These metabolite–immune axes have translational leverage in HCC: acetate/SCFAs and D-lactate findings support metabolite or microbiome-based adjuvants to sensitize the liver TME; [81, 192, 195] IPA enhances CD8 + T cell-mediated anti-PD-1 therapeutic response in multiple tumor types [107, 194]. This evidence concerns the gene PDCD1 and hepatocellular carcinoma.