CTLA4 and cancer: Unfortunately, recent studies have shown that Sirpα/CD47 signaling is often abnormally enhanced in the tumor microenvironment, leading to decreased phagocytosis by tumor-associated macrophages (TAMs) and subsequent cancer progression.19,20 Interestingly, Sirpα/CD47 blockade therapies can also enhance the anticancer effects of anti-PD-1, anti-PD-L1, and anti-CTLA-4 antibody immune checkpoint inhibitors that target T cell activation.11,17 Therefore, the blockade of the Sirpα/CD47 axis with specific antibodies has shown great potential in cancer therapy.19