The Microbiome Colorectal Cancer Puzzle: Initiator, Propagator, and Avenue for Treatment and Research

Abstract

The human gut microbiome has an ever-increasing role in the instigation and progression of colorectal cancer (CRC). Recent investigations have focused on identifying the key causative bacterial species and the composition and structure of the microbiome as a whole that ultimately lead to tumorigenesis in the colon. Understanding the bacterial mechanisms that promote CRC provides a rich area for the development of new screening modalities and therapeutics that may improve patient outcomes. This article reviews the various mechanisms that bacteria in the gut use to induce and/or promote tumor formation, discusses the application of the microbiome in the prevention and therapy of CRC, and provides directions for future research endeavors aiming to develop a more complete understanding of this complex phenomenon.

The Role of the Microbiome on the Pathogenesis and Treatment of Colorectal Cancer

“…The balance of microbes can undergo significant alterations resulting in major changes to the overall composition of the microbiome. This unfavorably altered composition is coined “dysbiosis” [ 8 , 9 ].…”

“…Biofilm formation represents a change in the epithelium-microbiome interaction. This change provides a resilient structure that decreases the penetration of antibiotics, increases epithelial permeability via loss of E-cadherin, and allows continued interaction between tumor-promoting bacteria and host cells [ 8 , 20 , 45 ]. This continued interaction at the level of unprotected epithelial cells promotes pro-carcinogenic tissue inflammation, inducing mutations within the epithelial cells, resulting in the increased proliferation seen with the growth of tumors [ 45 ].…”

A systematic review of microbiome-derived biomarkers for early colorectal cancer detection

“…Increasing evidence points to the gut microbiome as a critical mediator of adenoma formation and CRC risk through parallel processes of co-metabolic dysfunction [11] , inflammation, epigenetic programming and DNA damage [12] . Multiple studies have identified the presence of intra-tumoural bacteria in precursors lesions of cancer [13] , [14] , [15] , [16] such as Fusobacterium nucleatum, Escherichia coli , and Bacteroides fragilis [17] . A loss of microbial diversity and increases in the abundance of both mucosal and faecal pathobionts can distinguish healthy persons from patients with CRC [18] , [19] , [20] .…”