The Gut Microbiome and Colorectal Cancer: An Integrative Review of the Underlying Mechanisms

Colorectal cancer (CRC) is the second leading cause of cancer-related mortality worldwide. While the incidence and mortality of CRC have decreased overall due to better screening, rates in adults under 50 have risen. CRC can manifest as inherited syndromes (10%), familial clustering (20%), or sporadic forms (70%). The gut microbiota, comprising mainly firmicutes and bacteroidetes, play a key role in CRC development and prevention. Indeed, CRC progression is influenced by the dynamic interaction between the gut microbiota, the intestinal barrier, the immune system, and the production of short-chain fatty acids. Not surprisingly, imbalance in the gut microbiota, termed dysbiosis, has been linked to CRC due to ensuing chronic inflammation, DNA damage, and oxidative stress. This may explain the notion that probiotics and fecal microbiota transplantation offer potential strategies for CRC prevention and treatment by restoring microbial balance and enhancing anti-cancer immune responses. This review appraises the roles of gut microbiota in promoting or preventing CRC. It also discusses the mechanistic interplay between microbiota composition, the intestinal barrier, and the immune system, with the hope of developing potential therapeutic strategies.