Cell Mol Gastroenterol Hepatol. 2021 Sep 07. pii: S2352-345X(21)00180-6. [Epub ahead of print]
The gastrointestinal (GI) tract is home to a complex and dynamic community of microorganisms, comprising bacteria, archaea, viruses, yeast and fungi. It is widely accepted that human health is shaped by these microbes and their collective microbial genome. This so-called "second genome" plays an important role in normal functioning of the host, contributing to processes involved in metabolism and immune modulation. Furthermore, the gut microbiota is also capable of generating energy and nutrients (e.g. short chain fatty acids and vitamins), which are otherwise inaccessible to the host, and are essential for mucosal barrier homeostasis. In recent years, numerous studies have pointed towards microbial dysbiosis as a key driver in many GI conditions, including cancers. Yet comprehensive mechanistic insights on how collectively gut microbes influence carcinogenesis remains limited. In addition to their role in carcinogenesis, the gut microbiota has now been demonstrated to play a key role in influencing clinical outcomes to cancer immunotherapy making them valuable targets in the treatment of cancer. It is also becoming apparent that, besides the gut microbiota's impact on therapeutic outcomes, cancer treatment may in turn influence GI microbiota composition. This review provides a comprehensive overview of microbial dysbiosis in GI cancers, specifically oesophageal, gastric and colorectal cancers, potential mechanisms of microbiota in carcinogenesis and their implications in diagnostics and cancer treatment.
Keywords: Gastrointestinal cancer; diagnostics; gut microbiota; therapeutics