Abstract
Commensal microbiota plays a critical role in the maintenance of human health. Microbes influence energy metabolism and nutrient absorption and help defend the host organism against pathogens. The composition of the gut microbiota is delicately balanced, and any alterations may lead to proinflammatory immune responses and initiation of disease processes, including cancer. Experimental evidence indicates that the human intestinal microbiota can influence tumour development and progression in the gastrointestinal tract by damaging DNA, activation of oncogenic signaling pathways, production of tumour-promoting metabolites, and suppression of the anti-tumour immune response. The aim of this article was to outline differences in human microbiota between healthy subjects and patients with gastrointestinal malignancies such as esophageal, stomach, liver, biliary tract, pancreas and colon inflammations, and cancers. A better understanding of microbiota changes in various gastrointestinal malignancies will enable a greater insight into the relationship between human microbiota composition and cancer development.
Highlights
The human microbiota is composed of bacteria, archaea, viruses, and eukaryotic microbes that reside in and on our bodies
Studies reveal that impairments in the innate immune system promote the outgrowth of Proteobacteria, and that increases in the Proteobacteria number enhance the immune response in the host gut, leading to colitis development [57,58]
Commensal microbiota is believed to have a beneficial influence on human health; numbers of studies aim to demonstrate if changes in gut microbiota contribute to the pathogenesis of gastrointestinal malignancies
Summary
The human microbiota is composed of bacteria, archaea, viruses, and eukaryotic microbes that reside in and on our bodies. Changes in microbiota composition may contribute to aberrant proinflammatory immune responses, susceptibility to invading pathogens, and initiation of disease processes, including cancer. Changes in gut microbiota could contribute to the pathogenesis of gastrointestinal cancers [1]. Gastrointestinal cancers such as those of the esophagus, stomach, liver, biliary tract pancreas, and colon account for one-third of total cancer incidence and mortality in developing countries. The growing prevalence of obesity in most regions of the world, as well as alcohol overuse and smoking, are known key agents that increase the incidence of gastrointestinal cancers, as well as gut hormones and nonalcoholic fatty liver disease (NAFLD). Experimental evidence indicates that the human intestinal microbiota can influence tumour development and progression in. Sci. 2020, 10, 585 the gastrointestinal tract by damaging DNA, activating oncogenic signaling pathways, initiating the production of tumour-promoting metabolites, and suppressing the antitumor immune response [2,3]
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