TIGIT affects CAR NK cell effector function in the solid tumor microenvironment by modulating immune synapse strength

Abstract Therapies using natural killer (NK) cells that express chimeric antigen receptors (CAR-NKs) have been successfully employed against hematological malignancies. However, solid tumors resist CAR NKs partly by enriching tumor microenvironments with ligands for NK cell inhibitory receptors. Although the NK inhibitory receptor TIGIT has been implicated in impaired anti tumor activity of endogenous NK cells, the consequences of TIGIT expression on engineered CAR NKs has not been explored. To address this gap, we compared TIGIT-expressing and TIGIT deleted human CAR-NKs targeting the GD2 solid tumor antigen in tumor immune microenvironment (TiME) co-cultures and in vivo TiME xenografts designed to mimic the immunosuppressive environment of solid tumors. TIGIT deleted GD2.CAR-NKs exhibited antitumor activity, expanded, and persisted within TIGIT ligand enriched solid tumor environments while TIGIT expressing CAR-NKs did not. Mechanistic experiments revealed that the improved tumor control resulting from TIGIT loss on CAR-NKs was not dependent on DNAM-1 activation or enhanced cytotoxic potential, but rather on downregulation of cell adhesion molecules, weakened cell avidity, and reduced synapse contact duration that, in concert, improved serial killing and allowed more efficient tumor destruction. Our study highlights a novel non canonical role for TIGIT in modulating CAR-NK activity that may guide strategies to overcome inhibitory NK receptors like TIGIT and improve efficacy of CAR NKs against solid tumors.