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A specific cholesterol metabolic pathway is established in a subset of HCCs for tumor growth Free
Ming Lu1,†, Xi-Han Hu1,†, Qin Li1, Ying Xiong1, Guang-Jing Hu1, Jia-Jia Xu1, Xiao-Nan Zhao1, Xi-Xiao Wei1, Catherine C.Y. Chang2, Yin-Kun Liu3, Fa-Jun Nan4, Jia Li4, Ta-Yuan Chang2, Bao-Liang Song1,*, and Bo-Liang Li1,*
1State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
2Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA
3Liver Cancer Institute of Zhong Shan Hospital, Fudan University, Shanghai 200031, China
4National Center for Drug Screening, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China *Correspondence to:Bo-Liang Li, E-mail: blli@sibcb.ac.cn; Bao-Liang Song, E-mail: blsong@sibcb.ac.cn
J Mol Cell Biol, Volume 5, Issue 6, December 2013, 404-415,  https://doi.org/10.1093/jmcb/mjt039
Keyword: ACAT2, CpG methylation, oxysterol secretion, inhibition of tumor growth, HCC

The liver plays a central role in cholesterol homeostasis. It exclusively receives and metabolizes oxysterols, which are important metabolites of cholesterol and are more cytotoxic than free cholesterol, from all extrahepatic tissues. Hepatocellular carcinomas (HCCs) impair certain liver functions and cause pathological alterations in many processes including cholesterol metabolism. However, the link between an altered cholesterol metabolism and HCC development is unclear. Human ACAT2 is abundantly expressed in intestine and fetal liver. Our previous studies have shown that ACAT2 is induced in certain HCC tissues. Here, by investigating tissue samples from HCC patients and HCC cell lines, we report that a specific cholesterol metabolic pathway, involving induction of ACAT2 and esterification of excess oxysterols for secretion to avoid cytotoxicity, is established in a subset of HCCs for tumor growth. Inhibiting ACAT2 leads to the intracellular accumulation of unesterified oxysterols and suppresses the growth of both HCC cell lines and their xenograft tumors. Further mechanistic studies reveal that HCC-linked promoter hypomethylation is essential for the induction of ACAT2 gene expression. We postulate that specifically blocking this HCC-established cholesterol metabolic pathway may have potential therapeutic applications for HCC patients.