Epigenetic identification of ubiquitin carboxyl-terminal hydrolase L1 as a functional tumor suppressor and biomarker for hepatocellular carcinoma and other digestive tumors

Authors

  • Jun Yu,

    1. Institute of Digestive Disease and Department of Medicine, Chinese University of Hong Kong, Hong Kong
    2. State Key Laboratory in Oncology in South China, Sir YK Pao Center for Cancer, Chinese University of Hong Kong, Hong Kong
    3. Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
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  • Qian Tao,

    Corresponding author
    1. Cancer Epigenetics Laboratory, Department of Clinical Oncology, Chinese University of Hong Kong, Hong Kong
    2. State Key Laboratory in Oncology in South China, Sir YK Pao Center for Cancer, Chinese University of Hong Kong, Hong Kong
    3. Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
    • Room 315, Cancer Center, Department of Clinical Oncology, PWH, Chinese University of Hong Kong, Hong Kong
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    • fax: (852)-2648-8842.

  • Kin F. Cheung,

    1. Institute of Digestive Disease and Department of Medicine, Chinese University of Hong Kong, Hong Kong
    2. State Key Laboratory in Oncology in South China, Sir YK Pao Center for Cancer, Chinese University of Hong Kong, Hong Kong
    3. Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
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  • Hongchuan Jin,

    1. Cancer Epigenetics Laboratory, Department of Clinical Oncology, Chinese University of Hong Kong, Hong Kong
    2. State Key Laboratory in Oncology in South China, Sir YK Pao Center for Cancer, Chinese University of Hong Kong, Hong Kong
    3. Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
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  • Fan Fong Poon,

    1. Cancer Epigenetics Laboratory, Department of Clinical Oncology, Chinese University of Hong Kong, Hong Kong
    2. State Key Laboratory in Oncology in South China, Sir YK Pao Center for Cancer, Chinese University of Hong Kong, Hong Kong
    3. Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
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  • Xian Wang,

    1. Cancer Epigenetics Laboratory, Department of Clinical Oncology, Chinese University of Hong Kong, Hong Kong
    2. State Key Laboratory in Oncology in South China, Sir YK Pao Center for Cancer, Chinese University of Hong Kong, Hong Kong
    3. Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
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  • Hongyu Li,

    1. Cancer Epigenetics Laboratory, Department of Clinical Oncology, Chinese University of Hong Kong, Hong Kong
    2. State Key Laboratory in Oncology in South China, Sir YK Pao Center for Cancer, Chinese University of Hong Kong, Hong Kong
    3. Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
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  • Yuen Y. Cheng,

    1. Institute of Digestive Disease and Department of Medicine, Chinese University of Hong Kong, Hong Kong
    2. State Key Laboratory in Oncology in South China, Sir YK Pao Center for Cancer, Chinese University of Hong Kong, Hong Kong
    3. Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
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  • Christoph Röcken,

    1. Institute of Pathology, Charite University Hospital, Berlin, Germany
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  • Matthias P. A. Ebert,

    1. Department of Medicine II, Technical University of Munich, Munich, Germany
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  • Anthony T. C. Chan,

    1. Cancer Epigenetics Laboratory, Department of Clinical Oncology, Chinese University of Hong Kong, Hong Kong
    2. State Key Laboratory in Oncology in South China, Sir YK Pao Center for Cancer, Chinese University of Hong Kong, Hong Kong
    3. Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
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  • Joseph J. Y. Sung

    Corresponding author
    1. Institute of Digestive Disease and Department of Medicine, Chinese University of Hong Kong, Hong Kong
    2. State Key Laboratory in Oncology in South China, Sir YK Pao Center for Cancer, Chinese University of Hong Kong, Hong Kong
    3. Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong
    • Institute of Digestive Disease, Department of Medicine and Therapeutics, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, NT, Hong Kong
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    • fax: (852) 26461852.


  • Potential conflict of interest: Nothing to report.

Abstract

The ubiquitin carboxyl-terminal hydrolase L1 (UCHL1) is a carboxyl-terminal ubiquitin hydrolase regulating cellular ubiquitin levels, recently suggested as a tumor suppressor. However, the role of UCHL1 in hepatocellular carcinoma (HCC) is not clear. We investigated the expression and DNA methylation of the UCHL1 in primary HCC, liver metastases from digestive carcinomas, and primary digestive cancers. UCHL1 is expressed in all normal tissues and immortalized normal epithelial cell lines, but was low or silenced in 77% (10/13) of HCC cell lines, which is well correlated with its promoter methylation status. Methylation was further detected in 44% (12/27) of HCCs, but less in metastatic tumors generated from colorectal and stomach in the liver (19%, 3/16; P < 0.05). Methylation was also detected in primary digestive tumors, including 71% (22/31) of colon, 77% (53/69) of gastric, and 40% (18/45) of esophageal carcinomas, but none or occasionally in paired adjacent nontumor tissues. Detailed methylation analysis of 49 CpG sites at a 540-bp promoter region by bisulfite genomic sequencing confirmed the methylation. UCHL1 silencing could be reversed by chemical or genetic demethylation of the promoter, indicating direct epigenetic silencing. Restoring UCHL1 expression in silenced cell lines significantly inhibited their growth and colony formation ability by inhibiting cell proliferation, causing cell cycle arrest in G2/M phase and inducing apoptosis through the intrinsic caspase-dependent pathway. Moreover, UCHL1 directly interacts with p53 and stabilizes p53 through the ubiquitination pathway. Conclusion: Epigenetic inactivation of UCHL1 is common in primary HCCs and other digestive tumors. UCHL1 appears to be a functional tumor suppressor involved in the tumorigenesis of HCCs and other digestive cancers. (HEPATOLOGY 2008;48:508–518.)

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