Hsa-let-7g inhibits proliferation of hepatocellular carcinoma cells by downregulation of c-Myc and upregulation of p16INK4A

Authors

  • Fei-Fei Lan,

    1. Laboratory of Integrated Biosciences, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
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  • Hua Wang,

    1. Stanley Ho Center for Emerging Infectious Diseases, and Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China
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  • Yang-Chao Chen,

    1. Stanley Ho Center for Emerging Infectious Diseases, and Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China
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  • Chu-Yan Chan,

    1. Stanley Ho Center for Emerging Infectious Diseases, and Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China
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  • Samuel S. Ng,

    1. Department of Chemistry, The University of Hong Kong, Hong Kong, China
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  • Kui Li,

    1. Laboratory of Integrated Biosciences, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
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  • Dan Xie,

    1. State Key Laboratory of Oncology in Southern China, Cancer Center, Sun Yat-Sen University, Guangzhou, China
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  • Ming-Liang He,

    1. Stanley Ho Center for Emerging Infectious Diseases, and Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China
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  • Marie C. Lin,

    Corresponding author
    1. Brain Tumor Center, Department of Surgery, PWH, The Chinese University of Hong Kong, Hong Kong, China
    • Brain Tumor Center, Department of Surgery, PWH, The Chinese University of Hong Kong, Hong Kong, China
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    • Tel.: +852-2299-0776

  • Hsiang-Fu Kung

    Corresponding author
    1. Laboratory of Integrated Biosciences, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
    2. Stanley Ho Center for Emerging Infectious Diseases, and Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China
    3. State Key Laboratory of Oncology in Southern China, Cancer Center, Sun Yat-Sen University, Guangzhou, China
    • Room 511A, Stanley Ho Centre for Emerging Infectious Diseases, Basic Medical Sciences Building, The Chinese University of Hong Kong, Shatin, HKSAR, Hong Kong, China
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    • Tel.: +852-2603-7743, Fax: +852-2994-4988


Abstract

zMicroRNAs (miRNAs) are endogenously expressed small noncoding RNAs that regulate approximately one-third of human genes at post-transcription level. Previous studies have shown that miRNAs were implicated in many cellular processes and participated in the progress of various tumors including hepatocellular carcinoma (HCC). Among all miRNAs, the let-7 family is well recognized to play pivotal roles in tumorigenesis by functioning as potential growth suppressor. In the present study, we aimed to investigate the role of let-7 family, particularly the hsa-let-7g, in the molecular pathogenesis of HCC. By use of MTT, qPCR, Western blotting and 2-dimensional electrophoresis (2-DE), over-expression of hsa-let-7g was found to inhibit the proliferation of HCC cell line via negative and positive regulations of c-Myc and p16INK4A, respectively. The expression of hsa-let-7g was noted to be markedly lowered in the HepG2, Hep3B and Huh7 cells, yet higher in the Bel-7404 HCC cell line. Proliferation of HCC cell line was significantly inhibited after the transfection of hsa-let-7g mimics, while hsa-let-7g inhibitor transfection exerted an opposite effect. Concurrently, the mRNA and protein levels of c-Myc were found significantly decreased in HepG2 cells after transfection of hsa-let-7g mimics, but obviously increased in Bel-7404 cells after transfection of hsa-let-7g inhibitor. As revealed by 2-DE, a significant upregulation of p16INK4A was revealed after the gain-of-function study using hsa-let-7g. Therefore, we suggest that hsa-let-7g may act as a tumor suppressor gene that inhibits HCC cell proliferation by downregulating the oncogene, c-Myc, and upregulating the tumor suppressor gene, p16INK4A.

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