Objective: Kupffer cells (KCs) protect against hepatocellular carcinoma (HCC) by communicating with other immune cells. However, the underlying mechanism(s) of this process is incompletely understood. Design: FVB/NJ mice were hydrodynamically injected with AKT/Ras and Sleeping Beauty transposon to induce HCC. Mini-circle and Sleeping Beauty were used to overexpress microRNA-206 in KCs of mice. Flow cytometry and immunostaining were used to evaluate the change in the immune system. Results: Hydrodynamic injection of AKT/Ras into mice drove M2 polarisation of KCs and depletion of cytotoxic T cells (CTLs) and promoted HCC development. M1-to-M2 transition of KCs impaired microRNA-206 biogenesis. By targeting Klf4 (kruppel like factor 4) and, thereby, enhancing the production of M1 markers including C-C motif chemokine ligand 2 (CCL2), microRNA-206 promoted M1 polarisation of macrophages. Indeed, microRNA-206-mediated increase of CCL2 facilitated hepatic recruitment of CTLs via CCR2. Disrupting each component of the KLF4/CCL2/CCR2 axis impaired the ability of microRNA-206 to drive M1 polarisation of macrophages and recruit CTLs. In AKT/Ras mice, KC-specific expression of microRNA-206 drove M1 polarisation of KCs and hepatic recruitment of CTLs and fully prevented HCC, while 100% of control mice died from HCC. Disrupting the interaction between microRNA-206 and Klf4 in KCs and depletion of CD8⁺ T cells impaired the ability of miR-206 to prevent HCC. Conclusions: M2 polarisation of KCs is a major contributor of HCC in AKT/Ras mice. MicroRNA-206, by driving M1 polarisation of KCs, promoted the recruitment of CD8⁺ T cells and prevented HCC, suggesting its potential use as an immunotherapeutic approach.

Hepatitis B virus (HBV)-encoded X protein (HBx) plays a critical role in HBV-related hepatocarcinoma development. In this study, we demonstrate that HBx is specifically modified by NEDD8. We found that E3 ligase HDM2 promotes NEDDylation of HBx to enhance HBx stability by preventing its ubiquitination-mediated degradation. Consistently, analysis of 160 hepatocellular carcinoma patient specimens indicated that the amount of HDM2 protein correlates with HBx protein level. We identified that HBx K91 and K95 as the key HBx NEDDylation sites and observed that the NEDDylation-deficient HBx has shorter half-life. We generated Huh7 cell lines which ectopically express wild-type and NEDDylation-deficient HBx and found that NEDDylation-deficient HBx showed less chromatin localization and less DDB1 binding. Consistently, the expression of HBx-regulated genes (IL-8, MMP9, and YAP) and HBV transcription (the activity of HBV enhancer and the amount of pgRNA transcribed from cccDNA) were significantly higher in cells expressing wild-type (WT) HBx than that in cells expressing mutant HBx. In addition, HBx-expressing cells proliferated faster than control and mutant HBx-expressing cells. We also showed that the ability of WT HBx-expressing cells to form tumors in nude mice was significantly higher than that of mutant HBx-expressing cells. In conclusion, we revealed that E3 ligase HDM2 promotes NEDDylation of HBx to enhance HBx stability and chromatin localization, which in turn favors HBx-dependent transcriptional regulation, cell proliferation, and HBV-driven tumor growth. IMPORTANCE Hepatitis B virus (HBV) HBx protein plays a critical role in viral replication and hepatocarcinogenesis. However, the regulation of HBx stability is not well understood. We found that HBx is modified by NEDD8 and that the HDM2 E3 ligase promotes HBx NEDDylation to enhance HBx stability by inhibiting its ubiquitination. We provide a new evidence to show the positive correlation between HDM2 and HBx in clinical hepatocellular carcinoma (HCC) samples. We also identified the major NEDDylation sites on HBx. Our studies indicate that the defective NEDDylation of HBx negatively affects its ability to activate the transcription of downstream genes and promote cell proliferation and tumor growth in vivo . Taken together, our findings reveal a novel posttranslational modification of HBx by HDM2 which regulates its stability, subcellular localization, and functions. These findings indicate that HDM2 is an important regulator on HBx and a potential diagnosis/therapeutic marker for HBV-associated HCC.

