SIRPA and cancer: As a novel immunotherapy target, to date, there are four major strategies of anti-CD47 treatment: (1) CD47 antibody can enhance cancer cell phagocytosis of macrophages by blocking the binding of CD47-SIRPα; (2) CD47 antibody or SIRPα-Fc fusion protein can also exert cytotoxic effects through the Fc segment; (3) CD47 antibody could directly induce tumor cells apoptosis via a caspase-independent mechanism; (4) CD47 antibody could work with prophagocytic molecules to make DC phagocytose tumor cells, and then present the antigen to T cells, thereby activating the adaptive immune response.