Inhibition of DHODH Activates Pyroptosis and cGAS-STING Pathways to Enhance NK cell Infiltration Mediated Anti-tumor Immunity in Melanoma

Cancer cells are heavily reliant on de novo pyrimidine synthesis. Suppression of pyrimidine metabolism directly inhibits tumor growth and fosters immune activation within the tumor microenvironment. Dihydroorotate dehydrogenase (DHODH), a crucial enzyme governing de novo pyrimidine synthesis, is a critical player in this context. Inhibition of DHODH not only reverses immunosuppression but also instigates a mild innate immune response. However, the impact of DHODH inhibition on natural killer (NK) cells remains unexplored. In this study, we found that inhibition of DHODH efficiently promotes NK cells infiltration in tumors. Suppression of DHODH led to increased oxidative stress in mitochondria, the release of mtDNA, and activation of caspase 3, which in turn activated the cGAS-STING pathway and pyroptosis in cancer cells, respectively, contributing to NK cells induced antitumor immune responses in melanoma. Additionally, we developed EA6, a novel DHODH inhibitor with higher efficacy in promoting NK cells infiltration. In summary, this study underscores that modulation of pyrimidine metabolism can effectively trigger antitumor immune responses, with a specific emphasis on NK cells. This finding opens new avenues for enhancing the efficacy of targeted nucleotide metabolism in cancer therapy. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/644471v1_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@88d4fcorg.highwire.dtl.DTLVardef@156fe1aorg.highwire.dtl.DTLVardef@448086org.highwire.dtl.DTLVardef@152079c_HPS_FORMAT_FIGEXP M_FIG C_FIG The anti-tumor mechanisms of DHODH inhibition. Inhibition of DHODH activates cGAS-STING pathways to enhance NK cell infiltration. And the tumor-infiltrating NK cells facilitate melanoma cells pyroptosis which providing a positive feedback mechanism for DHODH-mediated anti-tumor immunity.