The effect of EBV on WIF1, NLK, and APC gene methylation and expression in gastric carcinoma and nasopharyngeal cancer

The viral etiology of EBV-associated gastric cancers contributes to their unique pathology, clinical outcomes, treatment responses and immune landscape

Epstein-Barr virus (EBV) is a pathogen known to cause a number of malignancies, often taking years for them to develop after primary infection. EBV-associated gastric cancer (EBVaGC) is one such malignancy, and is an immunologically, molecularly and pathologically distinct entity from EBV-negative gastric cancer (EBVnGC). In comparison with EBVnGCs, EBVaGCs overexpress a number of immune regulatory genes to help form an immunosuppressive tumor microenvironment (TME), have improved prognosis, and overall have an "immune-hot" phenotype. This review provides an overview of the histopathology, clinical features and clinical outcomes of EBVaGCs. We also summarize the differences between the TMEs of EBVaGCs and EBVnGCs, which includes significant differences in cell composition and immune infiltration. A list of available EBVaGC and EBVnGC gene expression datasets and computational tools are also provided within this review. Finally, an overview is provided of the various chemo- and immuno-therapeutics available in treating gastric cancers (GCs), with a focus on EBVaGCs.

Comprehensive Analysis Based on the TCGA Database Identified SCIN as a Key DNA Methylation-Driver Gene in Epstein-Barr Virus-Associated Gastric Cancer

An important feature of EBV-associated gastric cancer (EBVaGC) is extensive methylation of viral and host genomes. This study aims to analyze DNA methylation-driven genes (DMDG) in EBVaGC through bioinformatics methods, providing an important bioinformatics basis for the differential diagnosis and treatment of potential methylation biomarkers in EBVaGC. We downloaded the mRNA expression profiles and methylation datasets of EBVaGC and EBV-negative gastric cancer (EBVnGC) through the TCGA database to screen methylated-differentially expressed genes (MDEGs). DNA methylation-driver genes were identified based on MethylMix algorithm and key genes were further identified by LASSO regression and Random Forest algorithm. Then, we performed gene enrichment analysis for key genes and validated them by GEO database. Gene expression differences in EBVaGC and EBVnGC cell lines was determined by quantitative real-time PCR (qRT-PCR) and western blotting and in GT38 cell and SNU719 cell which all treated by 5-Aza-CdR. Finally, the effect of key gene on the migration and proliferation capacity of EBVaGC cells was determined by Transwells assay and Cell counting Kit-8 (CCK-8) assay. We obtained a total of 687 hypermethylation-low expression genes (Hyper-LGs) and further obtained 53 DNA methylation-driver genes based on the MethylMix algorithm. A total of six key genes (SCIN, ETNK2, PCDH20, PPP1R3C, MATN2, and HOXA5) were identified by LASSO regression and Random Forest algorithm. Among them, SCIN expression was significantly lower in EBVaGC cell lines than in EBVnGC cell lines, and its expression was significantly recovered in EBVaGC cell lines treated with 5-Aza-CdR. Overexpression of SCIN can promote the proliferation and migration capacity of EBVaGC cells. Our study will provide some bioinformatics basis for the study of EBVaGC-related methylation. SCIN may be used as potential methylation biomarkers for the diagnosis and treatment of EBVaGC.

A comprehensive insight into the correlation between ncRNAs and the Wnt/β-catenin signalling pathway in gastric cancer pathogenesis

During the past decades, gastric cancer (GC) has emerged as one of the most frequent malignancies with a growing rate of prevalence around the world. Despite considerable advances in therapeutic methods, the prognosis and management of patients with gastric cancer (GC) continue to be poor. As one of the candidate molecular targets in the treatment of many types of cancer, the Wnt/β-catenin pathway includes a family of proteins that have important functions in adult tissue homeostasis and embryonic development. The aberrant regulation of Wnt/β-catenin signaling is strongly correlated with the initiation and development of numerous cancers, including GC. Therefore, Wnt/β-catenin signaling has been identified as one of the main targets for extending therapeutic approaches for GC patients. Non-coding RNAs (ncRNAs), including microRNAs and long ncRNAs, are important components of epigenetic mechanisms in gene regulation. They play vital roles in various molecular and cellular processes and regulate many signaling pathways, such as Wnt/β-catenin pathways. Insights into these regulatory molecules involved in GC development may lead to the identification of potential targets for overcoming the limitations of current therapeutic approaches. Consequently, this review aimed to provide a comprehensive overview of ncRNAs interactions involved in Wnt/β-catenin pathway function in GC with diagnostic and therapeutic perspectives. Video Abstract.

