Neutrophils in cancer, a love–hate affair

Neutrophils dominate the immunological landscape of multiple types of solid tumours in mice and humans and exert different pro‐ or antitumoral activity. This functional heterogeneity has prompted a search for different subsets and classifications of tumour‐infiltrating neutrophils with the idea of better delineating their specific roles in cancer. In this review, we describe current studies that highlight specific mechanisms by which neutrophils exert pro‐ or antitumoral function and focus on how distinct tumour types induce unique functional states in neutrophils, co‐opt granulopoiesis, modulate neutrophil ageing and prolong the neutrophil life span. In addition, we discuss how the tissue‐specific tumour stroma and the stage of the cancer influence the function and number of tumour‐infiltrating neutrophils. Finally, we explore different approaches to enhance the therapeutic efficacy in cancer types dominated by neutrophils. Neutrophils display a remarkable plasticity and are able to acquire multiple functionalities adapted to the environment. In cancer, neutrophils support tumour progression and metastasis through specific cell functions that allow for immune evasion of cancer cells and tumour growth but also exert antitumoral functions, especially at early stages of tumour development. This functional heterogeneity confers neutrophils a unique capability to shape tumour progression and may have major implications in cancer.