Galectin-1 controls the proliferation and migration of liver Sinusoidal endothelial cells and their interaction with hepatocarcinoma cells

Abstract

Galectin-1 (Gal1), a beta-galactoside-binding protein elevated in hepatocellular carcinoma (HCC), promotes epithelial-mesenchymal transition (EMT) and its expression correlates with HCC growth, invasiveness and metastasis. During the early stages of HCC, transforming growth factor beta1 (TGF-B1 ) acts as a tumor suppressor; however in advanced stages, HCC cells lose their cytostatic response to TGF-B1 and undergo EMT. Here, we investigated the role of Gal1 on liver endothelial cell biology, and the interplay between Gal1 and TGF-B1 in HCC progression. By Western blot and immunofluorescence, we analyzed Gal1 expression, secretion and localization in HepG2 and HuH-7 human HCC cells, and in SK-HEP-1 human liver sinusoidal endothelial cells (SECs). We used loss-of-function and gain-of-function experiments to down- or up-regulate Gal1 expression, respectively, in HepG2 cells. We cultured SK-HEP-1 cells with conditioned media from HCC cells secreting different levels of Gal1, and demonstrated that Gal1 derived from tumor hepatocytes induced its own expression in SECs. Colorimetric and scratch-wound assays revealed that secretion of Gal1 by HCC cells induced SEC proliferation and migration. Moreover, by fluorescence microscopy we demonstrated that Gal1 promoted glycan-dependent heterotypic adhesion of HepG2 cells to SK-HEP-1 SECs. Furthermore, TGF-B1 induced Gal1 expression and secretion by HCC cells, and promoted HepG2 cell adhesion to SK-HEP-1 SECs through a Gal1-dependent mechanism. Finally, Gal1 modulated HepG2 cell proliferation and sensitivity to TGF-B1 -induced growth inhibition. Our results suggest that Gal1 and TGF-B1 might function coordinately within the HCC microenvironment to regulate tumor growth, invasion, metastasis and angiogenesis