EpCAM-regulated intramembrane proteolysis induces a cancer stem cell-like gene signature in hepatitis B virus-infected hepatocytes

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• 作者：Saravana Kumar Kailasam Mani¹ ; ² ; Hao Zhang¹ ; ² ; Ahmed Diab¹ ; ² ; Pete E. Pascuzzi² ; ³ ; Lydie Lefran&ccedil ; ois⁴ ; Nadim Fares⁴ ; Brigitte Bancel⁴ ; Philippe Merle⁴ ; Ourania Andrisani¹ ; ² ; ^{andrisao@purdue.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：cccDNA ; circular covalently closed DNA ; EpCAM ; epithelial cell adhesion molecule ; EpICD ; EpCAM intracellular domain ; hCSCs ; hepatic cancer stem cells ; HBV ; hepatitis B virus ; HBc ; hepatitis B virus core antigen ; HCC ; hepatocellular carcinoma ; PRC2 ; polycomb repressor complex 2 ; RIP ; regulated intramembrane proteolysis
• 刊名：Journal of Hepatology
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：65
• 期：5
• 页码：888-898
• 全文大小：2355 K

文摘

Hepatocytes in which the hepatitis B virus (HBV) is replicating exhibit loss of the chromatin modifying polycomb repressive complex 2 (PRC2), resulting in re-expression of specific, cellular PRC2-repressed genes. Epithelial cell adhesion molecule (EpCAM) is a PRC2-repressed gene, normally expressed in hepatic progenitors, but re-expressed in hepatic cancer stem cells (hCSCs). Herein, we investigated the functional significance of EpCAM re-expression in HBV-mediated hepatocarcinogenesis.

Methods

Employing molecular approaches (transfections, fluorescence-activated cell sorting, immunoblotting, qRT-PCR), we investigated the role of EpCAM-regulated intramembrane proteolysis (RIP) in HBV replicating cells in vitro, and in liver tumors from HBV X/c-myc mice and chronically HBV infected patients.

Results

EpCAM undergoes RIP in HBV replicating cells, activating canonical Wnt signaling. Transfection of Wnt-responsive plasmid expressing green fluorescent protein (GFP) identified a GFP ⁺ population of HBV replicating cells. These GFP⁺/Wnt⁺ cells exhibited cisplatin- and sorafenib-resistant growth resembling hCSCs, and increased expression of pluripotency genes NANOG, OCT4, SOX2, and hCSC markers BAMBI, CD44 and CD133. These genes are referred as EpCAM RIP and Wnt-induced hCSC-like gene signature. Interestingly, this gene signature is also overexpressed in liver tumors of X/c-myc bitransgenic mice. Clinically, a group of HBV-associated hepatocellular carcinomas was identified, exhibiting elevated expression of the hCSC-like gene signature and associated with reduced overall survival post-surgical resection.

Conclusions

The hCSC-like gene signature offers promise as prognostic tool for classifying subtypes of HBV-induced HCCs. Since EpCAM RIP and Wnt signaling drive expression of this hCSC-like signature, inhibition of these pathways can be explored as therapeutic strategy for this subtype of HBV-associated HCCs.

Lay summary

In this study, we provide evidence for a molecular mechanism by which chronic infection by the hepatitis B virus results in the development of poor prognosis liver cancer. Based on this mechanism our results suggest possible therapeutic interventions.