Brief review on the roles of neutrophils in cancer development

Abstract

Neutrophils, which are traditionally regarded as a hallmark of inflammation, are also a member of the intratumoral immune cells. The roles of neutrophils in cancer development are diverse and undefined. So far, they are known to be involved in tumor initiation and tumor cell proliferation and metastasis. They show heterogeneity in both phenotypes and functions during early versus late stage of cancer development. Because they are also associated with the clinical outcomes of various types of solid tumors, cancer treatments that target neutrophils might be highly effective. In this review, we briefly cover the latest findings on the multiple roles of neutrophils in cancer development and point out the future directions as well.

Keywords: MDSC; cancer; heterogeneity; neutrophil-to-lymphocyte ratio; neutrophils.

FIGURE 1

Neutrophils are attracted by CXCR2 ligands and infiltrate the tumor microenvironment to become intratumoral immune cells. Neutrophils support cancer development mainly through 3 pathways: (1) their support of cancer initiation through the secretion of reactive oxygen species, reactive nitrogen species, and some proteases; (2) their facilitation of metastasis through the suppression of natural killer cells, enhancement of extravasation, and escorting of tumor cells to spread and seed; and (3) their support of tumor growth through the inhibition of CD8⁺ T cells and promotion of angiogenesis. VEGFA, vascular endothelial growth factor A