Effects of lymphocyte profile on development of EBV-induced lymphoma subtypes in humanized mice.

Epstein-Barr virus (EBV) infection causes both Hodgkin's lymphoma (HL) and non-Hodgkin's lymphoma (NHL). The present study reveals that EBV-induced HL and NHL are intriguingly associated with a repopulated immune cell profile in humanized mice. Newborn immunodeficient NSG mice were engrafted with human cord blood CD34(+) hematopoietic stem cells (HSCs) for a 8- or 15-wk reconstitution period (denoted (8w)hN and (15w)hN, respectively), resulting in human B-cell and T-cell predominance in peripheral blood cells, respectively. Further, novel humanized mice were established via engraftment of hCD34(+) HSCs together with nonautologous fetal liver-derived mesenchymal stem cells (MSCs) or MSCs expressing an active notch ligand DLK1, resulting in mice skewed with human B or T cells, respectively. After EBV infection, whereas NHL developed more frequently in B-cell-predominant humanized mice, HL was seen in T-cell-predominant mice (P = 0.0013). Whereas human splenocytes from NHL-bearing mice were positive for EBV-associated NHL markers (hBCL2(+), hCD20(+), hKi67(+), hCD20(+)/EBNA1(+), and EBER(+)) but negative for HL markers (LMP1(-), EBNA2(-), and hCD30(-)), most HL-like tumors were characterized by the presence of malignant Hodgkin's Reed-Sternberg (HRS)-like cells, lacunar RS (hCD30(+), hCD15(+), IgJ(-), EBER(+)/hCD30(+), EBNA1(+)/hCD30(+), LMP(+)/EBNA2(-), hCD68(+), hBCL2(-), hCD20(-/weak,) Phospho STAT6(+)), and mummified RS cells. This study reveals that immune cell composition plays an important role in the development of EBV-induced B-cell lymphoma.

Deregulation of immune response genes in patients with Epstein-Barr virus-associated gastric cancer and outcomes.

BACKGROUND & AIMS: Patients with Epstein-Barr virus-associated gastric carcinoma (EBVaGC) have a better prognosis than those with gastric cancer not associated with EBV infection (EBVnGC). This is partly because EBV infection recruits lymphocytes, which infiltrate the tumor. A high degree of tumor heterogeneity is likely to be associated with poor response. We investigated differences in gene expression patterns between EBVaGC and EBVnGC. METHODS: We used gene expression profile analysis to compare tumor and nontumor gastric tissues from 12 patients with EBVaGC and 14 patients with EBVnGC. Findings were validated by whole transcriptome RNAseq and real-time quantitative polymerase chain reaction analyses. CD3(+) primary T cells were isolated from human blood samples; migration of these cells and of Jurkat cells were measured in culture with EBV-infected and uninfected gastric cancer cells. RESULTS: Based on Pearson correlation matrix analysis, EBVaGCs had a higher degree of homogeneity than EBVnGCs. Although 4550 genes were differentially expressed between tumor and nontumor gastric tissues of patients with EBVnGC, only 186 genes were differentially expressed between tumor and nontumor gastric tissues of patients with EBVaGC (P < .001). This finding supports the concept that EBVaGCs have fewer genetic and epigenetic alterations than EBVnGCs. Expression of major histocompatibility complex class II genes and genes that regulate chemokine activity were more often deregulated in EBVaGCs compared with nontumor tissues. In culture, more T cells migrated to EBV-infected gastric cancer cells than to uninfected cells; migration was blocked with a neutralizing antibody against CXCR3 (a receptor for many chemokines). CONCLUSIONS: Fewer genes are deregulated in EBVaGC than in EBVnGC. Most changes in EBVaGCs occur in immune response genes. These changes might allow EBVaGC to recruit reactive immune cells; this might contribute to the better outcomes of these patients compared with those with EBVnGC.

GAGE12 mediates human gastric carcinoma growth and metastasis.