The role of EBV-encoded miRNA in EBV-associated gastric cancer

Epstein-Barr virus (human herpesvirus 4, EBV) is a linear double-stranded DNA virus that infects over 90% of the population worldwide. However, our understanding of EBV's contribution to tumorigenesis of EBV-associated GC (EBVaGC) remains incomplete. Recent advancements in EBVaGC research have highlighted that EBV-encoded microRNAs (miRNAs) play prominent roles in critical cellular processes such as migration, cell cycle, apoptosis, cell proliferation, immune response, and autophagy. Notably, the largest group of EBV-encoded miRNAs, known as BamHI-A rightward transcripts (BARTs), exhibit bidirectional effects in EBVaGC. For instance, they present both anti-apoptotic and pro-apoptotic functions and enhance chemosensitivity while also conferring resistance to 5-fluorouracil. Despite these findings, the comprehensive mechanisms through which miRNAs contribute to EBVaGC are yet to be fully elucidated. In this work, we summarize the current evidence of the roles of miRNA in EBVaGC, particularly with the application of multi-omic techniques. Additionally, we discuss the application of miRNA in EBVaGC in retrospective analyses and provide novel perspectives on the use of miRNA in EBVaGC in translational medicine.

Epstein-Barr Virus Regulates Endothelin-1 Expression through the ERK/FOXO1 Pathway in EBV-Associated Gastric Cancer

Epstein-Barr virus-associated gastric carcinoma (EBVaGC) is one of the four subtypes of gastric carcinoma and its unique clinicopathological mechanism is unclear. Herein, the expression of endothelin-1 (ET-1) in EBVaGC was lower than of Epstein-Barr virus-negative gastric carcinoma (EBVnGC) and associated with a low frequency of lymph node metastasis of EBVaGC. Functional studies showed that the activation of ET-1/endothelin receptor type A (ETAR) axis could promote cell growth, migration, and antiapoptosis. The expression of the ET-1 gene was unrelated to methylation of its promoter region and miRNAs (-1, -125a, -125b). After being treated with MEK1/2 inhibitor (PD0325901), the inactivation of ERK1/2 pathway resulted in downregulation of ET-1 and forkhead box O1 (FOXO1) expression. Further, FOXO1 knockdown decreased the ET-1 expression. These findings indicated that ET-1 could be involved in development of gastric cancer and EBV could suppress the expression of ET-1 via the regulation of the transcription factor FOXO1 through the MAPK/ERK pathway. IMPORTANCE The relationship between Epstein-Barr virus and gastric cancer has been relatively clear. However, there are still many unresolved mechanisms of the virus in tumorigenesis. In recent years, activation of the endothelin-1 signaling axis has been found to play an important role in tumorigenesis, which is involved in tumor angiogenesis and epithelial-mesenchymal transition. EBV genes. In our study, we found that ET-1 was low-expressed in EBV-positive gastric cancer cells, which was due to the inhibition of ERK signaling by EBNA1 through the repression of FOXO1 expression. The low expression of ET-1 limits the proliferation, migration, and anti-apoptotic ability of tumor cells. These findings contribute to further understanding of the role of EBV in EBV-associated gastric cancer.

Role of non-coding RNAs and exosomal non-coding RNAs in retinoblastoma progression

Retinoblastoma (RB) is a rare aggressive intraocular malignancy of childhood that has the potential to affect vision, and can even be fatal in some children. While the tumor can be controlled efficiently at early stages, metastatic tumors lead to high mortality. Non-coding RNAs (ncRNAs) are implicated in a number of physiological cellular process, including differentiation, proliferation, migration, and invasion, The deregulation of ncRNAs is correlated with several diseases, particularly cancer. ncRNAs are categorized into two main groups based on their length, i.e. short and long ncRNAs. Moreover, ncRNA deregulation has been demonstrated to play a role in the pathogenesis and development of RB. Several ncRNAs, such as miR-491-3p, miR-613,and SUSD2 have been found to act as tumor suppressor genes in RB, but other ncRNAs, such as circ-E2F3, NEAT1, and TUG1 act as tumor promoter genes. Understanding the regulatory mechanisms of ncRNAs can provide new opportunities for RB therapy. In the present review, we discuss the functional roles of the most important ncRNAs in RB, their interaction with the genes responsible for RB initiation and progression, and possible future clinical applications as diagnostic and prognostic tools or as therapeutic targets.

