Laminin-5 with transforming growth factor-β1 induces epithelial to mesenchymal transition in hepatocellular carcinoma

Abstract

Background & Aims: How hepatocellular carcinoma (HCC) cells acquire the ability to invade surrounding tissue is unknown, but epithelial mesenchymal transition (EMT) likely plays a role. We investigate how transforming growth factor (TGF)-β1 and extracellular matrix protein Laminin-5 (Ln-5) induce EMT and cancer invasion. Methods: Snail, Slug, E-cadherin, β-catenin and Ln-5 were investigated on HCC tissues and on HCC cell lines. Results: We show that in HCC but not in peritumoral tissue of the same HCC patients, Ln-5, Snail, and Slug are up-regulated, E-cadherin is down-regulated and β-catenin is translocated into the nuclei. In vitro, HCC "invasive" cells, partially EMT-transformed, show low levels of E-cadherin. In presence of Ln-5, Snail, and Slug are up-regulated, E-cadherin is down-regulated, β-catenin is translocated into the nuclei, and cells undergo a dramatic morphological change, becoming scattered and undergoing a complete EMT. This effect is reversed by anti-α3 but not by anti-α6 integrin blocking antibody. HCC "noninvasive" cells are not EMT-transformed, and have constitutively high levels of E-cadherin. In presence of Ln-5, cells undergo partial EMT, Snail, and Slug are up-regulated, E-cadherin is down-regulated but cells do not scatter. However, the presence of both Ln-5 and TGF-β1 completes the EMT process, β-catenin is translocated into the nuclei, cells scatter and become invasive, recalling the "invasive" cells. In this case, too, the effect is reversed by anti-α3 integrin blocking antibody. Conclusions: Our study shows that Ln-5 and TGF-β1 cooperatively induce EMT in HCC, suggesting the microenvironment as a potential target for new biological therapies. © 2005 by the American Gastroenterological Association.