Could a dysbiosis in the gastric microbiota be the source of stomach cancer?
A team of researchers may have established a connection between dysbiosis in the gastric microbiota and the onset of certain stomach cancers.
There is a clear correlation between Helicobacter pylori infection and gastric adenocarcinoma. Helicobacter pylori causes chronic inflammation of the gastric mucosa (gastritis), which can lead to carcinogenesis. However, it seems that some cancers are not related to Helicobacter pylori infection.
These results were provided by a team of Portuguese researchers, who studied and characterized the gastric bacterial flora of 54 patients with stomach cancer and then compared it to that of 81 people with chronic gastritis. The composition of the gastric microbiotas is different in the two types of patients. Patients with adenocarcinoma present gastric dysbiosis characterized by a reduction in microbial diversity, increased number of Proteobacteria, Lactobacillus, Clostridium, and Rhodococcus and a lower proportion of H. pylori. This imbalance leads to an increase in enzymatic activity by nitrite reductases and nitrate reductases, which metabolize nitrogen by producing carcinogenic nitrogen compounds.
This discovery is the first to prove that potentially genotoxic gastric dysbiosis associated with stomach cancer differs from the dysbiosis observed in chronic gastritis. This provides new elements to directly implicate the gastric microbiota in the onset of stomach cancer, which is responsible for a million new cases each year around the world.
Ferreira RM et al. Gastric microbial community profiling reveals a dysbiotic cancer-associated microbiota. Gut. 2017 Nov 4. pii: gutjnl-2017-314205. https://www.ncbi.nlm.nih.gov/pubmed/29102920