HBx mutations promote hepatoma cell migration through the Wnt/?-catenin signaling pathway.
ABSTRACT: HBx mutations (T1753V, A1762T, G1764A, and T1768A) are frequently observed in hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). Aberrant activation of the Wnt/?-catenin signaling pathway is involved in the development of HCC. However, activation of the Wnt/?-catenin signaling pathway by HBx mutants has not been studied in hepatoma cells or HBV-associated HCC samples. In this study, we examined the effects of HBx mutants on the migration and proliferation of HCC cells and evaluated the activation of Wnt/?-catenin signaling in HBx-transfected HCC cells and HBV-related HCC tissues. We found that HBx mutants (T, A, TA, and Combo) promoted the migration and proliferation of hepatoma cells. The HBx Combo mutant potentiated TOP-luc activity and increased nuclear translocation of ?-catenin. Moreover, the HBx Combo mutant increased and stabilized ?-catenin levels through inactivation of glycogen synthase kinase-3?, resulting in upregulation of downstream target genes such as c-Myc, CTGF, and WISP2. Enhanced activation of Wnt/?-catenin was found in HCC tissues with HBx TA and Combo mutations. Knockdown of ?-catenin effectively abrogated cell migration and proliferation stimulated by the HBx TA and Combo mutants. Our results indicate that HBx mutants, especially the Combo mutant, allow constitutive activation of the Wnt signaling pathway and may play a pivotal role in HBV-associated hepatocarcinogenesis.
Project description:Hepatitis B virus (HBV) infection is a prominent cause of hepatocellular carcinoma (HCC) but the underlying molecular mechanisms are complex and multiple pathways have been proposed such as the activation of the Wnt-/?-catenin-signalling and dysregulation of E-cadherin/?-catenin adherens junctions. This study aimed to identify mechanisms of how HBV infection and replication as well as HBV X protein (HBx) gene expression in the context of an HBV genome influence Wnt-/?-catenin-signalling and formation of adherens junctions and to which extent HBx contributes to this. Regulation of E-cadherin/?-catenin junctions and ?-catenin-signalling as well as the role of HBx were investigated using constructs transiently or stably inducing replication of HBV+/-HBx in hepatoma cell lines. In addition, HCC and adjacent non-tumorous tissue samples from HBV-infected HCC patients and drug interference in HBV-infected cells were studied. Although HBV did not alter overall expression levels of E-cadherin or ?-catenin, it diminished their cell surface localization resulting in nuclear translocation of ?-catenin and activation of its target genes. In addition, HBV gene expression increased the amount of phosphorylated c-Src kinase. Treatment with Src kinase inhibitor Dasatinib reduced HBV replication, prevented adherens junction disassembly and reduced ?-catenin-signalling, while Sorafenib only did so in cells with mutated ?-catenin. Interestingly, none of the HBV induced alterations required HBx. Thus, HBV stimulated ?-catenin-signalling and induced disassembly of adherens junctions independently of HBx through Src kinase activation. These pathways may contribute to hepatocellular carcinogenesis and seem to be more efficiently inhibited by Dasatinib than by Sorafenib.
Project description:OBJECTIVES:Interleukin-34 (IL-34) is associated with hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC). However, the role and associated mechanisms of IL-34 in HBV-related HCC remain unclear. In this study, the expression, biological function and associated mechanisms of IL-34 in HBV-related HCC cells were investigated. METHODS:IL-34 expression induced by HBV and HBV X (HBX) gene was measured in hepatoma cells. The role of CCAAT/enhancer-binding protein ? (CEBP/?) in HBX-induced IL-34 expression was examined. The signal pathways involved in the expression of CEBP/? and IL-34 induced by HBX were assessed. The role of IL-34 in the proliferation and migration of HCC cells, and related mechanisms were explored. RESULTS:Dependent on HBX, HBV increased IL-34 expression in hepatoma cells, and HBX upregulated and interacted with CEBP/? to enhance the activity of IL-34 promoters. CEBP/? mediated by HBX was associated with the activation of PI3-K and NF-?B pathways to promote IL-34 expression. Via CSF1-R and CD138, IL-34 promoted the proliferation and migration of hepatoma cells, and contributed to the activation of ERK and STAT3 pathways and the upregulation of Bcl-xl and c-Myc mediated by HBX. CONCLUSION:We demonstrate that IL-34 contributes to HBX-mediated functional abnormality of HCC cells and provides a novel insight into the molecular mechanism of carcinogenesis mediated by HBX.
