SIRPA and neoplasm: The pyroglutamylation of CD47 is essential for the binding between CD47 and SIRPα, and QPCTL is the key enzyme for pyroglytamylation of CD47.338,363 Targeting QPCTL significantly attenuates the binding ability of CD47 to SIRPα and increases phagocytosis of tumor cells by macrophages, thus regulating tumor immunity (Fig. 7a),50,52,364 and targeting QPCTL avoids anemia since QPCTL is not expressed on mature RBCs.