Gut Bifidobacterium longum is associated with better native liver survival in patients with biliary atresia.

Background & Aims: The gut microbiome plays an important role in liver diseases, but its specific impact on biliary atresia (BA) remains to be explored. We aimed to investigate the microbial signature in the early life of patients with BA and to analyze its influence on long-term outcomes. Methods: Fecal samples (n = 42) were collected from infants with BA before and after Kasai portoenterostomy (KPE). The stool microbiota was analyzed using 16S rRNA next-generation sequencing and compared with that of age-matched healthy controls (HCs). Shotgun metagenomic sequencing analysis was employed to confirm the bacterial composition in 10 fecal samples before KPE. The correlation of the microbiome signature with liver function and long-term outcomes was assessed. Results: In the 16S rRNA next-generation sequencing analysis of fecal microbiota, the alpha and beta diversity analyses revealed significant differences between HCs and patients with BA before and after KPE. The difference in microbial composition analyzed by linear discriminant analysis and random forest classification revealed that the abundance of Bifidobacterium longum (B. longum) was significantly lower in patients before and after KPE than in HCs. The abundance of B. longum was negatively correlated with the gamma-glutamyltransferase level after KPE (p <0.05). Patients with early detectable B. longum had significantly lower total and direct bilirubin 3 months after KPE (p <0.005) and had a significantly lower liver transplantation rate (hazard ratio: 0.16, 95% CI 0.03-0.83, p = 0.029). Shotgun metagenomic sequencing also revealed that patients with BA and detectable B. longum had reduced total and direct bilirubin after KPE. Conclusion: The gut microbiome of patients with BA differed from that of HCs, with a notable abundance of B. longum in early infancy correlating with better long-term outcomes. Impact and implications: Bifidobacterium longum (B. longum) is a beneficial bacterium commonly found in the human gut. It has been studied for its potential impacts on various health conditions. In patients with biliary atresia, we found that a greater abundance of B. longum in the fecal microbiome is associated with improved clinical outcomes. This suggests that early colonization and increasing B. longum levels in the gut could be a therapeutic strategy to improve the prognosis of patients with biliary atresia.

Antagonism Between Gut Ruminococcus gnavus and Akkermansia muciniphila Modulates the Progression of Chronic Hepatitis B.

BACKGROUND & AIMS: A long immune-tolerant (IT) phase lasting for decades and delayed HBeAg seroconversion (HBe-SC) in patients with chronic hepatitis B (CHB) increase the risk of liver diseases. Early entry into the immune-active (IA) phase and HBe-SC confers a favorable clinical outcome with an unknown mechanism. We aimed to identify factor(s) triggering IA entry and HBe-SC in the natural history of CHB. METHODS: To study the relevance of gut microbiota evolution in the risk of CHB activity, fecal samples were collected from CHB patients (n = 102) in different disease phases. A hepatitis B virus (HBV)-hydrodynamic injection (HDI) mouse model was therefore established in several mouse strains and germ-free mice, and multiplatform metabolomic and bacteriologic assays were performed. RESULTS: Ruminococcus gnavus was the most abundant species in CHB patients in the IT phase, whereas Akkermansia muciniphila was predominantly enriched in IA patients and associated with alanine aminotransferase flares, HBeAg loss, and early HBe-SC. HBV-HDI mouse models recapitulated this human finding. Increased cholesterol-to-bile acids (BAs) metabolism was found in IT patients because R gnavus encodes bile salt hydrolase to deconjugate primary BAs and augment BAs total pool for facilitating HBV persistence and prolonging the IT course. A muciniphila counteracted this activity through the direct removal of cholesterol. The secretome metabolites of A muciniphila, which contained small molecules structurally similar to apigenin, lovastatin, ribavirin, etc., inhibited the growth and the function of R gnavus to allow HBV elimination. CONCLUSIONS: R gnavus and A muciniphila play opposite roles in HBV infection. A muciniphila metabolites, which benefit the elimination of HBV, may contribute to future anti-HBV strategies.

A Pilot Study of Biliary Atresia Newborn Screening Using Dried Blood Spot Matrix Metalloproteinase-7.

