Differences in gastric carcinoma microenvironment stratify according to EBV infection intensity; implications for possible immune adjuvant therapy
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ABSTRACT: Our goal of this study was to perform quantitative and global assessment of EBV gene expression in gastric carcinomas and assess EBV associated cellular pathway alterations. Examination of a gastric carcinoma cell line naturally infected with EBV, SNU-719 using poly-A and ribodepletion RNA-seq data sets
Project description:Our goal of this study was to perform quantitative and global assessment of EBV gene expression in gastric carcinomas and assess EBV associated cellular pathway alterations.
Project description:We investigate the expression of miRNA in exosome of EBV-positive gastric carcinoma cells. The exosomes of EBV-positive and negative gastric carcinoma cells were separated by ultracentrifugation, the morphology of exosomes was identified by transmission electron microscopy, the exosome size was analyzed by Nanosight, and the expression of exosome membrane protein CD63 and CD81 was detected by western blot. High-throughput sequencing was used to detect miRNA expression profiles in gastric cancer cell lines and their exosomes. Under the ultra-microscopic electron microscope, the exosomes are seen as a typical translucent cup-like structure or a flat spherical structure. The nanoparticle tracking analyzer (Nanosight) showed that the exosomes were between 30 and 150 nm in diameter. Western blot(WB) assays showed that exosomes secreted by EBVaGC and EBVnGC cells expressed specific exosome membrane-associated proteins CD63 and CD81. High-throughput sequencing revealed that EBVaGC(SNU-719) and EBVnGC(AGS) and their secreted exosomes were highly expressed with certain human miRNAs, among which AGS-exo was highly expressed with hsa-miR-23b-3p, hsa-miR-320a-3p, and hsa-miR-4521. SNU-719-exo was highly expressed as hsa-miR-21-5p, hsa-miR-148a-3p and hsa-miR-7-5p. Nearly all EBV-related miRNAs (EBV-miRNA) were expressed in SNU-719 cells and their exosomes, among which EBV-miR-BART1-5p, EBV-miR-BART17-3p and EBV-miR-BART18-5p were the highest in SNU-719 cells, EBV-miR-BART1-5p, EBV-miR-BART18-5p and EBV-miR-BART17-3p were the highest in SNU-719-exo.
Project description:Aim: EBV encode at least 44 miRNAs involved in immune regulation and disease progression. Exosomes can be used as carriers of EBV-miRNA-BART intercellular transmission and affect the biological behavior of cells. We characterized exosomes and established a co-culture experiment of exosomes to explore the mechanism of miR-BART1-3p transmission through the exosome pathway and its influence on tumor cell proliferation and invasion. Materials and methods: Exosomes of EBV-positive and EBV-negative gastric cancer cells were characterized by transmission electron microscopy, Nanosight and western blotting, and miRNA expression profiles in exosomes were sequenced with high throughput. Exosomes with high or low expression of miR-BART1-3p were co-cultured with AGS cells to study the effects on proliferation, invasion and migration of gastric cancer cells. The target genes of EBV-miR-BART1-3p were screened and predicted by PITA, miRanda, RNAhybrid, virBase and Diana-Tarbase v.8 databases, and the expression of the target genes after co-culture was detected by qPCR. Results:The exosomes secreted by EBV positive and negative gastric cancer cells range in diameter from 30 nm to 150nm and express the exosomal signature proteins CD63 and CD81. High throughput sequencing showed that exosomes expressed some human miRNAs, among which has-miR-23b-3p, has-miR-320a-3p and has-miR-4521 were highly expressed in AGS-exo. has-miR-21-5p, has-miR-148a-3p and has-miR-7-5p were highly expressed in SNU-719-exo. All EBV miRNAs were expressed in SNU-719 cells and their exosomes, among which EBV- miR-Bart1-5p, EBV- miR-bart22 and EBV- miR-bart16 were the highest in SNU-719 cells. EBV-miR-BART1-5p, EBV-miR-BART10-3p and EBV-miR-BART16 were the highest in SNU-719-exo. After miR-BART1-3p silencing in gastric cancer cells, the proliferation, healing, migration and invasion of tumor cells were significantly improved. Laser confocal microscopy showed that exosomes could carry miRNA into recipient cells. After co-culture with miR-BART1-3p silenced exosomes, the proliferation, healing, migration and invasion of gastric cancer cells were significantly improved. The target gene of miR-BART1-3p was FMA168A, MACC1, CPEB3, ANKRD28 and USP37 after screening by targeted database. CPEB3 was not expressed in all exosome co-cultured cells, while ANKRD28, USP37, MACC1 and FAM168A were all expressed to varying degrees. USP37 and MACC1 are down-regulated after up-regulation of miR-BART1-3p, which may be the key target genes for miR-BART1-3p to regulate the proliferation of gastric cancer cells through exosomes. Conclusions: miR-BART1-3p can affect the growth of tumor cells through exosome pathway. The proliferation, healing, migration and invasion of gastric cancer cells were significantly improved after co-culture with exosomes of miR-BART1-3p silenced expression. USP37 and MACC1 may be potential target genes of miR-BART1-3p in regulating cell proliferation.
