B7-H3-targeted natural killer cells effectively kill atypical teratoid / rhabdoid tumors and extend survival in orthotopic xenografts

Abstract Background Atypical teratoid/rhabdoid tumors (AT/RTs) are the most common malignant CNS tumor in infants, and patients suffer from low survival rates and treatment-related morbidities. These tumors frequently overexpress the pan-cancer antigen B7-H3 (CD276), which can be targeted with immunotherapy. We hypothesized that adding a B7-H3-targeting cytotoxic chimeric antigen receptor (CAR) to NK cells can enhance killing against AT/RTs. Methods We designed a library of variable affinity B7-H3-targeted CARs, which were transduced into primary healthy donor-derived NK cells. We verified B7-H3 expression in a panel of AT/RT cell lines and further engineered luciferase and nuclear GFP-expressing AT/RT (CHLA-04, CHLA-06, BT12, BT37) as well as a CHLA-06-derived B7-H3 knockout. We tested CAR-NK cell functionality using in vitro co-culture cytotoxicity assays. We delivered anti-B7-H3 CAR-NK cells intratumorally or intracerebroventricularly (ICV) to AT/RT orthotopic xenografts and monitored for tumor growth and animal survival. Results B7-H3-targeted CAR-NK cells demonstrated target-specific cytotoxicity when compared to unmodified NK cells. Knockout of B7-H3 in target cells abolished the increased CAR-mediated target killing. When delivered intratumorally to CHLA-06 orthotopic xenograft-bearing mice, anti-B7-H3 CAR-NK cells eliminated tumor cells and prolonged survival. When CAR-NK cells were delivered ICV against a CNS disseminated tumor model of BT12, treated mice had significantly improved survival. Conclusions Anti-B7-H3 CAR-NK cells effectively kill AT/RTs in multiple pre-clinical in vitro and in vivo models in an antigen-specific manner. Evidence of efficacy in translationally relevant models provides support for using B7-H3-targeting CAR-NK cells in high-risk AT/RT patients.