OBJECTIVES: Timely diagnosis is a critical challenge and is associated with improved survival of biliary atresia (BA) patients. We aimed to measure matrix metalloproteinase-7 (MMP-7) levels in BA patients within 3 days of birth using the dried blood spot (DBS) method and evaluate its potential as a screening tool. METHODS: The study enrolled 132 patients, including 25 patients diagnosed with BA and 107 non-BA patients with other congenital or perinatal conditions from the National Taiwan University Children Hospital. The stored DBS samples collected from 48 to 72 hours of life were retrieved from newborn screening centers. MMP-7 on the DBS was quantified using a sensitive sandwich enzyme-linked immunosorbent assay (ELISA). RESULTS: The MMP-7 levels of BA patients on the DBS were significantly higher than those of non-BA patients (19.2 ± 10.4 vs 5.6 ± 2.7 ng/mL, P value < 0.0001). MMP-7 levels in non-BA patients, including 5 patients with hepatobiliary structural anomaly, 9 patients with intrahepatic cholestasis, and 93 patients with other perinatal diseases, were 11.6 ± 4.2 ng/mL, 6.9 ± 3.0 ng/mL, and 5.2 ± 2.1 ng/mL, respectively. The DBS MMP-7 level showed good accuracy for identifying BA, with an area under the curve of 93.7% [95% confidence interval (CI): 87.7%-99.7%]. The MMP-7 cutoff at 8.0 ng/mL showed a sensitivity of 92.0% (95% CI: 75.0%-98.6%) and specificity of 92.5% (95% CI: 85.9%-96.1%) for detecting BA from other congenital or perinatal diseases. CONCLUSIONS: MMP-7 DBS analysis can be used to distinguish BA from other conditions as early as 3 days of age.

PIM1-Induced Cytoplasmic Expression of RBMY Mediates Hepatocellular Carcinoma Metastasis.

BACKGROUND & AIMS: Metastasis indicates a grave prognosis in patients with hepatocellular carcinoma (HCC). Our previous studies showed that RNA binding motif protein Y-linked (RBMY) is potentially a biomarker for poor survival in HCC patients, but its role in metastasis is largely unclear. METHODS: A total of 308 male patients with primary HCC were enrolled. RBMY expression was traced longitudinally by immunostaining from the manifestation of a primary HCC tumor to the formation of a distant metastasis, and its upstream regulators were screened with a protein microarray. A series of metastasis assays in mouse models and HCC cell lines were performed to explore new functional insights into RBMY. RESULTS: Cytoplasmic expression of RBMY was associated with rapid distant metastasis (approximately 1 year after resection) and had a predictive power of 82.4% for HCC metastasis. RBMY conferred high migratory and invasive potential upon phosphorylation by the provirus integration in Moloney 1 (PIM1) kinase. Binding of PIM1 to RBMY caused mutual stabilization and massive translocation of RBMY from nuclei to mitochondria, thereby preventing mitochondrial apoptosis and augmenting mitochondrial generation of adenosine triphosphate/reactive oxygen species to enhance cell motility. Depletion of RBMY suppressed Snail1/zinc finger E-box binding homeobox transcription factor 1-mediated epithelial-mesenchymal transition and dynamin-related protein 1-dependent mitochondrial fission. Inactivation and knockout of PIM1 down-regulated the expression of RBMY. In nude mice, cytoplasmic RBMY promoted liver-to-lung metastasis by increasing epithelial-mesenchymal transition, mitochondrial proliferation, and mitochondrial fission, whereas nuclear-restricted RBMY impeded the mitochondrial switch and failed to induce lung metastasis. CONCLUSIONS: This study showed the regulation of HCC metastasis by PIM1-driven cytoplasmic expression of RBMY and suggested a novel therapeutic target for attenuating metastasis.

Hepatitis B virus X gene impacts on the innate immunity and immune-tolerant phase in chronic hepatitis B virus infection.

