OBJECTIVETo determine the differentially expressed serum proteins in patients with hepatoma carcinoma and identify a putative diagnostic marker.

METHODThe isobaric tags for relative and absolute quantitation (iTRAQ) labeling method and LC-MALDI-TOF/TOF MS detection method were used to quantify serum proteins in hepatocellular carcinoma patients (n =20) and healthy individuals (n =20). Real-time reverse transcription-polymerase chain reaction was used to verify the differentially expressed proteins by analyzing the corresponding mRNA expression levels in the hepatic carcinoma and healthy hepatocyte samples, as well as in 30 pairs of patient-matched hepatic carcinoma and adjacent normal tissue samples. Western blot analysis was used to verify the protein expression in hepatic carcinoma cells.

RESULTFifty-one proteins were significantly differentially expressed between the hepatic carcinoma group and healthy controls. The iTRAQ protein profile showed that the serum level of clusterin was significantly lower in hepatoma carcinoma patients. The mRNA level of clusterin was 20-fold lower in hepatic carcinoma cells than in healthy hepatocytes, and was 2.38-fold lower in hepatoma tissues than that in adjacent normal tissues. The clusterin protein levels were significantly lower in hepatic carcinoma cells (8.06 vs normal hepatocytes: 27.81; P less than 0.01).

CONCLUSIONThe serum expression of clusterin is significantly decreased in both serum and tissues of hepatic carcinoma patients. The relationship between hepatic carcinoma and clusterin should be evaluated in future studies.