| Hepatocellular carcinoma (HCC) is one of the malignant tumors worldwide with high morbidity and mortality. It is the third most common cause of death from cancer in the world, while in China it ranks in the second highest cancer killer. HCC is highly invasive, poor prognosis, so early diagnosis and treatment of liver cancer is of particular importance. AFP (alpha-fetoprotein, AFP) on the clinical diagnosis of HCC is the most common tumor markers, but low sensitivity(70%)/specificity(64%), a separate application on HCC diagnosis easily lead to misdiagnosis and missed diagnosis. So, discover new biomarkers of HCC is the indicator of major research hot spots.Proteomics,which can dynamic, holistic and quantitative study the types and quantity changes of total proteins during progression of disease. It is an effective and high-throughput mode for exploring mechanism of disease and for searching targets of diagnosis or therapy. Even more, with the proteomics methods, we could found much more new protein markers and key elements than traditional means.In our study, we analyzed the difference of proteins between HCC and health control sera by proteomics. We got some differential proteins that have potential application and validation the differential expression protein complement C3 in the cells (SMMC-7721 and HL-7702) and tissues (HCC and adjacent tissues). Objective: iTRAQ labeling and MALDI TOF/TOF tandem mass spectrometry was used to analysis HCC serum proteomic, screening potential HCC biomarkers in sera.Methods: We analyzed the sera of 20 HCC patients and 20 healthy volunteers using iTRAQ labeling and MALDI-TOF-MS. The results were compared with the reported protein data which were identified by differential proteins screening MALDI-TOF-MS from January 2003 to August 2010 in PubMed.Results: We identified 51 proteins that had significant differential expression in different sera. Among these proteins, 23 proteins were up-regulated in HCC compared with the control, and 28 proteins were down-regulated in HCC.Furthermore we found 262 HCC related biomarkers by searching 22 publications. 8 proteins had also been identified in our research, and 6 proteins in our research had the similar expression level to those in publications.Conclusion: We identified 6 differential proteins in sera (Ceruloplasmin,Alpha-1-antitrypsin,Apolipoprotein E,Complement C3,Serum amyloid P-component and Apolipoprotein A-â… ) which expressed the similar level as known studies. These proteins may be potential HCC biomarker and be worthy of further study.Objective: To verify the differential protein C3 screened by iTRAQ technique in cells (SMMC-7721 and HL-7702) and tissues (HCC and adjacent tissues), confirm the relationship of HCC and C3 expression.Method: Applied RT-PCR method detection the levels of mRNA expression of C3 in cells and 30 tissues, and detected the levels of proteins expression in cells by Western bolt.Result: (1) The protein levels of complement C3 in HL-7702 was 3.25 times of SMMC-7721; the mRNA levels of complement C3 in HL-7702 was 4.29 times of SMMC-7721. (2) The mRNA levels of complement C3 in adjacent tissues was 22.27 times of HCC tissues.Conclusion: The protein and mRNA of C3 has significant differential expression in SMMC-7721and HL-7702, the mRNA of C3 has significant differential expression in HCC tissues and adjacent tissues, and with a same tendency of iTRAQ result. Our study revealed C3 as a complement protein possibly had some relationship with HCC; the suppression of this protein may promote the liver cancer.
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