BACKGROUND AND AIMS: The immunologic features involved in the immune-tolerant phase of chronic hepatitis B (CHB) virus (HBV) infection are unclear. The hepatitis B virus X (HBx) protein disrupts IFN-ß induction by downregulating MAVS and may destroy subsequent HBV-specific adaptive immunity. We aimed to analyse the impacts of genetic variability of HBx in CHB patients on the immune-tolerant phase during long-term follow-up. METHODS: Children with CHB in the immune-tolerant phase were recruited and followed longitudinally. HBx gene sequencing of infecting HBV strains was performed, and the effects of HBx mutations on the immune-tolerant phase were assessed. Restoration of the host immune response to end the immune-tolerant phase was investigated by immunoblotting, immunostaining, ELISA and reporter assays of MAVS/IFN-ß signalling in liver cell lines, patient liver tissues and the HBV plasmid replication system. RESULTS: A total of 173 children (median age, 6.92 years) were recruited. Patients carrying HBx R87G, I127V and R87G + I127V double mutations exhibited higher cumulative incidences of immune-tolerant phase breakthrough (p = .011, p = .006 and p = .017 respectively). Cells transfected with HBx R87G and I127V mutants and pHBV1.3-B6.3 replicons containing the HBx R87G and I127V mutations exhibited statistically increased levels of IFN-ß, especially under poly(I:C) stimulation or Flag-MAVS cotransfection. HA-HBx wild-type interacted with Flag-MAVS and enhanced its ubiquitination, but this ability was diminished in the R87G and I127V mutants. CONCLUSIONS: HBx suppresses IFN-ß induction. R87G and I127V mutation restored IFN-ß production by preventing MAVS degradation, contributing to curtailing the HBV immune-tolerant phase in CHB patients.

Epstein-Barr Virus Enhances Cancer-Specific Aberrant Splicing of TSG101 Pre-mRNA.

Tumor viruses gain control of cellular functions when they infect and transform host cells. Alternative splicing is one of the cellular processes exploited by tumor viruses to benefit viral replication and support oncogenesis. Epstein-Barr virus (EBV) participates in a number of cancers, as reported mostly in nasopharyngeal carcinoma (NPC) and Burkitt lymphoma (BL). Using RT-nested-PCR and Northern blot analysis in NPC and BL cells, here we demonstrate that EBV promotes specific alternative splicing of TSG101 pre-mRNA, which generates the TSG101∆154-1054 variant though the agency of its viral proteins, such as EBNA-1, Zta and Rta. The level of TSG101∆154-1054 is particularly enhanced upon EBV entry into the lytic cycle, increasing protein stability of TSG101 and causing the cumulative synthesis of EBV late lytic proteins, such as VCA and gp350/220. TSG101∆154-1054-mediated production of VCA and gp350/220 is blocked by the overexpression of a translational mutant of TSG101∆154-1054 or by the depletion of full-length TSG101, which is consistent with the known role of the TSG101∆154-1054 protein in stabilizing the TSG101 protein. NPC patients whose tumor tissues express TSG101∆154-1054 have high serum levels of anti-VCA antibodies and high levels of viral DNA in their tumors. Our findings highlight the functional importance of TSG101∆154-1054 in allowing full completion of the EBV lytic cycle to produce viral particles. We propose that targeting EBV-induced TSG101 alternative splicing has broad potential as a therapeutic to treat EBV-associated malignancies.

The ESCRT-III molecules regulate the apical targeting of bile salt export pump.

