SK-Hep1: not hepatocellular carcinoma cells but a cell model for liver sinusoidal endothelial cells

SK-Hep1 cells serve as a cell model of hepatocellular carcinoma and hepatocyte biology. However, SK-Hep1 cells are markedly different from normal hepatocytes and other hepatocellular carcinoma cells in their gene expression and protein levels. Furthermore, endothelial-specific makers and morphological characteristics are found in SK-Hep1 cells, indicating an endothelial origin. To confirm their cell phenotype, we investigated and compared the surface ultrastructure, endothelial function, and molecular markers of SK-Hep1 cells in vitro and in vivo. The results revealed that SK-Hep1 cells expressed endothelial-specific makers and exhibited the endothelial function of endocytosis and tubular formation. Capillary-like structures with CD31 expression were also observed in SK-Hep1 allografts in nude mice. Moreover, SK-Hep1 cells possessed fenestrae without diaphragms, consistent with liver sinusoidal endothelial cells, as seen by electron microscopy. In conclusion, SK-Hep1 cells would be better considered a cell model for liver sinusoidal endothelial cells instead of hepatocellular carcinoma cells.