Metabolic and functional pathways of gut microbiota in patients with gastric cancer.

We analysed the differences in bacterial composition between 475 Japanese patients with advanced gastric cancer (median age, 70 years; median BMI 20.0) and 106 healthy individuals using a comprehensive metagenome shotgun analysis. Among the patients with advanced gastric cancer, 71% were male, 37% had relapsed, and 55.5% previously underwent gastrectomy. Bifidobacterium, Anaerostipes, and Parabacteroides were predominant in healthy individuals, whereas Streptococcus, Lactobacillus, and Odoribacter were predominant in patients with advanced gastric cancer. Additionally, Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that butanoate and pyruvate metabolism was enriched in healthy individuals, whereas factors, such as ABC transporters and ribosomes, were enriched in patients with advanced gastric cancer. Cluster analysis broadly classified patients with advanced gastric cancer and healthy individuals into two clusters; however, clustering using pathway data more clearly classified patients with advanced gastric cancer and healthy individuals than clustering using flora analysis. Moreover, healthy individuals showed higher bacterial flora diversity than those with advanced gastric cancer. Although the dataset we used was limited and may be difficult to generalise, we identified some molecular characteristics and functional pathways of the microbial genera within the intestines of patients with advanced gastric cancer.