Expression and significance of Bmi-1 in hepatocellular carcinoma tissue and portal vein tumor thrombus

Abstract

Objective To detect the mRNA and protein expressions of Bmi-1 in hepatocellular carcinoma (HCC) tissue,pericarcinomatous tissue,portal vein tumor thrombus and normal liver tissue,and to investiage the significance of Bmi-1 in the genesis and progression of HCC.Methods Forty tissues of HCC were collected from the Tongji Hospital of Huazhong University of Science and Technology from January 2005 to December 2009.The mRNA and protein expressions of Bmi-1 in the HCC tissues (40 cases),pericarcinomatous tissues (40 cases),portal vein tumor thrombus ( 11 cases) and normal liver tissues ( 10 cases) were detected by immunohistochemistry,Western blot and real-time polymerase chain reaction.The relationship between the expressions of Bmi-1 and the clinicopathological factors was analyzed.Differences in each group were compared by using the Nemenyi test or Dunnet t test,and the relationship between the clinicopathological factors and the protein expression in the HCC tissues was analyzed by the chi-square test or Fisher exact probability.The survival curve was drawn by the Kaplan-Meier method,and the survival rate was analyzed by the Log-rank test.Results The median relative mRNA expressions of Bmi-1 in the normal liver tissues,pericarcinomatous tissues,HCC tissues and portal vein tumor thrombus were 0.96,2.60,7.51 and 29.95,respectively.The results of immunohistochemistry showed that the high protein expression rates of Bmi-1 in the normal liver tissues,pericarcinomatous tissues,HCC tissues and portal vein tumor thrombus were 10.0％,20.0％,67.5％ and 100.0％,respectively.The high protein expression rates of Bmi-1 in the HCC tissues and portal vein tumor thrombus were significantly higher than those in the normal liver tissues and pericarcinomatous tissues (x2 =17.25,22.77;22.04,23.95,P ＜ 0.05 ). High protein expression of Bmi-1 was also detected in 11 cases of HCC tissues with portal vein tumor thrombus.The results of western blot were consistent with those of the immunohistochemistry.The mRNA and protein expressions of Bmi-1 were correlated with Edmondson grade and portal vein metastasis ( x2 =5.572,P ＜ 0.05 ),whereas they were irrelevant to the tumor size,serum levels of α-fetoprotein and hepatitis B surface antigen ( x2 =0.000,0.019,0.663,P ＞0.05).Patients with high expression of Bmi-1 had poor prognosis.Conclusions Bmi-1 is correlated with the genesis and progression of HCC as well as the formation of portal vein tumor thrombosis.Patients with high Bmi-1 expression have poorer prognosis when compared with those with low Bmi-1 expression. Key words: Liver neoplasms; Bmi-1 gene; Portal vein tumor thrombus