The gastric microbiome, its interaction with Helicobacter pylori, and its potential role in the progression to stomach cancer

Advances in sequencing technology have greatly enhanced the ability of scientists to identify additional microbial species that may be potentially associated with various disease states, such as cancer, although establishing cause versus effect presents multiple challenges. [...]understanding how dysbiosis impacts aberrant host inflammatory responses and downstream carcinogenic cascades will be critical to accurately define the role of niche-specific microbiota in oncogenesis. [...]it has been well established that, in a subset of persons, infection with H. pylori leads to achlorhydria and decreased acid secretion. [...]long-term H. pylori colonization and neutralization of the gastric environment may directly contribute to alterations in the gastric microbiota. [...]infection with H. pylori leads to achlorhydria of the stomach in a subset of colonized persons; thus, long-term H. pylori colonization and neutralization of the gastric environment may directly contribute to alterations in the gastric microbiota. Since the gastric microbiota is more austere in terms of microbial breadth and depth compared to the intestinal microbiota, future studies should focus on assessing whether the composition of the gastric microbiome in different anatomical regions of the stomach exerts differential effects on cancer risk. Details regarding patient populations, including age, gender, diet, and other comorbidities need to be assessed and compared in a rigorous fashion to discern whether any of these variables affect the potential for the gastric microbiome to influence disease. Since studies of the gastric microbiota have largely focused on bacterial communities, more in depth studies elucidating effects of other microorganisms that potentially populate the stomach in addition to bacteria, including fungi, protists, archaea, and viruses, are needed to fully characterize the gastric microbiome and its relationship with cancer risk.