N6-methyladenosine methylation regulates the tumor microenvironment of Epstein-Barr virus-associated gastric cancer

BACKGROUND N6-methyladenosine(m6A)methylation modification exists in Epstein-Barr virus(EBV)primary infection,latency,and lytic reactivation.It also modifies EBV latent genes and lytic genes.EBV-associated gastric cancer(EBVaGC)is a distinctive molecular subtype of GC.We hypothesized EBV and m6A methylation regulators interact with each other in EBVaGC to differentiate it from other types of GC.AIM To investigate the mechanisms of m6A methylation regulators in EBVaGC to determine the differentiating factors from other types of GC.METHODS First,The Cancer Gene Atlas and Gene Expression Omnibus databases were used to analyze the expression pattern of m6A methylation regulators between EBVaGC and EBV-negative GC(EBVnGC).Second,we identified Gene Ontology(GO)and Kyoto Encyclopedia of Genes and Genomes(KEGG)functional enrichment of m6A-related differentially expressed genes.We quantified the relative abundance of immune cells and inflammatory factors in the tumor microenvironment(TME).Finally,cell counting kit-8 cell proliferation test,transwell test,and flow cytometry were used to verify the effect of insulin-like growth factor binding protein 1(IGFBP1)in EBVaGC cell lines.RESULTS m6A methylation regulators were involved in the occurrence and development of EBVaGC.Compared with EBVnGC,the expression levels of m6A methylation regulators Wilms tumor 1-associated protein,RNA binding motif protein 15B,CBL proto-oncogene like 1,leucine rich pentatricopeptide repeat containing,heterogeneous nuclear ribonucleoprotein A2B1,IGFBP1,and insulin-like growth factor 2 binding protein 1 were significantly downregulated in EBVaGC(P<0.05).The overall survival rate of EBVaGC patients with a lower expression level of IGFBP1 was significantly higher(P=0.046).GO and KEGG functional enrichment analyses showed that the immunity pathways were significantly activated and rich in immune cell infiltration in EBVaGC.Compared with EBVnGC,the infiltration of activated CD4+T cells,activated CD8+T cells,monocytes,activated dendritic cells,and plasmacytoid dendritic cells were significantly upregulated in EBVaGC(P<0.001).In EBVaGC,the expression level of proinflammatory factors interleukin(IL)-17,IL-21,and interferon-γ and immunosuppressive factor IL-10 were significantly increased(P<0.05).In vitro experiments demonstrated that the expression level of IGFBP1 was significantly lower in an EBVaGC cell line(SNU719)than in an EBVnGC cell line(AGS)(P<0.05).IGFBP1 overexpression significantly attenuated proliferation and migration and promoted the apoptosis levels in SNU719.Interfering IGFBP1 significantly promoted proliferation and migration and attenuated the apoptosis levels in AGS.CONCLUSION m6A regulators could remodel the TME of EBVaGC,which is classified as an immune-inflamed phenotype and referred to as a“hot”tumor.Among these regulators,we demonstrated that IGFBP1 affected proliferation,migration,and apoptosis.

Development of Epstein-Barr virus-associated gastric cancer:Infection,inflammation,and oncogenesis

Epstein-Barr virus(EBV)-associated gastric cancer(EBVaGC)cells originate from a single-cell clone infected with EBV.However,more than 95%of patients with gastric cancer have a history of Helicobacter pylori(H.pylori)infection,and H.pylori is a major causative agent of gastric cancer.Therefore,it has long been argued that H.pylori infection may affect the development of EBVaGC,a subtype of gastric cancer.Atrophic gastrointestinal inflammation,a symptom of H.pylori infection,is observed in the gastric mucosa of EBVaGC.Therefore,it remains unclear whether H.pylori infection is a cofactor for gastric carcinogenesis caused by EBV infection or whether H.pylori and EBV infections act independently on gastric cancer formation.It has been reported that EBV infection assists in the oncogenesis of gastric cancer caused by H.pylori infection.In contrast,several studies have reported that H.pylori infection accelerates tumorigenesis initiated by EBV infection.By reviewing both clinical epidemiological and experimental data,we reorganized the role of H.pylori and EBV infections in gastric cancer formation.

Clinical and pathological characterization of epstein-barr virus-associated gastric carcinomas in portugal

