Acylglycerol kinase inhibits macrophage anti-tumor activity via limiting mtDNA release and cGAS-STING-type I IFN response.

Abstract

Background: Tumor associated macrophages (TAMs) are critical components in regulating the immune statuses of the tumor microenvironments. Although TAM has been intensively studied, it is unclear how mitochondrial proteins such as AGK regulate the TAMs' function. Methods: We investigated the AGK function in TAMs using macrophage-specific Agk deficient mice with B16 and LLC syngeneic tumor models. Flow cytometry was used to evaluate the stemness and activation of CD8⁺ T cells. The enhanced release of mtDNA into the cytosol in the Agk-deficient BMDMs was measured by RT-PCR and immunofluorescence; the cGAS-STING-type I IFN pathway was evaluated by immunoblotting. Mitochondria functions were evaluated by electron microscope and seahorse equipment. Results: We have noted an increased expression of AGK in TAMs of multiple tumor types, which was negatively correlates with the tumor tissue immune scores. In the B16 and LLC tumor models, macrophage Agk-deficient mice have reduced tumor growth and enhanced populations of CD8⁺ Tpex. AGK-deficient macrophages have increased mitochondrial damage and mtDNA release into the cytosol, which leads to enhanced cGAS-STING-type I IFN activation. Blockade of the type I IFN signaling pathway with anti-IFNAR reversed the phenotype in Agk-deficient mice. Conclusions: Our findings define a critical role of AGK in maintaining the macrophage mitochondrial homeostasis that is associated with mtDNA release and following cGAS-STING activation and type I IFN pathway. Targeting AGK in TAMs may represent a novel strategy to enhance anti-tumoral activity.