CAR-Dependent Bile Acid Adaptation Programs CD8 T Cell Function in Liver Cancer 2310297

Abstract Introduction Bile acids are amphipathic molecules synthesized in pericentral hepatocytes derived from cholesterol that facilitate lipid digestion and absorption. In addition to their role in fat emulsification, bile acids act as signaling molecules that regulate numerous metabolic and immune processes through their interactions with nuclear receptors, including the farnesoid X receptor, pregnane X receptor, vitamin D receptor, and constitutive androstane receptor (CAR). These receptors orchestrate bile acid homeostasis, modulate inflammatory pathways, and influence immune cell function. While the role of each of these bile acid receptors has been extensively studied in hepatocytes, their role within immune cells, particularly in CD8 T cells, is understudied. He we demonstrate CAR deletion modulates CD8 T cell persistence and effector function in mouse models of hepatocellular carcinoma (HCC). Methods We delivered AAV8-TBG-Cre-U6-gRNA (Baat or scramble) to AST-Cas9 mice (Albumin-floxStop-SV40 large T antigen), to induce tumor while simultaneously knocking out BAAT enzyme in hepatocytes to perturb bile acid metabolism. Wild type or CAR deficient SV40-specific T cells we adoptively transferred 2 wks dpi and assessed at 5 wks dpi via flow cytometry and scRNAseq. CAR was overexpressed using retrovirus in in-vitro activated CD8s cultured in the presence of various bile acids and cytokine and assessed for its ability to modulate efflux of Rh123 Results In-vitro over-expression assays highlight a role for CAR and cytokine in the induction of bile acid efflux transporters. Adoptive transfer of CAR deficient tumor specific T cells highlights the role of CAR in T cell intrinsic adaptation to bile acid signaling in inflamed hepatic environments. Conclusion Our findings highlight a broader role for CAR in regulating immune cell adaptation to tissue-specific metabolic stress. Funding Source Principal investigator has institutional start-up funds Topic Categories Immune Response Regulation: Molecular Mechanisms (IRM)