The spontaneous metastasis from human gastric carcinoma (GC) remains poorly reproduced in animal models. Here, we established an experimental mouse model in which GC progressively developed in the orthotopic stomach wall and metastasized to multiple organs; the tumors colonized in the ovary exhibited typical characteristics of Krukenberg tumor. The expression of mesenchymal markers was low in primary tumors and high in those in intravasating and extravasating veins. However, the expression of epithelial markers did not differ, indicating that the acquisition of mesenchymal markers without a concordant loss of typical epithelial markers was associated with metastasis. We identified 35 differentially expressed genes (DEGs) in GC cells metastasized to ovary, among which overexpression of GAGE12 family genes, the top-ranked DEGs, were validated. In addition, knockdown of the GAGE12 gene family affected transcription of many of the aforementioned 35 DEGs and inhibited trans-well migration, tumor sphere formation in vitro and tumor growth in vivo. In accordance, GAGE12 overexpression augmented migration, tumor sphere formation and sustained in vivo tumor growth. Taken together, the GAGE12 gene family promotes GC growth and metastasis by modulating the expression of GC metastasis-related genes.

Co-transplantation of human fetal thymus, bone and CD34(+) cells into young adult immunodeficient NOD/SCID IL2Rγ(null) mice optimizes humanized mice that mount adaptive antibody responses.

Both the thymus (T) and bone (B) are necessary hematopoietic niches in adult humans. We previously showed that co-transplantation of human fetal T and B tissues into neonatal immunodeficient NOD/SCID IL2Rγ(null) (NSG, N) mice facilitated hematopoiesis. However, transplantation into neonatal mice resulted in high frequency of early death, making it unrealistic for repetitive experiments. In this study, young adult N mice were pre-engrafted with T and B, T alone, B alone or no tissues. The animals were irradiated and injected with autologous fetal liver (FL)-derived CD34(+) cells (34). The resultant mice were TB34N, T34N, B34N and 34N, respectively, and challenged with T cell dependent antigens (Ags). The humanized TB34N mice showed best performance of these mouse models in many aspects resembling the adult human Ag-experienced spleen. The TB34N mice exhibited better hematopoietic reconstitution; balanced development of T- and B-cell, and common progenitor cells; follicular lymphoid structures with a functional germinal center (GC) enriched with follicular dendritic cells (FDCs) and plasma cells (PCs); secretion of hIgG in the sera in response to Ags at comparable levels to those of human; derivations of hIgG mAb-secreting hybridoma clones. Collectively, the humanized TB34N mice could develop an adaptive immunity that was capable of producing Ag-specific hIgG at a significant level via class switching. This unprecedented TB34N platform in humanized mice would be useful in dissecting human immunity, for generating human Abs and clinical applications.

The full-length DNA sequence of Epstein Barr virus from a human gastric carcinoma cell line, SNU-719.

The consistent presence of Epstein-Barr virus (EBV) in malignant cells of EBV-associated gastric carcinoma (EBVaGC) suggests it plays an important role during the development of EBVaGC. However, the entire genomic sequence of EBV from EBVaGC has yet to be determined. This study first determined, annotated, and analyzed the full genomic sequence of EBV from the naturally infected gastric carcinoma cell line SNU-719 using next-generation sequencing and comparative analyses. In consistent with the notion that EBV sequence isolates better reflect their geographic area than tissue origin, the SNU-719 EBV (named as GC1) was categorized as an East Asian type I EBV. Compared with the prototype B95.8 sequence, SNU-719 EBV contained 1372 variations, with 937 and 435 within coding and non-coding regions, respectively. Of the 937 variations, 465 were non-synonymous changes, while 472 synonymous changes included partial internal deletions in the coding regions of LMP1 and gp350. The RNAseq transcriptome revealed that multiple BART transcripts comprised the majority of EBV RNA reads. The SNU-719 EBV expressed high levels of BART, LF3, BHLF1, and BNLF2. Evidence of RNA editing at multiple sites in the host chromosome was found; however, no evidence of genome integration was seen. The annotated SNU-719 EBV sequence will be a useful reference in future EBVaGC studies.

