MicroRNA-100 promotes the autophagy of hepatocellular carcinoma cells by inhibiting the expression of mTOR and IGF-1R
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Yi-Yuan Ge1,*, Qing Shi1,*, Zhi-Yuan Zheng1, Jiao Gong1,2, Chunxian Zeng1, Jine Yang1 and Shi-Mei Zhuang1,2
1 Key Laboratory of Gene Engineering of the Ministry of Education, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, P.R. China
2 Key Laboratory of Liver Disease of Guangdong Province, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, P.R. China
* These authors contributed equally to this work
Shi-Mei Zhuang, email:
Keywords: miR-100, autophagy, mTOR, IGF-1R, hepatocellular carcinoma
Received: February 25, 2014 Accepted: July 8, 2014 Published: July 9, 2014
We found that restoration of miR-100 expression resulted in accumulation of LC3B-II and decrease of p62 in hepatocellular carcinoma (HCC) cells, whereas antagonism of miR-100 reduced the level of LC3B-II. Moreover, a significant correlation between miR-100 downregulation and p62 upregulation was observed in human HCC tissues, suggesting an autophagy-promoting effect of miR-100. Subsequent investigations disclosed that knockdown of Atg7 but not Beclin-1 attenuated the miR-100-induced LC3B-II elevation. Furthermore, miR-100 overexpression caused massive cell death, which was abrogated by both the Atg7 silencing and chloroquine treatment. Simultaneously, miR-100 expression led to increased fraction of cells with Annexin V-staining and loss of mitochondrial potential, implying that miR-100 may promote the Atg7-dependent autophagy and subsequent apoptotic cell death. Consistently, mouse xenograft models revealed that miR-100 inhibited the in vivo growth of HCC cells. We further showed that miR-100 suppressed the expression of mTOR and IGF-1R by binding to their 3’ untranslated region, and knockdown of mTOR or IGF-1R phenocopied the pro-autophagy effect of miR-100, indicating that miR-100 may promote autophagy by reducing mTOR and IGF-1R level. Collectively, our data uncover a new regulatory mechanism of autophagy and a novel function of miR-100, and provide a potential therapeutic target for HCC.
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