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)-beta1 and extracellular matrix protein Laminin-5 (Ln-5) induce EMT and cancer invasion.
Methods: Snail, Slug, E-cadherin, beta-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 beta-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, beta-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-alpha3 but not by anti-alpha6 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-beta1 completes the EMT process, beta-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-alpha3 integrin blocking antibody.
Conclusions: Our study shows that Ln-5 and TGF-beta1 cooperatively induce EMT in HCC, suggesting the microenvironment as a potential target for new biological therapies.