The nuclear chaperone nucleophosmin escorts an Epstein-Barr Virus nuclear antigen to establish transcriptional cascades for latent infection in human B cells.

Epstein-Barr Virus (EBV) is an oncogenic γ-herpesvirus that capably establishes both latent and lytic modes of infection in host cells and causes malignant diseases in humans. Nuclear antigen 2 (EBNA2)-mediated transcription of both cellular and viral genes is essential for the establishment and maintenance of the EBV latency program in B lymphocytes. Here, we employed a protein affinity pull-down and LC-MS/MS analysis to identify nucleophosmin (NPM1) as one of the cellular proteins bound to EBNA2. Additionally, the specific domains that are responsible for protein-protein interactions were characterized as EBNA2 residues 300 to 360 and the oligomerization domain (OD) of NPM1. As in c-MYC, dramatic NPM1 expression was induced in EBV positively infected B cells after three days of viral infection, and both EBNA2 and EBNALP were implicated in the transactivation of the NPM1 promoter. Depletion of NPM1 with the lentivirus-expressed short-hairpin RNAs (shRNAs) effectively abrogated EBNA2-dependent transcription and transformation outgrowth of lymphoblastoid cells. Notably, the ATP-bound state of NPM1 was required to induce assembly of a protein complex containing EBNA2, RBP-Jκ, and NPM1 by stabilizing the interaction of EBNA2 with RBP-Jκ. In a NPM1-knockdown cell line, we demonstrated that an EBNA2-mediated transcription defect was fully restored by the ectopic expression of NPM1. Our findings highlight the essential role of NPM1 in chaperoning EBNA2 onto the latency-associated membrane protein 1 (LMP1) promoters, which is coordinated with the subsequent activation of transcriptional cascades through RBP-Jκ during EBV infection. These data advance our understanding of EBV pathology and further imply that NPM1 can be exploited as a therapeutic target for EBV-associated diseases.

Endoscopic papillary large balloon dilation for the management of recurrent difficult bile duct stones after previous endoscopic sphincterotomy.

BACKGROUND: Endoscopic management of recurrent bile duct stones after endoscopic sphincterotomy (EST) is effective and safe. However, repeat EST for extension of a previous EST for recurrent bile duct stones may involve substantial risk. The aim of the present study was to evaluate the safety and efficacy of endoscopic papillary large balloon dilation (EPLBD) without repeat EST for recurrent difficult bile duct stones after previous EST. PATIENTS AND METHODS: From January 2006 to October 2010, a total of 52 patients were enrolled; all had undergone EPLBD (balloon diameter: 12-20 mm) to remove recurrent difficult bile duct stones after previous EST. In all patients, stone removal had failed with conventional methods using a basket and/or balloon. The size of the balloon for EPLBD was selected to fit the diameter of the common bile duct or the largest stone. RESULTS: The median interval between initial EST and stone recurrence was 2.2 years (range 1-10). Median diameters of thelargest stone and balloon were 20.1 mm (range 12-40) and 14.7 mm (range 12-20), respectively. Complete stone removal was achieved in all patients (100%). The median number of endoscopic retrograde cholangiopancreatography sessions needed for complete stone removal was 1.6 (range 1-3). Additional lithotripsy was required in 16 patients (30.7%). No procedure-related complications were documented, with the exception of four cases of asymptomatic hyperamylasemia. The recurrence rate of CBD stones after bile duct clearance was 17.3% (9/52) during the follow-up period (mean 27.0 ± 14.1 months). CONCLUSIONS: EPLBD without repeat EST is effective and relatively safe for the extraction of recurrent difficult bile duct stones after previous EST.

Small molecule and peptide-mediated inhibition of Epstein-Barr virus nuclear antigen 1 dimerization.

