Gene expression in HCV-associated hepatocellular carcinoma - upregulation of a gene encoding a protein related to the ubiquitin-conjugating enzyme

Background/Aims: To investigate gene expression in HCV-associated human hepatocellular carcinomas (HCC) by identifying up- and down-regulated genes. Methods: Differential display RT-PCR was used to compare levels of gene expression in tumorous and non-tumorous tissues from the same livers. Differential expression was confirmed using a ribonuclease protection assay (RPA). The relative expression levels of one candidate gene were studied in various normal tissues and malignant cell lines using a multiple tissue expression (MTE) array. Further characterisation of this gene was carried out using nucleotide sequence analysis programmes and Northern hybridisation. Results: Fifty-two differentially expressed cDNA fragments were identified and 29 were cloned, sequenced and compared with the nucleotide sequence database. RPA confirmed reproducibly that one particular cDNA was upregulated in the tumour cells. Analysis using the MTE array revealed that this selected candidate gene is expressed at high levels in various human tumour cell lines. The expression levels in HCV-associated HCC were higher than in other tumours. Investigation revealed that this novel gene lies on chromosome 17. The transcript is approximately 2.5 kb in size and encodes a protein similar to the ubiquitin-conjugating enzyme. Conclusions: The ubiquitin system may be involved in HCV-related hepatocarcinogenesis and in the development of other cancers.