Evaluation of induced cancer cell phagocytosis by cancer-macrophage bridging molecule

Abstract

Cluster of Differentiation 47 (CD47) is a cell surface protein which is a representative immune evasion factor, sending a "don't eat me" signal to macrophages by binding to macrophage Signal Regulatory Protein α (SIRPα). This is a mechanism by which cancer cells evade the innate immune system. Recent research on CD47 and SIRPα shed light to development of the cancer therapeutics, leading to growing demands for the assessment of the immune evasion effect caused by CD47. However, exclusive effect of CD47 was not easy to be assessed when tested with the cancer cell due to uncontrolled factors, such as cross-reactivity with other native proteins, various membrane composition, or cell heterogeneity. To effectively control these factors, we aimed to create artificial CD47 beads. We coated purified mouse CD47 to Neutravidin modified beads using biotin interaction. Next, this CD47 bead were treated to macrophage cells, and engulfment efficiency of this bead was assessed using flow cytometry. As expected, we observed a reduced engulfment efficiency of CD47 beads compared to uncoated bead. This revealed that the difference arises solely from CD47. This result proposes a novel model for studying the immune evasion effects exclusively attributed to CD47.