Objective:To screen and identify the differentially expressed proteins in the serum ofα-fetoprotein (AFP)-negative patients with liver cancer and AFP-negative patients with liver cirrhosis.Methods:Six patients with AFP-negative liver cancer and 6 patients with AFP-negative liver cirrhosis were enrolled.The low abundance proteins in serum samples from each group were isolated by MARS system.Then the differentially expressed proteins between the two groups were screened by two-di-mensional fluorescence difference gel electrophoresis (2D-DIGE)technology.Furthermore,Western blotting was used to verify the differentially expressed proteins.Results:Totally,29 differentially expressed proteins have been identified by 2D-DIGE technology.Among those proteins,22 proteins were over-expressed in the serum from AFP-negative liver cancer patients, while 7 proteins were down-expressed.These differential proteins included kininogen 1 ,tetranectin,lumican,complement 1 R and zinc-alpha-2-glycoprotein (ZAGP).By Western blotting,it was confirmed that the expression of ZAGP in patients with AFP-negative liver cancer was significantly lower than that in patients with AFP-negative liver cirrhosis (P <0.05),which was in accordance with the result of DIGE.Conclusions:A series of differentially expressed proteins were identified in the serum from AFP-negative patients with liver cirrhosis or liver cancer by using proteomic technology.These proteins might be used as molecular markers for the early diagnosis and assistant diagnosis of AFP-negative patients with liver cancer.