Table 2.

Specific microorganism or dysbiosis of microbiome in esophageal and gastric cancers

Specific microorganism or dysbiosis of the microbiome	Findings (References)
Esophageal cancer
Oral microbiome	Low microbial diversity in the oral cavity was associated with the presence of esophageal squamous cell carcinoma (Chen et al. 2015; Yu et al. 2014). High amount of Tannerella forsythia in the oral cavity was associated with the presence of esophageal adenocarcinoma (Peters et al. 2017).
Fusobacterium nucleatum	The amount of Fusobacterium nucleatum was higher in esophageal carcinoma tissue than in adjacent nontumor tissue. High amount of Fusobacterium nucleatum in esophageal carcinoma tissue was associated with shorter patient survival, and the amount of Fusobacterium nucleatum correlated with tumor expression of the chemokine CCL20, which has been shown to promote the accumulation of regulatory T cells (Yamamura et al. 2016).
Escherichia coli	High amount of Escherichia coli in esophageal tissue was associated with Barrett’s esophagus and esophageal adenocarcinoma (Zaidi et al. 2016).
Campylobacter concisus	High amount of Campylobacter concisus in esophageal tissue was associated with Barrett’s esophagus (Blackett et al. 2013).
Gastric cancer
Helicobacter pylori	The infection with Helicobacter pylori in gastric tissue is associated with increased risk of gastric cancer, and Helicobacter pylori is categorized as a class I carcinogen by the World Health Organization (Ajani et al. 2017).
Gastric mucosal microbiome	Microbial diversity decreased gradually from gastritis to intestinal metaplasia to gastric cancer (Aviles-Jimenez et al. 2014). Microbial diversity and the amount of Helicobacter were decreased in gastric cancer tissue, and oral microbes, including Parvimonas micra, Peptostreptococcus stomatis, and Fusobacterium nucleatum, were significantly increased in both cardia and non-cardia gastric cancer tissue (Coker et al. 2018; Ferreira et al. 2018; Liu et al. 2019). Low amount of Lactobacillales in gastric nontumor tissue was associated with metastatic gastric cardia adenocarcinoma (Yu et al. 2017).
Tongue-coating microbiome	High amount of Firmicutes and low amount of Bacteroidetes in the tongue coating microbiome were associated with gastric cancer (Wu et al. 2018).