A double-negative feedback loop between EZH2 and miR-26a regulates tumor cell growth in hepatocellular carcinoma

Zhuang,Chunbo; Wang,Pei; Huang,Da; Xu,Luming; Wang,Xiaobei; Wang,Lin; Hu,Lihua

doi:10.3892/ijo.2016.3336

A double-negative feedback loop between EZH2 and miR-26a regulates tumor cell growth in hepatocellular carcinoma

Authors:
- Chunbo Zhuang
- Pei Wang
- Da Huang
- Luming Xu
- Xiaobei Wang
- Lin Wang
- Lihua Hu
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Affiliations: Department of Clinical Laboratory Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China, Department of Gastroenterology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China, Regenerative Medicine Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China
Published online on: January 13, 2016 https://doi.org/10.3892/ijo.2016.3336
Pages: 1195-1204

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Abstract

Accumulating evidence demonstrates the important roles of microRNAs (miRNAs) in tumor development and progression. miR-26a has been reported to be downregulated in several types of cancers including hepatocellular carcinoma, but the underlying mechanism of how miR-26a is repressed remains largely unknown. In the present study, we performed western blot analysis, qRT-PCR, luciferase reporter assay and chromatin immunoprecipitation assay to investigate the relationship between miR-26a and the enhancer of zest homologue 2 (EZH2). CCK-8 assay and colony formation assay were carried out to explore the effect of miR-26a on HCC cells proliferation. We demonstrated that miR-26a was epigenetically repressed by EZH2-mediated H3K27 trimethylation within the miR-26a promoter. Moreover, we confirmed that EZH2 was also a direct target of miR-26a in HCC cells, thus, creating a double-negative feedback loop. Furthermore, miR-26a restoration increased the expressions of its host genes (CTDSPL and CTDSP2). Overexpression of EZH2 abrogated miR-26a induction of CTDSPL and CTDSP2. Restoring the balance of the double-negative feedback loop by miR-26a overpression or EZH2 silence significantly inhibited HCC cell growth. Overexpression of EZH2 rescued the growth inhibition effect of miR-26a. These findings suggest that an imbalanced double-negative feedback loop between EZH2 and miR-26a exists in HCC cells, which contributes to miR-26a deregulation and regulates tumor cells proliferation.

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