Bacterial overgrowth and diversification of microbiota in gastric cancer

Abstract

ObjectiveMicrobiota is potentially linked to the development of cancer. However, the features of microbiota in gastric cancer remain unclear. The aim of this study was to characterize the gastric microbiota in cancer.MethodsA total of 315 patients, including 212 patients with chronic gastritis and 103 patients with gastric cancer, were enrolled in the study. The bacterial load of gastric mucosa was determined using quantitative PCR. To analyze the biodiversity, structure, and composition of microbiota, amplicons of the 16S rRNA gene from 12 patients were pyrosequenced. The sequences were processed and subsequently analyzed.ResultsThe amount of bacteria in gastric mucosa was estimated to be 6.9×108 per gram tissue on average. It was higher in Helicobacter pylori-infected patients (7.80±0.71) compared with those uninfected (7.59±0.57, P=0.005). An increased bacterial load up to 7.85±0.70 was detected in gastric cancer compared with chronic gastritis (P=0.001). The unweighted principal coordinate analysis showed that the structure of microbiota in gastric cancer was more diversified. Five genera of bacteria with potential cancer-promoting activities were enriched in gastric cancer. The weighted principal coordinate analysis showed that the presence of Helicobacter pylori markedly altered the structure of microbiota, but had little influence on the relative proportions of the other members in the microbiota.ConclusionFindings from this study indicated an altered microbiota in gastric cancer with increased quantity of bacteria, diversified microbial communities, and enrichment of bacteria with potential cancer-promoting activities. These alterations could contribute toward the gastric carcinogenesis.

Gastric microbiota features associated with cancer risk factors and clinical outcomes: A pilot study in gastric cardia cancer patients from Shanxi, China

“…This expectation is contradictory to our finding that Hp relative abundance was higher in cases with more advanced disease ( i.e ., higher tumor grade). Consistent with our findings, a recent study of 212 patients with chronic gastritis and 103 GCA cases in China evaluated using quantitative PCR showed that bacterial load in the gastric mucosa was higher in cancer cases than in patients with gastritis, and that the bacterial load correlated positively with the absolute quantity of Hp ( R = 0.38, p < 0.001) . This observation is consistent with a potential role for Hp in tumor progression.…”

Findings in exudates can help distinguish benign gastric ulcers from ulcerated adenocarcinomas

“…Although they found no differences in bacterial load and severity of mucosal inflammation, they noted that patients with gastric cancer harboured a significantly increased bacterial load as compared with patients who had chronic gastritis alone, in agreement with our observations. Cancers were also associated with a more diverse microbiota, including Proteobacteria , Firmicutes , Bacteroides , Fusobacteria , and Actinobacteria . These findings and those of other studies confirm frequent bacterial colonisation of the stomach in patients with mucosal atrophy and hypochlorhydria, and support the hypothesis that bacterial overgrowth may contribute to the development of gastric carcinoma …”

Interaction of Helicobacter Pylori with Other Microbiota Species in the Development of Gastric Cancer

“…Andersson et al showed that the stomach displayed a diverse microbiota composition when H. pylori is absent or insignificant whereas samples positive for H.pylori were predominated by this bacterium [8]. It was higher in H. pylori -infected patients compared with those uninfected individuals (P=0.005) [9]. The unweighted principal coordinate analysis showed that the communities of microbiota in gastric cancer were more diversified.…”

“…Five genera of bacteria with potential carcinogic activities were enriched in patients with gastric cancer, including Lactobacillus, Escherichia-Shigella, Nitrospirae, Burkholderia fungorum, and unculturable Lachnospiraceae species. Of particular interest, Nitrospirae was present in all patients with gastric cancer but absent in patients with chronic gastritis [9].…”