Bile acids in cancer: From metabolism to immunomodulation

Bile acids have emerged as compartmentalized immunometabolic signals that link host metabolism, microbial ecology, and tumor immunity. Altered bile acid profiles are common across malignancies and are associated with tumor progression, immune tone, and responsiveness to immunotherapy. Bile acids shape the gut microbiota, and in turn, microbial enzymes diversify the bile acid pool, generating distinct bile acid species that can remodel the tumor immune landscape. Depending on species identity, concentration, and context, bile acids can support immune surveillance or enforce immune escape by reshaping antigen priming, lymphocyte fitness, myeloid suppression, and immune cell trafficking. Here, we synthesize emerging concepts defining a microbiome-bile acid-immune axis in cancer and highlight therapeutic opportunities to harness bile acid signaling as next-generation strategies in oncology.