Histone lysine methyltransferase, suppressor of variegation 3-9 homolog 1, promotes hepatocellular carcinoma progression and is negatively regulated by microRNA-125b

Authors

  • Dorothy Ngo-Yin Fan,

    1. State Key Laboratory for Liver ResearchThe University of Hong Kong, Hong Kong, China
    2. Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
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  • Felice Ho-Ching Tsang,

    1. State Key Laboratory for Liver ResearchThe University of Hong Kong, Hong Kong, China
    2. Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
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  • Aegean Hoi-Kam Tam,

    1. State Key Laboratory for Liver ResearchThe University of Hong Kong, Hong Kong, China
    2. Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
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  • Sandy Leung-Kuen Au,

    1. State Key Laboratory for Liver ResearchThe University of Hong Kong, Hong Kong, China
    2. Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
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  • Carmen Chak-Lui Wong,

    1. State Key Laboratory for Liver ResearchThe University of Hong Kong, Hong Kong, China
    2. Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
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  • Lai Wei,

    1. State Key Laboratory for Liver ResearchThe University of Hong Kong, Hong Kong, China
    2. Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
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  • Joyce Man-Fong Lee,

    1. State Key Laboratory for Liver ResearchThe University of Hong Kong, Hong Kong, China
    2. Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
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  • Xianghuo He,

    1. State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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  • Irene Oi-Lin Ng,

    1. State Key Laboratory for Liver ResearchThe University of Hong Kong, Hong Kong, China
    2. Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
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  • Chun-Ming Wong

    Corresponding author
    1. State Key Laboratory for Liver ResearchThe University of Hong Kong, Hong Kong, China
    2. Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
    • PhD or Irene Oi-Lin Ng, MD, PhD, State Key Laboratory for Liver Research and Department of Pathology, University Pathology Building, The University of Hong Kong, Queen Mary Hospital, 102 Pofulam Road, Pokfulam, Hong Kong
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    • fax: (852) 2817 5496


  • Potential conflict of interest: Nothing to report.

  • The study was supported by the University of Hong Kong Seed Funding Program for Basic Research (200711159020; to C.M.W.), the Research Grants Council General Research Fund (HKU 778508M; to C.M.W.), and the Research Grants Council Collaborative Research Fund (HKU 1/06C and HKU 7-CRG/09; to I.O.L.N.). I.O.L.N. is a Loke Yew Endowed Professor in Pathology.

Abstract

Hepatocellular carcinoma (HCC) is a major liver malignancy. We previously demonstrated that deregulation of epigenetic regulators is a common event in human HCC. Suppressor of variegation 3-9 homolog 1 (SUV39H1), the prototype of histone methyltransferase, is the major enzyme responsible for histone H3 lysine 9 trimethylation, which, essentially, is involved in heterochromatin formation, chromosome segregation, and mitotic progression. However, the implication of SUV39H1 in hepatocarcinogenesis remains elusive. In this study, we found that SUV39H1 was frequently up-regulated in human HCCs and was significantly associated with increased Ki67 expression (P < 0.001) and the presence of venous invasion (P = 0.017). To investigate the role of SUV39H1 in HCC development, both gain- and loss-of-function models were established. SUV39H1 overexpression remarkably enhanced HCC cell clonogenicity, whereas knockdown of SUV39H1 substantially suppressed HCC cell proliferation and induced cell senescence. In addition, ectopic expression of SUV39H1 increased the migratory ability of HCC cells, whereas a reduced migration rate was observed in SUV39H1 knockdown cells. The significance of SUV39H1 in HCC was further demonstrated in a nude mice model; SUV39H1 knockdown drastically inhibited in vivo tumorigenicity and abolished pulmonary metastasis of HCC cells. We also identified microRNA-125b (miR-125b) as a post-transcriptional regulator of SUV39H1. Ectopic expression of miR-125b inhibited SUV39H1 3'-untranslated-region–coupled luciferase activity and suppressed endogenous SUV39H1 expression at both messenger RNA and protein levels. We have previously reported frequent down-regulation of miR-125b in HCC. Interestingly, miR-125b level was found to be inversely correlated with SUV39H1 expression (P = 0.001) in clinical specimens. Our observations suggested that miR-125b down-regulation may account for the aberrant SUV39H1 level in HCC. Conclusion: Our study demonstrated that SUV39H1 up-regulation contributed to HCC development and metastasis. The tumor-suppressive miR-125b served as a negative regulator of SUV39H1. (HEPATOLOGY 2013)

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