A research team led by the Department of Clinical Oncology, Centre of Cancer Medicine, School of Clinical Medicine, LKS Faculty of Medicine, the University of Hong Kong (HKUMed), has identified a critical factor contributing to the failure of liver cancer immunotherapy. The study discovered that the gut bacterium Phocaeicola vulgatus can disrupt the immune system, leading to resistance to immunotherapy in some liver cancer patients. This research reveals the significant impact of gut microbiota on cancer treatment, and proposes ‘microbiome modulation therapy’, which involves modifying gut microecology or supplementing with key metabolites to enhance the effectiveness of liver cancer immunotherapy. The findings, published in the international journal Cell Reports Medicine, offer a novel direction for improving immunotherapy efficacy.