BACKGROUND: The bile salt export pump (BSEP) is a pivotal apical/canalicular bile salt transporter in hepatocytes that drives the bile flow. Defects in BSEP function and canalicular expression could lead to a spectrum of cholestatic liver diseases. One prominent manifestation of BSEP-associated cholestasis is the defective canalicular localization and cytoplasmic retention of BSEP. However, the etiology of impaired BSEP targeting to the canalicular membrane is not fully understood. Our goal was to discover what molecule could interact with BSEP and affect its post-Golgi sorting. METHODS: The human BSEP amino acids (a.a.) 491-630 was used as bait to screen a human fetal liver cDNA library through yeast two-hybrid system. We identified a BSEP-interacting candidate and showed the interaction and colocalization in the co-immunoprecipitation in hepatoma cell lines and histological staining in human liver samples. Temperature shift assays were used to study the post-Golgi trafficking of BSEP. We further determine the functional impacts of the BSEP-interacting candidate on BSEP in vitro. A hydrodynamically injected mouse model was established for in vivo characterizing the long-term impacts on BSEP. RESULTS: We identified that charged multivesicular body protein 5 (CHMP5), a molecule of the endosomal protein complex required for transport subcomplex-III (ESCRT-III), interacted and co-localized with BSEP in the subapical compartments (SACs) in developing human livers. Cholestatic BSEP mutations in the CHMP5-interaction region have defects in canalicular targeting and aberrant retention at the SACs. Post-Golgi delivery of BSEP and bile acid secretion were impaired in ESCRT-III perturbation or CHMP5-knockdown hepatic cellular and mouse models. This ESCRT-III-mediated BSEP sorting preceded Rab11A-regulated apical cycling of BSEP. CONCLUSIONS: Our results showed the first example that ESCRT-III is essential for canalicular trafficking of apical membrane proteins, and provide new targets for therapeutic approaches in BSEP associated cholestasis.

Cancer-Specifically Re-Spliced TSG101 mRNA Promotes Invasion and Metastasis of Nasopharyngeal Carcinoma.

TSG101 (Tumor susceptibility 101) gene and its aberrantly spliced isoform, termed TSG101∆154-1054, are tightly linked to tumorigenesis in various cancers. The aberrant TSG101∆154-1054 mRNA is generated from cancer-specific re-splicing of mature TSG101 mRNA. The TSG101∆154-1054 protein protects the full-length TSG101 protein from ubiquitin-mediated degradation, implicating TSG101∆154-1054 protein in the progression of cancer. Here, we confirmed that the presence of TSG101∆154-1054 mRNA indeed caused an accumulation of the TSG101 protein in biopsies of human nasopharyngeal carcinoma (NPC), which was recapitulated by the overexpression of TSG101∆154-1054 in the NPC cell line TW01. We demonstrate the potential function of the TSG101∆154-1054 protein in the malignancy of human NPC with scratch-wound healing and transwell invasion assays. By increasing the stability of the TSG101 protein, TSG101∆154-1054 specifically enhanced TSG101-mediated TW01 cell migration and invasion, suggesting the involvement in NPC metastasis in vivo. This finding sheds light on the functional significance of TSG101∆154-1054 generation via re-splicing of TSG101 mRNA in NPC metastasis and hints at its potential importance as a therapeutic target.

Intestinal Dysbiosis Featuring Abundance of Ruminococcus gnavus Associates With Allergic Diseases in Infants.

