Macrophages, as the first line of innate immunity, kill pathogens and cancer cells through phagocytosis.15 Recent studies have shown that macrophages express signal regulatory protein α (Sirpα), a receptor protein that distinguishes “self” and “non-self”, while normal tissue cells express the “self” ligand protein CD47.16–18 When the CD47 protein of normal cells binds to the Sirpα receptor on macrophages, the macrophages sense the “self” signal (also called the “don’t eat me” signal) and stop phagocytosis, preventing the destruction of self-tissues. Here, CD47 is linked to cancer.