Quantitative proteome analysis of HCC cell lines with different metastatic potentials by SILAC.

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide and metastasis is the main cause for treatment failure and high fatality of HCC. In order to make further exploration into the mechanism of HCC metastasis and to search for the candidates of diagnostic marker and therapeutic target, stable-isotope labeling by amino acids in cell culture (SILAC) technique was employed to conduct differential proteome analysis on HCC cell lines--MHCC97L and HCCLM6 with low and high metastatic potentials. In total, 2335 reliable proteins were identified using LTQ-FT mass spectrum, among which 91 proteins were upregulated and 61 proteins were downregulated in HCCLM6. Most of the upregulated proteins were involved in adherence, morphogenesis, and lipid synthesis, while lots of the downregulated proteins were involved in electron transport, which might be crucial for HCC metastasis. Six dysregulated proteins were validated by Western blotting in the cell lines. Interestingly, the upregulation of solute carrier family 12 member 2 (SLC 12A2) and protein disulfide-isomerase A4 (PDIA4) were further confirmed in the culture supernatants by Western blotting and in the sera of HCC patients with different metastatic potentials by ELISA. Our study provided not only the valuable insights into the HCC metastasis mechanisms but also the potential candidate biomarkers for prediction of HCC metastasis.