Abstract C050: Simultaneous STING and lymphotoxin-β receptor activation boosts the fitness of tertiary lymphoid structures and prevents future tumor recurrence and metastasis

Abstract Tertiary lymphoid structures (TLS) are found in various types of cancer, and abundant TLS formation is associated with better patient response to immunotherapies and conventional chemotherapies. A therapeutic strategy that remodels the tumor immune landscape to induce TLS formation could provide a breakthrough for treatment-resistant tumors. Here, we show successful induction of TLS in various mouse tumor models by simultaneously activating two innate immune effectors, STING and lymphotoxin-β receptor (LTβR), using their agonists. Using this approach, fully mature, functional TLS were induced in all treated mice, in different tumor types and anatomical sites—TLS developed in adenocarcinomas and sarcomas in the pancreas, mammary gland, skeletal muscle, and subcutaneous tissues. We were also able to induce TLS in the glioma-harboring brain. T cell depletion study demonstrated that both CD4+ and CD8+ T cell subsets are required for the development of TLS. STING activation alone was insufficient for inducing B cell-containing TLS or eliciting long-term therapeutic effects. However, when combined with LTbR activation, it improved the fitness of TLS with B cell expansion and differentiation to IgG-producing long-lived plasma cells and memory cells, exhibiting lymph node-like germinal center B cell responses within tumors. In addition, the treatment induced high endothelial venule formation, increased CD4+ T cell recruitment, memory CD8+ T cell expansion, and the accumulation of TCF1+ stem-like CD8+ T cells around TLS. These immune responses resulted in strong suppression of tumor growth, recurrence, and metastasis, with excellent survival benefit, demonstrating that the treatment facilitated successful immunization against tumor cells. Furthermore, the efficacy of anti-PD-1 immune checkpoint blockade was substantially improved in resistant tumors upon simultaneous activation of STING and LTbR pathways. CD8+ T cells were mainly responsible for the immediate early response to the agonist combination therapy. The delayed but prolonged response was mediated by humoral immunity of B cells, which exerted a lasting anti-tumor effect together with the cellular immunity of CD8+ T cells and NK cells. This study lays the ground for the therapeutic induction of TLS in cancer using immune-modulating biologic agents. Unlike other reported strategies, TLS induction by this method does not require viral antigens or artificial genetic manipulations to boost immune response, making it feasible for clinical applications. The high-affinity tumor-specific IgG-producing long-lived plasma cells and memory B and T cells generated in these TLS could provide lifelong protection against tumor recurrence and metastases. Effective tumor immunization by this strategy is expected to improve other cancer immunotherapies and suggests broad therapeutic applications in cancer. Since STING agonists are clinically available and humanized agonistic antibodies to LTβR can be developed, this strategy is readily translatable to clinical use for cancer treatment. Citation Format: Yasuhiro Kikuchi, Maxwell Duah, Fumiaki Kanamori, Masanobu Komatsu. Simultaneous STING and lymphotoxin-β receptor activation boosts the fitness of tertiary lymphoid structures and prevents future tumor recurrence and metastasis abstract. In: Proceedings of the AACR Immuno-Oncology Conference (AACR IO): Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2026 Feb 18-21; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2026;14(2 Suppl):Abstract nr C050.