Project description:Epstein-Barr virus (EBV) is associated with roughly 10% of gastric carcinomas worldwide (EBVaGC). Although previous investigations provide a strong link between EBV and gastric carcinomas, these studies were performed using selected EBV gene probes. Using a cohort of gastric carcinoma RNA-seq data sets from The Cancer Genome Atlas (TCGA), we performed a quantitative and global assessment of EBV gene expression in gastric carcinomas and assessed EBV associated cellular pathway alterations. EBV transcripts were detected in 17% of samples but these samples varied significantly in EBV coverage depth. In four samples with the highest EBV coverage (hiEBVaGC - high EBV associated gastric carcinoma), transcripts from the BamHI A region comprised the majority of EBV reads. Expression of LMP2, and to a lesser extent, LMP1 were also observed as was evidence of abortive lytic replication. Analysis of cellular gene expression indicated significant immune cell infiltration and a predominant IFNG response in samples expressing high levels of EBV transcripts relative to samples expressing low or no EBV transcripts. Despite the apparent immune cell infiltration, high levels of the cytotoxic T-cell (CTL) and natural killer (NK) cell inhibitor, IDO1, was observed in the hiEBVaGCs samples suggesting an active tolerance inducing pathway in this subgroup. These results were confirmed in a separate cohort of 21 Vietnamese gastric carcinoma samples using qRT-PCR and on tissue samples using in situ hybridization and immunohistochemistry. Lastly, a panel of tumor suppressors and candidate oncogenes were expressed at lower levels in hiEBVaGC versus EBV-low and EBV-negative gastric cancers suggesting the direct regulation of tumor pathways by EBV.
Project description:[Aim] EBVaGC accounts for about 10% of gastric cancer and has a better prognosis than EBVnGC, but its molecular mechanism is still unclear. We investigated the role of EBV-miR-BART1-3p in the occurrence and development of EBVaGC by applying bioinformatics methods, high-throughput sequencing, in vitro experiments, target gene screening and verification, differential gene protein interaction network and gene regulatory network construction. [Materials and Methods] The data set GSE51575 was normalized, and the outlier samples were deleted. Finally, gene expression profiles of 11 EBVaGC and 14 EBVnGC tumor tissues and non-tumor control tissues were obtained. Differential gene function analysis was performed, and molecular regulatory network was constructed. The mRNA expression levels of SNU-719 (EBV-positive gastric cancer cell line), AGS, AGS-NC (EBV-negative gastric cancer cell line) and AGS-OE (lentivirus-transfected miR-BART1-3p overexpression cell line) were detected by high-throughput next-generation sequencing technology, and differential gene expression characteristics were analyzed. To investigate the effect of miR-BART1-3p overexpression on mRNA expression level of gastric cancer cells and construct the protein interaction network of differential genes and the regulatory network of miR-BART1-3p gene. DIANA-MR micro-T, miRnada, miRDB, TarBase v.8, and ViRBase online databases were used to predict the target genes of miR-BART1-3p and GO enrichment analysis of target gene function was performed. Real-time fluorescence quantitative PCR was used to detect the expression levels of miR-BART1-3p and target genes in SNU719, AGS-OE and AGS gastric cancer cells. The effects of overexpression of EBV-miR-BART1-3p on proliferation, apoptosis, invasion, and migration of gastric cancer cells were investigated by CCK-8, cell cloning, cell scratch and Transwell. [Results] By analyzing the gene expression profile of the GSE51575 dataset, we found that EBVaGC up-regulated the expression of immune cell membrane protein receptors and chemokine family, and was involved in inducing tumor immunity, suggesting a better prognosis. EBVnGC significantly up-regulated the expression of AURK, BUB1B, CCNA2 and CDC20, suggesting the risk of malignant progression and recurrence. High-throughput next-generation sequencing of SNU719 and AGS to detect differences in gene expression revealed that EBVaGC cells (SNU719) up-regulated the expression of genes that inhibit malignant progression as well as potential tumor immunotherapy targets. These results are consistent with those found in the GSE51575 dataset. Fifteen miR-BART1-3p target genes, including FAM168A, TET3, HBP1, ZBTB5, ATXN7L3, KMT5C, SPARC and BMF, were predicted and screened by online tools. After the overexpression of miR-BART1-3p in AGC(EBVnGC) cells, the proliferation, migration, and invasion ability were significantly inhibited, and the signaling pathway promoting tumor progression was also limited in activation. [Conclusions] The overexpression of miR-BART1-3p may inhibit the proliferation and invasion and migration of gastric cancer cells by inhibiting the activation of STAT3/ pSTAT3 and PI3K/AKT signaling pathways and may become a target for the treatment of EBVaGC, which is worthy of further study.
Project description:Gastric cancer is one of the most common cancers worldwide. Epstein-Barr virus-associated gastric cancer accounts for approximately 10% of all gastric cancers. EBV expresses its own proteins and miRNAs (BART miRNAs) and regulates host gene expression. In this study, we examined the effect of EBV infection on host mRNA expression. Differential gene expression was analyzed between EBV-negative human gastric cancer cell line AGS and EBV-positive human gastric cancer cell line AGS-EBV.
