Neutrophil extracellular traps sequester circulating tumor cells and promote metastasis
Jonathan Cools-Lartigue, Jonathan Spicer, Braedon McDonald, Stephen Gowing, Simon Chow, Betty Giannias, France Bourdeau, Paul Kubes, Lorenzo Ferri
Jonathan Cools-Lartigue, Jonathan Spicer, Braedon McDonald, Stephen Gowing, Simon Chow, Betty Giannias, France Bourdeau, Paul Kubes, Lorenzo Ferri
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Research Article Oncology

Neutrophil extracellular traps sequester circulating tumor cells and promote metastasis

Abstract

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.

Authors

Jonathan Cools-Lartigue, Jonathan Spicer, Braedon McDonald, Stephen Gowing, Simon Chow, Betty Giannias, France Bourdeau, Paul Kubes, Lorenzo Ferri

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Figure 4

NET production by neutrophils is sufficient to increase tumor cell adhesion within hepatic sinusoids.

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NET production by neutrophils is sufficient to increase tumor cell adhes...
(A) A schematic representation of the experimental design is depicted. All mice used were subjected to neutrophil depletion via intraperitoneal injection of anti-GR1 (150 μg). Twenty-four hours later, 1 × 106 bone marrow–derived neutrophils (or control buffer) from syngeneic mice were reinfused via the intrasplenic route. This was followed by injection of 3 × 104 H59-GFP cells into the spleen 20 minutes later. Ten minutes later, epifluorescence microscopy was used for quantification of adherent cells. IVM, intravital microscopy. (B) Quantification of arrested tumor cells within hepatic sinusoids 10 minutes following intrasplenic injection of H59-GFP cells. Injection of 500 nM PMA without neutrophils prior to tumor cell injection resulted in low levels of tumor cell adhesion. Infusion of unstimulated neutrophils increased tumor cell adhesion above control, but this was significantly lower than when neutrophils were pretreated with 500 nM PMA. This increase is abrogated if PMA treatment of neutrophils occurs in the presence of NEi (10 μm) or DNAse 1 (1,000 U) prior to reinfusion. Adherent cells were quantified by counting the number of cells per hpf in 8 to 10 hpf (×20) per experiment. Data are presented as mean ± SEM from n = 4–5 mice per group. Significance was determined using 1-way ANOVA with Tukey’s HSD post-hoc analysis. ***P < 0.0001, #P < 0.05 compared with control.