RhoE is frequently down-regulated in hepatocellular carcinoma (HCC) and suppresses HCC invasion through antagonizing the Rho/Rho-Kinase/Myosin phosphatase target pathway

Authors

  • Wei Ma,

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

    1. State Key Laboratory for Liver Research, University of Hong Kong
    2. Department of Pathology, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
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  • Edmund Kwok-Kwan Tung,

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

    1. State Key Laboratory for Liver Research, University of Hong Kong
    2. Department of Pathology, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
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  • Irene Oi-Lin Ng

    Corresponding author
    1. State Key Laboratory for Liver Research, University of Hong Kong
    2. Department of Pathology, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
    • Room 127B, University Pathology Building, Department of Pathology, University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong
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    • fax: 852-2872-5197


  • Potential conflict of interest: Nothing to report.

  • Funded in part by Hong Kong Research Grants Council Collaborative Research Fund (HKU 7/CRF/09) and General Research Fund (HKU775811M). I.O.L. Ng is Loke Yew Professor in Pathology.

Abstract

Deregulation of Rho guanosine triphosphatase (GTPase) pathways plays an important role in tumorigenesis and metastasis of hepatocellular carcinoma (HCC). RhoE/Rnd3 belongs to an atypical subfamily of the RhoGTPase, the Rnd family, as it lacks the intrinsic GTPase activity and remains always in its active GTP-bound form. In this study we investigated the role of RhoE in HCC. We examined the expression of RhoE in primary HCC samples from patients predominantly infected with the hepatitis B virus (HBV) and found that the RhoE messenger RNA (mRNA) level was frequently down-regulated (83.1%, 59/71) in HCCs. Low expression of RhoE in the tumors was significantly associated with shorter disease-free survival (P = 0.020) of the patients. Knockdown of RhoE by short-hairpin RNA using a lentiviral approach led to increased cell motility and invasiveness in SMMC7721 and BEL7402 HCC cells. Moreover, in vivo an orthotopic liver injection model in nude mice further demonstrated that knockdown of RhoE enhanced local invasion of HCC cells in the livers, with more invasive tumor front and increased incidence of venous invasion. Mechanistically, stable knockdown of RhoE in HCC cells significantly enhanced the phosphorylation of myosin phosphatase, promoted assembly of stress fibers, and increased the formation of plasma membrane blebbings, all these changes and activities being associated with activation of the Rho/Rho-kinase (ROCK) pathway. Conclusion: RhoE was frequently down-regulated in predominantly HBV-associated HCCs and this down-regulation was associated with a more aggressive HCC phenotype. RhoE regulated the cytoskeleton remodeling and suppressed HCC motility and invasiveness by way of inhibiting the Rho/ROCK axis. (HEPATOLOGY 2013)

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