Project description:C-terminal-truncated hepatitis B virus (HBV) X (HBx) (ctHBX) is frequently detected in hepatocellular carcinoma (HCC) through HBV integration into the host genome. However, the molecular mechanisms underlying ctHBx-associated oncogenic signaling have not yet been clarified. To elucidate the biological role of ctHBx in hepato-oncogenesis, we functionally analyzed ctHBx-mediated regulation of the activin membrane-bound inhibitor bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) through transforming growth factor-? (TGF-?) or ?-catenin (CTNNB1) in HCC cells and in an animal model, and we compared its role to that of the full-length HBx protein. Ectopic ctHBx expression generated more colonies in anchorage-dependent and -independent growth assays than did HBx expression alone. ctHBx downregulated BAMBI to a greater degree than did HBx in HCC cells. HBx activated the Wnt/?-catenin pathway, which positively regulated the BAMBI expression through T-cell factor 1 signaling, whereas ctHBx negatively regulated the Wnt/?-catenin pathway. BAMBI downregulated the ?-catenin and TGF-?1 signaling pathways. TGF-?1 positively regulated BAMBI expression thorough Smad3 signaling. Furthermore, knockdown of BAMBI was more tumorigenic in HCC cells. Therefore, downregulation of both ?-catenin and TGF-?1 signaling by BAMBI might contribute to tumor suppression in mice xenotransplanted with HepG2 or SH-J1 cells. Taken together, ctHBx may have a more oncogenic role than HBx through its inhibition of tumor-suppressive ?-catenin/BAMBI signaling.
Project description:Clinical studies have associated hepatitis B virus core promoter (CP) mutations with an increased risk of hepatocellular carcinoma. The CP region overlaps with the HBV X (HBx) gene, which has been implicated in hepatocarcinogenesis. The cyclin kinase inhibitor p21WAF1/CIP1 is an important regulator of cell cycle progression and proliferation. We determined whether HBx mutants that result from mutations in the CP deregulate p21 and these processes.We constructed a series of HBx mutants with changes in the CP region that correspond to A1762T/G1764A (TA), T1753A, T1768A, or a combination of these (combo) and expressed them, along with wild-type HBx under control of its endogenous promoter, in primary human hepatocytes (PHHs) and HepG2 cells. We then analyzed the effects of CP mutations on expression and degradation of p21 and the effects on cell cycle progression and proliferation.The combo mutant decreased levels of p21 and increased cyclin E expression in PHHs and HepG2 cells. The combo mutant, but not HBx with single or double CP mutations, accelerated p21 degradation in HepG2 cells. The combo mutant increased expression of S-phase kinase-associated protein 2 (SKP2) in PHHs and Huh7 cells. Silencing of SKP2 abrogated the effects of CP mutations on p21 expression. The kinetics of p21 expression correlated with changes in cell cycle distribution. The combo mutant accelerated cell cycle progression; p21 overexpression restored G1 arrest.HBx mutants with changes that correspond to a combination of CP mutations up-regulate SKP2, which then down-regulates p21 via ubiquitin-mediated proteasomal degradation. CP mutations might increase the risk of hepatocellular carcinoma via this pathway.
