Synthetic NKG2D receptor (SNR) armored CAR-T cells overcome antigen heterogeneity of solid tumor

CAR-T cell therapy has demonstrated remarkable success in hematologic malignancies; however, its effectiveness against solid tumors remains limited due to tumor antigen heterogeneity. NKG2DLs, including MICA/B and the ULBP family, are stress-induced molecules frequently upregulated on the surface of tumor cells and components of the tumor microenvironment, providing attractive targets for immunotherapy. To broaden the targeting capability beyond conventional Claudin18.2-directed CAR-T cells, we engineered a Synthetic NKG2D Receptor (SNR). The SNR comprises the extracellular domain of NKG2D fused with the intracellular signaling domains of DAP10 and DAP12, enabling effective targeting of NKG2D ligands (NKG2DLs).

Expression of NKG2DLs and CLDN18.2 were detected by immunohistochemistry on a gastric cancer tissue microarray. We designed SNR CAR-T cells by linking CLDN18.2 CAR with SNR by a 2A self-cleaving peptide. We assessed their cytotoxicity, tumor infiltration, persistence, and antitumor efficacy using in vitro assays, patient-derived xenograft (PDX) models, and murine syngeneic models. Additionally, transcriptomic analysis and flow cytometry were performed to evaluate exhaustion and memory markers.

SNR CAR-T cells demonstrated enhanced cytotoxicity against tumor cells with heterogeneous CLDN18.2 expression, effectively lysing both CLDN18.2-positive and NKG2DL-positive tumor cells in vitro. In PDX and murine models, SNR CAR-T cells exhibited superior antitumor efficacy, leading to significant tumor regression and CAR-T expansion compared to conventional CAR-T cells. Furthermore, SNR CAR-T cells displayed reduced expression of exhaustion markers and increased expression of memory-associated markers. Enhanced tumor infiltration, proliferation and cytotoxicity within the tumor microenvironment, and a reduced presence of myeloid-derived suppressor cells (MDSCs) and tumor neovasculature were observed. Importantly, SNR CAR-T cell therapy was well-tolerated, with no significant toxicity noted in all the treated animals.

The SNR CAR-T cell approach addresses tumor antigen heterogeneity and suppressive tumor microenvironment, offering a promising therapeutic strategy for solid tumors and paving the way for its future clinical applications.