Roles of transforming growth factor-β signaling in liver disease

In this editorial we expand the discussion on the article by Zhang et al published in the recent issue of the World Journal of Hepatology. We focus on the diagnostic and therapeutic targets identified on the basis of the current understanding of the molecular mechanisms of liver disease. Transforming growth factor-beta (TGF-beta) belongs to a structurally related cytokine super family. The family members display different time- and tissue-specific expression patterns associated with autoimmunity, inflammation, fibrosis, and tumorigenesis; and, they participate in the pathogenesis of many diseases. TGF-beta and its related signaling pathways have been shown to participate in the progression of liver diseases, such as injury, inflammation, fibrosis, cirrhosis, and cancer. The often studied TGF-beta/Smad signaling pathway has been shown to promote or inhibit liver fibrosis under different circumstances. Similarly, the early immature TGF-beta molecule functions as a tumor suppressor, inducing apoptosis; but, its interaction with the mitogenic molecule epidermal growth factor alters this effect, activating anti-apoptotic signals that promote liver cancer development. Overall, TGF-beta signaling displays contradictory effects in different liver disease stages. Therefore, the use of TGF-beta and related signaling pathway molecules for diagnosis and treatment of liver diseases remains a challenge and needs further study. In this editorial, we aim to review the evidence for the use of TGF-beta signaling pathway molecules as diagnostic or therapeutic targets for different liver disease stages.