Latent Epstein-Barr virus (EBV) infection is associated with human B cell lymphomas and certain carcinomas. EBV episome persistence, replication, and gene expression are dependent on EBV-encoded nuclear antigen 1 (EBNA1)'s DNA binding domain (DBD)/dimerization domain (DD)-mediated sequence-specific DNA binding activity. Homodimerization of EBNA1 is essential for EBNA1 DNA binding and transactivation. In this study, we characterized a novel small molecule EBNA1 inhibitor EiK1, screened from the previous high throughput screening (HTS). The EiK1 compound specifically inhibited the EBNA1-dependent, OriP-enhanced transcription, but not EBNA1-independent transcription. A Surface Plasmon Resonance Biacore assay revealed that EiK1 associates with EBNA1 amino acid 459-607 DBD/DD. Consistent with the SPR data, in vitro gel shift assays showed that EiK1 suppressed the activity of EBNA1 binding to the cognate familial repeats (FR) sequence, but not control RBP-Jκ binding to the Jκ site. Subsequently, a cross-linker-mediated in vitro multimerization assay and EBNA1 homodimerization-dependent yeast two-hybrid assay showed that EiK1 significantly inhibited EBNA1 dimerization. In an attempt to identify more highly specific peptide inhibitors, small peptides encompassing the EBNA1 DBD/DD were screened for inhibition of EBNA1 DBD-mediated DNA binding function. The small peptide P85, covering EBNA1 a.a. 560-574, significantly blocked EBNA1 DNA binding activity in vitro, prevented dimerization in vitro and in vivo, associated with EBNA1 in vitro, and repressed EBNA1-dependent transcription in vivo. Collectively, this study describes two novel inhibitors of EBNA1 dimerization. This study demonstrates that EBNA1 homodimerization can be effectively targeted by a small molecule or peptide.

Twist1 causes the transcriptional repression of claudin-4 with prognostic significance in esophageal cancer.

Twist1 is a transcription factor that is involved in epithelial-mesenchymal transition by suppressing intercellular adhesion. In this study, we aimed to determine the role of Twist1 in the regulation of claudin-4 expression and investigate its specific mechanisms and clinical implications using human esophageal carcinoma cell lines and tissues. As a result, up-regulation of Twist1 decreased both gene and protein expression levels of endogenous claudin-4 and the suppression was mediated by direct binding of Twist1 to the canonical E-box in the promoter region of claudin-4. In addition, there was a significant inverse correlation of claudin-4 with Twist1 in esophageal cancer tissues. High Twist1 and low claudin-4 expression was associated with the poorest prognosis and was more highly correlated with adverse outcome than any other subgroup with statistical significance (p=0.001). Our results indicate that Twist1 induces the repression of claudin-4 expression during the epithelial-mesenchymal transition in esophageal carcinoma.

Roscovitine inhibits EBNA1 serine 393 phosphorylation, nuclear localization, transcription, and episome maintenance.

Latent Epstein-Barr virus (EBV) infection causes human lymphomas and carcinomas. EBV usually persists as an episome in malignant cells. EBV episome persistence, replication, and gene expression are dependent on EBNA1 binding to multiple cognate sites in oriP. To search for inhibitors of EBNA1- and oriP-dependent episome maintenance or transcription, a library of 40,550 small molecules was screened for compounds that inhibit EBNA1- and oriP-dependent transcription and do not inhibit EBNA1- and oriP-independent transcription. This screening identified roscovitine, a selective inhibitor of cyclin-dependent kinase 1 (CDK1), CDK2, CDK5, and CDK7. Based on motif predictions of EBNA1 serine 393 as a CDK phosphorylation site and (486)RALL(489) and (580)KDLVM(584) as potential cyclin binding domains, we hypothesized that cyclin binding to EBNA1 may enable CDK1, -2, -5, or -7 to phosphorylate serine 393. We found that Escherichia coli-expressed EBNA1 amino acids 387 to 641 were phosphorylated in vitro by CDK1-, -2-, -5-, and -7/cyclin complexes and serine 393 phosphorylation was roscovitine inhibited. Further, S393A mutation abrogated phosphorylation. S393A mutant EBNA1 was deficient in supporting EBNA1- and oriP-dependent transcription and episome persistence, and roscovitine had little further effect on the diminished S393A mutant EBNA1-mediated transcription or episome persistence. Immunoprecipitated FLAG-EBNA1 was phosphorylated in vitro, and roscovitine inhibited this phosphorylation. Moreover, roscovitine decreased nuclear EBNA1 and often increased cytoplasmic EBNA1, whereas S393A mutant EBNA1 was localized equally in the nucleus and cytoplasm and was unaffected by roscovitine treatment. These data indicate that roscovitine effects are serine 393 specific and that serine 393 is important in EBNA1- and oriPCp-dependent transcription and episome persistence.

