HEPN1, a novel gene that is frequently down-regulated in hepatocellular carcinoma, suppresses cell growth and induces apoptosis in HepG2 cells

Background/Aims: Examining genes associated with human hepatocellular carcinoma (HCC) by subtractive hybridisation, we identified a novel transcript, designated as HEPN1, in non-tumorous liver. In this study, we aimed to evaluate HEPN1 gene expression in HCC patients, to characterise and to explore the functional significance of HEPN1 in vitro. Methods: One-step reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR were employed to determine HEPN1 expression in 23 paired (HCC and the adjacent non-HCC) liver specimens. Sequence analyses were performed by bioinformatics. Transfection studies were carried out by expressing HEPN1, V5-fused HEPN1, and green fluorescent protein-fused HEPN1, individually, in HepG2 cells. Results: Significant downregulation of HEPN1 (P<0.0001) was detected in 22/23 of HCC patients tested. Gene HEPN1 maps to chromosome 11q24.2; and the predicted gene product, a 10-kDa peptide with 88 amino acids, has no homology to known proteins. When transfected into HepG2 cells, HEPN1 reduced cell viability to 37.5±2.5% (P=0.001), and induced apoptosis with typical morphological changes as demonstrated by microscopy and Annexin V assay. Conclusions: Our data show that HEPN1 is frequently silenced in HCC, and that exogenous HEPN1 exhibits antiproliferative effect on HepG2 cells, suggesting that silencing of HEPN1 may be associated with carcinogenesis of hepatocytes.