Identification of proteins differentially expressed between capillary endothelial cells of hepatocellular carcinoma and normal liver in an orthotopic rat tumor model using 2-D DIGE

Hepatocellular carcinoma (HCC) is one of the deadliest cancers with few treatment options. It is a hypervascular tumor in which angiogenesis plays a critical role in its progression. Tumor capillary endothelial cells (TECs) in HCC are known to originate from liver sinusoid endothelial cells, which then go through a capillarization process to become morphologically as well as functionally different TECs. In this work, we investigated proteins differentially expressed between freshly isolated TECs and sinusoid endothelial cells from well-formed rat HCC using 2-D DIGE coupled with MALDI-TOF/TOF MS. Thirty-eight unique proteins were identified to be differentially expressed more than twofold between the two endothelial cell types. Amongst the differentially expressed proteins, two novel endothelial markers, EH domain-containing protein 3 and galectin-3, were confirmed by Western blot and immunohistochemistry in both rat and human HCC samples. We showed that EH domain-containing protein 3 is significantly down-regulated in TECs, but galectin-3 is up-regulated. We propose possible roles of these two proteins in tumor vessel development in HCC.