Ruptured duodenal varices arising from the main portal vein successfully treated with endoscopic injection sclerotherapy: a case report.

Duodenal varices result from retroperitoneal portosystemic shunts that usually come from the pancreaticoduodenal vein and drain into the inferior vena cava. Because they are a rare but fatal cause of gastrointestinal bleeding, a prompt hemostatic intervention is mandatory. A 62-year-old man who had a history of excessive alcohol consumption presented with massive hematemesis and melena. Emergent endoscopy revealed ruptured varices with an adhering whitish fibrin clot on the postbulbar portion of the duodenum. Abdominal computed tomography demonstrated a cirrhotic liver with venous collaterals around the duodenum and extravasated contrast in the second and third portions. The collaterals originated from the main portal vein and drained via the right renal vein into the inferior vena cava. Endoscopic injection sclerotherapy with cyanoacrylate was successful in achieving hemostasis, and resulted in the near eradication of duodenal varices at a 6-month follow-up.

Collection and decomposition of oil mist via corona discharge and surface dielectric barrier discharge.

Oil mist emitted during cooking is one of the major sources of atmospheric particulate matter in urban areas. A conventional electrostatic precipitator (ESP) is used in some large restaurants; it requires regular electrode cleaning to maintain particle collection performance. However, oil mist generated during cooking is viscous and difficult to clean with water. Herein, we introduce a methodology and a device for cleaning collected oil mist using surface dielectric barrier discharge (surface-DBD) plasma. Our device uses corona discharge for the collection of oil mist. Subsequently, the oil mist collected is decomposed to gas-phase species by surface-DBD plasma. A maximum collection efficiency of 93.25% (for 230 nm di-ethyl hexyl sebacate (DEHS) particle) is obtained at a flow velocity of 1.5 m/s. The maximum oil mist decomposition efficiency is 96.4%. More than 80% of the decomposed oil mist is converted to CO2 and CO under all test conditions. Some of the byproducts other than CO and CO2 are released as particles. Higher frequency results in higher oil mist decomposition efficiency, but also higher byproduct formation of particles. The mechanism of oil mist decomposition by surface-DBD plasma is discussed using optical emission spectroscopy data.

Roles of TRAF2 and TRAF3 in Epstein-Barr virus latent membrane protein 1-induced alternative NF-kappaB activation.

Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1)-induced NF-kappaB activation is essential for EBV-transformed B cell survival. LMP1 has two C-terminal cytoplasmic domains referred to as C-Terminal Activation Regions (CTAR) 1 and 2 that activate the alternative and canonical NF-kappaB pathways, respectively. While CTAR2 activates TRAF6, IKKbeta and IKKgamma-dependent canonical NF-kappaB pathway, CTAR1 interacts with TRAF2 and TRAF3 and activates NIK and IKKalpha-dependent alternative NF-kappaB pathway involving p100 processing into functional p52. Using IKKalpha(-/-), IKKbeta(-/-), IKKgamma(-/-), TRAF2(-/-), TRAF3(-/-), TRAF6(-/-), and NIK(aly/aly) mouse embryonic fibroblasts (MEFs), potential roles of these proteins in LMP1-induced alternative NF-kappaB activation were investigated. Deficiency in IKKalpha or functional NIK, but not in IKKbeta, IKKgamma, or TRAF6, severely impaired LMP1-induced p100 processing. Notably, p100 was constitutively processed in TRAF2(-/-) or TRAF3(-/-) MEFs independently of LMP1 suggesting that TRAF2 or TRAF3 may play a regulatory role in p100 processing. Subsequently, TRAF2 or TRAF3 over-expression in HEK293 cells significantly blocked LMP1-induced p100 processing. The LMP1 CTAR1 expression in 293HEK cells activated the alternative p65/p52 complex while CTAR2 failed to do so. Taken together, LMP1 activates alternative NF-kappaB pathway through functional NIK and IKKalpha that is regulated by TRAF2 or TRAF3.