Viral miRNA regulation of host gene expression

Viruses have evolved a multitude of mechanisms to combat barriers to productive infection in the host cell. Virally-encoded miRNAs are one such means to regulate host gene expression in ways that benefit the virus lifecycle. miRNAs are small non-coding RNAs that regulate protein expression but do not trigger the adaptive immune response, making them powerful tools encoded by viruses to regulate cellular processes. Diverse viruses encode for miRNAs but little sequence homology exists between miRNAs of different viral species. Despite this, common cellular pathways are targeted for regulation, including apoptosis, immune evasion, cell growth and differentiation. Herein we will highlight the viruses that encode miRNAs and provide mechanistic insight into how viral miRNAs aid in lytic and latent infection by targeting common cellular processes. We also highlight how viral miRNAs can mimic host cell miRNAs as well as how viral miRNAs have evolved to regulate host miRNA expression. These studies dispel the myth that viral miRNAs are subtle regulators of gene expression, and highlight the critical importance of viral miRNAs to the virus lifecycle.

The promoter aberrant methylation status of TMEM130 is associated with gastric cancer

BACKGROUND AND AIMS

Gastric cancer (GC) is a malignant tumor that seriously affects human health and Epstein-Barr virus (EBV)-associated gastric cancer (EBVaGC) is a molecular subtype of GC. This study aims to determine the relationship between the methylation status of the TMEM130 gene and GC, and to explore the influence of EBV infection.

METHODS

qRT-PCR was conducted to investigate the transcriptional expression of TMEM130 in GC. BSP and MSP assays were used to detect the methylation level of the TMEM130 promoter. The cell migration ability was detected by Transwell and western blot after transfection of TMEM130 plasmids in GC cells.

RESULTS

The transcriptional expression of TMEM130 decreased in GC with hypermethylation of the promoter region. The DNA methyltransferase inhibitor could increase the mRNA expression of TMEM130. Moreover, hypermethylation of the TMEM130 promoter in GC tissues was associated with EBV infection. Overexpression of TMEM130 in GC cell lines suppresses cell migration ability.

CONCLUSION

This study was the first to research the expression and function of TMEM130 and found that TMEM130 gene hypermethylation might contribute to GC migration and EBV infection as a cause of hypermethylation of the TMEM130 gene. TMEM130 is a promising biomarker for the diagnosis of GC.

Prognostic Epstein-Barr Virus (EBV) miRNA biomarkers for survival outcome in EBV-associated epithelial malignancies: Systematic review and meta-analysis

Background

The EBV-associated epithelial tumours consist 80% of all EBV-associated cancer, where the nasopharyngeal cancer (NPC) and EBV-associated gastric carcinoma (EBVaGC) are considered as the most frequent EBV-associated epithelial tumours. It has been shown that the BART-encoded miRNAs are abundantly expressed in EBV-associated epithelial tumours, hence, these miRNAs may serve as diagnostic and prognostic biomarkers for EBV-associated epithelial tumours. Therefore, the purpose of this systematic review and meta-analysis is to assess these EBV miRNAs as prognostic biomarkers for NPC and GC.

Method

This systematic review was developed based on PRISMA guidelines and utilizing PubMed, Web of Science, Scopus, Cochrane, and Google scholar databases. The retrieved articles were thoroughly screened in accordance with the selection criteria. The hazard ratio (HR) and 95% confidence interval (CI) for patient survival outcomes were used to evaluate EBV miRNA expression levels. To assess the risk of bias, funnel plot symmetry and Egger’s bias test were employed.

Result

Eleven studies met the selection criteria for inclusion, and four were included in the meta-analysis. Most of the articles considered in this study were from China, with one study from South Korea. The overall pooled effect size estimation (HR) for upregulated EBV miRNAs was 3.168 (95% CI: 2.020–4.969), demonstrating that upregulated EBV miRNA expression enhanced the mortality risk in NPC and GC patients by three times.

Conclusion

To the best of our knowledge, this is the first meta-analysis that investigates the significance of EBV miRNAs as prognostic biomarkers in NPC and GC patients. The pooled effect estimates of HR of the various studies revealed that higher EBV miRNA expression in NPC and GC may result in a worse survival outcome. To assess the clinical significance of EBV miRNAs as prognostic biomarkers, larger-scale prospective studies are needed.

Epstein–Barr Virus Infection in Lung Cancer: Insights and Perspectives

Lung cancer (LC) is the leading cause of cancer death worldwide. Tobacco smoke is the most frequent risk factor etiologically associated with LC, although exposures to other environmental factors such as arsenic, radon or asbestos are also involved. Additionally, the involvement of some viral infections such as high-risk human papillomaviruses (HR-HPVs), Merkel cell polyomavirus (MCPyV), Jaagsiekte Sheep Retrovirus (JSRV), John Cunningham Virus (JCV), and Epstein–Barr virus (EBV) has been suggested in LC, though an etiological relationship has not yet been established. EBV is a ubiquitous gamma herpesvirus causing persistent infections and some lymphoid and epithelial tumors. Since EBV is heterogeneously detected in LCs from different parts of the world, in this review we address the epidemiological and experimental evidence of a potential role of EBV. Considering this evidence, we propose mechanisms potentially involved in EBV-associated lung carcinogenesis. Additional studies are warranted to dissect the role of EBV in this very frequent malignancy.

