SIRPA and neoplasm: CD47, a widely expressed integrin-associated transmembrane protein that functions in part to protect cells from phagocytosis,57,58 is the ligand for signal regulatory protein alpha (SIRPα, also known as CD172a), and CD47–SIRPα binding initiates the ‘don’t eat me’ signal, inhibiting phagocytosis.59 Exosomes could be functionalized in order to improve retention time in blood with CD47 overexpression.60–62 Once engineered exosomes arrive in tumor sites, CD47 immune checkpoint blockade endows CRC with the macrophages-mediated phagocytosis by blocking CD47 signal.25,63,64