Abstract 3791: Tumor cells surviving DNA damage acquire antigen presenting functions to stimulate anti-tumor immunity

Immunogenic cell death (ICD) is a process where dead cells expose damage-associated molecular patterns to stimulate the immune system. Although the ICD paradigm focuses on immunogenicity induced by cell death, we determined that live but stressed/DNA-damaged tumor cells also modulate their immunogenicity in order to engage and stimulate anti-tumor immunity. However, the intracellular signaling pathways activated to increase tumor cell immunogenicity are not well characterized.Tumor immunogenicity was evaluated using a combination of co-culture experiments and in vivo murine models. B16F10 melanoma and ID8 ovarian cancer cell lines expressing ovalbumin were treated with various DNA-damaging agents, then incubated with bone-marrow derived dendritic cells (DCs) or treated with IFNγ for 24hrs, followed by incubation with OT-I CD8+ T cells. T cell activation was assessed by IFNγ and Granzyme B production, measured by flow cytometry. Treatment with the topoisomerase II inhibitors etoposide, doxorubicin, or mitoxantrone potently induced T cell activation and anti-tumor immunogenicity. Notably, T cell activation was only induced by the live cell fraction after toposimerase treatment, with minimal immunogenic activity conferred by DC- and/or T cell co-incubation with the dead cell fraction. In vivo models of B16F10 showed that intratumoral injection of a cellular adjuvant increased efficacy of systemic checkpoint blockade as shown by increased overall survival and generation of a memory response in survivors. In vitro transwell assays demonstrated that contact between tumor cells and T cells was necessary, and the requirement for DCs could be bypassed by exogenous administration of IFNγ to the tumor cells after DNA damage. Further studies showed that IFNγ-treated DNA-damaged tumor cells increased expression of positive co-stimulatory ligands and induced Granzyme B production in T cells, indicating the presence of both Signals 2 and 3 required for T cell activation. Activation of T cells by stressed/damaged tumor cells required a high affinity TCR:pMHCI interaction. Inhibition of TBK1, a molecule down stream of cGAS/STING, partially reduced immunogenicity.Overall, tumor cells surviving topoisomerase II-induced DNA damage activate T cells through DC-dependent and DC-independent pathways more potently than dead/apoptotic cells. These studies suggest that certain types of DNA damage can increase the efficacy of anti-cancer immunotherapy by coordinated stress and immune signaling in the live but stressed/injured tumor cells. Citation Format: Tiffany R. Emmons, Ganapathy Sriram, Aadhithya Manimaran, Emma Martin, Anna Lian, Tiffany Stephens, Hannah Hicks, Michael B. Yaffe. Tumor cells surviving DNA damage acquire antigen presenting functions to stimulate anti-tumor immunity [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 3791.