CircEAF2 counteracts Epstein-Barr virus-positive diffuse large B-cell lymphoma progression via miR-BART19-3p/APC/β-catenin axis

Background

Epstein-Barr virus (EBV) represents an important pathogenic factor of lymphoma and is significantly associated with poor clinical outcome of diffuse large B-cell lymphoma (DLBCL). Circular RNAs (circRNAs) play an essential role in lymphoma progression. However, the underlying mechanism of circRNA on DLBCL progression related to EBV remains largely unknown.

Methods

CircRNA was screened by high-throughput sequencing in tumor samples of 12 patients with DLBCL according to EBV infection status. Expression of circEAF2, as well as the relationship with clinical characteristics and prognosis, were further analyzed in tumor samples of 100 DLBCL patients using quantitative real-time PCR. Gain- and loss-of-function experiments were conducted to investigate the biological functions of circEAF2 both in vitro and in vivo. The underlying mechanism of circRNA on DLBCL progression were further determined by RNA sequencing, RNA pull down assay, dual-luciferase reporter assay, rescue experiments and western blotting.

Results

We identified a novel circRNA circEAF2, which was downregulated in EBV + DLBCL and negatively correlated with EBV infection and DLBCL progression. In EBV-positive B lymphoma cells, circEAF2 overexpression induced lymphoma cell apoptosis and sensitized lymphoma cells to epirubicin. As mechanism of action, circEAF2 specifically targeted EBV-encoded miR-BART19-3p, upregulated APC, and suppressed downstream β-catenin expression, resulting in inactivation of Wnt signaling pathway and inhibition of EBV + DLBCL cell proliferation. In EBV-positive B-lymphoma murine models, xenografted tumors with circEAF2 overexpression presented decreased Ki-67 positivity, increased cell apoptosis and retarded tumor growth.

Conclusions

CircEAF2 counteracted EBV + DLBCL progression via miR-BART19-3p/APC/β-catenin axis, referring circEAF2 as a potential prognostic biomarker. Therapeutic targeting EBV-encoded miRNA may be a promising strategy in treating EBV-associated lymphoid malignancies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-021-01458-9.

The detection of specific hypermethylated WIF1 and NPY genes in circulating DNA by crystal digital PCR™ is a powerful new tool for colorectal cancer diagnosis and screening

Background

In oncology, liquid biopsy is of major relevance from theranostic point of view. The searching for mutations in circulating tumor DNA (ctDNA) in case of colorectal cancers (CRCs) allows the optimization of patient care. In this context, independent of mutation status biomarkers are required for its detection to confirm the presence of ctDNA in liquid biopsies. Indeed, the hypermethylation of NPY and WIF1 genes appear to be an ideal biomarker for the specific detection of ctDNA in CRCs. The objective of this work is to develop the research of hypermethylation of NPY and WIF1 by Crystal Digital PCR™ for the detection of ctDNA in CRCs.

Methods

Detection of hypermethylated NPY and WIF1 was developed on Cristal digital PCR™. Biological validation was performed from a local cohort of 22 liquid biopsies and 23 tissue samples from patients with CRC. These patients were treated at the University Hospital of Besancon (France).

Results

The local cohort study confirmed that NPY and WIF1 were significantly hypermethylated in tumor tissues compared to adjacent non-tumor tissues (WIF1 p < 0.001; NPY p < 0.001; non-parametric Wilcoxon paired-series test). Histological characteristics, tumor stages or mutation status were not correlated to the methylation profiles. On the other hand, hypermethylation of NPY or WIF1 in liquid biopsy had a 95.5% [95%CI 77–100%] sensitivity and 100% [95%CI 69–100%] specificity.

Conclusion

Using Crystal digital PCR™, this study shows that hypermethylation of NPY and WIF1 are constant specific biomarkers of CRCs regardless of a potential role in carcinogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08816-2.

LncRNA TP73-AS1 promotes the development of Epstein-Barr virus associated gastric cancer by recruiting PRC2 complex to regulate WIF1 methylation

BACKGROUND

Epstein-Barr virus associated gastric cancer (EBVaGC) become a growing health problem. TP73-AS1 showed high expression in EBVaGC cells. However, the function role and underlying mechanism of TP73-AS1 need further exploration.