BACKGROUND & AIMS: Dysbiosis of the intestinal microbiota has been associated with development of allergies in infants. However, it is not clear what microbes might contribute to this process. We investigated what microbe(s) might be involved in analyses of infant twins and mice. METHODS: We studied fecal specimens prospectively in a twin cohort (n = 30) and age-matched singletons (n = 14) born at National Taiwan University Children's Hospital, Taipei, Taiwan, from April 2011 to March 2013. Clinical parameters (gestational age, birth body weight, mode of delivery and feeding, immunizations, and medical events) were recorded. Fecal samples were collected beginning immediately after birth and for 1 year; the children were followed until 3 years of age and allergic symptoms (repetitive and continuous for at least 6 months) were noted. A skin prick test was used to ascertain atopy. Bacterial communities in fecal samples were profiled by 16S ribosomal RNA-based polymerase chain reaction-temporal temperature gradient gel electrophoresis and next-generation sequencing. BALB/c mice without and with ovalbumin sensitization/challenge were infected with candidate bacteria by oral gauge intragastric intubation. Fecal, serum, lung, and colon tissue samples were collected from mice and analyzed for mechanisms of allergy development. RESULTS: During the investigation period, 20 children (45.5%) developed allergic diseases, including respiratory (allergic rhinitis and asthma) and skin (atopic dermatitis and eczema) allergies. Lachnospiraceae were detected at significantly higher frequency in allergic infants than nonallergic infants (P < .004); the high fecal count of Lachnospiraceae in allergic subjects appeared at 2 months of age and persisted until 12 months of age. The enrichment of Lachnospiraceae in allergic infants was attributed to the overgrowth of Ruminococcus gnavus, which tended to have a low frequency in nonallergic subjects (P = .0004). Increased R gnavus was observed before the onset of allergic manifestations, and was associated with respiratory allergies (P < .002) or respiratory allergies coexistent with atopic eczema (P < .001). In mice, endogenous R gnavus grew rapidly after sensitization and challenge with ovalbumin. Mice gavaged with purified R gnavus developed airway hyper-responsiveness and had histologic evidence of airway inflammation (asthma). Expansion of R gnavus in mice stimulated secretion of cytokines (interleukin [IL] 25, IL33, and thymic stromal lymphopoietin) by colon tissues, which activated type 2 innate lymphoid cells and dendritic cells to promote differentiation of T-helper 2 cells and production of their cytokines (IL4, IL5, and IL13). This led to infiltration of the colon and lung parenchyma by eosinophils and mast cells. CONCLUSIONS: In a study of a twin cohort (some infants with, some without allergies), we associated development of allergies, particularly respiratory allergies, with increased fecal abundance of R gnavus. Mice fed R gnavus developed airway inflammation, characterized by expansion of T-helper 2 cells in the colon and lung, and infiltration of colon and lung parenchyma by eosinophils and mast cells.

TSGΔ154-1054 splice variant increases TSG101 oncogenicity by inhibiting its E3-ligase-mediated proteasomal degradation.

Tumor susceptibility gene 101 (TSG101) elicits an array of cellular functions, including promoting cytokinesis, cell cycle progression and proliferation, as well as facilitating endosomal trafficking and viral budding. TSG101 protein is highly and aberrantly expressed in various human cancers. Specifically, a TSG101 splicing variant missing nucleotides 154 to 1054 (TSGΔ154-1054), which is linked to progressive tumor-stage and metastasis, has puzzled investigators for more than a decade. TSG101-associated E3 ligase (Tal)- and MDM2-mediated proteasomal degradation are the two major routes for posttranslational regulation of the total amount of TSG101. We reveal that overabundance of TSG101 results from TSGΔ154-1054 stabilizing the TSG101 protein by competitively binding to Tal, but not MDM2, thereby perturbing the Tal interaction with TSG101 and impeding subsequent polyubiquitination and proteasomal degradation of TSG101. TSGΔ154-1054 therefore specifically enhances TSG101-stimulated cell proliferation, clonogenicity, and tumor growth in nude mice. This finding shows the functional significance of TSGΔ154-1054 in preventing the ubiquitin-proteasome proteolysis of TSG101, which increases tumor malignancy and hints at its potential as a therapeutic target in cancer treatment.

RBMY, a novel inhibitor of glycogen synthase kinase 3ß, increases tumor stemness and predicts poor prognosis of hepatocellular carcinoma.

UNLABELLED: Male predominance of hepatocellular carcinoma (HCC) occurs particularly among young children aged 6-9 years, indicative of a possible role of the Y chromosome-encoded oncogene in addition to an androgenic effect. The discovery of oncogenic activation of RBMY (RNA-binding motif on Y chromosome), which is absent in normal hepatocytes but present in male HCC tissues, sheds light on this issue. Herein, we report on a critical hepatocarcinogenic role of RBMY and its ontogenic origin. During liver development, the Ser/Thr phosphorylated RBMY is expressed in the cytoplasm of human and rodent fetal livers. It is then silenced in mature hepatocytes and restricted to scarce expression in the bile ductular cells. Upon hepatocarcinogenesis, a noteworthy increase of cytoplasmic and nuclear RBMY is observed in HCC tissues; however, only the former is expressed dominantly in hepatic cancer stem cells and correlates significantly to a poor prognosis and decreased survival rate in HCC patients. Cytoplasmic expression of RBMY, which is mediated by binding to nuclear exporter chromosome region maintenance 1 and further enriched upon Wnt-3a stimulation, confers upon tumor cells the traits of cancer stem cell by augmenting self-renewal, chemoresistance, cell-cycle progression, proliferation, and xenograft tumor growth. This is achieved mechanistically through increasing Ser9 phosphorylation-inactivation of glycogen synthase kinase 3ß by RBMY, thereby impeding the glycogen synthase kinase 3ß-dependent degradation of ß-catenin and eventually inducing the nuclear entry of ß-catenin for the transcription of downstream oncogenes. CONCLUSION: RBMY is a novel oncofetal protein that plays a key role in attenuating glycogen synthase kinase 3ß activity, leading to aberrant activation of Wnt/ß-catenin signaling, which facilitates malignant hepatic stemness; because of its absence from normal human tissues except the testis, RBMY represents a feasible therapeutic target for the selective eradication of HCC cells in male patients.

