NKG2D overexpression potentiates CAR-T cells through costimulation by tumor NKG2D ligands

Chimeric antigen receptor (CAR)-T cell therapy has achieved remarkable success in hematologic malignancies, but durable efficacy remains limited by insufficient CAR-T cell persistence. Here, we show that activated CAR-T cells upregulate multiple NKG2D ligands (NKG2DLs), increasing their susceptibility to natural killer (NK) cell-mediated CAR-T cell cytotoxicity. To address this vulnerability, we engineer CAR-T cells to overexpress full-length NKG2D (CAR-NG). NKG2D overexpression reduces the surface accessibility of endogenous NKG2DLs without decreasing their total protein abundance. In parallel, engagement of tumor-expressed NKG2DLs in trans provides additional costimulatory signals, enhancing CAR-T cell activation and proliferation while attenuating exhaustion-associated phenotypes. In hematologic and solid tumor models, CAR-NG cells exhibit reduced susceptibility to NK-cell-mediated cytotoxicity, improved tumor control, increased in vivo expansion, deeper tumor infiltration, and no evident additional toxicity compared with conventional CAR-T cells. These findings identify NKG2D overexpression as an engineering strategy that enhances CAR-T antitumor activity primarily through tumor NKG2DL-dependent trans costimulation.