The study investigates the role of DNA exonuclease Trex1 in enhancing radiotherapy-induced anti-tumor immunity. Trex1 is induced by radiation doses above 12–18 Gy in various cancer cells, which degrades cytosolic DNA accumulated after irradiation, thereby attenuating the immunogenicity of the tumor. This degradation of DNA is crucial for the activation of the type-I interferon (IFN-I) pathway via the cGAS-STING pathway, which is essential for recruiting and activating Baf3-dependent dendritic cells (DCs). The presence of these DCs is necessary for priming CD8+ T cells that mediate systemic tumor rejection (abscopal effect) in the context of immune checkpoint blockade. The findings suggest that Trex1 induction may guide the selection of radiation dose and fractionation in patients treated with immunotherapy to enhance anti-tumor responses.The study investigates the role of DNA exonuclease Trex1 in enhancing radiotherapy-induced anti-tumor immunity. Trex1 is induced by radiation doses above 12–18 Gy in various cancer cells, which degrades cytosolic DNA accumulated after irradiation, thereby attenuating the immunogenicity of the tumor. This degradation of DNA is crucial for the activation of the type-I interferon (IFN-I) pathway via the cGAS-STING pathway, which is essential for recruiting and activating Baf3-dependent dendritic cells (DCs). The presence of these DCs is necessary for priming CD8+ T cells that mediate systemic tumor rejection (abscopal effect) in the context of immune checkpoint blockade. The findings suggest that Trex1 induction may guide the selection of radiation dose and fractionation in patients treated with immunotherapy to enhance anti-tumor responses.