The ESCRT machinery is recruited by the viral BFRF1 protein to the nucleus-associated membrane for the maturation of Epstein-Barr Virus.

The cellular endosomal sorting complex required for transport (ESCRT) machinery participates in membrane scission and cytoplasmic budding of many RNA viruses. Here, we found that expression of dominant negative ESCRT proteins caused a blockade of Epstein-Barr virus (EBV) release and retention of viral BFRF1 at the nuclear envelope. The ESCRT adaptor protein Alix was redistributed and partially colocalized with BFRF1 at the nuclear rim of virus replicating cells. Following transient transfection, BFRF1 associated with ESCRT proteins, reorganized the nuclear membrane and induced perinuclear vesicle formation. Multiple domains within BFRF1 mediated vesicle formation and Alix recruitment, whereas both Bro and PRR domains of Alix interacted with BFRF1. Inhibition of ESCRT machinery abolished BFRF1-induced vesicle formation, leading to the accumulation of viral DNA and capsid proteins in the nucleus of EBV-replicating cells. Overall, data here suggest that BFRF1 recruits the ESCRT components to modulate nuclear envelope for the nuclear egress of EBV.

p53 and Sp1 cooperate to regulate the expression of Epstein-Barr viral Zta protein.

Epstein-Barr virus (EBV) belongs to the gammaherpesvirus family. To produce infectious progeny, EBV reactivates from latency into the lytic cycle by expressing the determinative lytic transactivator, Zta. In the presence of histone deacetylase inhibitor (HDACi), p53 is a prerequisite for the initiation of the EBV lytic cycle by facilitating the expression of Zta. In this study, a serial mutational analysis of Zta promoter (Zp) indicated an important role for the ZID element in responding to HDACi induction and p53 binds to this ZID element together with Sp1, a universal transcription factor. Abolition of the DNA-binding ability of Sp1 reduces the inducibility of ZID by HDACi and also reduces the amount of p53 binding to ZID. Finally, it was shown that EBV in p53-positive-lymphoblastoid cell lines (LCLs) can enter into the lytic cycle spontaneously; however, knockdown of p53 in LCLs leads to retardation of EBV reactivation.

Regulation of IAPs gene family by interleukin-1 alpha and Epstein-Barr virus in nasopharyngeal carcinoma.

BACKGROUND: Inhibitors of apoptosis proteins (IAPs), which counteract apoptosis by potently inhibiting caspase activation, are promising targets of new anti-tumor therapy. However, their roles in the pathogenesis of nasopharyngeal carcinoma (NPC), an Epstein-Barr virus (EBV)-associated carcinoma, are not fully understood. Herein, we investigated the expression and regulation of IAPs in NPC. METHODS AND RESULTS: Using real-time quantitative polymerase chain reaction (PCR) analysis, we found that among the IAPs family only the transcription of survivin, HIAP-1, and HIAP-2 was consistently up-regulated in NPC and metastatic NPC tissues. Immunohistochemical staining showed that their proteins were more predominantly expressed in tumor cells nests. Noteworthy, these IAPs were upregulated by interleukin-1 alpha stimulation or EBV infection, and subsequently resulted in triggering rapid proliferation of NPC verified by strong Ki-67 staining. CONCLUSION: Survivin, HIAP-1, and HIAP-2 were distinctly upregulated in NPC, suggesting they may play significant roles in NPC tumorigenesis and serve as tumor markers with prognostic and therapeutic implications.

