Liver regeneration associated protein ALR exhibits anti-metastatic potential in hepatocellular carcinoma

Progression of HCC depends on different factors like metastasis and invasiveness. Previously, we have shown that the hepatotrophic protein ALR (Augmenter of Liver Regeneration) is highly expressed in cirrhotic livers and HCC. The aim of our study was to investigate the functional role of ALR in hepatocancerogenesis. Therefore the cytosolic ALR was re induced in hepatoma cell line HepG2 by stable transfection with a human ALR expression vector. We analyzed cell growth of HepG2-ALR in vitro and in vivo using a nude mice model. Interestingly, we could not detect an altered proliferation rate of HepG2-ALR cells neither in vitro nor in vivo. HepG2-ALR cells displayed an enhanced afiinity to adhere to the culture dish and a significant lower ability to migrate and invade compared to wild type cells. This finding is underlined by an immunohistochemical study which revealed that ALR expression in HCC is inversely correlated with tumor grading and angioinvasion. Using immunohistochemistry and western blot techniques, we demonstrated that ALR induces the protein expression of both E-cadherin and Zo-1. Furthermore, in HepG2-ALR cells are expression levels of MMP-1, MMP-3 and SNAIL reduced, which may explain the enhanced E-cadherin expression observed in vitro and in vivo. In addition, we could demonstrate that the activity of both MMP-1 and MMP-3 is significantly reduced in ALR re-expressing cells compared to wildtype HepG2 cells. Subcutaneously grown tumours originated from ALR-HepG2 cells displayed less necrotic areas, more epithelial-like cell growth as well as less polymorphisms and atypical mitotic figures than tumours derived from HepG2 cells. In conclusion, we summarize that the expression of cytosolic ALR reduces hepatoma cell migration, augments epithelial growth and therefore may act as an anti-metastatic and EMT reversing protein.