Oncotarget

Research Papers:

CSIG promotes hepatocellular carcinoma proliferation by activating c-MYC expression

Qian Cheng _, Fuwen Yuan, Fengmin Lu, Bo Zhang, Tianda Chen, Xiangmei Chen, Yuan Cheng, Na Li, Liwei Ma and Tanjun Tong

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Oncotarget. 2015; 6:4733-4744. https://doi.org/10.18632/oncotarget.2900

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Abstract

Qian Cheng1, Fuwen Yuan1, Fengmin Lu2, Bo Zhang3, Tianda Chen1, Xiangmei Chen2, Yuan Cheng4, Na Li1, Liwei Ma1, Tanjun Tong1

1The Peking University Research Center on Aging, Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing, China

2Department of Microbiology, Peking University Health Science Center, Beijing, China

3Department of Pathology, Peking University Health Science Center, Beijing, China

4Department of Histology and Embryology, Peking University Health Science Center, Beijing, China

Correspondence to:

Tanjun Tong, e-mail: ttj@bjmu.edu.cn

Keywords: CSIG, HCC, MYC, proliferation, protein degradation

Received: August 31, 2014     Accepted: December 15, 2014     Published: February 28, 2015

ABSTRACT

Cellular senescence-inhibited gene (CSIG) protein significantly prolongs the progression of replicative senescence, but its role in tumorigenesis is unclear. To reveal the role of CSIG in HCC, we determined its expression in HCC tissues and surrounding tissues and its functions in tumor cell proliferation in vitro and in vivo. CSIG protein was overexpressed in 86.4% of the human HCC cancerous tissues as compared with matched surrounding tissues, and its protein expression was greater in HCC cells than the non-transformed hepatic cell line L02. Furthermore, upregulation of CSIG significantly increased the colony formation of SMMC7721 and HepG2 cells, and silencing CSIG could induce cell cycle arrest and cell apoptosis. The tumorigenic ability of CSIG was confirmed in vivo in a mouse xenograft model. Our results showed that CSIG promoted the proliferation of HepG2 and SMMC7721 cells in vivo. Finally, CSIG protein directly interacted with c-MYC protein and increased c-MYC protein levels; the ubiquitination and degradation of c-MYC protein was increased with knockdown of CSIG. CSIG could also increase the expression of c-MYC protein in SMMC7721 cells in vivo, and it was noted that the level of c-MYC protein was also elevated in most human cancerous tissues with high level of CSIG.


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