HBx mediated Increase of SIRT1 Contributes to HBV-related Hepatocellular Carcinoma Tumorigenesis

Abstract

Objective: Hepatocellular carcinoma (HCC) is one of the main causes of cancer-related deaths worldwide, and chronic hepatitis B virus (HBV) infection is strongly associated with HCC development, but the pathogenesis of HBV-related HCC remains obscure. Sirtuin 1 (SIRT1) has been implicated to enhance the replication of HBV and to promote the tumorigenesis of HCC. In this study, we aim to investigate the functional role of SIRT1 on HBV viral protein and HBV-induced HCC. Methods: Tumorous liver tissues from patient diagnosed with HBV-related HCC were collected and further divided into two groups (with or without metastasis). Then, the mRNA and protein level of SIRT1 in those tissues were detected by real time PCR and Western blot, respectively. Meanwhile, the protein level of epithelial-mesenchymal transition (EMT) relative markers in those tissues was determined by Western blot. Furthermore, the expression of SIRT1 in HBV-expressing HCC cells was examined. Next, the relationship between viral proteins and SIRT1 expression were determined by real time PCR and Western blot. In addition, the potential role of HBx-upregulated SIRT1 in HCC proliferation, migration and invasion were analyzed by cell viability assays, cell proliferation assay, wound healing assay, transwell assay and Western blot. Results: In this study, we found that the expression of SIRT1 was obviously increased in patients with metastasis compared to the patients without metastasis. Consistently, the expression of SIRT1 was also upregulated in HBV-expressing HCC cells compared to the controls. Further investigation showed that viral protein HBx was responsible for the elevated SIRT1 in HBV-expressing HCC cells. Meanwhile, the expression of HBx could be upregulated by SIRT1. Additionally, functional studies showed that HBx-elevated SIRT1 could promote HCC cell proliferation, migration and invasion. Importantly, HBx induced HCC proliferation and migration could be suppressed by Nicotinamide in a dose dependent manner. Conclusions: Our findings uncovered the positive role of SIRT1 in HBx-mediated tumorigenesis which implicated the potential role of SIRT1 in HBV-related HCC treatment.

NAMPT promotes hepatitis B virus replication and liver cancer cell proliferation through the regulation of aerobic glycolysis

“…Sirtuin 6 promotes the transcription and replication of HBV by upregulating the expression of peroxisome proliferator-activated receptor α (34). In addition, sirtuin 1 has been shown to be essential for HBV-associated liver cancer tumorigenesis (35)(36)(37). Therefore, the reduction of NAD synthesis by NAMPT inhibition may be an effective and promising method for the treatment of patients with HBV-associated liver cancer.…”

Sirtuins as Potential Therapeutic Targets for Hepatitis B Virus Infection

“…Specifically, Wang et al showed that, compared with those in the hepatoma cell line HepG2, the levels of SIRT1 mRNA and its protein were increased in HepG2.2.15 (HepG2 harboring HBV genome). Additionally, the HBV-mediated alteration in SIRT1 expression was further confirmed in HepAD38 cells, in which HBVs were continuously produced in the presence of tetracycline ( 14 ). Among the HBV-encoded proteins, only HBx has been found to increase SIRT1 expression at the mRNA and protein levels ( 14 ).…”

“…Additionally, the HBV-mediated alteration in SIRT1 expression was further confirmed in HepAD38 cells, in which HBVs were continuously produced in the presence of tetracycline ( 14 ). Among the HBV-encoded proteins, only HBx has been found to increase SIRT1 expression at the mRNA and protein levels ( 14 ). The expression of HBx could also be upregulated by SIRT1 in the HBV-expressing hepatocytes.…”

“…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 – 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 non-structural viral protein, HBx ( 9 ). Specifically, Wang et al showed that, compared with those in the hepatoma cell line HepG2, the levels of SIRT1 mRNA and its protein were increased in HepG2.2.15 (HepG2 harboring HBV genome).…”

“…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).…”