Gut Microbiota, Fusobacteria, and Colorectal Cancer

The gut microbiota has emerged as an environmental contributor to colorectal cancer (CRC) in both animal models and human studies. It is now generally accepted that bacteria are ubiquitous colonizers of all exposed human body surfaces, including the entire alimentary tract (5). Recently, the concept that a normal bacterial microbiota is essential for the development of inflammation-induced carcinoma has emerged from studies of well-known colonic bacterial microbiota. This review explores the evidence for a role of fusobacteria, an anaerobic gram-negative bacterium that has repeatedly been detected at colorectal tumor sites in higher abundance than surrounding histologically normal tissue. Mechanistic studies provide insight on the interplay between fusobacteria, other gut microbiota, barrier functions, and host responses. Studies have shown that fusobacteria activate host inflammatory responses designed to protect against pathogens that promote tumor growth. We discuss how future research identifying the pathophysiology underlying fusobacteria colon colonization during colorectal cancer may lead to new therapeutic targets for cancer. Furthermore, disease-protective strategies suppressing tumor development by targeting the local tumor environment via bacteria represent another exciting avenue for researchers and are highlighted in this review.