Gene expression in HCV-associated HCC-identification of an upregulated gene encoding a protein related to ubiquitin conjugating enzyme

Abstract

Hepatocellular carcinoma is increasing in incidence throughout the world and the risk of developing hepatocellular carcinoma in chronic HCV infection has been estimated to be 100 times the risk in uninfected persons. To understand better the cellular changes in HCV-induced human hepatocellular carcinoma, differential display RT-PCR was used to compare levels of gene expression in tumour and non-tumour tissue from the same livers. Fifty two differentially expressed cDNA fragments were identified, 29 of them were cloned and sequenced and compared to the nucleotide sequence database. Differential expression was confirmed using a ribonuclease protection assay (RPA) which confirmed reproducibly that one particular cDNA was up-regulated in the tumour cells. The relative expression levels of this candidate gene were studied in various normal tissues and some malignant cell lines using multiple tissue expression (MTE) array which revealed that this gene is expressed at high levels in various cell lines derived from human tumours. The expression level in HCV-associated HCC was compared to other tumours using RPA which revealed that its expression levels in HCV-associated HCC was higher than its level in other tumours. Further characterisation of the gene was carried out using nucleotide sequence analysis programmes and northern hybridisation was carried out to estimate the gene size. Investigation of this clone revealed that this novel gene lies on chromosome 17. It is about 2.7 kb in size and encodes a protein similar to ubiquitin conjugating enzyme suggesting that the ubiquitin system might be involved in HCV related hepatocarcinogenesis.