EBV genome variations enhance clinicopathological features of nasopharyngeal carcinoma in a non-endemic region

The landscape of 142 Epstein-Barr viral whole genomes in gastric cancer

BACKGROUND

A substantial portion of gastric cancer (GC) is linked to Epstein-Barr virus (EBV) infection. The characteristics of this viral genome, such as specific viral strains and large structural variations, influence the progression of diseases like nasopharyngeal carcinoma and hematological malignancy. However, the EBV genomes from GC have not been thoroughly characterized.

METHODS

Our study involved 849 consecutive GC patients diagnosed at Nagoya City University Hospital, Japan (NCU cohort). We detected EBV from formalin-fixed, paraffin-embedded sections using a novel direct PCR-based rapid detection method. Additionally, we analyzed 142 EBV whole genomes (125 newly sequenced) from GC, comparing them with 205 genomes from other EBV-associated diseases.

RESULTS

We identified 32 (3.8%) patients associated with EBVaGC in the NCU cohort. Moreover, the direct PCR identified several GC specimens containing EBV-infected lymphocytes or their follicles. The dominant viral strain in GC was type 1 EBV, prevalent in most parts of the world, and no GC-specific strain was identified. We found no significant associations between single-nucleotide variants in the viral genome and GC. Structural variations of the EBV genome were infrequent in GC (4 cases, 2.1%), contrasting with EBV-associated hematological malignancy, which frequently carries large deletions.

CONCLUSIONS

This study is the first to uncover the genomic variations of EBV in GC. While EBV is definitively linked to GC, the characteristics of its genomes do not strongly correlate with disease development or progression. Our findings on viral genomes supplement the current understanding of human genomes in EBVaGC.

Distinct genomic features of Transeurasian strains of Epstein-Barr virus in East Asia

More than 95% of adult humans worldwide are latently infected with Epstein-Barr virus (EBV). Recent studies indicated that different EBV strains colonize different regions of Asia, where nasopharyngeal carcinoma (NPC) is endemic (southern China) or non-endemic (Japan/Korea). We searched for viral single nucleotide variant markers throughout the EBV genome by comparing the coding sequences of Japanese/Korean and NPC-endemic Chinese strains. We identified BamHI D fragment leftward reading frame 1 (BDLF1), BDLF2, and BDLF3 genes as viral geographical markers for distinguishing Japanese/Korean EBV strains from NPC-endemic Chinese EBV strains. Most significantly, BDLF-based EBV genotyping indicated that NPC-non-endemic Chinese and Mongolian EBV strains belong to the same group as Japanese/Korean EBV strains. We conclude that a particular type of EBV, designated as Transeurasian EBV, is prevalent among Transeurasian language speakers (Japanese, Korean, and Mongolian populations) and NPC-non-endemic Chinese populations.

Epstein-Barr virus as a potentiator of autoimmune diseases

The Epstein-Barr virus (EBV) is epidemiologically associated with development of autoimmune diseases, including systemic lupus erythematosus, Sjögren syndrome, rheumatoid arthritis and multiple sclerosis. Although there is well-established evidence for this association, the underlying mechanistic basis remains incompletely defined. In this Review, we discuss the role of EBV infection as a potentiator of autoimmune rheumatic diseases. We review the EBV life cycle, viral transcription programmes, serological profiles and lytic reactivation. We discuss the epidemiological and mechanistic associations of EBV with systemic lupus erythematosus, Sjögren syndrome, rheumatoid arthritis and multiple sclerosis. We describe the potential mechanisms by which EBV might promote autoimmunity, including EBV nuclear antigen 1-mediated molecular mimicry of human autoantigens; EBV-mediated B cell reprogramming, including EBV nuclear antigen 2-mediated dysregulation of autoimmune susceptibility genes; EBV and host genetic factors, including the potential for autoimmunity-promoting strains of EBV; EBV immune evasion and insufficient host responses to control infection; lytic reactivation; and other mechanisms. Finally, we discuss the therapeutic implications and potential therapeutic approaches to targeting EBV for the treatment of autoimmune disease.

