The tumor promoting mechanism of circulating and tumor tissue neutrophils

Neutrophils are the most common inflammation cells in the human body and the most abundant cells in the tumor microenvironment.Normal neutrophils are derived from bone marrow hematopoietic stem cells, which have the function of clearing pathogens and tissue repair.However, In the tumor background, the subpopulations of neutrophils can transform to Myeloid-derived suppressor cells (MDSCs), which is a kind of immature neutrophils with strong immunosuppressive effects.Circulating MDSCs inhibit the anti-tumor immunity of T lymphocytes by producing reactive oxygen species and arginase, and release neutrophil extracellular traps to promote tumor cell transport in blood.MDSCs in tumor tissues inhibit T lymphocytes function by expressing PD-L1, and can also release vascular endothelial growth factor to promote angiogenesis, release metal matrix protease to induce epithelial-mesenchymal transition, thereby aggravating tumor progression.Neutrophils play an important role in the development of tumorigenesis.This article reviews the origin of neutrophils and the mechanism by which neutrophils promote tumor progression in circulation and tumor tissues. Key words: Tumor microenvironment; Biological markers; Neutrophils; Myeloid-derived suppressor cells; Immunity inhibition