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Background: Histone deacetylase 8 (HDAC8), a member of class I HDACs, has been reported to be involved in transcriptional regulation, cell cycle progression, and developmental events, and several studies have shown that HDAC8 plays a critical role in tumorigenesis. However, the expression level and the potential role of HDAC8 in hepatocellular carcinoma (HCC) remain unclear. Aim: The purpose of this study was to investigate protein expression of HDAC8 in HCC tissues and the effects of HDAC8 knockdown on the proliferation and apoptosis of liver cancer cells, and to explore the possible mechanisms. Methods: First, we used quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR), immunohistochemical staining, and western blot to examine the mRNA and protein expression of HDAC8 in HCC cell lines and tissues. Then, we assessed the correlation between clinicopathological parameters and the protein expression of HDAC8. Furthermore, we employed the interfering RNA method to explore the potential role of HDAC8 in HCC progression in vitro. Results: Our results showed that expression of HDAC8 was significantly up-regulated both in HCC cell lines and tumor tissues compared to human normal liver cell line LO2 and corresponding non-tumor tissues. Moreover, we found that HDAC8 knockdown could dramatically inhibit HCC cell proliferation and enhance the apoptosis rate in vitro. Western blot revealed that intrinsic apoptotic pathway proteins, including BAX, BAD, and BAK, were elevated after HDAC8 knockdown. The cleavage of caspase-3 and PARP, which are downstream of intrinsic apoptotic pathway, were also enhanced. In addition, suppression of HDAC8 also elevated the expression of p53 and acetylation of p53 at Lys382, whereas the acetylation of p53 at Lys373 did not change. Conclusions: Our study revealed that HDAC8 was overexpressed in HCC. HDAC8 knockdown suppresses tumor growth and enhances apoptosis in HCC via elevating the expression of p53 and acetylation of p53 at Lys382. HDAC8 might serve as a potential therapeutic target in HCC. [ABSTRACT FROM AUTHOR]

Mitochondrial GTPase mitofusin-2 ( Mfn2) is a novel gene that remarkably suppresses the injury-mediated proliferation of vascular smooth muscle cells (VSMCs) and has a potential apoptotic effect via the mitochondrial apoptotic pathway. Hepatocellular carcinoma (HCC) tissues and matched normal tissues were examined for mfn2 expression. HCC cells were infected with adenovirus carrying Mfn2 (Ad-mfn2) or green fluorescent protein (Ad-GFP), used as a control. Short hairpin RNA (shRNA) was formed by shR-mfn2 and shR-Bax to repress mfn2 and Bax transcription, respectively. The effects of mfn2 on cell cycle distribution and apoptosis were measured by flow cytometric analysis. Significant downregulation of mfn2 was observed in HCC tissues compared with nearby normal tissues. Overexpression of mfn2 inhibited HCC cell proliferation and induced apoptosis by increasing the level of active caspase-3 and poly (ADP-ribose) polymerase (PARP) cleavage. Overexpression of mfn2 also induced cytochrome c release to the cytoplasm by enhancing Bax translocation from the cytoplasm to the mitochondrial membrane. Upregulation of mfn2 promoted apoptosis of HCC cells, and this was dramatically suppressed by shR-Bax. Our results show that the mfn2 gene is a potential tumor suppressor target that may significantly promote apoptosis via Bax and may inhibit proliferation in HCC cells. This gene may be an important therapeutic target for the treatment of tumors or hyperproliferative diseases. [ABSTRACT FROM AUTHOR]