TLR4 and neoplasm: The gut microbiota can profoundly affect the immune microenvironment of the liver and thereby trigger hepatocarcinogenesis via the following processes: (1) microbial activation of signaling like Toll-like receptor (TLR)-4; (2) microbial stimulation of tumor microenvironment (TME) cells; and (3) influence of gut microbiota-associated metabolites.