The impact of gut microbiota on colorectal cancer development

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths in many countries worldwide, both in men and women, and these rates tend to increase. The probability of developing CRC is about 4–5%, and the risk of its development is associated with individual characteristics of the body, bad habits, age, chronic diseases, and lifestyle. The microbiome in general, and the microbiota of individual loci in particular, play a major role in maintaining homeostasis in the human body. There are a number of studies examining the relationship between the microbiota of various biotopes, including the intestine, and CRC. The purpose of this review is to summarize studies on the role of intestinal microbiota in the development of colorectal cancer. According to some authors, changes in the composition of the microbiota are a direct cause of CRC development. In turn, other studies suggest the opposite point of view: carcinogenesis is a direct cause of qualitative and quantitative changes in the composition of the intestinal microbiota. Despite this, the literature contains a large amount of data on the possible role of specific microorganisms, such as Fusobacterium nucleatum, Bacteroide fragilis, toxigenic strains of Escherichia coli and other representatives of opportunistic flora in the development of the oncological process. At the moment, there is insufficient data on both specific microorganisms and the microbiota in general to make a clear conclusion about their role in the development of CRC, so further studies of the mechanisms underlying these processes are needed.