Abstract 6847: Development and application of DTR mouse models for immune cell ablation and tumor immunotherapy studies

Abstract Inducing the selective ablation of specific cell types is a powerful approach for studying complex cell-cell interactions, particularly within the immune system. While systemic depletion of immune cells can be achieved using chemicals or cytotoxic antibodies, the diphtheria toxin receptor (DTR)-diphtheria toxin (DT) system provides a more targeted, cost-effective, and minimally invasive alternative. The system leverages the fact that human DTR has a 103-105 times higher affinity for DT compared to rodent cells. This allows selective cell ablation in mice by introducing the human DTR gene into specific cell populations and subsequently administering DT in vivo. Using CRISPR/Cas9 technology, we generated a series of DTR mouse models targeting immune cell types, including CD8, Ncr1, Foxp3, CD11c, and seven additional cell-specific targets. These models were created on C57BL/6 or BALB/c genetic backgrounds, with the human DTR coding sequence driven by murine endogenous promoters. Successful gene insertions were validated using GFP or Tomato fluorescent reporter expression. Upon DT administration, these engineered DTR mice exhibited transient immune cell ablation within 48 hours, with cell levels recovering to baseline within 96 hours in the absence of repeated DT dosing. For functional validation, we used the Ncr1-DTR mouse model in an MC38 tumor inoculation study. DT treatment effectively depleted natural killer (NK) cells in the blood, highlighting the model's utility for immune cell depletion in specific experimental contexts. Overall, these results demonstrate that DTR mouse models are robust tools for dissecting immune cell functions, exploring intercellular interactions, and evaluating the mechanisms of immune-based therapies. Citation Format: Yang Yu, Yi Li, Hechun Ma, Shuang Li, Ruilin Sun. Development and application of DTR mouse models for immune cell ablation and tumor immunotherapy studies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6847.