Phenotyping neutrophil subpopulations in advanced lung cancer


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Robert Grecian1,Patricia Dos Santos Coelho1,Emily Watts1,Kev Dhaliwal1,Adam Byron1,Margaret Frame1,Moira Whyte1,Sarah Walmsley1
1Edinburgh University

Abstract

Background

The majority of patients with lung cancer present with late stage disease. Better understanding of immune responses to advanced cancer may aid in identification of new therapeutic targets. Blood neutrophil-to-lymphocyte ratio (NLR) is known to strongly correlate with clinical outcome, and expanded populations of low density blood neutrophils have been observed in cancer. However, less is known about the pathophysiological role neutrophils may play at the metastatic site, with an additional lack of human data in the literature. This research therefore aimed to identify the neutrophil subpopulations present in stage IV lung cancer and elucidate their function.

Method

Neutrophils were extracted from the blood and pleural fluid (metastatic site) of patients with non-small cell lung cancer (NSCLC), undergoing diagnostic or therapeutic procedures (n=33). These were compared with blood neutrophils from healthy donors, or blood and pleural fluid neutrophils from patients with pneumonia. Subpopulations were defined by density, morphology and surface marker expression using flow cytometry. Ex-vivo functional studies including apoptosis were performed.

Results

Median NLR was 6.8 (interquartile range (IQR) 3.8-11.7). There was an expanded population of CD66bhighCD11b+CD15+CD14-CD49d-CD10-CD62L-LOX-1+ low density neutrophils in advanced NSCLC, that were not present in health. Low density blood neutrophils formed 2.3% (median, IQR 0.8-9.6) of the total blood neutrophil population. Pleural fluid neutrophils constituted 8.6% (median, IQR 1.8-16.6) of pleural fluid leukocytes. Neutrophils of patients with NSCLC had a survival advantage ex-vivo in culture when compared to those of both healthy donors and those of patients with pneumonia.

Conclusion

In addition to density and morphology, the cell surface markers CD10, CD62L and LOX-1 may be useful in defining neutrophil subpopulations in advanced cancer. We found neutrophils in NSCLC to have a pro-survival phenotype that appears to be cancer-specific. Ongoing work will define whether these neutrophil groups are pro- or anti-tumour.