METHODS

The expressions of TP73-AS1, WIF1, EZH2, β-catenin and epithelial-mesenchymal transition (EMT)-related proteins were detected using qRT-PCR and Western blotting. Cell proliferation, apoptosis, migration and invasion were measured by CCK-8, colony formation, flow cytometry, wound healing and transwell assays, respectively. WIF1 promoter methylation was analyzed by MS-PCR (MSP). RNA immunoprecipitation assay (RIP) and Chromatin immunoprecipitation assay (ChIP) measured the interactions of TP73-AS1/EZH2 and EZH2/WIF1. Subcutaneous tumor growth was monitored in nude mice and immunohistochemistry (IHC) detected proliferation marker Ki-67 expression.

RESULTS

TP73-AS1 was increased while WIF1 was decreased in EBVaGC cells. Silencing of TP73-AS1 or overexpression of WIF1 repressed the growth and migration while promoted apoptosis of EBVaGC cells. Knockdown of WIF1 reversed the anticancer effect of TP73-AS1 silencing. TP73-AS1 promoted the binding of EZH2 to the WIF1 promoter by directly binding to EZH2, and thus inhibiting the expression of WIF1 by enhancing H3K27me3 level of WIF1 promoter. Moreover, TP73-AS1 activated Wnt/β-catenin signaling pathway and promoted EMT by down-regulating WIF1. TP73-AS1 silencing inhibited the progression of EBVaGC in nude mice by epigenetically regulating WIF1.

CONCLUSION

TP73-AS1 regulated the promoter methylation of WIF1 by recruiting PRC2 complex to WIF1 promoter region, thereby promoting the progression of EBVaGC. These observations provided a novel theoretical basis to investigate more effective therapies of EBVaGC.

miR-340 Promotes Retinoblastoma Cell Proliferation, Migration and Invasion Through Targeting WIF1

Background

MicroRNAs (miRNAs) function as important regulators of gene expression involved in tumor pathogenesis, including retinoblastoma. However, the expression profiles and potential roles in retinoblastoma are still largely unclear.

Material and Methods

Differentially expressed miRNAs (DEmiRs) and genes (DEGs) in retinoblastoma were extracted from Gene Expression Omnibus (GEO) repository. Expression levels of miR-340 and WIF1 were detected in retinoblastoma tissues and cell lines by qRT-PCR. Both gain-of-function and loss-of-function experiments were performed to explore the effects of miR-340 on cell proliferation, migration and invasion. Bioinformatics analysis and luciferase reporter assay were used to explore the interaction between miR-340 and WIF1.

Results

A total of 11 DEmiRs were identified in retinoblastoma tissue and blood samples. Among them, we validated that miR-340 was the most highly expressed miRNA and correlated with tumor size, ICRB stage and optic nerve invasion. miR-340 was observed to enhance the proliferation, migration and invasion capacity of retinoblastoma cells. We then identified 26 DEGs from 3 retinoblastoma GEO datasets and subsequently constructed a miRNA–mRNA regulatory network. Further analysis revealed that WIF1 was a direct target of miR-340. Moreover, overexpression of WIF1 could repress retinoblastoma progression induced by miR-340 in vitro and in vivo.

Conclusion

Collectively, miR-340 functioned as an oncomiRNA to promote retinoblastoma cell proliferation, migration and invasion via regulating WIF1. Our data also provided multiple miRNAs and genes that may contribute to a better understanding of retinoblastoma pathogenesis.

APC Promoter Methylation in Gastrointestinal Cancer

The adenomatous polyposis coli (APC) gene, known as tumor suppressor gene, has the two promoters 1A and 1B. Researches on APC have usually focused on its loss-of-function variants causing familial adenomatous polyposis. Hypermethylation, however, which is one of the key epigenetic alterations of the APC CpG sequence, is also associated with carcinogenesis in various cancers. Accumulating studies have successively explored the role of APC hypermethylation in gastrointestinal (GI) tumors, such as in esophageal, colorectal, gastric, pancreatic, and hepatic cancer. In sporadic colorectal cancer, the hypermethylation of CpG island in APC is even considered as one of the primary causative factors. In this review, we systematically summarized the distribution of APC gene methylation in various GI tumors, and attempted to provide an improved general understanding of DNA methylation in GI tumors. In addition, we included a robust overview of demethylating agents available for both basic and clinical researches. Finally, we elaborated our findings and perspectives on the overall situation of APC gene methylation in GI tumors, aiming to explore the potential research directions and clinical values.

