Neutrophil-mediated tumour angiogenesis: Subversion of immune responses to promote tumour growth

Neutrophils are rapidly responding, phagocytes that are an essential part of the host innate immune response to invading micro-organisms. Along with other leucocytes they also play a key role in directing repair at sites of tissue damage. Neutrophils accomplish many of their biological functions by releasing enzymes, anti-microbial agents and cytokines when stimulated to degranulate. There is now increasing evidence to show that tumours are able to recruit neutrophils by secreting a number of tumour cell or stromal-derived chemoattractants. Once within the tumour microenvironment neutrophils, like macrophages, are polarised into a pro-tumour phenotype that can foster tumour growth by secreting factors that directly influence tumour cell proliferation, drive immunosuppression and promote tumour angiogenesis. In this review we discuss the likely mechanisms by which neutrophils are recruited into the tumour and then elaborate on how these cells may induce tumour vascularisation by the secretion of powerful pro-angiogenic factors. (C) 2013 Elsevier Ltd. All rights reserved.