(A) GSEA showing an increased IFN-β response in DCs with Ythdf1 deletion versus WT DCs. (B) WT and Ythdf1-cKO mice were injected s.c. with B16-OZ cells. Tumor-bearing mice underwent local IR (20 Gy, 1 dose) when the tumor volume reached 100–200 mm³, and tumors were excised on day 3 after IR for IFN-β ELISA (n = 5). (C–E) BMDCs from Ythdf1-cKO mice were cocultured with 40 Gy–pretreated or nonirradiated B16-OZ cells for 8 hours. Purified CD11c⁺ cells were incubated for another 2 days. Supernatants were collected to measure IFN-β by ELISA (n = 3) (C). Purified CD11c⁺ cells were collected to measure mRNA levels of Ifnb (D) and Isg15, Ifit3, and Cxcl10 (E) by qPCR (n = 3). (F) BMDCs from Ythdf1-cKO and Ythdf1/Ifnar1-cKO mice were cocultured with B16-OZ cells for 8 hours. Purified CD11c⁺ cells were incubated with CD8⁺ T cells from OT-I mice for another 3 days. IFN-γ–producing cells were enumerated by ELISPOT (n = 3). (G) B16-OZ tumors in WT and Ythdf1-cKO mice were treated with IR and/or 200 μg anti-IFNAR1 mAb injected i.t. twice weekly. Tumor growth was monitored after IR. (H and I) BMDCs from Ythdf1-cKO and Ythdf1/Sting-cKO mice were cocultured with B16-OZ cells for 8 hours. Purified CD11c⁺ cells were incubated for an additional 2 days. IFN-β levels in supernatants were measured by ELISA (n = 3) (H). Purified CD11c⁺ cells were incubated with CD8⁺ T cells from OT-I mice for another 3 days. Then IFN-γ–producing cells were enumerated by ELISPOT (n = 3) (I). Data are presented as the mean ± SEM and are representative of 2 or 3 independent experiments. (B–I) One-way ANOVA with Tukey’s multiple-comparison test (B–F, H, and I) and 2-way ANOVA with Tukey’s multiple-comparison test (G). *P < 0.05, **P < 0.01, and ***P < 0.001.