C-terminal truncated hepatitis B virus x protein is... : Hepatology (original) (raw)

Hepatobiliary Malignancies

C-terminal truncated hepatitis B virus x protein is associated with metastasis and enhances invasiveness by c-jun/matrix metalloproteinase protein 10 activation in hepatocellular carcinoma

Sze, Karen M.F.1,2; Chu, Glanice K.Y.1,2; Lee, Joyce M.F.1,2; Ng, Irene O.L.1,2,*,4

1State Key Laboratory for Liver Research, The University of Hong Kong, Hong Kong

2Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong

*Department of Pathology, The University of Hong Kong, Queen Mary Hospital, University Pathology Building, Room 127B, Pokfulam, Hong Kong

Email: [email protected]

Received 1 December 2011; Accepted 8 July 2012

3Potential conflict of interest: Nothing to report.

2The study was funded by the Hong Kong Research Fund for the Control of Infectious Diseases (05050022), the Hong Kong Research Grants Council Collaborative Research Fund (HKU 1/06C and 7/CRF/09), and the Hong Kong University Small Project Fund (200707176172). I.O.L.N. is Loke Yew Professor in Pathology.

4fax: 852-2872-5197

Abstract

Random integration of hepatitis B virus (HBV) DNA into the host genome is frequent in human hepatocellular carcinoma (HCC) and this leads to truncation of the HBV DNA, particularly at the C-terminal end of the HBV X protein (HBx). In this study, we investigated the frequency of this natural C-terminal truncation of HBx in human HCCs and its functional significance. In 50 HBV-positive patients with HCC, full-length HBx was detected in all nontumorous livers. However, full-length HBx was found in only 27 (54%) of the HCC tumors, whereas natural carboxylic acid (COOH)-truncated HBx was found in the remaining 23 (46%) tumors. Upon clinicopathological analysis, the presence of natural COOH-truncated HBx significantly correlated with the presence of venous invasion, a hallmark of metastasis (P = 0.005). Inducible stable expression of the COOH-truncated HBx protein (with 24 amino acids truncated at the C-terminal end) enhanced the cell-invasive ability of HepG2 cells, as compared to full-length HBx, using the Matrigel cell-invasion assay. It also resulted in increased C-Jun transcriptional activity and enhanced transcription of matrix metalloproteinase 10 (MMP10), whereas activation of the MMP10 promoter by COOH-truncated HBx was abolished when the activator protein 1–binding sites on the MMP10 promoter were mutated. Furthermore, silencing of MMP10 by short interfering RNA in HBxΔC1-expressing HepG2 cells resulted in significant reduction of cell invasiveness. Conclusions: Our data suggest that COOH truncation of HBx, particularly with 24 amino acids truncated at the C-terminal end, plays a role in enhancing cell invasiveness and metastasis in HCC by activating MMP10 through C-Jun. (Hepatology 2013)

Abbreviations: aa, amino acid; Ab, antibody; AP-1, activator protein 1; cDNA, complementary DNA; CFA, colony formation assay; ChIP, chromatin immunoprecipitation; COOH, carboxylic acid; CREB, cyclic adenosine monophosphate response element-binding protein; DMEM, Dulbecco's modified Eagle's minimal essential medium; FBS, fetal bovine serum; HBsAg, hepatitis B surface antigen; HBV, hepatitis B virus; HBx, hepatitis B virus X protein; HCC, hepatocellular carcinoma; IHC, immunohistochemistry; hTERT, human telomerase reverse transcriptase; MMP10, matrix metalloproteinase protein 10; mRNA, messenger RNA; NF-κB, nuclear factor kappa B; nt, nucleotide(s); RT-PCR, reverse-transcriptase polymerase chain reaction; SDS, sodium dodecyl sulfate; siRNA, short interfering RNA; TBP, TATA-binding protein; WT, wild type.