Exploring the anti-EBV potential of suberoylanilide hydroxamic acid: Induction of apoptosis in infected cells through suppressing BART gene expression and inducing lytic infection

Epstein-Barr virus (EBV) is linked to lymphoma and epithelioma but lacks drugs specifically targeting EBV-positive tumors. BamHI A Rightward Transcript (BART) miRNAs are expressed in all EBV-positive tumors, suppressing both lytic infection and host cell apoptosis. We identified suberoylanilide hydroxamic acid (SAHA), an inhibitor of histone deacetylase enzymes, as an agent that suppresses BART promoter activity and transcription of BART miRNAs. SAHA treatment demonstrated a more pronounced inhibition of cell proliferation in EBV-positive cells compared to EBV-negative cells, affecting both p53 wild-type and mutant gastric epithelial cells. SAHA treatment enhanced lytic infection in wild-type EBV-infected cells, while also enhancing cell death in BZLF1-deficient EBV-infected cells. It reduced BART gene expression by 85% and increased the expression of proapoptotic factors targeted by BART miRNAs. These findings suggest that SAHA not only induces lytic infection but also leads to cell death by suppressing BART miRNA transcription and promoting the apoptotic program.

Meta-analysis of Epstein-Barr virus genomes in Southern Chinese identifies genetic variants and high risk viral lineage associated with nasopharyngeal carcinoma

Genetic variants in Epstein-Barr virus (EBV) have been strongly associated with nasopharyngeal carcinoma (NPC) in South China. However, different results regarding the most significant viral variants, with polymorphisms in EBER2 and BALF2 loci, have been reported in separate studies. In this study, we newly sequenced 100 EBV genomes derived from 61 NPC cases and 39 population controls. Comprehensive genomic analyses of EBV sequences from both NPC patients and healthy carriers in South China were conducted, totaling 279 cases and 227 controls. Meta-analysis of genome-wide association study revealed a 4-bp deletion downstream of EBER2 (coordinates, 7188-7191; EBER-del) as the most significant variant associated with NPC. Furthermore, multiple viral variants were found to be genetically linked to EBER-del forming a risk haplotype, suggesting that multiple viral variants might be associated with NPC pathogenesis. Population structure and phylogenetic analyses further characterized a high risk EBV lineage for NPC revealing a panel of 38 single nucleotide polymorphisms (SNPs), including those in the EBER2 and BALF2 loci. With linkage disequilibrium clumping and feature selection algorithm, the 38 SNPs could be narrowed down to 9 SNPs which can be used to accurately detect the high risk EBV lineage. In summary, our study provides novel insight into the role of EBV genetic variation in NPC pathogenesis by defining a risk haplotype of EBV for downstream functional studies and identifying a single high risk EBV lineage characterized by 9 SNPs for potential application in population screening of NPC.

Recent Advances in Assessing the Clinical Implications of Epstein-Barr Virus Infection and Their Application to the Diagnosis and Treatment of Nasopharyngeal Carcinoma

Reports about the oncogenic mechanisms underlying nasopharyngeal carcinoma (NPC) have been accumulating since the discovery of Epstein-Barr virus (EBV) in NPC cells. EBV is the primary causative agent of NPC. EBV-host and tumor-immune system interactions underlie the unique representative pathology of NPC, which is an undifferentiated cancer cell with extensive lymphocyte infiltration. Recent advances in the understanding of immune evasion and checkpoints have changed the treatment of NPC in clinical settings. The main EBV genes involved in NPC are LMP1, which is the primary EBV oncogene, and BZLF1, which induces the lytic phase of EBV. These two multifunctional genes affect host cell behavior, including the tumor-immune microenvironment and EBV behavior. Latent infections, elevated concentrations of the anti-EBV antibody and plasma EBV DNA have been used as biomarkers of EBV-associated NPC. The massive infiltration of lymphocytes in the stroma suggests the immunogenic characteristics of NPC as a virus-infected tumor and, at the same time, also indicates the presence of a sophisticated immunosuppressive system within NPC tumors. In fact, immune checkpoint inhibitors have shown promise in improving the prognosis of NPC patients with recurrent and metastatic disease. However, patients with advanced NPC still require invasive treatments. Therefore, there is a pressing need to develop an effective screening system for early-stage detection of NPC in patients. Various modalities, such as nasopharyngeal cytology, cell-free DNA methylation, and deep learning-assisted nasopharyngeal endoscopy for screening and diagnosis, have been introduced. Each modality has its advantages and disadvantages. A reciprocal combination of these modalities will improve screening and early diagnosis of NPC.