Background: Hepatic inflammation is the major risk factor of hepatocellular carcinoma (HCC). However, the underlying mechanism by which hepatic inflammation progresses to HCC is poorly understood. This study was designed to investigate the role of ETS translocation variant 4 (ETV4) in linking hepatic inflammation to HCC. Methods: Quantitative real‐time PCR and immunoblotting were used to detect the expression of ETV4 in HCC tissues and cell lines. RNA sequencing and luciferase reporter assays were performed to identify the target genes of ETV4. Hepatocyte‐specific ETV4 ‐knockout ( ETV4 ^{fl/fl, alb‐cre} ) and transgenic ( ETV4 ^Hep‐TG ) mice and diethylnitrosamine‐carbon tetrachloride (DEN‐CCL ₄ ) treatment experiments were applied to investigate the function of ETV4 in vivo . The Cancer Genome Atlas (TCGA) database mining and pathological analysis were carried out to determine the correlation of ETV4 with tumor necrosis factor‐alpha (TNF‐α) and mitogen‐activated protein kinase 11 (MAPK11). Results: We revealed that ETV4 was highly expressed in HCC. High levels of ETV4 predicted a poor survival rate of HCC patients. Then we identified ETV4 as a transcription activator of TNF‐α and MAPK11. ETV4 was positively correlated with TNF‐α and MAPK11 in HCC patients. As expected, an increase in hepatic TNF‐α secretion and macrophage accumulation were observed in the livers of ETV4 ^Hep‐TG mice. The protein levels of TNF‐α, MAPK11, and CD68 were significantly higher in the livers of ETV4 ^Hep‐TG mice compared with wild type mice but lower in ETV4 ^{fl/fl, alb‐cre} mice compared with ETV4 ^fl/fl mice as treated with DEN‐CCL ₄ , indicating that ETV4 functioned as a driver of TNF‐α/MAPK11 expression and macrophage accumulation during hepatic inflammation. Hepatocyte‐specific knockout of ETV4 significantly prevented development of DEN‐CCL ₄ ‐induced HCC, while transgenic expression of ETV4 promoted growth of HCC. Conclusions: ETV4 promoted hepatic inflammation and HCC by activating transcription of TNF‐α and MAPK11. Both the ETV4/TNF‐α and ETV4/MAPK11 axes represented two potential therapeutic targets for highly associated hepatic inflammation and HCC. ETV4+TNF‐α were potential prognostic markers for HCC patients.

Recent studies have indicated that a number of long noncoding RNAs (lncRNAs) are dysregulated in hepatocellular carcinoma, while their aberrant expressions are associated with tumorigenesis and poor prognosis. To identify hepatitis B virus (HBV)‐related lncRNAs, we used RNA deep sequencing to quantify the abundances of lncRNAs in HepG2 cells and HBV transgenic HepG2‐4D14 cells. Here, we demonstrate that lnc‐HUR1 is significantly upregulated in HepG2‐4D14 cells. We found that HBV‐encoded hepatitis B x protein can enhance the transcription of lnc‐HUR1. Overexpression of lnc‐HUR1 promotes cell proliferation, whereas knockdown of lnc‐HUR1 inhibits cell growth. We identified that lnc‐HUR1 can interact with p53 and inhibit its transcriptional regulation on downstream genes, such as p21 and B cell lymphoma 2–associated X protein. We generated lnc‐HUR1 transgenic mice and performed the partial hepatectomy (PHx) to examine liver regeneration. The data showed that the ratio of liver weight to body weight in lnc‐HUR1 transgenic mice is higher than that in wild‐type (WT) littermates at day 2 and day 3 following hepatectomy. Consistently, the results of bromodeoxyuridine staining on liver sections following hepatectomy indicate that the ratio of bromodeoxyuridine‐positive cells in lnc‐HUR1 transgenic mice is significantly higher than that in WT mice, suggesting that lnc‐HUR1 promotes cell proliferation during liver regeneration. Next, we performed the experiment of diethylnitrosamine‐induced tumorigenesis. The data demonstrate that tumor number in lnc‐HUR1 transgenic mice is higher compared with control mice, indicating that lnc‐HUR1 enhances diethylnitrosamine‐induced tumorigenesis. Conclusion: We reveal that HBV‐upregulated lnc‐HUR1 promotes cell proliferation and tumorigenesis by interacting with p53 to block downstream gene transcription. Our findings suggest that lnc‐HUR1 plays an important role in HBV‐related hepatocellular carcinoma development and may serve as a therapeutic marker for hepatocellular carcinoma. (Hepatology 2018; 00:000‐000).

