Kindlin3-Dependent CD11b/CD18-Integrin Activation Is Required for Potentiation of Neutrophil Cytotoxicity by CD47-SIRPα Checkpoint Disruption

The CD47-signal regulatory protein-alpha (SIRP alpha) immune checkpoint constitutes a therapeutic target in cancer, and initial clinical studies using inhibitors of CD47-SIRP alpha interactions in combination with tumor-targeting antibodies show promising results. Blockade of CD47-SIRP alpha interaction can promote neutrophil antibody-dependent cellular cytotoxicity (ADCC) toward antibody-opsonized targets. Neutrophils induce killing of antibody-opsonized tumor cells by a process identified as trogoptosis, a necrotic/lytic type of cancer cell death that involves trogocytosis, the antibody-mediated endocytic acquisition of cancer membrane fragments by neutrophils. Both trogocytosis and killing strictly depend on CD11b/CD18-(Mac-1)-mediated neutrophil-cancer cell conjugate formation, but the mechanism by which CD47-SIRP alpha checkpoint disruption promotes cytotoxicity has remained elusive. Here, by using neutrophils from patients with leukocyte adhesion deficiency type III carrying FERMT3 gene mutations, hence lacking the integrin-associated protein kindlin3, we demonstrated that CD47-SIRP alpha signaling controlled the inside-out activation of the neutrophil CD11b/CD18-integrin and cytotoxic synapse formation in a kindlin3-dependent fashion. Our findings also revealed a role for kindlin3 in trogocytosis and an absolute requirement in the killing process, which involved direct interactions between kindlin3 and CD18 integrin. Collectively, these results identified a dual role for kindlin3 in neutrophil ADCC and provide mechanistic insights into the way neutrophil cytotoxicity is governed by CD47-SIRP alpha interactions.

Automated summary

The CD47-SIRPα immune checkpoint is a therapeutic target in cancer, with inhibitors of this interaction showing promising results in clinical studies. The role of kindlin3 in promoting neutrophil cytotoxicity and synapse formation in a CD47-SIRPα-dependent manner has been demonstrated, highlighting its importance in ADCC processes. The study provides mechanistic insights into how neutrophil cytotoxicity is regulated by CD47-SIRPα interactions and the essential role of kindlin3 in this process.