C-terminal truncated hepatitis B virus X protein promotes hepatocellular carcinogenesis through induction of cancer and stem cell-like properties
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Kai-Yu Ng1, Stella Chai1, Man Tong1, Xin-Yuan Guan2,3, Chi-Ho Lin4, Yick-Pang Ching1,3, Dan Xie5, Alfred Sze-Lok Cheng6, Stephanie Ma1,3
1School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong
2Department of Clinical Oncology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong
3State Key Laboratory for Liver Research, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong
4Centre for Genomic Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong
5State Key Laboratory of Oncology in Southern China, Sun Yat-Sen University Cancer Center, Guangzhou, China
6School of Biomedical Sciences, The Chinese University of Hong Kong, Sha Tin, Hong Kong
Stephanie Ma, e-mail: email@example.com
Keywords: cancer stem cells, HBx, HCC, tumor-initiating cells, RNA-Seq
Received: August 23, 2015 Accepted: March 02, 2016 Published: March 19, 2016
Tumor relapse after chemotherapy typifies hepatocellular carcinoma (HCC) and is believed to be attributable to residual cancer stem cells (CSCs) that survive initial treatment. Chronic infection with hepatitis B virus (HBV) has long been linked to the development of HCC. Upon infection, random HBV genome integration can lead to truncation of hepatitis B virus X (HBx) protein at the C-terminus. The resulting C-terminal-truncated HBx (HBx-ΔC) was previously shown to confer enhanced invasiveness and diminished apoptotic response in HCC cells. Here, we found HBx-ΔC to promote the appearance of a CD133 liver CSC subset and confer cancer and stem cell-like features in HCC. HBx-ΔC was exclusively detected in HCC cell lines that were raised from patients presented with a HBV background with concomitant CD133 expression. Stable overexpression of the naturally occurring HBx-ΔC mutants, HBx-Δ14 or HBx-Δ35, in HCC cells Huh7 and immortalized normal liver cells MIHA resulted in a significant increase in the cells ability to self-renew, resist chemotherapy and targeted therapy, migrate and induce angiogenesis. MIHA cells with the mutants stably overexpressed also resulted in the induction of CD133, mediated through STAT3 activation. RNA sequencing profiling of MIHA cells with or without HBx-ΔC mutants stably overexpressed identified altered FXR activation. This, together with rescue experiments using a selective FXR inhibitor suggested that C-terminal truncated HBx can mediate cancer stemness via FXR activation. Collectively, we find C-terminal truncated HBx mutants to confer cancer and stem cell-like features in vitro and to play an important role in driving tumor relapse in HCC.
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