Introduction -- Gut microbiome in health and diseases -- Microbiome in colorectal cancer -- Microbiome in gastric cancer -- Microbiome in liver cancer -- Virus, fungi and archaea in gastrointestinal cancer -- Microbial metabolomics in gastrointestinal cancer -- Diet and gut microbiome in gastrointestinal cancer -- Diet and gut microbiome in fatty liver and its associated liver cancer -- Host-microbiome interaction in gastrointestinal cancer -- Gut microbiome and immune responses in gastrointestinal cancer -- Animal models in the study of microbiome in gastrointestinal cancer -- High-throughput sequencing data analyses for microbiome profiling -- Gut microbiota modulation: probiotics and prebiotics in gastrointestinal cancer -- Roles of gut microbiota in efficacy of anticancer treatment of gastrointestinal cancer -- Targeting gut microbiota to treat gastrointestinal cancer.