Interferon alpha inhibits the nuclear factor kappa B activation triggered by X gene product of hepatitis B virus in human hepatoma cells

Atypical inflammatory kinase IKBKE phosphorylates and inactivates FoxA1 to promote liver tumorigenesis

Physiologically, FoxA1 plays a key role in liver differentiation and development, and pathologically exhibits an oncogenic role in prostate and breast cancers. However, its role and upstream regulation in liver tumorigenesis remain unclear. Here, we demonstrate that FoxA1 acts as a tumor suppressor in liver cancer. Using a CRISPR-based kinome screening approach, noncanonical inflammatory kinase IKBKE has been identified to inhibit FoxA1 transcriptional activity. Notably, IKBKE directly binds to and phosphorylates FoxA1 to reduce its complex formation and DNA interaction, leading to elevated hepatocellular malignancies. Nonphosphorylated mimic Foxa1 knock-in mice markedly delay liver tumorigenesis in hydrodynamic transfection murine models, while phospho-mimic Foxa1 knock-in phenocopy Foxa1 knockout mice to exhibit developmental defects and liver inflammation. Notably, Ikbke knockout delays diethylnitrosamine (DEN)-induced mouse liver tumor development. Together, our findings not only reveal FoxA1 as a bona fide substrate and negative nuclear effector of IKBKE in hepatocellular carcinioma (HCC) but also provide a promising strategy to target IKBEK for HCC therapy.

HBx-induced NF-κB signaling in liver cells is potentially mediated by the ternary complex of HBx with p22-FLIP and NEMO

Sustained activation of NF-κB is one of the causative factors for various liver diseases, including liver inflammation and hepatocellular carcinoma (HCC). It has been known that activating the NF-κB signal by hepatitis B virus X protein (HBx) is implicated in the development of HCC. However, despite numerous studies on HBx-induced NF-κB activation, the detailed mechanisms still remain unsolved. Recently, p22-FLIP, a cleavage product of c-FLIP_L, has been reported to induce NF-κB activation through interaction with the IκB kinase (IKK) complex in primary immune cells. Since our previous report on the interaction of HBx with c-FLIP_L, we explored whether p22-FLIP is involved in the modulation of HBx function. First, we identified the expression of endogenous p22-FLIP in liver cells. NF-κB reporter assay and electrophoretic mobility shift assay (EMSA) revealed that the expression of p22-FLIP synergistically enhances HBx-induced NF-κB activation. Moreover, we found that HBx physically interacts with p22-FLIP and NEMO and potentially forms a ternary complex. Knock-down of c-FLIP leading to the downregulation of p22-FLIP showed that endogenous p22-FLIP is involved in HBx-induced NF-κB activation, and the formation of a ternary complex is necessary to activate NF-κB signaling. In conclusion, we showed a novel mechanism of HBx-induced NF-κB activation in which ternary complex formation is involved among HBx, p22-FLIP and NEMO. Our findings will extend the understanding of HBx-induced NF-κB activation and provide a new target for intervention in HBV-associated liver diseases and in the development of HCC.

N-acetylcysteine improves antitumoural response of Interferon alpha by NF-kB downregulation in liver cancer cells

Background

Liver cancer is one of the most common malignancies in the world and at the moment, there is no drug intervention effective for the treatment of liver tumours. Investigate the effect of N-acetylcysteine (NAC), which has been studied for its antitumoural properties, on the toxicity of hepatocarcinoma (HCC) cells in vitro when used with the drug interferon alpha-2A (IFN), which is used clinically to treat HCC.

Results

NAC, IFN and NAC plus IFN reduced cell viability, as determined by MTT assay. More importantly, NAC potentiates the cytotoxic effect of IFN, with the best response achieved with 10 mM of NAC and 2.5 x 10⁴ of IFN. These results were confirmed by Annexin/PI staining through flow cytometry and morphologic analyses. Co-treatment reduced the expression of the nuclear transcription factor kappa-B (NF-kB). In a similar way to NAC, RNAi against p65 potentiated the toxic effect of IFN, suggesting that, indeed, NAC may be enhancing the effect of IFN through inhibition of NF-kB.

Conclusions

Our results support the notion that NAC may be an important drug for the treatment of liver tumours as primary or adjuvant therapy. IFN has a limited clinical response, and therefore, the anti-proliferative properties of NAC in the liver should be explored further as an alternative for non-responders to IFN treatment.

