Overexpression of p28/gankyrin in human hepatocellular carcinoma and its clinical significance.

To investigate the expression of p28/gankyrin gene and its role in the carcinogenetic process of human hepatocellular carcinoma (HCC). 64 specimens of HCC and para-carcinoma tissues, 22 specimens of non-tumor liver tissues (7 normal, 15 cirrhosis), 10 specimens of normal human tissues and 5 hepatoma cell lines were studied for the expression of p28/gankyrin by Northern blot. The expression of p28/gankyrin protein was detected immunohistochemically by using the specific polyclonal antibody. Northern blot analysis indicated that the expression of p28/gankyrin mRNA was intensively distributed in brain and heart, weakly in lung, spleen and muscle, undetectable in digestive system including liver, pancreas, stomach, small and large intestines. p28/gankyrin mRNA was absent in normal liver, weakly detected in liver cirrhosis and in 18 of 64 para-carcinoma liver tissues. In contrast, the expression of p28/gankyrin mRNA was intensively detected in all 5 hepatoma cell lines tested, markedly increased in 57 of 64 and moderately increased in 5 of 64 HCC samples. In comparison with liver cirrhosis and para-carcinoma liver tissues, the average expression of p28/gankyrin mRNA in HCC was increased 3.6- (2.901+/-0.507 vs 0.805+/-0.252, P<0.05) and 5.2-fold (2.901+/-0.507 vs 0.557+/-0.203, P<0.01), respectively. In addition, p28/gankyrin mRNA expression level was higher in HCC with portal vein tumor thrombus and microscopic hepatic vein involvement (P=0.021 and P=0.047, respectively). The overexpression of p28/gankyrin protein in HCC was targeted in hepatic tumor cells, not in bile duct cells and other interstitial cells. Overexpression of p28/gankyrin in HCC plays an important role and contributes to the metastasis potential in the process of carcinogenesis. p28/gankyrin may become a specific biological tissue marker for the pathological diagnosis of HCC.