The majority of patients with cancer undergo at least one surgical procedure as part of their treatment. Severe postsurgical infection is associated with adverse oncologic outcomes; however, the mechanisms underlying this phenomenon are unclear. Emerging evidence suggests that neutrophils, which function as the first line of defense during infections, facilitate cancer progression. Neutrophil extracellular traps (NETs) are extracellular neutrophil-derived DNA webs released in response to inflammatory cues that trap and kill invading pathogens. The role of NETs in cancer progression is entirely unknown. We report that circulating tumor cells become trapped within NETs in vitro under static and dynamic conditions. In a murine model of infection using cecal ligation and puncture, we demonstrated microvascular NET deposition and consequent trapping of circulating lung carcinoma cells within DNA webs. NET trapping was associated with increased formation of hepatic micrometastases at 48 hours and gross metastatic disease burden at 2 weeks following tumor cell injection. These effects were abrogated by NET inhibition with DNAse or a neutrophil elastase inhibitor. These findings implicate NETs in the process of cancer metastasis in the context of systemic infection and identify NETs as potential therapeutic targets.
IntroductionCancer remains a devastating cause of mortality worldwide, with the majority of patients dying as a result of metastasis (1-3). Currently, locoregional control in the form of complete oncologic resection remains an essential curative modality for nearly all solid tumors and provides improved overall and disease-free survival (2, 4,5). Control of distant recurrence is predominantly achieved through systemic chemotherapy, with variable results (6-8). However, standard oncologic interventions can have negative consequences. First, manipulation of the primary tumor during surgery is associated with increased numbers of circulating tumor cells (CTCs) (9). Second, infectious complications occur as a result of cancer progression itself, such as bowel obstruction or pneumonia (10, 11), and due to complications of standard cancer treatments, such as chemotherapy and surgery (12)(13)(14).Postsurgical infections occur with alarming frequency, with an incidence approaching 40% in some series (15)(16)(17). Given that the majority of the nearly 2 million patients diagnosed with cancer in 2012 in the United States alone underwent at least one surgical procedure, the tremendous potential burden of infection becomes apparent (18). One disturbing feature of severe infectious complications in patients with cancer is their association with adverse oncologic outcomes independent of the morbidity associated with the infectious insult (14,(19)(20)(21). This phenomenon has been observed across a broad range of malignancies, including lung, esophageal, breast, ovarian, and colorectal cancer, whereby severe postoperative infectious complications, such as pneumonia, peritonitis, and sepsis, are significantly associated wit...