Epstein-Barr virus nuclear antigen 1 does not cause lymphoma in C57BL/6J mice.

To test whether transgenic Epstein-Barr virus nuclear antigen 1 (EBNA1) expression in C57BL/6 mouse lymphocytes causes lymphoma, EBNA1 expressed in three FVB lineages at two or three times the level of latent infection was crossed up to six successive times into C57BL/6J mice. After five or six crosses, 14/36, (38%) EBNA1 transgenic mice, 11/31 (36%) littermate EBNA1-negative controls, and 9/25 (36%) inbred C57BL/6J mice housed in the same facility had lymphoma. These data indicate that EBNA1 does not significantly increase lymphoma prevalence in C57BL/6J mice.

Skewed Dendritic Cell Differentiation of MyD88-Deficient Donor Bone Marrow Cells, Instead of Massive Expansion as Myeloid-Derived Suppressor Cells, Aggravates GVHD.

Graft-versus-host disease (GVHD), a life-threatening complication after bone marrow transplantation (BMT), is induced by activation of alloreactive donor T cells. Our previous study demonstrated that transplantation of myeloid differentiation factor 88 (MyD88)-deficient knockout (KO) bone marrow (BM) resulted in aggravation of GVHD. Here, to understand the cellular mechanism, we performed longitudinal in vivo imaging and flow cytometric analyses followed by transcriptome and functional examination of donor MyD88-KO BM progenies in GVHD hosts, using a major histocompatibility complex-matched but minor histocompatibility antigen-mismatched C57BL/6→BALB.B model. In GVHD hosts with MyD88-KO BMT, donor BM-derived CD11b+Gr-1+ cells were found to undergo cell death, a fate significantly different from the explosive expansion shown by the wild type (WT) counterparts, and also from the moderate expansion of the WT or MyD88-KO BM-derived cells in non-GVHD hosts. It was also revealed that MyD88-KO CD11b+Gr-1+ cells preferred differentiation into CD11c+ dendritic cells (DCs) to expansion as myeloid-derived suppressor cells in GVHD hosts or in high inflammatory in vitro conditions. These CD11c+ DCs comprised the majority of MyD88-KO CD11b+Gr-1+ apoptotic cells in GVHD hosts. Their ability to cross-present alloantigens of host origin contributed to the enhancement of T cell alloreactivity, causing GVHD aggravation and eventually death through the killing function of activated T cells. These results provide insights into the roles of MyD88 in myelopoiesis of donor BM and the protective effects in GVHD hosts, helpful information for development of a strategy to control GVHD.

Endoscopic transcystic stent placement for an intrahepatic abscess due to gallbladder perforation.

Perforation of the gallbladder with cholecystohepatic communication is a rare cause of liver abscess. Because it is a rare entity, the treatment modality has not been fully established. We report for the first time a patient with an intrahepatic abscess due to gallbladder perforation successfully treated by endoscopic stent placement into the gallbladder who had a poor response to continuous percutaneous drainage.

Host immune response index in gastric cancer identified by comprehensive analyses of tumor immunity.

