Abstract B022: Targeting the innate immune checkpoint TREX1 elicits antitumor immunity through tumor-intrinsic cGAS-STING signaling

Abstract Three-prime repair exonuclease 1 (TREX1) is the major DNase in mammalian cells that degrades cytosolic DNA to prevent activation of the cGAS-STING pathway. Genotoxic stress, DNA damage, and radiotherapy induce TREX1 expression in cancer cells, allowing them to evade innate immune activation of type I interferon (IFN-I)-mediated antitumor response. How TREX1 can be targeted for cancer immunotherapy remains elusive. Here, we show that genetic deletion of TREX1 in tumors elicits robust antitumor immunity through tumor-intrinsic cGAS-STING activation, IFN-I signaling, and recruitment of CD8+ T cells. To therapeutically target TREX1, we perform a high-throughput small-molecule inhibitor screen of TREX1 using a cell-free DNase assay. We identify two lead compounds that inhibit TREX1 DNase activity at low micromolar concentrations, induce IFN-I signaling in cancer cells, and inhibit tumor growth in mice in a type I IFN receptor-dependent manner. Additionally, TREX1 inhibitor treatment sensitizes B16-F10 melanoma to anti-PD-1 immunotherapy. We further show that Trex1 knockout cancer cells elicit systemic antitumor immunity and can be used as autologous cancer vaccines to protect against future tumor challenge and metastasis. We also establish an inducible whole-body Trex1 knockout mouse model to simulate “on-demand” systemic TREX1 inactivation in adult mice. Sustained TREX1 loss in adult mice suppresses a broad range of solid tumors and metastatic tumors. Although TREX1 deficiency is associated with severe autoimmune diseases, inducible Trex1 knockout in adult mice does not cause immune toxicity, demonstrating feasibility of an immune-safe therapeutic window. Together, our data present multiple therapeutic modalities for targeting TREX1 using small-molecule inhibitors and as an autologous cancer vaccine, as well as antitumor efficacy and immune safety, which should pave the way for developing TREX1-targeted cancer immunotherapy. Citation Format: Cong Xing, Nan Yan. Targeting the innate immune checkpoint TREX1 elicits antitumor immunity through tumor-intrinsic cGAS-STING signaling [abstract]. In: Proceedings of the AACR IO Conference: Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2025 Feb 23-26; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(2 Suppl):Abstract nr B022.