Conversely, Granot et al. showed that tumour-entrained neutrophils (i.e. stimulated by the primary tumour) can inhibit metastatic seeding via hydrogen peroxide (H2O2) killing of disseminated tumour cells.36 It has recently been shown that H2O2 from neutrophils kills tumour cells by triggering a lethal influx of calcium via transient receptor potential cation channel subfamily M member 2 (TRPM2), an H2O2-dependent calcium-permeable channel expressed on cancer cells.37 Here, TRPM2 is linked to cancer.