Hepatitis B virus (HBV) infection causes chronic hepatitis in hundreds of millions of people worldwide, which can eventually lead to hepatocellular carcinoma (HCC). Previously, we found that HBV mRNAs can absorb microRNA-15a (miR-15a) to affect apoptosis through the Bcl-2 pathway. We asked whether HBV could inhibit apoptosis and promote tumorigenesis through different pathways. In this study, we found that the transforming growth factor β (TGF-β) pathway-inhibitory factor Smad7 is a novel target of miR-15a. We demonstrated that HBV can upregulate the level of Smad7 by downregulating miR-15a. Furthermore, we examined the level of Smad7 in liver samples from HBV-infected HCC patients and found that HBV mRNAs are positively correlated with the level of Smad7. By taking the approach of using immunoblotting and luciferase reporter assays, we revealed that HBV can abrogate TGF-β signaling via upregulating Smad7. By using annexin V staining and caspase 3/7 activity assays, we found that HBV can inhibit TGF-β-induced apoptosis of HepG2 cells. We also showed that HBV can promote tumor growth in BALB/c nude mice through upregulating the expression of Smad7. In conclusion, we demonstrated that HBV can upregulate Smad7 expression and inhibit TGF-β signaling, which makes the cells resistant to TGF-β-induced apoptosis and promotes tumorigenesis. IMPORTANCE Hepatitis B virus (HBV) infection causes chronic hepatitis, which can eventually lead to hepatocellular carcinoma (HCC). TGF-β signaling is closely linked to liver fibrosis, cirrhosis, and subsequent HCC progression and plays a unique role in the pathogenesis of HCC. At the early stage of tumor formation, TGF-β functions as a tumor suppressor that inhibits cell proliferation and induces apoptosis. Previously, we found that HBV mRNAs can sponge off miR-15a to affect apoptosis through the Bcl-2 pathway. In this study, we identified that the TGF-β-inhibitory factor Smad7 is a novel target of miR-15a. We reveal that HBV can abrogate TGF-β signaling via upregulating Smad7, inhibit TGF-β-induced apoptosis, as well as promote tumor development. Our study provides evidence to support the idea that viral RNAs can exert their functions as competing endogenous RNAs (ceRNAs) toward microRNA and participate in important cellular processes.

Hepatitis B virus (HBV) causes chronic hepatitis in hundreds of millions of people worldwide, which can eventually lead to hepatocellular carcinoma (HCC). The molecular mechanisms underlying HBV persistence are not well understood. In this study, we found that HBV inhibited the chemotherapy drug etoposide-induced apoptosis of hepatoma cells. Further analysis revealed that HBV mRNAs possess a microRNA 15a/16 (miR-15a/16)-complementary site (HBV nucleotides [nt] 1362 to 1383) that acts as a sponge to bind and sequester endogenous miR-15a/16. Consequently, Bcl-2, known as the target of miR-15a/16, was upregulated in HBV-infected cells. The data from HBV-transgenic mice further confirmed that HBV transcripts cause the reduction of miR-15a/16 and increase of Bcl-2. More importantly, we examined the levels of HBV transcripts and miR-15a/16 in HBV-infected HCC from patients and found that the amount of HBV mRNA and the level of miR-15a/16 were negatively correlated. Consistently, the level of Bcl-2 mRNA was upregulated in HBV-infected patients. In conclusion, we identified a novel HBV mRNA–miR-15a/16–Bcl-2 regulatory pathway that is involved in inhibiting etoposide-induced apoptosis of hepatoma cells, which may contribute to facilitating chronic HBV infection and hepatoma development.