Enhanced hepatocarcinogenesis in mouse models and human hepatocellular carcinoma by coordinate KLF6 depletion and increased messenger RNA splicing

Authors

  • Diana Vetter,

    1. Department of Medicine/Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY
    2. Department of Abdominal Surgery, University Hospital of Zurich, Zurich, Switzerland
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  • Michal Cohen-Naftaly,

    1. Department of Medicine/Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY
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  • Augusto Villanueva,

    1. HCC Translational Research Laboratory, Barcelona-Clinic Liver Cancer Group, Liver Unit. Institut d'Investigacions Biomediques August Pi i Sunyer (IDIBAPS), Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Hospital Clinic, Barcelona, Spain
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  • Youngmin A. Lee,

    1. Department of Medicine/Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY
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  • Peri Kocabayoglu,

    1. Department of Medicine/Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY
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  • Rebekka Hannivoort,

    1. Department of Medicine/Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY
    2. Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
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  • Goutham Narla,

    1. Department of Medicine/Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY
    2. Departments of Genetics & Genomic Sciences, Mount Sinai School of Medicine, New York, NY
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  • Josep M. Llovet,

    1. Department of Medicine/Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY
    2. HCC Translational Research Laboratory, Barcelona-Clinic Liver Cancer Group, Liver Unit. Institut d'Investigacions Biomediques August Pi i Sunyer (IDIBAPS), Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Hospital Clinic, Barcelona, Spain
    3. Institució Catalana de Recerca i Estudis Avançats, Hospital Clinic, Barcelona, Spain
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  • Swan N. Thung,

    1. Department of Pathology, Mount Sinai School of Medicine, New York, NY
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  • Scott L. Friedman

    Corresponding author
    1. Department of Medicine/Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY
    • Division of Liver Diseases, Box 1123, Mount Sinai School of Medicine, 1425 Madison Ave., Room 11-70C, New York, NY 10029-6574
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    • fax: 212-849-2574


  • Potential conflict of interest: Nothing to report.

Abstract

KLF6-SV1 (SV1), the major splice variant of KLF6, antagonizes the KLF6 tumor suppressor by an unknown mechanism. Decreased KLF6 expression in human hepatocellular carcinoma (HCC) correlates with increased mortality, but the contribution of increased SV1 is unknown. We sought to define the impact of SV1 on human outcomes and experimental murine hepatocarcinogenesis and to elucidate its mechanism of action. In hepatitis C virus (HCV)-related HCC, an increased ratio of SV1/KLF6 within the tumor was associated with features of more advanced disease. Six months after a single injection of diethylnitrosamine (DEN), SV1 hepatocyte transgenic mice developed more histologically advanced tumors, whereas Klf6-depleted mice developed bigger tumors compared to the Klf6fl(+/+) control mice. Nine months after DEN, SV1 transgenic mice with Klf6 depletion had the greatest tumor burden. Primary mouse hepatocytes from both the SV1 transgenic animals and those with hepatocyte-specific Klf6 depletion displayed increased DNA synthesis, with an additive effect in hepatocytes harboring both SV1 overexpression and Klf6 depletion. Parallel results were obtained by viral SV1 transduction and depletion of Klf6 through adenovirus-Cre infection of primary Klf6fl(+/+) hepatocytes. Increased DNA synthesis was due to both enhanced cell proliferation and increased ploidy. Coimmunoprecipitation studies in 293T cells uncovered a direct interaction of transfected SV1 with KLF6. Accelerated KLF6 degradation in the presence of SV1 was abrogated by the proteasome inhibitor MG132. Conclusion: An increased SV1/KLF6 ratio correlates with more aggressive HCC. In mice, an increased SV1/KLF6 ratio, generated either by increasing SV1, decreasing KLF6, or both, accelerates hepatic carcinogenesis. Moreover, SV1 binds directly to KLF6 and accelerates its degradation. These findings represent a novel mechanism underlying the antagonism of tumor suppressor gene function by a splice variant of the same gene. (HEPATOLOGY 2012)

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