Intestinal microbiota, chronic inflammation, and colorectal cancer

Abstract

In addition to genetic and epigenetic factors, various environmental factors, including diet, play important roles in the development of colorectal cancer (CRC). Recently, there is increasing interest in the intestinal microbiota as an environmental risk factor for CRC, because diet also influences the composition of the intestinal microbiota. The human intestinal microbiota comprises about 100 trillion microbes. This microbiome thrives on undigested dietary residues in the intestinal lumen and produces various metabolites. It is well known that the dietary risk factors for CRC are mediated by dysbiosis of the intestinal microbiota and their metabolites. In this review, we describe the bacterial taxa associated with CRC, including Fusobacterium nucleatum, enterotoxigenic Bacteroides fragilis, Escherichia coli, and butyrate-producing bacteria. We also discuss the host-diet interaction in colorectal carcinogenesis.

Keywords: Carcinogenesis; Colorectal neoplasms; Inflammation; Microbiota.

Fig. 1. The proposed pathogenesis of colorectal carcinogenesis. MAPK, mitogen-activated protein kinase; NF-κB, nuclear factor-κB; PI3K/AKT, phosphoinositide 3-kinase/protein kinase B; TNF-α, tumor necrosis factor α; IL, interleukin.