While under pathological conditions, S100A9 is released extracellularly by immune cells such as neutrophils, monocytes, macrophages, and dendritic cells, as well as necrotic myocardial cells, endothelial cells, and cancer cells, thereby performing corresponding functions such as modulating immune responses27, 41, 42, 43, 44, 45 (Figure 1). Here, S100A9 is linked to cancer.