NG25 Enhances Anti-Tumor Immunity in KRAS-Mutant Colorectal Cancer

Purpose: The poor prognosis of KRAS -mutant colorectal cancer is attributed to its immunosuppressive tumor microenvironment and the lack of effective targeted therapies. Transforming growth factor-β-activated kinase 1 (TAK1), serving as a critical upstream regulator of both the NF-κB and MAPK signaling pathways, promotes tumor progression through its aberrant activation. In this study, we aimed to investigate the anti-tumor and immunomodulatory effects of the TAK1 inhibitor NG25 in KRAS -mutant colorectal cancer, focusing on its impact on T cell differentiation, PD-L1 expression, and tumor immune microenvironment remodeling. Methods: The anti-tumor and immune-enhancing effects of NG25 were evaluated through an in vitro tumor cell-lymphocyte co-culture system, and the orthotopic colorectal cancer models in both immunodeficient Balb/c nude mice and immunocompetent Balb/c mice. Results: NG25 significantly suppressed the tumor progression in immunocompetent Balb/c mice, while concurrently increasing the spleen and thymus indices and promoting the proliferation of T and B lymphocytes. In tumor microenvironment, NG25 treatment could promote CD8⁺ T cell infiltration and increase the proportion of CD3⁺CD8⁺ T cell subsets. Mechanistic studies revealed that NG25 downregulates PD-L1 expression on both KRAS -mutant tumor cells and T cells through inhibiting TAK1/NF-κB axis. However, this regulatory effect was absent in KRAS wild-type tumor cells. Conclusion: NG25 blocks the NF-κB signaling pathway by targeting TAK1, remodels the immunosuppressive microenvironment of KRAS -mutated colorectal cancer, reduces PD-1 expression and enhances the anti-tumor effect of CD8⁺ T cells. This study provides a theoretical basis for TAK1-targeted therapy and offers a new strategy for immunotherapy of KRAS -mutated colorectal cancer. Keywords: NG25, tumor immunosuppression, KRAS mutation, colorectal cancer