AIM To determine the prevalence of epstein-barr virus(eb V)-associated gastric carcinomas in the North Region of Portugal and to study its clinicopathological characteristics. METHODS We have performed a retrospective study including a total of 179 consecutive patients with gastric cancer(GC) submitted to gastrectomy during 2011 at the Portuguese Oncology Institute of Porto. Clinical and pathological data was collected from individual clinical records and inserted on a database with unique codification. Tumour tissues were collected from the institutional tumour bank. eb V was detected by in situ hybridization for the detection of eb V-encoded small RNAs(ebe Rs) and eb V latent proteins(LMP1 and LMP2 A) were detected by immunohistochemistry.RESULTS The analysis showed that eb V-associated gastric carcinomas(eb Va GC) represents 8.4%(15/179) of all GC cases, with a significant differential distribution among histological types(P < 0.001): 100%(3/3) of medullary carcinomas, 100%(1/1) of adenosquamous carcinoma, 8.7%(8/92) of tubular adenocarcinomas, 8.0%(2/25) of mixed carcinomas and 2%(1/51) in poorly cohesive carcinomas. The analysis revealed a higher predominance of eb Va GC in the upper third and middle(cardia, fundus and body) of the stomach(P = 0.041), a significant lower number of regional lymph nodes invasion(P = 0.025) and a tendency for better prognosis(P = 0.222). eb V latent protein expression revealed that all eb Va GC cases were LMP1-negative, nevertheless 6 cases(40%) expressed LPM2 A, which reveals that these cases show a distinct eb V-Latency profile(latency II-like).CONCLUSION eb Va GC represents 8.4% of all GC in the North Region of Portugal. The eb V-infected patients have specific clinic-pathological features that should be further explored to develop new strategies of management and treatment.

Cost-effective low-coverage whole-genome sequencing assay for the risk stratification of gastric cancer

BACKGROUND Gastric cancer(GC), a multifactorial disease, is caused by pathogens, such as Helicobacter pylori(H. pylori) and Epstein-Barr virus(EBV), and genetic components.AIM To investigate microbiomes and host genome instability by cost-effective,low-coverage wholegenome sequencing,as biomarkers for GC subtyping.METHODS Samples from 40 GC patients were collected from Taizhou Hospital,Zhejiang Province,affiliated with Wenzhou Medical University.DNA from the samples was subjected to low-coverage wholegenome sequencing with a median genome coverage of 1.86×(range:1.03×to 3.17×) by Illumina×10,followed by copy number analyses using a customized bioinformatics workflow ultrasensitive chromosomal aneuploidy detector.RESULTS Of the 40 GC samples,20 (50%) were found to be enriched with microbiomes.EBV DNA was detected in 5 GC patients (12.5%).H.pylori DNA was found in 15 (37.5%) patients.The other 20(50%) patients were found to have relatively higher genomic instability.Copy number amplifications of the oncogenes,ERBB2 and KRAS,were found in 9 (22.5%) and 7 (17.5%) of the GC samples,respectively.EBV enrichment was found to be associated with tumors in the gastric cardia and fundus.H.pylori enrichment was found to be associated with tumors in the pylorus and antrum.Tumors with elevated genomic instability showed no localization and could be observed in any location.Additionally,H.pylori-enriched GC was found to be associated with the Borrmann type Ⅱ/Ⅲ and gastritis history.EBV-enriched GC was not associated with gastritis.No statistically significant correlation was observed between genomic instability and gastritis.Furthermore,these three different molecular subtypes showed distinct survival outcomes (P=0.019).EBV-positive tumors had the best prognosis,whereas patients with high genomic instability (CIN+) showed the worst survival.Patients with H.pylori infection showed intermediate prognosis compared with the other two subtypes.CONCLUSION Thus,using low-coverage whole-genome sequencing,GC can be classified into three categories based on disease etiology;this classification may prove useful for GC diagnosis and precision medicine.

Multi-layered control of PD-L1 expression in Epstein-Barr virus-associated gastric cancer

Gastric cancer(GC)is the fifth most common cancer worldwide.In approximately 10%of GC cases,cancer cells show ubiquitous and monoclonal Epstein-Barr virus(EBV)infection.A significant feature of EBV-associated GC(EBVaGC)is high lymphocytic infiltration and high expression of immune checkpoint proteins,including programmed death-ligand 1(PD-L1).This highlights EBVaGC as a strong candidate for immune checkpoint blockade therapy.Indeed,several recent studies have shown that EBV positivity in GC correlates with positive response to programmed cell death protein 1(PD-1)/PD-L1 blockade therapy.Understanding the mechanisms that control PD-L1 expression in EBVaGC can indicate new predictive biomarkers for immunotherapy,as well as therapeutic targets for combination therapy.Various mechanisms have been implicated in PD-L1 expression regulation,including structural variations,post-transcriptional control,oncogenic activation of intrinsic signaling pathways,and increased sensitivity to extrinsic signals.This review provides the most recent updates on the multilayered control of PD-L1 expression in EBVaGC.

Treatment of gastric carcinoma with lymphoid stroma by immunotherapy:A case report

BACKGROUND Gastric cancer with lymphoid stroma(GCLS)is a rare type of gastric cancer characterized by abundant lymphocytic infiltration of the stroma.It is an EpsteinBarr virus-associated gastric cancer with a better prognosis than typical gastric cancer but with similar symptoms.GCLS diagnosis is based on pathological,histological and immunohistochemical examination and there are no standardized guidelines for treatment.CASE SUMMARY This case report describes a 72-year-old man with a 6-mo history of abdominal pain.Endoscopy revealed ulcerative lesions in the stomach and gastric cancer was suspected.A preoperative endoscopic biopsy indicated undifferentiated carcinoma and postoperative pathological,histological and immunohistochemical analyses of the resected specimen confirmed a final diagnosis of GCLS.CONCLUSION The patient showed high programmed cell death-ligand 1 expression and recovered well after immunotherapy.