the inflammatory pathways and mechanistic changes that occur after cancer related surgery, both of which are pivotal for the development of new therapeutic strategies to prevent tumor recurrence, and subsequently decrease morbidity and mortality, in a variety of clinical settings.