How Dysbiosis (Microbiota interruption) leads to colorectalCancer

Background and Aim : The human intestinal microbiota is a collection of differentmicroorganisms, systematically participates in the nutrition, metabolism, and immune functionsof the human body. When the intestinal microbiota is affected by multiple factors such as diet,environment, and host genes, dysbiosis occurs, which alters the microbiota composition andbacterial bioactivity. Therefore, dysbiosis may cause diseases such as inflammatory bowel diseaseand colorectal cancer (CRC). This study investigates the relationship between dysbiosis and CRCMethods : This research was conducted using keywords, including colon cancer, Microbiome,dysbiosis, and inflammation, published in reliable databases such as PubMed, Scopus, and GoogleScholar during January ۲۰۲۰ to January ۲۰۲۲. According to the inclusion and exclusion criteria ofthe related articles, their information was extracted and entered into the checklist and finallyanalyzed.Results : Based on the various studies, dysbiosis can induce CRC through inflammatory reaction,immune response, damage to DNA, and modulation of cell proliferation. Fusobacterium andBacteroides fragilis cause the development of CRC due the modulation of the immune response.While, Escherichia coli cause cancer by damaging DNA. Some genera in Enterobacteriaceae, suchas Salmonella and Shigella stimulate the transepithelial migration of neutrophils and then reducethe number of bacteria producing SCFAs (Short chain fatty acids). Evidences show that dysbiosisresults in alterations of the physiological function, which leads to the pathogenesis of variousdiseases. Dysbiosis often occurs in CRC tissues and adjacent mucosa. However, due to thedifferent classification criteria and methods used in past studies, new methods are currently beingdeveloped to identify more important species related to the development and progression of CRC.Conclusion : According to the findings of this study, dysbiosis is one of the most important causesof CRC. Therefore, the altered microbiota or metabolites of substituted microorganisms arepromising tools for appropriate and timely diagnosis of CRC.