CD47 and cancer: Through the overexpression of anti-phagocytic surface proteins, also known as the “don’t eat me” signal, such as CD47 [27], programmed cell death ligand 1 (PD-L1) [28], and the beta-2 microglobulin subunit of the major histocompatibility class I complex (B2M) [29], cancer cells can evade clearance by macrophages.