TLR4 and hepatocellular carcinoma: The gut microbiota can facilitate hepatocellular carcinoma (HCC) tumorigenesis through several key mechanisms, which include chronic inflammation sustained by dysbiosis, the bacterial production of metabolites and toxins such as lipopolysaccharides (LPS) from Gram-negative bacteria that activate hepatic toll-like receptors (especially TLR4), leading to inflammation, hepatocyte damage, and fibrosis, all of which create a pro-carcinogenic environment.