Critical role of p53 in histone deacetylase inhibitor-induced Epstein-Barr virus Zta expression.

The tumor suppressor gene p53 plays a central role in the maintenance of normal cell growth and genetic integrity, while its impact on the Epstein-Barr virus (EBV) life cycle remains elusive. We found that p53 is important for histone deacetylase inhibitor-induced EBV lytic gene expression in nasopharyngeal carcinoma cells. Restoration of p53 in p53-null, EBV-infected H1299 cells augments the potential for viral lytic cycle initiation. Evidence from reporter assays demonstrated that p53 contributes to the expression of the immediate-early viral Zta gene. Further analysis indicated that the DNA-binding ability of p53 and phosphorylation of Ser392 may be critical. This study provides the first evidence that p53 is involved in the regulation of EBV lytic cycle initiation.

Essential role of PKCdelta in histone deacetylase inhibitor-induced Epstein-Barr virus reactivation in nasopharyngeal carcinoma cells.

Histone deactylase inhibitors (HDACi) are common chemotherapeutic agents that stimulate Epstein-Barr virus (EBV) reactivation; the detailed mechanism remains obscure. In this study, it is demonstrated that PKCdelta is required for induction of the EBV lytic cycle by HDACi. Inhibition of PKCdelta abrogates HDACi-mediated transcriptional activation of the Zta promoter and downstream lytic gene expression. Nuclear translocation of PKCdelta is observed following HDACi stimulation and its overexpression leads to progression of the EBV lytic cycle. Our study suggests that PKCdelta is a crucial mediator of EBV reactivation and provides a novel insight to study the regulation of the EBV lytic cycle.

Upregulation of discoidin domain receptor 2 in nasopharyngeal carcinoma.

BACKGROUND: Nasopharyngeal carcinoma (NPC) is associated with Epstein-Barr virus (EBV) and has high metastatic potential. Discoidin domain receptors (DDR1, DDR2) are receptor-type tyrosine kinases activated by collagen. Their ability to induce expression of matrix metalloproteinase is related with tumor invasion. Therefore, we aim to investigate DDRs gene expression and its regulation in NPC. METHODS AND RESULTS: By use of real-time quantitative polymerase chain reaction (Q-PCR), DDR2 gene expression but not DDR1 was significantly higher in primary and metastatic NPC. DDR2 was predominantly distributed in NPC tumor cells rather than in infiltrating lymphocytes. EBV Z-transactivator (Zta) transfection may distinctly elevate DDR2 level. Furthermore, data from reporter assay indicate that Zta could transactivate DDR2 promoter activity, suggesting the possible upregulation mechanism. CONCLUSION: DDR2 was differentially upregulated in NPC and modulated by EBV Zta protein. DDR2 may play a role in NPC invasion and serve as a diagnostic and therapeutic target.

Role of the TSG101 gene in Epstein-Barr virus late gene transcription.

Rta, an Epstein-Barr virus (EBV)-encoded immediate-early protein, governs the reactivation of the viral lytic program by transactivating a cascade of lytic gene expression. Cellular transcription factors such as Sp1, ATF2, E2F, and Akt have been demonstrated to mediate Rta transactivation of lytic genes. We report herein that Rta associates with another potent transcription factor, tumor susceptibility gene 101 (TSG101), to promote the activation of EBV late genes. Results from an EBV cDNA array reveal that depletion of TSG101 by siRNA potently inhibits the transcription of five Rta-responsive EBV late genes, BcLF1, BDLF3, BILF2, BLLF1, and BLRF2. Depletion of TSG101 impairs the Rta transactivation of these late promoters severely. Moreover, a concordant augmentation of Rta transactivating activity is observed when TSG101 is overexpressed following ectopic transfection. Mechanistically, Rta interaction with TSG101 causes the latter to accumulate principally in the nuclei, wherein the proteins colocalize and are recruited to the viral promoters. Of note, TSG101 is crucial for the efficient binding of Rta to these late promoters. As a result, cells with defective TSG101 fail to express late viral proteins, leading to a decrease in the yield of virus particles. Thus, the contribution of TSG101 to Rta-mediated late gene activation is of great importance for completion of the EBV productive lytic cycle. These observations consolidate a role for TSG101 in the replication of EBV, a DNA virus, that differs from what is observed for RNA viruses, where TSG101 aids mainly in the endosomal sorting of enveloped late viral proteins for assembly at the plasma membrane.

