Tumor suppressive role of mitochondrial sirtuin 4 in induction of G2/M cell cycle arrest and apoptosis in hepatitis B virus-related hepatocellular carcinoma

Abstract

Hepatocellular carcinoma (HCC) is developed from uncontrolled cell growth after the malignant transformation of hepatocytes. The hepatitis B virus (HBV) X protein (HBx) has shown to induce cell cycle progression and hepatocarcinogenesis. A sub-fraction of HBx is localized in the mitochondria. Sirtuin 4 (SIRT4), a mitochondrial protein, has been demonstrated to play a tumor-suppressive role in many cancers, including HCC. However, little is known about the association between mitochondrial HBx and SIRT4 during hepatocarcinogenesis. We aimed to investigate the clinical significance and functional role of SIRT4 in HBV-related HCC. SIRT4 expression was significantly lower in the HCC tissues collected from 30 patients with HBV-related HCC than in normal liver tissues from control patients (p < 0.0001). TCGA data analysis indicated that SIRT4 expression was also lower in patients with HBV infection than in those without, and SIRT4 levels were positively associated with better patient survival. Similarly, HCC cell lines had lower SIRT4 expression than normal liver cell lines (all p < 0.01). Among the HCC cell lines, those harbored HBV had a lower SIRT4 expression than those without HBV (p < 0.0001). In vitro experiments revealed that stable HBx transfection suppressed SIRT4 expression in both HepG2 and Huh7 cells (both p < 0.001). Ectopic SIRT4 overexpression alone could induce cellular senescence through arresting cell-cycle progression at G2/M, and inducing cell apoptosis in HCC cells. Mechanistically, SIRT4 upregulated cell-cycle governing genes p16 and p21 protein expression, suppressed CyclinB1/Cdc2 and Cdc25c which normally induce cell-cycle progression, and suppressed survivin to induce apoptosis. Our findings demonstrate the interaction between HBV and SIRT4 in the context of HCC. SIRT4 involves in G2/M DNA damage checkpoint control and genomic stability in hepatocarcinogenesis, which could be targeted for future anticancer strategies.

Anti‑malarial drug dihydroartemisinin downregulates the expression levels of CDK1 and CCNB1 in liver cancer

“…Similarly, a study has demonstrated that HBV X protein induces cell cycle progression ( 38 ). Sirtuin 4 (SIRT4) suppresses CyclinB1/Cdc2 in HCC, and the expression levels of SIRT4 in HBV-infected patients are lower than those in uninfected patients ( 38 ).…”

“…However, the present study revealed that DHA had no significant effect on the protein expression levels of CCNB1 in HepG2 cells. This result may be due to the fact that the integration of hepatitis B virus (HBV) induced CCNB1 expression in HepG2215 cells compared with HepG2 cells ( 38 ). Similarly, a study has demonstrated that HBV X protein induces cell cycle progression ( 38 ).…”

“…This result may be due to the fact that the integration of hepatitis B virus (HBV) induced CCNB1 expression in HepG2215 cells compared with HepG2 cells ( 38 ). Similarly, a study has demonstrated that HBV X protein induces cell cycle progression ( 38 ). Sirtuin 4 (SIRT4) suppresses CyclinB1/Cdc2 in HCC, and the expression levels of SIRT4 in HBV-infected patients are lower than those in uninfected patients ( 38 ).…”

Sirtuins as Potential Therapeutic Targets for Hepatitis B Virus Infection

“…Notably, current evidence shows that the expression of all SIRT proteins can be modulated by HBV. In particular, expression levels of SIRT1 (6), SIRT2 (7), SIRT5 (8), and SIRT7 were found to be increased in HBV-infected cells (8,9), whereas those of SIRT3, SIRT4, and SIRT6 were decreased in HBV-infected hepatocytes (10)(11)(12)21). Of note, studies have also demonstrated that changes in the expression level of SIRT1 (14), SIRT2 (7), SIRT3 (11), SIRT4 (10), and SIRT7 are associated with a nonstructural viral protein, HBx (9).…”

“…Sirtuins (SIRTs) are nicotinamide adenine dinucleotide (NAD) + -dependent histone deacetylases that regulate various biological processes, including stress responses, apoptosis, and metabolism (4,5). In particular, emerging evidence shows that SIRTs play a significant role in chronic HBV infection (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16).…”