Alterations in Gastric Mucosal Microbiota in Gastric Carcinogenesis: A Systematic Review and Meta-Analysis

Abstract

Background: The gastric microbiota profile alters during gastric carcinogenesis. We aimed to identify the alterations in the alpha diversity and relative abundance of bacterial phyla and genera of gastric microbiota in the development of gastric cancer (GC).Methods: The systematic review was performed based on a published protocol with the registration number CRD42020206973. We searched through PubMed, EMBASE and Cochrane databases, as well as conference proceedings and references of review articles (May 2021) for observational studies reporting either the relative abundance of bacterial phyla or genera, or alpha diversity indexes in both GC and non-cancer groups. Selection of studies and data extraction were performed independently by two researchers, with disagreements resolved through discussion. Risk of bias was assessed using the self-modified Newcastle-Ottawa Scale. Results of random-effects meta-analyses were presented as mean differences (MD).Results: Our systematic review included 751 GC patients and 792 non-cancer patients from 14 case-control studies. Gastric cancer group had fewer operational taxonomic units (OTUs) (MD = −68.52, 95%CI: −126.65 to −10.39) and a lower Simpson index (MD = −0.13, 95%CI: −0.20 to −0.07) compared with non-cancer group. At the phylum level, gastric cancer group had a higher abundance of Firmicutes (MD = 7.11, 95%CI: 1.76 to 12.46). At the genus level, Streptococcus (MD = 3.03, 95%CI: 0.07 to 6.00) and Lactobacillus (MD = 5.15, 95%CI: 1.27 to 9.04) were found to be enriched in GCgroup. The relative abundance of the rest bacterial phyla or genera analyzed in our study did not significantly differ between two groups. Subgroup analyses indicated that the source of samples was the major source of interstudy heterogeneity.Conclusion: This systematic review suggested that gastric microbiota dysbiosis occurred in gastric carcinogenesis, with alpha diversity declined and microbiota composition altered.

Gastric microbiota in gastric cancer: Different roles of Helicobacter pylori and other microbes

“…In recent years, the characterization of the gastric microbiota associated with GC has been identified, indicating that gastric microbiota dysbiosis occur in gastric carcinogenesis ( Yang et al., 2021 ). In the year of 2009, the team of Prof. Engstrand compared the gastric microbiota of patients with GC and controls using the terminal restriction fragment length polymorphism (T-RFLP) and 16S rRNA gene cloning and sequencing.…”

Gastric microbiota in gastric cancer and precancerous stages: Mechanisms of carcinogenesis and clinical value

“…Lactic acid bacteria (LAB) such as Streptococcus , Lactobacillus , Bifidobacterium and Lactococcus members are also enriched in GC 5,69 . They can supply exogenous lactate.…”

“…67,68 Lactic acid bacteria (LAB) such as Streptococcus, Lactobacillus, Bifidobacterium and Lactococcus members are also enriched in GC. 5,69 TA B L E 1 (Continued) can be very harmful in the context of cancer. Lactate provides malignant cells with a fuel source to support their accelerated growth and can activate hypoxia-inducible factor-1 to induce epithelialmesenchymal transition.…”

Exploring the Microbiome in Gastric Cancer: Assessing Potential Implications and Contextualizing Microorganisms beyond H. pylori and Epstein-Barr Virus

“…In addition to richness, GC patients have increased diversity in their gastric microbiota [55]. At the phylum level, Firmicutes are significantly higher in GC patients [56]. In terms of genera, some genera of bacteria are enriched in GC patients, while others show a decrease.…”