A promising predictive biomarker combined EBV NDA with PNI for nasopharyngeal carcinoma in nonendemic area of China

In endemic areas, EBV DNA is used to guide diagnosis, detect recurrence and distant metastasis of NPC. Until now, the importance of EBV DNA in the prediction of NPC has received little attention in non-endemic regions. To explore the prognostic value of EBV DNA alone or in combination with PNI in NPC patients from a non-endemic area of China. In this retrospective study, 493 NPC patients were enrolled. Clinical pathologic data, pre-treatment plasma EBV DNA, and laboratory tests were all performed. A standard anticancer treatment was prescribed, and follow up data were collected. EBV DNA was found to be positively related to clinical stage (r = 0.357, P < 0.001), T stage (r = 0.193, P < 0.001), N stage (r = 0.281, P < 0.001), and M stage (r = 0.215, P < 0.001). The difference in EBV DNA loads between clinical stage, T, N and M stage was statistically significant (P < 0.001). In this study, the best cutoff value for EBV-DNA to distinguish the prognosis of NPC was 262.7 copies/ml. The 5-year OS of patients in the EBV-DNA ≤ 262.7 copies/ml group and EBV-DNA > 262.7 copies/ml group was 88% and 65.3%, respectively (P < 0.001). EBV-DNA and PNI were found to be independent prognostic factors for OS in multivariate analysis (P < 0.05). EBV-DNA was independent prognostic factors for PFS. In predicting NPC patients OS, the novel combination marker of EBV DNA and PNI outperformed TNM staging (AUC: 0.709 vs. 0.675). In addition, the difference between EBV + PNI and EBV + TNM was not statistically significant for OS or PFS (P > 0.05). This novel combination biomarker was a promising biomarker for predicting NPC survival and may one day guide treatment option.

The role of Epstein-Barr virus in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a metastasis-prone malignancy closely associated with the Epstein-Barr virus (EBV). Despite ubiquitous infection of EBV worldwide, NPC incidences displayed predominance in certain ethnic groups and endemic regions. The majority of NPC patients are diagnosed with advanced-stage disease, as a result of anatomical isolation and non-specific clinical manifestation. Over the decades, researchers have gained insights into the molecular mechanisms underlying NPC pathogenesis as a result of the interplay of EBV infection with several environmental and genetic factors. EBV-associated biomarkers were also used for mass population screening for the early detection of NPC. EBV and its encoded products also serve as potential targets for the development of therapeutic strategies and tumour-specific drug delivery. This review will discuss the pathogenic role of EBV in NPC and efforts in exploiting the potential of EBV-associated molecules as biomarkers and therapeutic targets. The current knowledge on the role of EBV and its associated products in NPC tumorigenesis, development and progression will offer a new outlook and potential intervention strategy against this EBV-associated malignancy.

Functional Implications of Epstein-Barr Virus Lytic Genes in Carcinogenesis

Epstein-Barr virus (EBV) is associated with a diverse range of tumors of both lymphoid and epithelial origin. Similar to other herpesviruses, EBV displays a bipartite life cycle consisting of latent and lytic phases. Current dogma indicates that the latent genes are key drivers in the pathogenesis of EBV-associated cancers, while the lytic genes are primarily responsible for viral transmission. In recent years, evidence has emerged to show that the EBV lytic phase also plays an important role in EBV tumorigenesis, and the expression of EBV lytic genes is frequently detected in tumor tissues and cell lines. The advent of next generation sequencing has allowed the comprehensive profiling of EBV gene expression, and this has revealed the consistent expression of several lytic genes across various types of EBV-associated cancers. In this review, we provide an overview of the functional implications of EBV lytic gene expression to the oncogenic process and discuss possible avenues for future investigations.

