Colorectal cancer: The epigenetic role of microbiome

Figure 4 Different gut microbiota generate different oncometabolites. Bacteroides expresses specific signaling substances to activate toll-like receptor 2 (TLR 2), which functions in two different ways; activation of FOX3 to trigger Treg activation leading to inflammation. The other way is the activation of T helper 17 cells that also triggers inflammation. Flagellin, a product of flagellated bacteria, activates also TLR 5 to activate innate lymphoid cells 3 and then IL 17 and 22 that initiate inflammation. TLR 5 also works on nuclear factor κB to activate miR-21 that has a role in initiating cancer carcinogenesis (CRC). Meanwhile, Fusobacteria can stimulate a specific type of TLR that activates nuclear factor of activated T cell via calmodulin-based calcineurin to initiate CRC. CRC: Colorectal cancer; IL: Interleukin; ILC: lymphoid cells; NF-κB: Nuclear factor-κB; NFAT: Nuclear factor of activated T cell; TLR: Toll-like receptor; Treg: T regulatory cell.