Fusobacterium nucleatum: an emerging bug in colorectal tumorigenesis.

The human intestinal microbiota is a plethora of diverse microbial species, wherein certain bacteria considered as driver bacteria with procarcinogenic features contribute directly toward colonic epithelium cell damage to initiate colorectal carcinogenesis. However, some bacteria, in particular Fusobacterium nucleatum, which is otherwise a normal resident of the oral microflora and a relatively poor colonizer of the healthy gut, have also been considered to play a role in the development of colorectal cancer. Many studies have reported that F. nucleatum is associated with colorectal adenomas and advanced-stage colorectal cancer, but its precise role in the early stages of colorectal tumorigenesis is poorly understood. Here, we review some of the important features of F. nucleatum, its association with inflammatory bowel disease, modulation of the tumor-immune microenvironment, and E-cadherin/β-catenin signaling.