Hepatitis B virus X protein induces IKKα nuclear translocation via Akt-dependent phosphorylation to promote the motility of hepatocarcinoma cells

Hepatitis B virus (HBV) X protein (HBx) has been implicated in HBV-associated carcinogenesis through activation of IκB kinase (IKK)/nuclear factor kappa B (NF-κB) signaling pathway. Besides activating NF-κB in the cytoplasm, IKKα was found in the nucleus to regulate gene expression epigenetically in response to various stimuli. However, it is unknown whether nuclear IKKα plays a role in HBx-associated tumor progression. Moreover, the molecular mechanism underlying IKKα nuclear transport also remains to be elucidated. Here, we disclosed HBx as a new inducer of IKKα nuclear transport in hepatoma cells. HBx induced IKKα nuclear transport in an Akt-dependent manner. HBx-activated Akt promoted IKKα nuclear translocation via phosphorylating its threonine-23 (Thr23). In addition, IKKα ubiquitination enhanced by HBx and Akt also contributed to the IKKα accumulation in the nucleus, indicating the involvement of ubiquitination in Akt-increased IKKα nuclear transport in response to HBx. Furthermore, inhibition of IKKα nuclear translocation by mutation of its nuclear localization signal and Thr23 diminished IKKα-dependent cell migration. Taken together, our findings shed light on the molecular mechanism of IKKα nuclear translocation and provide a potential role of nuclear IKKα in HBx-mediated hepatocellular carcinoma (HCC) progression.

PKR-dependent mechanisms of interferon-α for inhibiting hepatitis B virus replication

Interferon-α (IFN-α) inhibits the replication of hepatitis B virus (HBV) in vivo and in vitro, but the molecular mechanism of this inhibition has been elusive. We found that while HBV replication in transfected human hepatoma Huh-7 cell was severely inhibited by IFN-α treatment as reported previously, this inhibition was markedly impaired in the cell in which the expression of IFN-inducible, double-stranded RNA-dependent protein kinase (PKR) was stably and specifically suppressed through RNA-interference. Intracellular level of viral capsids was down-regulated likewise in a PKR-dependent manner, whereas that of HBV transcripts including the viral RNA pregenome was not affected by IFN-α treatment. Ectopic expression of PKR also resulted in the reduction of viral capsids with concomitant increase of phosphorylated eIF2α. These results suggested that PKR functions as a key mediator of IFN-α in opposing HBV replication, most likely through the inhibition of protein synthesis.

Impact of hepatitis B virus (HBV) x gene mutations on hepatocellular carcinoma development in chronic HBV infection

The hepatitis B virus (HBV) PreS mutations C1653T, T1753V, and A1762T/G1764A were reported as a strong risk factor of hepatocellular carcinoma (HCC) in a meta-analysis. HBV core promoter overlaps partially with HBx coding sequence, so the nucleotide 1762 and 1764 mutations induce HBV X protein (HBx) 130 and 131 substitutions. We sought to elucidate the impact of HBx mutations on HCC development. Chronically HBV-infected patients were enrolled in this study: 42 chronic hepatitis B (CHB) patients, 23 liver cirrhosis (LC) patients, and 31 HCC patients. Direct sequencing showed HBx131, HBx130, HBx5, HBx94, and HBx38 amino acid mutations were common in HCC patients. Of various mutations, HBx130+HBx131 (double) mutations and HBx5+HBx130+HBx131 (triple) mutations were significantly high in HCC patients. Double and triple mutations increased the risk for HCC by 3.75-fold (95% confidence interval [CI] = 1.101 to 12.768, P = 0.033) and 5.34-fold (95% CI = 1.65 to 17.309, P = 0.005), respectively, when HCC patients were compared to CHB patients. Functionally, there were significantly higher levels of NF-κB activity in cells with the HBx5 mutant and with the double mutants than that of wild-type cells and the triple-mutant cells. The triple mutation did not increase NF-κB activity. Other regulatory pathways seem to exist for NF-κB activation. In conclusion, a specific HBx mutation may contribute to HCC development by activating NF-κB activity. The HBx5 mutation in genotype C2 HBV appears to be a risk factor for the development of HCC and may be used to predict the clinical outcomes of patients with chronic HBV infection.

Role of nuclear factor kappaB in liver health and disease

NF-kappaB (nuclear factor kappaB) is a heterodimeric transcription factor that is constitutively expressed in all cell types and has a central role as a transcriptional regulator in response to cellular stress. In the present review, we discuss the role of NF-kappaB signalling in the maintenance of liver homoeostasis as well as in the pathogenesis of a wide variety of conditions affecting the liver, including viral hepatitis, steatohepatitis, cirrhosis and hepatocellular carcinoma. Much of the current knowledge of NF-kappaB signalling in the liver relates to the canonical pathway, the IKK [IkappaB (inhibitor of kappaB) kinase] complex and the RelA subunit. We explore the weaknesses of the experimental approaches to date and suggest that further work is needed to investigate in detail the discreet functions of each of the Rel subunits in liver physiology and disease.