Critical review of Epstein-Barr virus microRNAs relation with EBV-associated gastric cancer

Epstein-Barr virus (EBV)-associated gastric cancer (EBVaGC) is regarded as the most prevalent malignant tumor triggered by EBV infection. In recent years, increasing attention has been considered to recognize more about the disease process's exact mechanisms. There is accumulating evidence that showing epigenetic modifications play critical roles in the EBVaGC pathogenesis. MicroRNAs (miRNAs), as critical epigenetic modulators, are single-strand short noncoding RNA (length ~ <200 bp), which regulate gene expression through binding to the 3'-untranslated region (3'-UTR) of target RNA transcripts and either degrade or repress their activities. In the latest research on EBV, it was found that this virus could encode miRNAs. Mechanistically, EBV-encoded miRNAs are involved in carcinogenesis and the progression of EBV-associated malignancies. Moreover, these miRNAs implicated in immune evasion, identification of pattern recognition receptors, regulation of lymphocyte activation and lethality, modulation of infected host cell antigen, maintain of EBV infection status, promotion of cell proliferation, invasion and migration, and reduction of apoptosis. As good news, not only has recent data demonstrated the crucial function of EBV-encoded miRNAs in the pathogenesis of EBVaGC, but it has also been revealed that aberrant expression of exosomal miRNAs in EBVaGC has made them biomarkers for detection of EBVaGC. Regarding these substantial characterizes, the critical role of EBV-encoded miRNAs has been a hot topic in research. In this review, we will focus on the multiple mechanisms involved in EBVaGC caused by EBV-encoded miRNAs and briefly discuss their potential application in the clinic as a diagnostic biomarker.

EBV-Positive Gastric Cancer: Current Knowledge and Future Perspectives

Gastric cancer is the fifth most common malignant tumor and second leading cause of cancer-related deaths worldwide. With the improved understanding of gastric cancer, a subset of gastric cancer patients infected with Epstein–Barr virus (EBV) has been identified. EBV-positive gastric cancer is a type of tumor with unique genomic aberrations, significant clinicopathological features, and a good prognosis. After EBV infects the human body, it first enters an incubation period in which the virus integrates its DNA into the host and expresses the latent protein and then affects DNA methylation through miRNA under the action of the latent protein, which leads to the occurrence of EBV-positive gastric cancer. With recent developments in immunotherapy, better treatment of EBV-positive gastric cancer patients appears achievable. Moreover, studies show that treatment with immunotherapy has a high effective rate in patients with EBV-positive gastric cancer. This review summarizes the research status of EBV-positive gastric cancer in recent years and indicates areas for improvement of clinical practice.

Mutation profiling in eight cases of vagal paragangliomas

Background

Vagal paragangliomas (VPGLs) belong to a group of rare head and neck neuroendocrine tumors. VPGLs arise from the vagus nerve and are less common than carotid paragangliomas. Both diagnostics and therapy of the tumors raise significant challenges. Besides, the genetic and molecular mechanisms behind VPGL pathogenesis are poorly understood.

Methods

The collection of VPGLs obtained from 8 patients of Russian population was used in the study. Exome library preparation and high-throughput sequencing of VPGLs were performed using an Illumina technology.

Results

Based on exome analysis, we identified pathogenic/likely pathogenic variants of the SDHx genes, frequently mutated in paragangliomas/pheochromocytomas. SDHB variants were found in three patients, whereas SDHD was mutated in two cases. Moreover, likely pathogenic missense variants were also detected in SDHAF3 and SDHAF4 genes encoding for assembly factors for the succinate dehydrogenase (SDH) complex. In a patient, we found a novel variant of the IDH2 gene that was predicted as pathogenic by a series of algorithms used (such as SIFT, PolyPhen2, FATHMM, MutationTaster, and LRT). Additionally, pathogenic/likely pathogenic variants were determined for several genes, including novel genes and some genes previously reported as associated with different types of tumors.

Conclusions

Results indicate a high heterogeneity among VPGLs, however, it seems that driver events in most cases are associated with mutations in the SDHx genes and SDH assembly factor-coding genes that lead to disruptions in the SDH complex.

The Utility of Gastrointestinal Endoscopic Examination Versus Positron Emission Tomography-Computed Tomography in the Detection of Second Primary Lesions in Korean Patients With Head and Neck Cancer

OBJECTIVE

Head and neck cancer often accompany a synchronous secondary primary lesion in the digestive tract. The aim of this study was to compare detection rates between positron emission tomography-computed tomography (PET-CT) and esophagogastroduodenoscopy (G-fiber) or colonoscopy (C-fiber) in the initial staging and to analyze risk factors for premalignant, malignant, and total synchronous secondary primary lesions.

