Abstract PR001: Intratumoral B cells are essential for anti-tumor immune responses of tertiary lymphoid structures: Impact of STING and LTβR activation in pancreatic cancer
Authors: Duah Maxwell , Kikuchi Yasuhiro , Stansel Tomoko , Csomos Krisztian , Hiraoka Nobuyoshi , Walter Jolan , Ware Carl F , Komatsu Masanobu 
Published: February 2025

Abstract
B cells are emerging as key players in anti-tumor immunity. Their ability to produce antibodies against tumor-associated antigens makes them potent agents in cancer immunotherapy. However, B cell-based therapies remain underutilized compared with T cell-focused approaches. Tumor-infiltrating B cells can form tertiary lymphoid structures (TLS) that resemble lymphoid follicles of inflamed lymph nodes. Significant evidence indicates that TLS are associated with enhanced anti-tumor immunity, and the presence of TLS correlates with improved prognosis and better therapeutic responses across various cancers. However, the development of B cell-dependent anti-tumor immunity might be generated mainly in the tumor-draining lymph nodes, and TLS formation may be a bystander effect of the strong local immune responses. Thus, direct evidence for TLS-B cells contributing to anti-tumor immunity is lacking. Recently, our laboratory discovered that simultaneous activation of innate immune effectors, stimulator of interferon genes (STING) and lymphotoxin beta receptor (LTβR), by their agonists induces mature TLS with germinal center B cell responses in various mouse tumor models. In the current study, we investigated the role of TLS using CD79a knockout mice, which cannot develop TLS due to B cell deficiency. We also leveraged hybridoma technology to generate monoclonal antibodies from TLS-B cells for potential tumor targeting. We show that, in wild type mice, the STING activation improved the fitness of LTβR-induced TLS with B cell maturation to IgG+ long-lived plasma cells and memory cells. This treatment reduced the tumor size and heightened the efficacy of anti-PD-1 immune checkpoint inhibition, leading to complete cure. When used as neoadjuvant therapy, it prevented tumor recurrence and metastasis with 100% survival post-tumor rechallenge, indicating the effective immunization against tumors. Functional TLS formed in different tumor types and anatomical sites using this approach. Hybridoma clones developed from TLS-B cells of these tumors generated monoclonal IgG antibodies targeting mouse pancreatic cancer cells, which effectively induced NK cell-mediated cytotoxicity. In contrast, B cell-deficient CD79a KO mice failed to develop TLS while still being capable of developing high endothelial venules in primary tumors. T cell infiltration did not appear to be reduced by the B cell deficiency. However, these mice showed significantly reduced survival (40%) after tumor rechallenge, underscoring the importance of TLS-B cells for coordinated anti-tumor immune responses. These findings underscore the critical role of B cells in the development of functional TLS and strong anti-tumor immunity. The STING and LTβR agonist combination therapeutically induces TLS to produce tumor-specific high-affinity antibodies with significant tumor-killing potential. This approach highlights a promising strategy for targeting immune-cold tumors that are refractory to standard immunotherapies, paving the way for innovative immunotherapies that harness the power of B cells.
Citation Format: Maxwell Duah, Yasuhiro Kikuchi, Tomoko Stansel, Krisztian Csomos, Nobuyoshi Hiraoka, Jolan Walter, Carl F Ware, Masanobu Komatsu. Intratumoral B cells are essential for anti-tumor immune responses of tertiary lymphoid structures: Impact of STING and LTβR activation in pancreatic cancer [abstract]. In: Proceedings of the AACR IO Conference: Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2025 Feb 23-26; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(2 Suppl):Abstract nr PR001.