The composition and functional profile of the microbial communities in human gastric cancer tissues and adjacent normal tissues

Helicobacter pylori (H. pylori) is known to be a major risk factor for the development of gastric cancer. In recent years, increasing attention is being paid to the role of non-H. pylori Helicobacters (NHPHs) in this disease and the role of microorganisms in local tumor microenvironment. In this study, we aimed to compare the microbial community composition and the predicted functional profile in paired cancer and adjacent normal tissues of gastric cancer patients. Cancer tissues and adjacent normal tissues were collected from 10 patients with gastric cancer under endoscopy, and genomic DNA was extracted. The V3-V4 region of the 16S rRNA gene was amplified by PCR and paired-end sequencing was performed on the Illumina MiSeq System. The data was analyzed using QIIME 2 software. The results showed that microbial richness and diversity as well as genetic diversity are significantly lower in cancer tissues compared with adjacent normal tissues. At the phylum level, the dominant taxa are Pro-teobacteria, Thermi, Actinobacteria, Bacteroidetes and Firmicutes in both groups. At the genus level, some taxa, such as Cupriavidus and Sphingomonas, are significantly enriched in cancer tissues, while other taxa, such as Ochrobactrum, are enriched in adjacent normal tissues. Moreover, those taxa enriched in cancer tissues are associated with the synthesis and degradation of ketone bodies. In conclusion, there is a significant difference in the composition of the mucosa-related microbial communities between cancer tissues and adjacent normal tissues in patients with gastric cancer.