Heterogenous presence of neutrophil extracellular traps in human solid tumours is partially dependent on IL-8

Our plain-English summary of Heterogenous presence of neutrophil extracellular traps in human solid tumours is partially dependent on IL-8, by C.E. de Andrea, M.C. Ochoa, M. Villalba-Esparza, et al (The Journal of Pathology, 2021).

The study

• Authors: C.E. de Andrea, M.C. Ochoa, M. Villalba-Esparza, Á. Teijeira, K.A. Schalper, M. Abengozar-Muela, I. Eguren-Santamaría, C. Sainz, S. Sánchez-Gregorio, S. Garasa, M. Ariz, C. Ortiz-de-Solorzano, M.E. Rodriguez-Ruiz, J.L. Perez-Gracia, M.D. Lozano, J.I. Echeveste, M.F. Sanmamed, I. Melero
• Journal: The Journal of Pathology
• Published: 2021;255(2):190-201
• Cited by: 104 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Neutrophil extracellular traps (NETs) are webs of extracellular nuclear DNA extruded by dying neutrophils infiltrating tissue. NETs constitute a defence mechanism to entrap and kill fungi and bacteria. Tumours induce the formation of NETs to the advantage of the malignancy via a variety of mechanisms shown in mouse models. Here, we investigated the presence of NETs in a variety of human solid tumours and their association with IL-8 (CXCL8) protein expression and CD8+ T-cell density in the tumour microenvironment. Multiplex immunofluorescence panels were developed to identify NETs in human cancer tissues by co-staining with the granulocyte marker CD15, the neutrophil marker myeloperoxidase and citrullinated histone H3 (H3Cit), as well as IL-8 protein and CD8+ T cells. Three ELISA methods to detect and quantify circulating NETs in serum were optimised and utilised. Whole tumour sections and tissue microarrays from patients with non-small cell lung cancer (NSCLC; n = 14), bladder cancer (n = 14), melanoma (n = 11), breast cancer (n = 31), colorectal cancer (n = 20) and mesothelioma (n = 61) were studied. Also, serum samples collected retrospectively from patients with metastatic melanoma (n = 12) and NSCLC (n = 34) were ELISA assayed to quantify circulating NETs and IL-8. NETs were detected in six different human cancer types with wide individual variation in terms of tissue density and distribution. At least in NSCLC, bladder cancer and metastatic melanoma, NET density positively correlated with IL-8 protein expression and inversely correlated with CD8+ T-cell densities. In a series of serum samples from melanoma and NSCLC patients, a positive correlation between circulating NETs and IL-8 was found. In conclusion, NETs are detectable in formalin-fixed human biopsy samples from solid tumours and in the circulation of cancer patients with a considerable degree of individual variation. NETs show a positive association with IL-8 and a trend towards a negative association with CD8+ tumour-infiltrating lymphocytes. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

© 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

In plain English

This laboratory study from Pamplona, Spain, looked for neutrophil extracellular traps (NETs), webs of DNA released by dying white blood cells called neutrophils, in stored tumour samples. Using a three-marker staining method, the authors examined samples from patients with non-small cell lung cancer (14), bladder cancer (14), breast cancer (31), colorectal cancer (20), mesothelioma (61) and metastatic melanoma (11). The article does not say whether the mesothelioma was pleural or peritoneal, and it does not study asbestos. NETs were found in all six cancer types, with wide variation between patients. In lung cancer, bladder cancer and melanoma, more NETs went with more of the signalling protein IL-8 and with fewer CD8+ T cells, a type of immune cell. The link with fewer CD8+ cells was less clear in melanoma. Mesothelioma was not included in this analysis. In blood serum from 12 melanoma and 34 lung cancer patients, circulating NETs were positively associated with IL-8. The authors concluded that NETs are detectable in human tumours and blood. They found a positive association with IL-8 and a trend towards a negative association with CD8+ cells. They noted the limitation of working on retrospective series.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory study of archived (retrospective) tumour tissue samples and stored serum samples, using multiplex immunofluorescence staining and ELISA tests
• Who was studied: Tissue samples seen at the Pathology Department of the Clínica Universidad de Navarra (Pamplona, Spain) from 14 patients with NSCLC, 14 with bladder cancer, 31 with breast cancer, 20 with colorectal cancer, 61 with mesothelioma (site not stated) and 11 with metastatic melanoma. Serum samples came from 12 patients with metastatic melanoma and 34 with NSCLC. The article gives no collection dates.
• Exposure: No asbestos or other environmental exposure was studied. The study measured NETs (identified by combined staining for CD15, myeloperoxidase and citrullinated histone H3) and their relationship with IL-8 protein and CD8+ T-cell density.
• Main results:
  • NETs were present in at least some cases of each of the six tumour types examined (including mesothelioma). The amount varied widely between cases of each disease.
  • Across the tumour samples, the density of neutrophils in the tissue strongly correlated with the percentage of tissue area covered by NETs. Not all neutrophils in the tumours formed NETs.
  • In NSCLC, bladder cancer and melanoma (the only tumour types in this analysis), IL-8 protein expression was positively associated with NET area.
  • In the same three tumour types, CD8+ T-cell density correlated negatively with NET area. The exception was melanoma, where the relationship was less pronounced.
  • Tissue IL-8 protein expression did not correlate with CD8+ T-cell infiltration in any of the three tumour types. The figures as printed were: NSCLC r = 0.15, p = 0.60; bladder cancer r = 0.43, p = 0.13; melanoma r = 0.32, p = 0.41.
  • In whole sections from four melanoma cases with NETs, NETs seemed more abundant in and around areas of tumour cell death (necrosis). Across small tiles of tissue, NET density correlated negatively with CD8+ T-cell density.
  • In serum from patients with metastatic melanoma (n = 12) and NSCLC (n = 34), circulating NETs, measured by three ELISA methods, showed a positive association with serum IL-8.
• The authors' conclusion: The authors concluded that NETs are detectable in formalin-fixed biopsy samples from solid tumours and in the blood of cancer patients, with considerable individual variation. They found a positive association with IL-8 and a trend towards a negative association with CD8+ tumour-infiltrating lymphocytes.
• Limitations the authors state:
  • The authors stated that the study was limited by working on retrospective series.

Topics

Medical terms in this study, explained in our Lexicon: Non-Small Cell Lung Cancer, Colorectal Cancer, Mesothelioma, Biopsy, Tumor-Infiltrating Lymphocytes, Pathology.

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