Project description:Hepatitis B virus X protein (HBx) and cancer stem-like cells (CSCs) have both been implicated in the occurrence and development of HBV-related hepatocellular carcinoma (HCC). However, whether HBx contributes to the stem-like properties of OV6+ CSCs in HCC remains elusive. In this study, we showed that the concomitant expression of HBx and OV6 was closely associated with the clinical outcomes and prognosis of patients with HBV-related HCC. HBx was required for the stem-like properties of OV6+ liver CSCs, including self-renewal, stem cell-associated gene expression, tumorigenicity and chemoresistance. Mechanistically, HBx enhanced expression of MDM2 by directly binding with MDM2 and inhibiting its ubiquitin-directed self-degradation. MDM2 translocation into the nucleus was also upregulated by HBx and resulted in enhanced transcriptional activity and expression of CXCL12 and CXCR4 independent of p53. This change in expression activated the Wnt/?-catenin pathway and promoted the stem-like properties of OV6+ liver CSCs. Furthermore, we observed that the expression of any two indicators from the HBx/MDM2/CXCR4/OV6 axis in HCC biopsies could predict the prognosis of patients with HBV-related HCC. Taken together, our findings indicate the functional role of HBx in regulating the stem-like properties of OV6+ CSCs in HCC through the MDM2/CXCL12/CXCR4/?-catenin signaling axis, and identify HBx, MDM2, CXCR4 and OV6 as a novel prognostic pathway and potential therapeutic targets for patients with HBV-related HCC patients.
Project description:Understanding the molecular pathogenesis of hepatocellular carcinoma (HCC) is essential to identify therapeutic targets. A hepatitis B virus (HBV) related double transgenic murine model was developed.Liver specific expression of HBV X protein (HBx) and insulin receptor substrate 1 (IRS1) was achieved and transgenic mice were followed from birth to age 21 months. Liver and tumor tissue were assessed for histologic changes as well as activation of signal transduction pathways by qRT-PCR and multiplex ELISA protein assays.Overexpression of HBx and IRS1 stimulates liver cell proliferation in the double transgenic mice. Only the male mice developed HCC starting at age 15-18 months. The IN/IGF1/IRS1/MAPK/ERK and IN/IGF1/IRS1/PI3K/AKT/GSK3? cascades were activated early (6-9 months) in the liver followed by WNT/?-catenin and Notch signaling. Aspartate ?-hydroxylase (ASPH) was found to link these upstream growth factor signaling pathways to downstream Notch activation in tumor tissues.Sustained overexpression of HBx and IRS1 led to constitutive activation of a tripartite growth factor signal transduction cascade in the liver and was necessary and sufficient to promote HCC development and progression.
Project description:A high incidence of tumor recurrence and metastasis has been reported in hepatocellular carcinoma (HCC) patients with chronic hepatitis B virus (HBV) infection. Although the pathological relevance and significance of hepatitis B virus X protein (HBx) in HBV-associated hepatocarcinogenesis attracted much attention in recent years, the role and molecular mechanism for HBx in hepatoma invasion and metastasis remains poorly understood. In the present study, we found that HBx expression could induce epithelial-mesenchymal transition in hepatoma and hepatic cells. This effect was shown due to stabilized Snail protein through activating the phosphatidylinositol 3-kinase/protein kinase B/glycogen synthase kinase-3? (PI3K/AKT/GSK-3?) signal pathway by HBx expression. Functional studies revealed that HBx expression could enhance hepatoma cell migration and invasion in vitro. Moreover, stable HBx expression could also facilitate intrahepatic and distant lung metastasis of HCC in a nude mice tumor metastasis model in vivo. The correlation between increased PI3K/AKT/GSK-3? signaling with elevated Snail protein level was also observed in HCC tumor tissues with intrahepatic metastasis or chronic HBV infection. These results revealed a novel function of HBx in promoting epithelial-mesenchymal transition through Snail protein stabilization by activating PI3K/AKT/GSK-3? signaling, thus facilitating tumor invasion and metastasis during HCC progression. This could provide a putative molecular mechanism for tumor recurrence and metastasis in HBV-associated HCC patients.
