Abstract 3211: A multiple blockade of PD-L1/TIGIT/TIM3 to enhance the therapeutic efficacy on B-cell lymphomas

Abstract Hodgkin lymphoma exhibits high PD-L1 expression and responds well to PD-1 blocking antibodies. In contrast, most non-Hodgkin lymphomas express multiple checkpoints, reducing their sensitivity to PD-1/PD-L1 blockade. These findings highlight the complexity of immune evasion mechanisms and the potential of combinatorial therapeutic approaches in lymphoma. We established cell lines overexpressing murine CD155 and luciferase using lentivirus to measure tumor growth in mouse models of B cell lymphoma. All experimental procedures were approved by the Institutional Animal Care and Use Committee of Seoul National University Hospital (protocol 22-0333-S1A0). Female Balb/c mice (7-10 weeks old) were used, sourced from Koatech. For A20 tumor models, 5×106 cells were injected intraperitoneally. Mice received isotype control or specific blocking antibodies (anti-PD-L1, TIGIT, TIM3) three times per week. Tumor growth was monitored weekly via luminescence. After four weeks, spleen and lymph nodes were collected for lymphocyte analysis. Data acquisition was performed using a BD Symphony A3 flow cytometer, and analysis was conducted with FlowJo V10 software. We compared intraperitoneal versus intravenous injection of several different cell doses of hCD20-mCD155-A20 cells to optimize the lymphoma murine model. Intraperitoneal injection of 5x106 cells was determined as the optimal dose, showing stable tumor growth for experimental analyses. Anti-PD-L1 and anti-TIGIT antibodies significantly inhibited tumor progression, whereas anti-TIM3 antibody promoted tumor growth. Mechanistic studies revealed that anti-PD-L1 antibody restored CD4+FoxP3- and CD8+ T cell populations and reduced Treg cells, modulating PD-1 expression differentially across immune subsets. Anti-TIGIT antibody increased the CD226/TIGIT ratio in splenic cells. Interestingly, treatment with anti-PD-L1 antibodies significantly increased the expression of both PD-1 and TIGIT on Tregs. Furthermore, the application of an anti-TIGIT blocking antibody decreased PD-1 expression on CD4+FoxP3- T cells, while concurrently enhancing PD-1 expression on CD8+ T cells. Immune checkpoint molecules on Tregs appear to be less affected compared to those on other immune cell populations. Conversely, anti-TIM3 antibody decreased effector T cells while increasing Tregs and PMN-MDSCs, fostering an immunosuppressive microenvironment. Our findings showed the distinct immunological effects of these checkpoint inhibitors, offering insights into their therapeutic potential and limitations in B cell lymphoma models. This research was a collaborative effort made possible through support from F. Hoffmann-La Roche for the imCORE Network. Citation Format: Jihyun Park, Seojeong Kim, Youngil Koh, Byung-Su Kim, Sung-Soo Yoon. A multiple blockade of PD-L1/TIGIT/TIM3 to enhance the therapeutic efficacy on B-cell lymphomas [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 3211.