To better understand the mechanism underlying hepatocellular carcinoma (HCC) metastasis and to search for potential markers for HCC prognosis, differential proteome analysis on two HCC cell strains with high and low metastatic potentials, MHCC97-H and MHCC97-L, was conducted using two-dimensional (2-D) gel electrophoresis followed by matrix-assisted laser desorption/time of flight mass spectrometry and liquid chromatography ion trap mass spectrometry. Image analysis of silver-stained 2-D gels revealed that 56 protein spots showed significant differential expression in MHCC97-H and MHCC97-L cells (Student's t-test, P < 0.05) and 4 protein spots were only detected in MHCC97-H cells. Fourteen protein spots were further identified using in-gel tryptic digestion, peptide mass fingerprinting and tandem mass spectrometry. The expressions of pyruvate kinase M2, ubiquitin carboxy-terminal hydrolase L1, laminin receptor 67 kDa, S100 calcium-binding protein A4, thioredoxin and cytokeratin 19 were elevated in MHCC97-H cells. However, manganese superoxide dismutase, calreticulin precursor, cathepsin D, lactate dehydrogenase B, non-metastatic cell protein 1, cofilin 1 and calumenin precursor were down-regulated in MHCC97-H cells. Intriguingly, most of these identified proteins have been reported to be associated with tumor metastasis. The functional implications of alterations in the levels of these proteins are discussed.

Hepatocellular carcinoma (HCC) is a malignancy of both underdeveloped and developing countries. Proteomes of ten pairs of clinical hepatitis B virus associated HCC tissue samples were obtained by high resolution two-dimensional gel electrophoresis. Comprehensive analyses of proteins associated with B-type HCC were focused on total differentially expressed proteins (> or = two-fold increase or decrease, Student's t-test, p < 0.05) from one pair of samples. Protein identification was done by peptide mass fingerprinting with matrix assisted laser desorption/ionization-time of flight mass spectrometry and liquid chromatography-tandem mass spectrometry. Comparative analyses of proteins associated with B-type HCC included repeat statistics in ten cases. A total of 100 protein spots, corresponding to 80 different gene products, were identified. Proteins whose expression levels were different by more than 2-fold in at least 50% of the cases (five of ten cases) were further analyzed and 45 proteins were selected out as candidates for HCC-associated proteins. Western blotting further validated up-regulated expressions of two candidate proteins in tumor tissues: proliferating cell antigen and stathmin 1. This comprehensive and comparative analyses of proteins associated with B-type HCC could provide useful molecular markers for diagnostics and prognostics and for therapeutic targets. The physiological significance of the differential expressions for several candidate proteins are discussed.