Cluster of Differentiation 47, or CD47, plays an essential role in cell growth, death, migration, and adhesion. CD47 binding to SIRP-α mediates phagocytosis by sending a “do not eat me” signal to phagocytes. CD47 proteins are often over expressed by tumor cells as a means for them to escape phagocytosis. As a result, cancerous tumor cells have the ability to proliferate and evade the immune system.