Project description:Time-series comprehensive DNA methylation analysis after EBV infection in the immortalised normal gastric epithelial cell line, GES1, and low methylation gastric cancer cell line, MKN7. Infinium HumanMethylation450 BeadChip was used to obtain DNA methylation profiles across 485,577 CpG sites. Samples included 9 GES1 with and without EBV infection, 5 MKN7 with and without EBV infection, EBV+ gastric cancer cell and xenograft, SNU719 and KT, 2 normal gastric mucosae, 2 low-methylation gastric cancer cases, and 2 high-methylation gastric cancer cases.
Project description:Aberrant promoter methylation is known to be deeply involved in human gastric carcinogenesis, while association of Epstein-Barr virus (EBV) to the aberrant methylation has not been fully clarified. We analyzed promoter methylation in clinical gastric cancer cases using illumina's Infinium beadarray, and hierarchical clustering analysis classified gastric cancer into three subgroups: low and high methylation epigenotypes in EBV-negative cases, and markedly higher methylation epigenotype that was completely matched to EBV-positive cases. Three epigenotypes were characterized by three groups of genes: genes methylated specifically in the EBV-positive epigenotype (EBV(+)-markers, e.g. CXXC4, TIMP2, PLXND1), genes methylated both in EBV-positive and high epigenotypes (High-markers, e.g. COL9A2, EYA1, ZNF365), and genes methylated all in EBV-positive, high and low epigenotypes of gastric cancer (Common-markers, e.g. AMPH, SORCS3, AJAP1). Polycomb repressive complex (PRC)-target genes in ES cells were significantly enriched in High- and Common-markers (P=2x10-15 and 2x10-34, respectively), but not in EBV(+)-markers (P=0.2), suggesting a different cause for EBV(+)-marker methylation. Recombinant EBV was infected to low epigenotype gastric cancer cell, MKN7. In all the three independently established clones, DNA methylation was induced in High- and EBV(+)-markers after 18 weeks, demonstrating that EBV-positive epigenotype should involve methylation of Common-, High-, and EBV(+)-markers simultaneously. The de novo methylated genes were overlapped well among the three clones, and the methylation caused gene repression. In summary, gastric cancer was classified into three DNA methylation epigenotypes, EBV-positive gastric cancer showed markedly high methylation epigenotype expanding to non-PRC target genes, and EBV infection per se could induce the EBV-positive epigenotype.
Project description:Aberrant promoter methylation is known to be deeply involved in human gastric carcinogenesis, while association of Epstein-Barr virus (EBV) to the aberrant methylation has not been fully clarified. We analyzed promoter methylation in clinical gastric cancer cases using illumina's Infinium beadarray, and hierarchical clustering analysis classified gastric cancer into three subgroups: low and high methylation epigenotypes in EBV-negative cases, and markedly higher methylation epigenotype that was completely matched to EBV-positive cases. Three epigenotypes were characterized by three groups of genes: genes methylated specifically in the EBV-positive epigenotype (EBV(+)-markers, e.g. CXXC4, TIMP2, PLXND1), genes methylated both in EBV-positive and high epigenotypes (High-markers, e.g. COL9A2, EYA1, ZNF365), and genes methylated all in EBV-positive, high and low epigenotypes of gastric cancer (Common-markers, e.g. AMPH, SORCS3, AJAP1). Polycomb repressive complex (PRC)-target genes in ES cells were significantly enriched in High- and Common-markers (P=2x10-15 and 2x10-34, respectively), but not in EBV(+)-markers (P=0.2), suggesting a different cause for EBV(+)-marker methylation. Recombinant EBV was infected to low epigenotype gastric cancer cell, MKN7. In all the three independently established clones, DNA methylation was induced in High- and EBV(+)-markers after 18 weeks, demonstrating that EBV-positive epigenotype should involve methylation of Common-, High-, and EBV(+)-markers simultaneously. The de novo methylated genes were overlapped well among the three clones, and the methylation caused gene repression. In summary, gastric cancer was classified into three DNA methylation epigenotypes, EBV-positive gastric cancer showed markedly high methylation epigenotype expanding to non-PRC target genes, and EBV infection per se could induce the EBV-positive epigenotype.
Project description:Background and aims: The aim of this study was to analyze the molecular characteristics of adenocarcinoma of the gastroesophageal junction (AGEJ) compared to esophageal (EAC) and gastric adenocarcinomas (GCFB) from The Cancer Genome Atlas (TCGA) and Seoul National University (SNU) cohorts using next-generation sequencing. Methods: Based on mRNA expression of EAC (n=78) and GCFB (n=102) from the TCGA cohort, a molecular classification model using the Bayesian compound covariate predictor classified AGEJ/cardia (n=48) from the TCGA cohort and AGEJ/upper third gastric adenocarcinoma (n=46) from the SNU cohort into the EAC-like or GCFB-like groups. The molecular characteristics between the EAC-like and GCFB-like groups were compared.