AKR1D1 suppresses liver cancer progression by promoting bile acid metabolism-mediated NK cell cytotoxicity

Bile acid metabolism and antitumor immunity are both disrupted during liver cancer progression. However, the complex regulatory relationship between them remains largely unclear. Here, we find that loss of aldo-keto reductase 1D1 (AKR1D1) promotes the accumulation of isolithocholic acid (iso-LCA) through gut microbiome dysregulation, thereby impairing the cytotoxic function of natural killer (NK) cells and leading to the accelerated development of hepatocellular carcinoma (HCC). Mechanistically, AKR1D1 deficiency leads to an increased proportion of Bacteroidetes ovatus (B. ovatus), which breaks down chenodeoxycholic acid (CDCA) into iso-LCA. Moreover, accumulated iso-LCA impairs the antitumor activity of hepatic NK cells in a phosphorylated-CREB1 (p-CREB1)-dependent manner. The potassium-sparing diuretic spironolactone treatment significantly enhances the inhibitory effect of anti-PD1 antibody on HCC progression by targeting iso-LCA-mediated tumor immune escape. Taken together, our results uncover a previously unappreciated link between AKR1D1 and HCC and suggest that targeting iso-LCA produced by B. ovatus might be a promising strategy to activate NK cell cytotoxicity to treat HCC.