Type 1 and Type 2 Epstein-Barr viruses induce proliferation, and inhibit differentiation, in infected telomerase-immortalized normal oral keratinocytes

Differentiated epithelial cells are an important source of infectious EBV virions in human saliva, and latent Epstein-Barr virus (EBV) infection is strongly associated with the epithelial cell tumor, nasopharyngeal carcinoma (NPC). However, it has been difficult to model how EBV contributes to NPC, since EBV has not been shown to enhance proliferation of epithelial cells in monolayer culture in vitro and is not stably maintained in epithelial cells without antibiotic selection. In addition, although there are two major types of EBV (type 1 (T1) and type 2 (T2)), it is currently unknown whether T1 and T2 EBV behave differently in epithelial cells. Here we inserted a G418 resistance gene into the T2 EBV strain, AG876, allowing us to compare the phenotypes of T1 Akata virus versus T2 AG876 virus in a telomerase-immortalized normal oral keratinocyte cell line (NOKs) using a variety of different methods, including RNA-seq analysis, proliferation assays, immunoblot analyses, and air-liquid interface culture. We show that both T1 Akata virus infection and T2 AG876 virus infection of NOKs induce cellular proliferation, and inhibit spontaneous differentiation, in comparison to the uninfected cells when cells are grown without supplemental growth factors in monolayer culture. T1 EBV and T2 EBV also have a similar ability to induce epithelial-to-mesenchymal (EMT) transition and activate canonical and non-canonical NF-κB signaling in infected NOKs. In contrast to our recent results in EBV-infected lymphoblastoid cells (in which T2 EBV infection is much more lytic than T1 EBV infection), we find that NOKs infected with T1 and T2 EBV respond similarly to lytic inducing agents such as TPA treatment or differentiation. These results suggest that T1 and T2 EBV have similar phenotypes in infected epithelial cells, with both EBV types enhancing cellular proliferation and inhibiting differentiation when growth factors are limiting.

Multiplex Epstein-Barr virus BALF2 genotyping detects high-risk variants in plasma for population screening of nasopharyngeal carcinoma

Background

Epstein-Barr Virus (EBV)-associated nasopharyngeal carcinoma (NPC) exhibits unusual geographic restriction despite ubiquitous lifelong infection. Screening programs can detect most NPC cases at an early stage, but existing EBV diagnostics are limited by false positives and low positive predictive value (PPV), leading to excess screening endoscopies, MRIs, and repeated testing. Recent EBV genome-wide association studies (GWAS) suggest that EBV BALF2 variants account for more than 80% of attributable NPC risk. We therefore hypothesized that high-risk BALF2 variants could be readily detected in plasma for once-lifetime screening triage.

Methods

We designed and validated a multiplex genotyping assay to detect EBV BALF2 polymorphisms in human plasma. Targeted next-generation sequencing was used to validate this assay, conduct association studies with clinical phenotype, and longitudinally genotype plasma to assess within-host haplotype stability. We examined the association between NPC and BALF2 haplotypes in a large non-endemic population and three prior EBV GWAS. Finally, we estimated NPC mortality reduction, resource utilization, and cost-effectiveness of BALF2 variant-informed screening using a previously-validated cohort model.

Results

Following analytical validation, the BALF2 genotyping assay had 99.3% concordance with sequencing in a cohort of 24 NPC cases and 155 non-NPC controls. BALF2 haplotype was highly associated with NPC in this non-endemic population (I613V: odds ratio [OR] 7.9; V317M: OR 178.8). No other candidate BALF2 polymorphisms were significantly associated with NPC or hematologic disorders.

Longitudinal genotyping revealed 97.8% within-host haplotype concordance, indicative of lifelong latent infection. In a meta-analysis of 755 NPC cases and 981 non-NPC controls, BALF2 I613V and V317M were significantly associated with NPC in both endemic and non-endemic populations.

Modeled variant-informed screening strategies achieved a 46% relative increase in PPV with 7% decrease in effective screening sensitivity, thereby averting nearly half of screening endoscopies/MRIs among endemic populations in east/southeast Asia.

Conclusions

EBV BALF2 haplotypes are temporally stable within hosts and can be readily detected in plasma via an inexpensive multiplex genotyping assay that offers near-perfect sequencing concordance. In endemic and non-endemic populations, I613V and V317M were highly associated with NPC and could be leveraged to develop variant-informed screening programs that mitigate false positives with small reductions in screening sensitivity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01625-6.