METHODS

A total of 739 patients with head and neck cancer who underwent PET-CT, G-fiber, or C-fiber were analyzed retrospectively.

RESULTS

Positron emission tomography-CT did not definitely detect any premalignant synchronous secondary primary lesions (0 [0%] of 739) but definitely detected 10 malignant synchronous secondary primary lesions (10 [1.35%] of 739). Esophagogastroduodenoscopy or C-fiber detected all 20 premalignant synchronous secondary primary lesions (20 [2.71%] of 739) and all 37 malignant synchronous secondary primary lesions (37 [5.00%] of 739). The patients with nasopharynx cancer tended to have premalignant synchronous secondary primary lesions (odds ratio [OR]: 3.793; 95% CI: 1.414-10.171; P = .008). Those with distant metastasis tended to have premalignant (OR: 4.743; 95% CI: 1.508-14.916; P = .009), malignant (OR: 3.803; 95% CI: 1.486-9.731; P = .005), and total synchronous secondary primary lesions (OR: 2.753; 95% CI: 1.159-6.538; P = .022).

CONCLUSIONS

Premalignant or malignant synchronous secondary primary lesions that were not definitely detected by PET-CT could be found in the endoscopic examination.

Role of miR-96/EVI1/miR-449a Axis in the Nasopharyngeal Carcinoma Cell Migration and Tumor Sphere Formation

The Wnt signaling pathway is one of the major signaling pathways used by cancer stem cells (CSC). Ecotropic Viral Integration Site 1 (EVI1) has recently been shown to regulate oncogenic development of tumor cells by interacting with multiple signaling pathways, including the Wnt signaling. In the present study, we found that the Wnt modulator ICG-001 could inhibit the expression of EVI1 in nasopharyngeal carcinoma (NPC) cells. Results from loss-of-function and gain-of-function studies revealed that EVI1 expression positively regulated both NPC cell migration and growth of CSC-enriched tumor spheres. Subsequent studies indicated ICG-001 inhibited EVI1 expression via upregulated expression of miR-96. Results from EVI1 3′UTR luciferase reporter assay confirmed that EVI1 is a direct target of miR-96. Further mechanistic studies revealed that ICG-001, overexpression of miR-96, or knockdown of EVI1 expression could restore the expression of miR-449a. The suppressive effect of miR-449a on the cell migration and tumor sphere formation was confirmed in NPC cells. Taken together, the miR-96/EVI1/miR-449a axis is a novel pathway involved in ICG-001-mediated inhibition of NPC cell migration and growth of the tumor spheres.

The Oncogenic Role of miR-BART19-3p in Epstein-Barr Virus-Associated Diseases

Accumulating evidence so far has shown that EBV's miRNAs have been found to be involved in cancer progression. However, the comprehensive EBV miRNA expression profiles and their biological significance in EBV-associated diseases are not well documented. A comprehensive profiling of EBV-encoded miRNAs expressed in CAEBV, EBV-HLH, and nasopharyngeal carcinoma (NPC) patients was constructed, and the results showed that miR-BART19-3p was upregulated in all these diseases. Ectopic expression of miR-BART19-3p induced EBV-negative cell proliferation and suppressed cell apoptosis. Molecularly, adenomatous polyposis coli (APC) was identified to be a direct target of miR-BART19-3p, and APC mRNA expression was inversely correlated with miR-BART19-3p in CAEBV samples. Our results demonstrated that miR-BART19-3p contributes to the tumorigenesis of EBV-associated diseases and may be a potential therapeutic target.

Comprehensive Analysis of the Canonical and Non-canonical Wnt Signaling Pathways in Gastric Cancer

BACKGROUND

Previous studies showed that dysregulation of Wnt signaling by gene mutation and abnormal gene expression is one of the causative factors for gastric cancer (GC). So far, a systematic and comprehensive analysis of gene mutation, gene expression, and DNA methylation profiles of the Wnt pathway associated with gastric carcinogenesis, however, has not yet been reported.

AIMS

To this end, we investigated all the above-mentioned genetic alterations associated with the canonical and non-canonical Wnt pathways in GC tumors, in order to understand the molecular mechanism underlying gastric carcinogenesis.

METHODS

The information on gene mutations and expression was obtained from data resources, such as TCGA, GSEA, and TCGA-STAD, and was analyzed with the cBioPortal platform. We also performed in vitro analysis on DDK2 gene, a Wnt inhibitor, to characterize its role in GC tumor cells.

