New member of aldose reductase family proteins overexpressed in human hepatocellular carcinoma.

The multistep process of liver carcinogenesis involves various genetic and phenotypic alterations. To identify genes whose expression is increased during hepatocarcinogenesis, differential-display polymerase chain reaction (DD-PCR) was used to examine differences in the mRNA composition of hepatocellular carcinoma (HCC) versus normal liver (nontumor) tissues. This approach identified 67 cDNAs that were preferentially expressed in HCC tissue. When these cDNAs were analyzed by reverse-Northern analysis, five were reproducibly expressed at high levels in HCC. Interestingly, Northern blot analysis revealed that one of the genes showed significantly increased mRNA levels in all five tested tumor samples, while its mRNA level in the nontumor samples was minimal. BLAST analysis revealed that this gene has high sequence identity with the genes from aldo-keto reductase family of proteins including the mouse fibroblast growth factor-induced gene (FR-1) (80% identity), mouse vas deferens protein (MVDP) (76%), and human aldose reductase (AR) (62%). Expression of this novel AR-related protein in all five tested HCCs suggests that this protein may play an important role in liver carcinogenesis.