The hepatitis B viral X protein activates NF-kappaB signaling pathway through the up-regulation of TBK1

The hepatitis B viral X protein (HBx) is a multifunctional protein that plays a role in the activation of the NF-kappaB signaling pathway. In this study, we demonstrate that HBx up-regulates expression of TANK-binding kinase-1 (TBK1) at the transcriptional level. Increased levels of TBK1 protein then induce the phosphorylation of NF-kappaB p65 at serine 536. Because TBK1 is up-regulated by HBx as part of its promotion of NF-kappaB activation, it is possible that increased TBK1 levels play a role in the development of hepatocellular carcinoma (HCC). From these data, we suggest that TBK1 may play a role in the HBx-mediated activation of the NF-kappaB signaling pathway and the development of HCCs.

Hepatocellular carcinoma cells containing hepatitis B virus X protein have enhanced invasive potential conditionally

AIMS

To establish a sustaining hepatitis B virus X protein expressed Chang liver cell line and to explore their biological behaviours of invasive potential induced by hepatitis B virus X protein.

METHODS

Polymerase chain reaction was used to amplify the HBx gene from the whole hepatitis B virus genome. The gene was then subcloned into the eukaryotic expression vector pcDNA3.1 to construct the pcDNA3.1-HBx plasmid. Gene transfection mediated by Lipofectamine was used to introduce the plasmid into the human liver cell line Chang, and stable expression of the HBx gene was detected.

RESULTS

HBx gene was cloned from the transfected Chang liver cells by reverse transcription-polymerase chain reaction, and confirmed by electrophoresis. The stably transfected Chang cells expressing HBx with malignant characteristics were verified and compared with control cells in terms of their growth curves, clonogenicity, wound healing abilities, migration and metastasis.

CONCLUSION

The stabilising human liver cell lines Chang liver containing HBx gene expression have been established successfully. The invasive potential of Chang cells was conditionally enhanced by HBx transfection.

Roxithromycin inhibits constitutive activation of nuclear factor {kappa}B by diminishing oxidative stress in a rat model of hepatocellular carcinoma

PURPOSE

Recently, 14-member macrolide antibiotics such as clarithromycin and roxithromycin have been shown to have anticancer and antiangiogenic effects. We investigated the suppressive effect of roxithromycin on accelerated hepatocellular carcinoma growth in a rat hepatocarcinogenetic model and compared results with effects from TNP-470.

EXPERIMENTAL DESIGN

Tumor was induced by oral diethylnitrosamine administration for 17 weeks. Normal saline, TNP-470 (50 mg/kg), or roxithromycin (40 or 100 mg/kg) was administered i.p. thrice per week from week 10 to 17.

RESULTS

Carcinomatous tissue growing outside dysplastic nodules and a marked expression of placental glutathione S-transferase were detected in rats with induced carcinogenesis. Tumor growth was accompanied by augmented expression of inducible nitric oxide synthase, activation of nuclear factor kappaB, and increased lipid peroxidation level. All these effects were absent in animals that received roxithromycin or TNP-470. The inhibitory effect of roxithromycin was dose dependent and no clear differences were noted between groups given roxithromycin 100 mg/kg and TNP-470 50 mg/kg.

CONCLUSIONS

Our results indicate that roxithromycin inhibits oxidative stress, nitric oxide production, and nuclear factor kappaB activation induced by experimental hepatocarcinogenesis. The data provide additional evidence for the potential use of roxithromycin in treatment of hepatocellular carcinoma prevention.

Interferon-gamma inhibits hepatitis B virus-induced NF-kappaB activation through nuclear localization of NF-kappaB-inducing kinase

BACKGROUND & AIMS

Nuclear factor-kappaB (NF-kappaB) signaling pathway is an important regulating pathway in liver diseases, including hepatocellular carcinoma. In our study, immunohistochemical analysis showed that NF-kappaB-inducing kinase (NIK), an upstream kinase of IkappaB kinases, nuclear localization occurs only in liver tissues obtained from hepatitis B surface antigen (HBsAg)(+) patients but not in tissues from HBsAg(-) patients. The aim of the present study was to identify the inducer of NIK nuclear localization and determine whether the NIK nuclear localization affects the hepatitis B virus (HBV)-mediated NF-kappaB activation.

METHODS

The experiments were performed on HepG2.2.15 cells and on HepG2 cells transfected with pHBV1.2x, a plasmid encoding all HBV messages, using NF-kappaB-dependent luciferase reporter gene assay, electrophoretic mobility shift assay, immunoblot analysis, and fluorescent microscopy analysis.

RESULTS

HBV induced NIK-dependent NF-kappaB activation. However, interferon (IFN)-gamma induced NIK nuclear localization and inhibited NF-kappaB activation in HepG2.2.15 cells and in HepG2 cells transfected with pHBV1.2x. When NIK nuclear localization was inhibited by deletion of nuclear localization signal on NIK, IFN-gamma did not induce the NIK nuclear localization and did not inhibit NF-kappaB activation.

CONCLUSIONS

IFN-gamma selectively inhibits HBV-mediated NF-kappaB activation. This inhibition is accomplished by NIK nuclear localization, which is a novel mechanism of NF-kappaB inhibition.