Neutrophil extracellular traps sequester circulating tumor cells and promote metastasis
Jonathan Cools-Lartigue, … , Paul Kubes, Lorenzo Ferri
Jonathan Cools-Lartigue, … , Paul Kubes, Lorenzo Ferri
Published July 1, 2013
Citation Information: J Clin Invest. 2013;123(8):3446-3458. https://doi.org/10.1172/JCI67484.
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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 5

NETs trap both human and murine tumor cells in vitro.

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NETs trap both human and murine tumor cells in vitro. (A) Under static c...
(A) Under static conditions, H59 and A549 cells demonstrate increased adhesion to neutrophil monolayers stimulated with PMA (800 nM) compared with unstimulated neutrophils. Addition of DNAse 1 (1,000 U) or pretreatment of neutrophils with NEi (5 μM) results in levels of adhesion comparable to control. (B) Tumor cells were perfused over neutrophil monolayers at shear rates of 1 dyne/cm/s–1. H59 and A549 cells demonstrate increased adhesion to neutrophils after stimulation with PMA (800 nM) compared with controls. This was abrogated by addition of DNAse 1 (1,000 U) or pretreatment of neutrophils with NEi (5 μM). Data are presented as mean ± SEM from n = 2–4 separate experiments. ***P < 0.01 versus control, DNAse, and NEi. #P < 0.05 versus control. Significance was determined using 1-way ANOVA with Tukey’s HSD post-hoc analysis. (C) Confocal imaging reveals that after PMA stimulation, A549 cells (red) become trapped within webs of extracellular DNA (green) in proximity to neutrophils (blue). (D) Scanning electron microscopy of A549- and PMA-stimulated neutrophils (800 nM) (original magnification, ×3,000). After PMA stimulation, neutrophils flatten (white arrow) and extrude strands consistent with NETs. Strands encompass a cluster of adherent tumor cells (black arrow). (E) Scanning electron microscopy demonstrates that NETs are in direct contact with adherent A549 tumor cells (original magnification, ×3,500). Scale bars: 40 μm (confocal microscopy); 5 μm (electron microscopy). See also Supplemental Figures 2 and 3.