Analysis of differentially expressed genes in hepatocellular carcinoma with hepatitis C virus by suppression subtractive hybridization.

Hepatitis C virus (HCV) infection is associated with pathogenesis of hepatocellular carcinoma (HCC). We carried out suppression subtractive hybridization to identify variable expression of genes linked to HCC with HCV infection. RNA from both tumorous (tester) and nontumorous (driver) liver tissues was isolated. The cDNA clones were subjected to MegaBACE PCR sequencing to identify those that hybridized to the subtracted library with preference. Nucleic acid sequences generated were searched against the human UniGene database. Among 576 clones screened in the tumorous liver tissue, we identified 30 genes and 28 expressed sequence tags (ESTs). Among 30 genes detected, 23 were with known functions and 7 with unknown functions. The known genes identified had diversified functions and could be divided into 10 functional categories. Twenty percent of these genes were previously known to be tumor related and those most frequently appearing were haptoglobin alpha(2FS)-beta precursor, haptoglobin related protein, and alpha-2-macroglobulin. Four out of 30 known genes (immunoglobulin lambda light chain, kappa immunoglobulin, spliceosomal protein, and X-ray repair cross-complementing protein) were related to chromosome translocation and nucleotide repair. These four genes may contribute to carcinogenesis caused by DNA-damaged agents and to the efficiency of anticancer therapy. The genes with unknown function, which were most frequently detected, were PRO2760 and PRO2955; both encode proteins that express in fetal liver. Twenty-one known and six novel genes were discovered in the nontumorous liver tissue. Apparently, these 27 genes were lost in the tumorous liver tissues. Therefore, using suppression subtractive hybridization, we have identified a number of genes associated with HCC with HCV infection. Most of these genes have not been reported in HCC. Further characterization of these differentially expressed known and unknown genes will provide useful information in understanding the genes responsible for the development of HCC.