Differential expression of osteoblast-specific factor 2 and polymeric immunoglobulin receptor genes in nasopharyngeal carcinoma.

BACKGROUND: The molecular mechanisms leading to development of nasopharyngeal carcinoma (NPC) are not well understood. To delineate the features of NPC, we tried to identify unique expression of cellular genes in the tumor biopsy specimens. METHODS AND RESULTS: By use of a combination of differential display and cDNA microarray analysis, we found two genes, 3E5 and 4A5, to show unique expression in the NPC biopsy specimens compared with nontumor nasopharyngeal tissues. Expression of 3E5, the osteoblast-specific factor-2 (OSF-2) gene, was detected at significantly higher levels in NPC biopsy specimens than that in control tissues, a finding confirmed using real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). A correlation between expression of OSF-2 and its regulatory cytokine transforming growth factor-beta was observed in nontumor tissues but not in NPC biopsy specimens. On the other hand, expression of 4A5, whose sequences represent the 3' untranslated region of the polymeric immunoglobulin receptor (pIgR) gene, was detected rarely in NPC specimens but frequently in nontumor controls. The expression of pIgR in normal epithelial cells, but not in NPC tumor cells, was verified by RT-PCR and immunohistochemical staining. CONCLUSIONS: NPC shows significant upregulation of OSF-2 and downregulation of pIgR. Expression of OSF-2 is likely to play a role in the pathogenesis of NPC. In addition, expression of OSF-2 and pIgR is disassociated with the expression of their regulatory cytokines in NPC biopsy specimens, suggesting that the tumors may have altered responses to certain cytokines.

Regulation of matrix metalloproteinase-1 by Epstein-Barr virus proteins.

Matrix metalloproteinases (MMPs) play crucial roles in tumor progression. To investigate the roles of MMPs in the progression of nasopharyngeal carcinoma (NPC), the expression of MMP-1, MMP-2, MMP-3, MMP-7, MMP-12, MMP-13, MMP-14, and MMP-19 was explored by microarray assay. Among them, MMP-1 was significantly up-regulated in NPC biopsies. These results were confirmed further by real-time quantitative PCR in additional NPC biopsies and comparison with normal tissues and other head and neck cancers. Moreover, the use of RNA from different cellular constituents of NPC biopsies revealed that MMP-1 was detected predominantly in epithelial cells. Immunohistochemical staining of paraffin-fixed NPC sections confirmed that MMP-1 protein was expressed in the epithelial tumor cells. Because EBV is strongly associated with NPC formation, we sought a correlation between viral gene expression and MMP-1 up-regulation. The results showed clearly that the amounts of transcripts, proteins, and enzyme activities of MMP-1 were increased in cells expressing EBV proteins, LMP1 (latent membrane protein 1) and Zta (Z transactivator; also named as BZLF1 or ZEBRA) but not EBNA-1 (EBV nuclear antigen-1). Additionally, the mobility of LMP1 and Zta transfectants was increased in scrape-wound migration assays. The invasiveness and ability to survive in a three-dimensional collagen gel also were enhanced in LMP1- and Zta-expressing cells. Furthermore, anti-MMP-1 antibody and peptide inhibitors could block the invasiveness and survival properties of LMP1 and Zta transfectants, suggesting a real contribution of MMP-1 to cell mobility and survival. Taken together, our data show that the viral LMP1 and Zta proteins regulate the expression and activity of MMP-1, and thereby confer the invasive properties of the cells. This study presents the first evidence that viral proteins are capable of regulating MMP-1 and also provides clues for the role of EBV in NPC progression.