Project description:Hepatitis B virus X protein plays a crucial role in the pathogenesis of hepatocellular carcinoma. We previously showed that the tumor suppressor ARID2 inhibits hepatoma cell cycle progression and tumor growth. Here, we evaluated whether hepatitis B virus X protein was involved in the modulation of ARID2 expression and hepatocarcinogenesis associated with hepatitis B virus infection. ARID2 expression was downregulated in HBV-replicative hepatoma cells, HBV transgenic mice, and HBV-related clinical HCC tissues. The expression levels of HBx were negatively associated with those of ARID2 in hepatocellular carcinoma tissues. Furthermore, HBx suppressed ARID2 at transcriptional level. Mechanistically, the promoter region of ARID2 gene inhibited by HBx was located at nt-1040/nt-601 and contained potential ATOH1 binding elements. In addition, ectopic expression of ATOH1 or mutation of ATOH1 binding sites within ARID2 promoter partially abolished HBx-triggered ARID2 transcriptional repression. Functionally, ARID2 abrogated HBx-enhanced migration and proliferation of hepatoma cells, whereas depletion of ATOH1 enhanced tumorigenecity of HCC cells. Therefore, our findings suggested that deregulation of ARID2 by HBx through ATOH1 may be involved in HBV-related hepatocellular carcinoma development.
Project description:We previously showed that hepatitis B virus (HBV) X protein (HBx) could promote the trimethylation of histone H3 lysine 9 (H3K9me3) to repress tumor suppressor genes in hepatocellular carcinoma (HCC). In this work, we analyze 23,148 human promoters using ChIP-chip to determine the effects of HBx on H3K9me3 enrichments in hepatoma cells with transfection of HBx-expressing plasmid. Immunohistochemistry for HBx and H3K9me3 was performed in 21 cases of HBV-associated HCC tissues. We identified that H3K9me3 immunoreactivity was significantly correlated with HBx staining in HCC tissues. ChIP-chip data indicated that HBx remarkably altered promoter enrichments of H3K9me3 in hepatoma cells. We identified 25 gene promoters, whose H3K9me3 enrichments are significantly altered in hepatoma cells transfected HBx-expressing plasmid, including 19 gaining H3K9m3, and six losing this mark. Most of these genes have not been previously reported in HCC, and BTBD17, MIR6089, ZNF205-AS1 and ZP1 have not previously been linked to cancer; only two genes (DAB2IP and ZNF185) have been reported in HCC. Genomic analyses suggested that genes with the differential H3K9me3 enrichments function in diverse cellular pathways and many are involved in cancer development and progression.
Project description:Tumor relapse after chemotherapy typifies hepatocellular carcinoma (HCC) and is believed to be attributable to residual cancer stem cells (CSCs) that survive initial treatment. Chronic infection with hepatitis B virus (HBV) has long been linked to the development of HCC. Upon infection, random HBV genome integration can lead to truncation of hepatitis B virus X (HBx) protein at the C-terminus. The resulting C-terminal-truncated HBx (HBx-?C) was previously shown to confer enhanced invasiveness and diminished apoptotic response in HCC cells. Here, we found HBx-?C to promote the appearance of a CD133 liver CSC subset and confer cancer and stem cell-like features in HCC. HBx-?C was exclusively detected in HCC cell lines that were raised from patients presented with a HBV background with concomitant CD133 expression. Stable overexpression of the naturally occurring HBx-?C mutants, HBx-?14 or HBx-?35, in HCC cells Huh7 and immortalized normal liver cells MIHA resulted in a significant increase in the cells ability to self-renew, resist chemotherapy and targeted therapy, migrate and induce angiogenesis. MIHA cells with the mutants stably overexpressed also resulted in the induction of CD133, mediated through STAT3 activation. RNA sequencing profiling of MIHA cells with or without HBx-?C mutants stably overexpressed identified altered FXR activation. This, together with rescue experiments using a selective FXR inhibitor suggested that C-terminal truncated HBx can mediate cancer stemness via FXR activation. Collectively, we find C-terminal truncated HBx mutants to confer cancer and stem cell-like features in vitro and to play an important role in driving tumor relapse in HCC.