Development of succinate dehydrogenase subunit B-deficient tumor models for preclinical immunotherapy testing.

Immunotherapy has advanced the treatment landscape for many challenging cancers by harnessing the immune system to eliminate tumor cells. However, its efficacy in rare tumors such as pheochromocytoma and paraganglioma (PCC/PGL), particularly those with succinate dehydrogenase B (SDHB) mutations, remains underexplored. These tumors often exhibit complex tumor microenvironments and immune evasion mechanisms, and their low incidence hinders clinical trials development. Together, these challenges underscore the need for robust preclinical models that closely mirror human disease and support therapeutic discovery. In this study, we developed and characterized murine models of SDHB-deficient tumors using CRISPR-mediated gene editing in pheochromocytoma (MPC and MTT) and renal carcinoma (RenCa) cell lines. These models recapitulate key metabolic and immunological features of human SDHB-mutated tumors, which exhibit loss of SDHB protein expression, providing a relevant platform for evaluating immunotherapeutic strategies. We subsequently tested intratumoral immunotherapy with Mannan-BAM, TLR ligands, and an Anti-CD40 antibody (MBTA), a combination designed to overcome tumor-induced immune suppression. Our results indicate that SDHB-deficient PCC tumors exhibit increased antigen presentation and strong immune activation, leading to rejection or delayed progression in immunocompetent mice. In contrast, Sdhb knock-out RenCa tumors consistently formed, allowing therapeutic testing. MBTA therapy effectively eradicated these tumors, prevented metastasis, and induced long-term immune memory. These findings highlight the value of genetically engineered, tissue-specific murine models in predicting immunotherapy outcomes in rare cancers. Moreover, they support the therapeutic potential of MBTA for treating SDHB-deficient renal cell carcinoma and provide a rationale for further translational studies.