a–d BALB/cAnNHsd mice were implanted subcutaneously with A20 B cell lymphoma cells (1 × 106 cells). Unloaded EVs, CDN1 (2 or 0.02 µg), and exoCDN1 (0.02 µg) were injected into tumor (n = 6 animals) via the CIVO platform. a After 4 and 24 h, tumor sections were stained with pTBK1, IFN-β mRNA, and cleaved caspase 3 (CC3). IFN-β positive area (b) and CC3 positive area (c) were measured. Data are presented as means ± s.e.m from replicate samples as indicated. *P < 0.05; **P < 0.01; ***P < 0.001 by one-way ANOVA with Tukey’s multiple comparison test. d Co-localization of F4/80 (yellow) and IFN-β (red) after free CDN (2 µg) and exoCDN1 (0.02 µg) treatment. White arrows indicate the co-localization of F4/80 and IFN-β.