TABLE 1.

Studies on dysbiosis of gastric microbiome in gastric cancer.

Authors	Year	Sample size	Result
Aviles-Jimenez et al.	2014	•5 patients each with non-atrophic gastritis, intestinal metaplasia, and gastric cancer of the intestinal type	•Bacterial diversity steadily decreased from non-atrophic gastritis to intestinal metaplasia to gastric cancer •A significant microbiota difference was observed between non-atrophic gastritis and gastric cancer
Wang et al.	2016	•212 patients with chronic gastritis and 103 patients with gastric cancer	•The amount of bacteria in gastric mucosa was higher in Helicobacter pylori-infected patients compared with those uninfected •An increased bacterial load was detected in gastric cancer compared with chronic gastritis •Five genera of bacteria were enriched in gastric cancer. Including Lactobacillus, Escherichia–Shigella, Nitrospirae, Burkholderia fungorum, and Lachnospiraceae
Jo et al.	2016	•63 antral mucosal and 18 corpus mucosal samples	•The number of nitrosating or nitrate-reducing bacteria (NB) other than H. pylori (non-HP-NB) was two times higher in the cancer groups than in the control groups, but it did not reach statistical significance
Yu et al.	2017	•160 gastric cancer patients with 80 from China and 80 from Mexico	•Helicobacter pylori is the most abundant member of gastric microbiota in both Chinese and Mexican samples, followed by oral-associated bacteria
Castaño-Rodríguez et al.	2017	•12 patients with gastric cancer, 20 patients with functional dyspepsia	•Increased richness and phylogenetic diversity but not Shannon’s diversity was found in gastric cancer as compared to controls •Several bacterial taxa were enriched in gastric cancer, including Lactococcus, Veilonella, and Fusobacteriaceae
Hsieh et al.	2018	•9 patients with gastritis, 7 patients with intestinal metaplasia, 11 patients with gastric cancer	•The frequency and abundance of H. pylori were significantly lower in the cancer group •Clostridium, Fusobacterium, and Lactobacillus species were frequently abundant in patients with gastric cancer
Ferreira et al.	2018	•54 patients with gastric carcinoma and 81 patients with chronic gastritis	•The gastric carcinoma microbiota was characterized by reduced microbial diversity, by decreased abundance of Helicobacter and by the enrichment of other bacterial genera, mostly represented by intestinal commensals
Coker et al.	2018	•21 superficial gastritis, 23 atrophic gastritis, 17 intestinal metaplasia and 20 gastric cancer subjects	•Significant mucosa microbial dysbiosis was observed in intestinal metaplasia and gastric cancer subjects, with significant enrichment of 21 and depletion of 10 bacterial taxa in gastric cancer compared with superficial gastritis •Peptostreptococcus stomatis, Streptococcus anginosus, Parvimonas micra, Slackia exigua, and Dialister pneumosintes had significant centralities in the gastric cancer ecological network
Liu et al.	2019a	•276 gastric cancer patients without preoperative chemotherapy •230 normal, 247 peritumoral and 229 tumoral tissues	•H. pylori, Prevotella copri and Bacteroides uniformis were significantly decreased in tumoral microhabitat •Prevotella melaninogenica, Streptococcus anginosus, and Propionibacterium acnes were increased in tumoral microhabitat
Ling et al.	2019	•64 gastric cancer patients without preoperative chemotherapy •59 tumoral tissues, 61 peritumoral tissues, and 60 normal tissues	•The diversity, composition and function of gastric mucosal microbiota also changed more significantly in tumoral tissues than those in normal and peritumoral ones •Stenotrophomonas and Selenomonas were positively correlated with BDCA2 + pDCs and Foxp3 + Tregs, respectively •Comamonas and Gaiella were negatively correlated with BDCA2 + pDCs and Foxp3 + Tregs, respectively
Chen et al.	2019	•62 pairs of matched gastric cancer tissues and adjacent non-cancerous tissues	•Microbial richness and diversity were increased in cancerous tissues •The bacterial taxa enriched in the cancer samples were predominantly represented by oral bacteria (such as Peptostreptococcus, Streptococcus, and Fusobacterium), while lactic acid-producing bacteria (such as Lactococcus lactis and Lactobacillus brevis) were more abundant in adjacent non-tumor tissues
Gunathilake et al.	2019	•268 gastric cancer patients and 288 controls	•Helicobacter pylori, Propionibacterium acnes and Prevotella copri are strong risk factors, whereas Lactococcus lactis is a protective factor, for gastric cancer development in Koreans
Gantuya et al.	2020	•48 gastric cancer and 120 non-cancer patients (20 normal gastric mucosa, 20 gastritis, 40 with atrophy and 40 intestinal metaplasia)	•The highest overall bacterial alpha diversity metrics were observed in the control group, followed by the intestinal metaplasia and cancer groups. The gastritis and atrophy groups had the least diversity
Wang Z. et al.	2020	•30 healthy controls, 21 non-atrophic chronic gastritis, 27 gastric intestinal metaplasia, 25 intraepithelial neoplasia, and 29 gastric cancer patients	•The bacterial diversity reduced progressively from non-atrophic chronic gastritis, through intestinal metaplasia, intraepithelial neoplasia to gastric cancer
Wang L. et al.	2020	•60 patients with chronic gastritis, 30 with early gastric cancer, and 30 with advanced gastric cancer	•The results demonstrated significant differences in the microbial profile and composition between early gastric cancer and advanced gastric cancer
Ravegnini et al.	2020	•10 adenocarcinoma and 10 signet-ring cell carcinoma and their paired non-tumor counterparts	•Signet-ring cell carcinomas were significantly enriched in the phyla Fusobacteria, Bacteroidetes, Patescibacteria, whereas in the adenocarcinoma type, Proteobacteria and Acidobacteria phyla were found