The group identified that these entrained neutrophils inhibit the seeding of disseminated cells in the lung by killing the cancer cells in an H2O2‐dependent manner,64 and that the cytotoxic ability of neutrophils is mediated through the NADPH oxidase–H2O2 pathway triggered by the secretion of H2O2 in neutrophils upon physical contact between cancer cells and neutrophils. Here, FMO5 is linked to cancer.