Expression of aspartyl beta-hydroxylase and its clinicopathological significance in hepatocellular carcinoma

The human aspartyl beta-hydroxylase is a highly conserved enzyme that hydroxylates epidermal growth factor-like domains in transformation-associated proteins. The aspartyl beta-hydroxylase gene is upregulated in many human malignancies. The purpose of this study was to investigate the expression of aspartyl beta-hydroxylase in hepatocellular carcinoma. Aspartyl beta-hydroxylase mRNA levels were measured in 161 hepatocellular carcinomas and paired nontumorous liver tissues by conventional and real-time RT-PCR. Immunohistochemical staining of aspartyl beta-hydroxylase was performed using EnVision Plus system. The results showed that aspartyl beta-hydroxylase was overexpressed in 150 of 161 hepatocellular carcinomas (93%), including 45 of 48 unifocal small hepatocellular carcinomas (94%). Aspartyl beta-hydroxylase was highly expressed in hepatocellular carcinoma cells in contrast to its low level of expression in non-neoplastic liver cells. The protein expression level of aspartyl beta-hydroxylase in the hepatocellular carcinoma was parallel with the mRNA expression level (r=0.6594, P<0.0001). A significantly higher tumor aspartyl beta-hydroxylase overexpression level was associated with the presence of intrahepatic metastasis and the progression of histological grades. In conclusion, aspartyl beta-hydroxylase is overexpressed frequently in hepatocellular carcinoma, including early-stage small hepatocellular carcinoma, indicating that overexpression of aspartyl beta-hydroxylase plays a role in the development and progression of hepatocellular carcinoma.