Tumor infiltrating lymphocytes (TIL) in Epstein-Barr virus (EBV)-associated/microsatellite-unstable (MSI) gastric carcinomas (GC) constitute immune-active principal cellular components of tumor microenvironment and contribute to better prognosis. With the remarkable success of cancer immunotherapies, there is an urgent need for a comprehensive understanding of tumor-immune interactions in patients with GC in the context of host immune response. To identify GC subtype-specific immune response gene set, we tested differentially expressed genes for MSI and EBV+ GC subtypes in randomly selected test set (n = 278) in merged ACRG-SMC microarray and TCGA RNA sequencing data set. We identified Host ImmunE Response index (HIERÏ) consisting of 29 immune genes classifying GC patients into robust 3 groups with prognostic significance. Immune-high cluster 1 was enriched with PD-L1High/EBV+/MSI/TILHigh with the best clinical outcome while immune-low cluster 3 displayed worst outcome and exemplified with PD-L1Low/EBV-/MSS. The results were validated in the same cohort (n = 279) and independent cohort (n = 181) with RNA from formalin-fixed paraffin-embedded (FFPE) tissue. Unexpectedly, nearly half of GC in cluster 1 were EBV-/MSS and 10% of cluster 3 GC were EBV+/MSI GC patients, suggesting that in addition to EBV+/MSI GC subtypes, EBV-/MSS subtype also constitutes almost half of high immune cluster and would be a good candidate for immune checkpoint inhibitor therapy. In contrary, almost 10% of EBV+/MSI GC patients may not respond to immune checkpoint inhibitor therapy. Thus, our HIERÏ gene signature demonstrates the potential to subclassify tumor immunity levels, predict prognosis and help immunotherapeutic decisions.

Targeted disruption of EBNA1 in EBV-infected cells attenuated cell growth.

Epstein Barr virus (EBV)-encoded nuclear antigen-1 (EBNA1) plays a pivotal in an EBV episome replication and persistence. Despite considerable attempts, there are no EBV drugs or vaccines. We attempted to eradicate EBV episomes by targeting EBNA1 using the transcription activator-like effector nucleases (TALEN) (E1TN). E1TN-mediated transient knockout (KO) of EBNA1 reduced EBNA1 expression, and caused significant loss of EBV genomes and progressive death of EBV-infected cells. Furthermore, when a mixture of EBV-infected Burkitt's lymphoma (BL) cells and EBV-negative BL cells was targeted by E1TN, EBV-negative cells were counter-selected while most EBV-infected cells died, further substantiating that EBNA1 KO caused selective death of EBV-infected cells. TALEN-mediated transient targeting of EBNA1 attenuated the growth of EBV-infected cells, implicating a possible therapeutic application of E1TN for EBV-associated disorders. [BMB Reports 2016; 49(4): 226-231].

Epstein-Barr Virus-Associated Gastric Carcinoma and Specific Features of the Accompanying Immune Response.

Epstein-Barr virus-associated gastric carcinoma (EBVaGC) is one of the four subtypes of gastric carcinoma (GC), as defined by the novel classification recently proposed by The Cancer Genome Atlas. EBVaGC has several clinicopathological features such as longer survival and higher frequency of lymphoepithelioma-like carcinoma (LELC) and carcinoma with Crohn's disease-like lymphoid reaction that distinguish it from EBV-negative GC. The intensity and pattern of host cellular immune response in GC have been found to significantly correlate with the prognosis of patients with GC, suggesting that immune reaction and tumor microenvironment have critical roles in the progression of GC, and in particular, EBVaGC. Here, we reviewed the cellular and molecular mechanisms underlying prominent immune reactions in patients with EBVaGC. In EBVaGC, deregulation of the expression of immune response-related genes promotes marked intra- or peritumoral immune cell infiltration. The expression of programmed death receptor-ligand 1 is known to be increased in EBVaGC, and therefore, it has been proposed as a favorable prognostic factor for patients with EBVaGC, albeit some data supporting this claim are controversial. Overall, the underlying mechanisms and clinical significance of the host cellular immune response in patients with EBVaGC have not been thoroughly elucidated. Therefore, further research is necessary to better understand the role of tumor microenvironment in EBVaGC.