Transforming Growth Factor-β as a Therapeutic Target in Hepatocellular Carcinoma

Hepatocellular carcinoma arises in patients as a consequence of long-standing preexisting liver illnesses, including viral hepatitis, alcohol abuse, or metabolic disease. In such preexisting liver diseases, TGF-beta plays an important role in orchestrating a favorable microenvironment for tumor cell growth and promoting epithelial-mesenchymal transition (EMT). TGF-beta signaling promotes hepatocellular carcinoma progression by two mechanisms: first, via an intrinsic activity as an autocrine or paracrine growth factor and, second, via an extrinsic activity by inducing microenvironment changes, including cancer-associated fibroblasts, T regulatory cells, and inflammatory mediators. Although there is an increasing understanding on how TGF-beta signaling is associated with tumor progression in hepatocellular carcinoma, it is not clear whether TGF-beta signaling is limited to a certain subgroup of patients with hepatocellular carcinoma or is a key driver of hepatocellular carcinoma during the entire tumorigenesis of hepatocellular carcinoma. Inhibitors of the TGF beta signaling have been shown to block hepatocellular carcinoma growth and progression by modulating EMT in different experimental models, leading to the clinical investigation of the TGF-beta inhibitor LY2157299 monohydrate in hepatocellular carcinoma. Preliminary results from a phase II clinical trial have shown improved clinical outcome and also changes consistent with a reduction of EMT. (C)2014 AACR.