Mucosa-Associated Microbiota in Gastric Cancer Tissues Compared With Non-cancer Tissues

Abstract

The link between microbiota and gastric cancer (GC) has attracted widespread attention. However, the phylogenetic profiles of niche-specific microbiota in the tumor microenvironment is still unclear. Here, mucosa-associated microorganisms from 62 pairs of matched GC tissues and adjacent non-cancerous tissues were characterized by 16S rRNA gene sequencing. Functional profiles of the microbiota were predicted using PICRUSt, and a co-occurrence network was constructed to analyze interactions among gastric microbiota. Results demonstrated that mucosa-associated microbiota from cancerous and non-cancerous tissues established micro-ecological systems that differed in composition, structure, interaction networks, and functions. Microbial richness and diversity were increased in cancerous tissues, with the co-occurrence network exhibiting greater complexity compared with that in non-cancerous tissue. 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. Colonization by Helicobacter pylori , which is a GC risk factor, also impacted the structure of the microbiota. Enhanced bacterial purine metabolism, carbohydrate metabolism and denitrification functions were predicted in the cancer associated microbial communities, which was consistent with the increased energy metabolism and concentration of nitrogen-containing compounds in the tumor microenvironment. Furthermore, the microbial co-occurrence networks in cancerous and non-cancerous tissues of GC patients were described for the first time. And differential taxa and functions between the two groups were identified. Changes in the abundance of certain bacterial taxa, especially oral microbiota, may play a role in the maintenance of the local microenvironment, which is associated with the development or progression of GC.

Alterations in Gastric Microbial Communities are Associated with Risk of Gastric Cancer in a Korean Population: A Case-Control Study

“…Interestingly, richness was signi cantly higher in GC cases in the current study population. A similar nding has been reported in the study compared cancer tissues with non-cancer tissues where there is a high microbial richness in GC tissues [21]. Moreover, we observed that there was a higher Shannon index in the controls than the GC group.…”

“…A study focused on the relationship between gastric dysbiosis and GC development found that there is an increased richness although the Shannon index is lower in the GC group compared to controls which is similar to our ndings [43]. On the contrary, a study conducted on microbiota in gastric mucosa in the GC tissues compared with the non-cancer tissues revealed that there is a signi cantly higher Shannon index in the cancer group compared with the healthy controls [21]. A study reported that 75.86% was captured by the rst two principal coordinates in the PCoA beta diversity plot according to the weighted UniFrac phylogenetic distance measure.…”

“…In addition, some of recent epidemiological studies have suggested the involvement of gastric microbiome in GC occurrence by the induction of chronic in ammation or down regulation of host immunity [17][18][19][20][21][22][23].…”

Microbiota Alterations in Gastrointestinal Cancers

“…It is known that microbiota-related analyses are able to give only a short overview owing to differences in mouse and human gastric tract structure and metabolism, among others. The gastric microbiota of GC patients was shown to be enriched in nitrosating bacteria; such nitrate-reducing activity increases the intragastric concentrations of nitrite and N-nitroso compounds, which have been reported to increase the risk of GC development [51,52].…”

“…Treponema denticola, Streptococcus mitis, Streptococcus anginosus [18] Fusobacterium nucleatum [3] Porphyromonas, Fusobacterium nucleatum [30] Gastric cancer Proteobacteria (Xanthomonadaceae and Enterobacteriaceae, as well as genera such as Citrobacter, Phyllobacterium and Achromobacte), Firmicutes (Lactobacillus, Clostridium), Bacteroidetes, Actinobacteria (Rhodococcus) and Fusobacteria [44,49,50] oral bacteria (Peptostreptococcus, Streptococcus, and Fusobacterium) [52] bacteria harbouring nitrosating enzymes [51,52] Pancreatic cancer…”