The microbiome has been suggested to play a role in the development of several types of cancer. The alteration of gastric microbiota has been hypothesized to contribute to an increased incidence of esophageal cancer. Some studies have shown that those with Barrett’s esophagus is associated with a different esophageal microbiota than an individual with a healthy esophagus.

Stomach cancer may be influenced by the microbiota by initiating an inflammatory response. This is due to the bacteria Helicobacter pylori, which is considered a type 1A carcinogen by the World Health Organization. Experimental studies now have show that there are interrelationships between H. pylori and other gastric bacteria. Usually, with the inflammatory cascade in the stomach, the patient will not develop cancer because the H. pylori bacterium is absent. However, with a reduction of normal stomach bacteria, H. pylori population can increase, lending to a greater chance of developing stomach cancer.

Usually, multiple genetic and epigenetic events lead to the pathogenesis of colorectal cancer. The mutations and genes that lead to colorectal cancer are already well-defined. However, the events that cause the mutations and modifications and unknown. Recent studies have determined that the intestinal microbiota, as well as diet and lifestyle can promote the development of colorectal cancer. It is suggested that probiotics may actually inhibit colorectal cancer by interfering with the immune system and modulating intestinal bacteria.

PASSOS, Maria do Carmo Friche, & MORAES-FILHO, Joaquim Prado. (2017). INTESTINAL MICROBIOTA IN DIGESTIVE DISEASES. Arquivos de Gastroenterologia, Epub July 06, 2017.