• Investigating changes in the microbiota in the stages of gastric cancer progression and its impact on the prevention and treatment of the disease
  • sara nemati,1,*
    1. Department of Biology, East Tehran Branch, Islamic Azad University, Tehran, Iran


  • Introduction: Research on the human microbiome has increased in recent years, and researchers have investigated the role of the microbiome in the process of various diseases, including infectious diseases, types of cancer, respiratory diseases, metabolic diseases, and autoimmune diseases. Including gastrointestinal cancers, which in the past caused an important challenge for researchers due to the extremely acidic conditions of the stomach and the limitations of previous culture methods. But today, with the advent of new PCR techniques and metagenomics analyses, the research on stomach microbiota has increased in the last decade.
  • Methods: By searching the term" intitle: " microbiota " AND gastric cancer AND Helicobacter pylori " in the Google Scholar search engine. Numerous articles were reviewed and screened, and 9 articles were finally carefully investigated.
  • Results: Currently, the existence of a direct relationship between the diversity of gastric microbiota and cancer progression has not been conclusively proven, but from a mechanistic point of view, the change of microbiota diversity with the progression of gastric cancer is a logical hypothesis. Researchers have shown that sometimes even though the Helicobacter pylori serology test is positive, in more than 90% of patients with acute gastritis caused by Helicobacter and in most patients with advanced gastric cancer AG, IM9, this bacterium is not observed in the stomach tissue; This indicates the disappearance of active Helicobacter pylori infection in the later stages of gastric cancer development. Studies have shown that the primary infection of Helicobacter pylori leads to atrophic gastritis and an increase in the pH level of the stomach, which causes the colonization of new microbes and increases the diversity of species. Compared to people with functional dyspepsia, patients with gastric cancer have high Lactococcus and Lactobacillus genera levels. Bacteria of these two genera in gastric cancer patients with lactic acid secretion can be a source of energy for tumor growth and angiogenesis. In addition, the manipulation of the stomach microbiota, apart from the eradication of Helicobacter pylori, has the potential of a new treatment method that can also affect the risk of stomach cancer. Research shows that microbes from the Lachnospiracea family are often downregulated in inflammatory processes, so these microbes may regulate inflammation. The Nitrospirae group is present in all patients with gastric cancer but completely absent in patients with chronic gastritis. Several members of the Nitrospirae group are involved in the metabolism of nitrates and nitrites. It has been proven that the consumption of high-salt foods and improper eating habits increase the production of carcinogenic N-nitroso compounds by these bacteria. Propionibacterium acnes, which is a well-known skin flora, is also abundant in gastric tumor tissues, and the production of short-chain fatty acids by it may contribute to the development of lymphocytic gastritis. Reduction of the number of Sphingobium yanoikuyae in patients with gastric cancer compared to patients with It has been shown in research to surface gastritis. This species is able to break down aromatic hydrocarbons that have potential carcinogenic effects. The number of Rhizobiales has increased in patients with intestinal metaplasia compared to patients with chronic superficial gastritis. According to recent data, researchers have found that the genetic transfer of the T4SS secretory pathway between Helicobacter pylori and members of the microbiota, if it occurs, leads to Helicobacter pylori carcinogenesis. Helicobacter pylori, along with other bacteria, can increase stomach cancer. Also, the decrease in gastric acid production along with gastric atrophy following Helicobacter pylori infection may cause the overgrowth of permanent bacteria in addition to the colonization of lower intestinal bacteria. These results suggest that the microbiota may play a role in the development of gastric cancer following Helicobacter pylori infection, but a diverse microbiota may not necessarily be required for the development of gastric cancer.
  • Conclusion: Gastric cancer increase or decrease the microbiota. As a result, observing certain changes in the microbiota can be used as an alternative to monitoring the progress of the disease.
  • Keywords: gastric cancer, microbiota, Helicobacter pylori, bacteria