title: Effect of Helicobacter pylori Infection on the Composition of Gastric Microbiota in the Development of Gastric Cancer.
abstract: BACKGROUND
  Gastric cancer is one of the most common cancer types worldwide. In China, gastric cancer has become one of the major threats for public health, ranking second on incidence and third on cause of cancer death. Despite the common risk factors that promote the development of gastric cancer, the huge quantity of microorganism colonies within the gastrointestinal tract, particularly Helicobacter pylori infection, demonstrates a correlation with chronic inflammation and gastric carcinogenesis, as epidemiological studies have determined that H. pylori infection confers approximately 75% of the attributable risk for gastric cancer.
  
  
  CONCLUSIONS
  The current article draws an overview on the correlation between the microbiota, inflammation and gastric tumorigenesis. H. pylori infection has been identified as the main risk factor as it triggers epithelial barrier disruption, survival signaling as well as genetic/epigenetic modulation. Apart from H. pylori, the existence of a diverse and complex composition of microbiota in the stomach has been identified, which supports a role of microbiota in the development of gastric cancer. Moreover, metagenomics studies focused on the composition and function of the microbiota have associated microbiota with gastric metabolic diseases and even tumorigenesis. Apart from the gastric microbiota, inflammation is another identified contributor to cancer development as well.
  
  
  CONCLUSIONS
  Though H. pylori infection and the non-H. pylori microbiota play a role in gastric cancer, the properties of gastric microbiota and mechanisms by which they participate in the genesis of gastric cancer are still not clearly depicted. Moreover, it remains to be understood how the presence of microbiota along with H. pylori infection affects the progress from gastric disease to cancer.
  
  
  CONCLUSIONS
  This article summarized a clue of the current studies on microbiota, H. pylori infection and the progression from gastric disease to cancer.
authors.affiliation: Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK-Shenzhen Research Institute, The Chinese University of Hong Kong, Shatin, Hong Kong, SAR, China.
authors.forename: Le
authors.initials: L
authors.lastname: Cao
authors.affiliation: Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK-Shenzhen Research Institute, The Chinese University of Hong Kong, Shatin, Hong Kong, SAR, China.
authors.forename: Ju
authors.initials: J
authors.lastname: Yu
keywords: Gastric carcinogenesis; Gastric microbiota; Helicobacter pylori