IDDF2024-ABS-0426 Targeting oncometabolite arachidonic acid empowers CD8+ T cell residency via rebuilding its metabolic fitness in HCC

<h3>Background</h3> The reprogramming of lipid metabolism is identified as correlated with immune suppression in hepatocellular carcinoma (HCC). The lipid metabolic barriers established in the HCC microenvironment limit CD8⁺ T cell infiltration and impair its anti-tumor immunity. It is urgent to explore the underlying mechanisms and develop novel therapeutic targets, shifting tumors from ‘cold’ to ‘hot.’ <h3>Methods</h3> First, we utilized the CRIPSR-Cas9 library targeting over 3000 metabolic genes transfected into naive P14 CD8⁺ T cells to screen the disadvantageous metabolic pathways in the chronic LCMV infection model <i>in vivo</i>. Next, the seahorse assay was performed to monitor the mitochondrial function of CD8⁺ T cells using the mito stress test. The potential interplay among the indicated rate-limiting enzyme, lipid metabolites, and screened metabolic pathways was identified and validated in clinical cohorts from the Queen Mary Hospital. Finally, the therapeutic effects of targeting the above elements were evaluated in a patient-derived orthotopic xenograft (PDOX) HCC model. <h3>Results</h3> Based on CRISPR screening, we found the arachidonic acid (ARA) metabolism to be the disadvantageous metabolic pathway that impairs the formation of liver-resident memory CD8⁺ T cells (T_RM with CXCR6⁺CD69⁺ phenotype), as shown in Figure 1 (IDDF2024-ABS-0426 Figure 1). Functionally, supplemented with ARA, it was harmful to the metabolic fitness and function (the secretion of IFNγ and TNFα) of T_RM isolated from tumor tissue ex vivo in a dose-dependent manner (IDDF2024-ABS-0426 Figure 2). Clinically, the accumulated ARA controlled by rate-limit enzyme fatty acid desaturase 1 (FADS1) was significantly associated with low infiltration of T_RM (IDDF2024-ABS-0426 Figure 3). Therapeutically, targeting the inhibition of FADS1 activity reducing the ARA accumulation in the HCC microenvironment by using D5D-IN-326 significantly increased the efficacy of GPC3-CAR-T cell in the PDOX HCC model with advanced stage (IDDF2024-ABS-0426 Figure 4). <h3>Conclusions</h3> We identified the role of the FADS1-ARA metabolism axis mediating the crosstalk between lipid oncometabolite and T-cell metabolism. Decreasing ARA accumulation could be a novel metabolic engineering approach to increase CD8⁺ T cell residency and immunotherapy accessibility in a translational application for HCC patients.