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 1

CLP results in widespread deposition of extracellular DNA, which colocalizes with neutrophils and expresses neutrophil-derived granules.

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CLP results in widespread deposition of extracellular DNA, which colocal...
(A) Under anesthesia, murine livers were externalized and imaged using SD-IVM, permitting real-time visualization of neutrophil trafficking and DNA extrusion. Intravascular administration of E-fluor 660 anti-GR1, Sytox Green, Alexa Fluor 555 anti-H2AX, or anti-NE was used to visualize polymorphonuclear neutrophils (PMN, blue), DNA (green), H2AX (red), and NE (yellow), respectively. DNA is visualized adjacent to PMN within hepatic sinusoids. DNA stains positive for histone H2AX and NE, in keeping with what has been described for NETs (48). Scale bars: 40 μm. Extracellular DNA was quantified within (B) hepatic sinusoids and (C) pulmonary capillaries by measuring total area of fluorescence per hpf over 5 hpf. Data are represented as relative area of fluorescence compared with sham. CLP was associated with increased amounts of extracellular DNA compared with sham. Neutrophil depletion or systemic administration of DNAse 1 or NEi after CLP results in decreased extracellular DNA staining compared with CLP alone. Data are presented as mean ± SEM from n = 3–5 mice per group. ***P < 0.001, *P < 0.05 versus sham as determined by 1-way ANOVA with Tukey’s HSD post-hoc analysis. See also Supplemental Figures 1 and 2.