RESULTS

We found that gene mutations of 43 Wnt genes and abnormal expression of 13 Wnt genes occurred at a high frequency in GC tumors, and gene amplification and deletion are the major mutation types. Clusters of DNA methylation associated with Wnt signaling genes and GC tumors were also revealed, and a significant increase in β-catenin activity was found in the hypermethylated group of GC tumors. In addition, overexpression of DKK2 gene significantly inhibited multiple biological processes of the GC cells, including their growth, clonal forming, migration, and invasion ability, and induced apoptosis of the GC cells.

CONCLUSIONS

Our current study suggested that gene mutation, abnormal gene expression, and altered DNA methylation profiles associated with the Wnt signaling may play an important role in gastric carcinogenesis, and DKK2 gene may act as a tumor suppressor in gastric cells.

The Function and Therapeutic Potential of Epstein-Barr Virus-Encoded MicroRNAs in Cancer

Epstein-Barr virus (EBV) is a ubiquitous human γ-herpesvirus that infects over 90% of the global population. EBV is considered a contributory factor in a variety of malignancies including nasopharyngeal carcinoma, gastric carcinoma, Burkitt lymphoma, and Hodgkin’s lymphoma. Notably, EBV was the first virus found to encode microRNAs (miRNAs). Increasing evidence indicates that EBV-encoded miRNAs contribute to the carcinogenesis and development of EBV-associated malignancies. EBV miRNAs have been shown to inhibit the expression of genes involved in cell proliferation, apoptosis, invasion, and immune signaling pathways. Therefore, EBV miRNAs perform a significant function in the complex host-virus interaction and EBV-driven carcinogenesis. However, the integrated mechanisms underlying the roles of EBV miRNAs in carcinogenesis remain to be further explored. In this review, we describe recent advances regarding the involvement of EBV miRNAs in the pathogenesis of EBV-associated malignancies and discuss their potential utility as cancer biomarkers. An in-depth investigation into the pro-carcinogenic role of EBV miRNAs will expand our knowledge of the biological processes associated with virus-driven tumors and contribute to the development of novel therapeutic strategies for the treatment of EBV-associated malignancies.

Molecular mechanisms of EBV-driven cell cycle progression and oncogenesis

The early stage of oncogenesis is linked to the disorder of the cell cycle. Abnormal gene expression often leads to cell cycle disorders, resulting in malignant transformation of human cells. Epstein–Barr virus (EBV) is associated with a diverse range of human neoplasms, such as malignant lymphoma, nasopharyngeal carcinoma and gastric cancer. EBV mainly infects human lymphocytes and oropharyngeal epithelial cells. EBV is latent in lymphocytes for a long period of time, is detached from the cytoplasm by circular DNA, and can integrate into the chromosome of cells. EBV expresses a variety of latent genes during latent infection. The interaction between EBV latent genes and oncogenes leads to host cell cycle disturbances, including the promotion of G₁/S phase transition and inhibition of cell apoptosis, thereby promoting the development of EBV-associated neoplasms. Molecular mechanisms of EBV-driven cell cycle progression and oncogenesis involve diverse genes and signal pathways. Here, we review the molecular mechanisms of EBV-driven cell cycle progression and promoting oncogenesis.

Epstein-Barr virus stably confers an invasive phenotype to epithelial cells through reprogramming of the WNT pathway

Epstein-Barr virus (EBV)-associated carcinomas, such as nasopharyngeal carcinoma (NPC), exhibit an undifferentiated and metastatic phenotype. To determine viral contributions involved in the invasive phenotype of EBV-associated carcinomas, EBV-infected human telomerase-immortalized normal oral keratinocytes (NOK) were investigated. EBV-infected NOK were previously shown to undergo epigenetic reprogramming involving CpG island hypermethylation and delayed responsiveness to differentiation. Here, we show that EBV-infected NOK acquired an invasive phenotype that was epigenetically retained after viral loss. The transcription factor lymphoid enhancer factor 1 (LEF1) and the secreted ligand WNT5A, expressed in NPC, were increased in EBV-infected NOK with sustained expression for more than 20 passages after viral loss. Increased LEF1 levels involved four LEF1 variants, and EBV-infected NOK showed a lack of responsiveness to β-catenin activation. Although forced expression of WNT5A and LEF1 enhanced the invasiveness of parental NOK, LEF1 knockdown reversed the invasive phenotype of EBV-infected NOK in the presence of WNT5A. Viral reprogramming of LEF1 and WNT5A was observed several passages after EBV infection, suggesting that LEF1 and WNT5A may provide a selective advantage to virally-infected cells. Our findings suggest that EBV epigenetically reprogrammed epithelial cells with features of basal, wound healing keratinocytes, with LEF1 contributing to the metastatic phenotype of EBV-associated carcinomas.