Tumor-Associated Neutrophils in Cancer: Going Pro

Abstract

The progression of cancer is not only about the tumor cell itself, but also about other involved players including cancer cell recruited immune cells, their released pro-inflammatory factors, and the extracellular matrix. These players constitute the tumor microenvironment and play vital roles in the cancer progression. Neutrophils-the most abundant white blood cells in the circulation system-constitute a significant part of the tumor microenvironment. Neutrophils play major roles linking inflammation and cancer and are actively involved in progression and metastasis. Additionally, recent data suggest that neutrophils could be considered one of the emerging targets for multiple cancer types. This review summarizes the most recent updates regarding neutrophil recruitments and functions in the tumor microenvironment as well as potential development of neutrophils-targeted putative therapeutic strategies.

Keywords: cancer metastasis; neutrophil extracellular traps; neutrophil polarization; neutrophils.

Figure 1

① Neutrophils mobilize from bone marrow, enter the circulatory system, and move using a chemotactic way to the primary tumor sites. ② Neutrophils promote cancer metastasis through the formation of NET. The NET traps the dormant tumor cells, which facilitates the establishment of the secondary tumor sites. ③ Cells in the tumor microenvironment release pro-tumor factors such as CXCR2 ligands into the circulatory system to recruit neutrophils to the tumor sites. ④ Neutrophils arrive in the pre-metastatic lung to establish the pre-metastatic niche for tumor cells.