Comparative Transcriptome Provides a Systematic Perspective on Epstein-Barr Virus-Associated Gastric Carcinoma Cell Lines.

PURPOSE: Epstein-Barr virus (EBV) is widely recognised to cause various tumours, and EBV-associated gastric carcinoma (EBVaGC) is a special type of GC. It has obviously different clinical features and pathological manifestations from EBV-negative gastric carcinoma, but its progression remains elusive. The underlying cancer progression of viral infection detected by genome-wide transcriptome analysis has been demonstrated in numerous diseases. METHODS: We performed comparative RNA sequencing to identify gene expression signatures between GC and EBVaGC cell lines. The differentially expressed (DE) genes were analysed using gene ontology and pathway enrichment. RESULTS: A total of 4438 DE mRNAs, 3650 DE long non-coding RNAs (lncRNAs), and 248 DE circular RNAs (circRNAs) were detected in GC cells after EBV infection, most of which were highly related to oncogenesis. Likewise, EBV-coding RNA and non-coding RNA were also well-supplemented in EBVaGC. According to bioinformatics, DE mRNAs may contribute to the completion of EBV-infected host cells and modulate mitosis. Binding to actin and participating in adherens junctions to promote contact between the virus and cells are a potential function of DE lncRNAs. The roles of DE circRNAs were enriched in DNA repair and protein modification, and a typical example of this is acting as an miRNA sponge. The establishment of a circRNA-miRNA-mRNA network helps to determine the key elements in the progression of EBVaGC. CONCLUSION: This study is the first to systematically reveal the transcriptome landscape of EBVaGC, which will provide an essential resource for genomic, genetic, and molecular mechanisms in the future.

Epstein-Barr virus-derived circular RNA LMP2A induces stemness in EBV-associated gastric cancer.

Cancer stem cells (CSCs) are cancer-initiating cells that are not only a source of tumorigenesis but also the cause of tumour progression, metastasis and therapy resistance. EBV-associated gastric cancer (EBVaGC) is a distinct subtype of gastric cancer with unique clinicopathological and molecular features. However, whether CSCs exist in EBVaGC, and the tumorigenic mechanism of EBV, remains unclear. Here, NOD/SCID mice were injected subcutaneously with the EBVaGC cell line SNU719 and treated with 5-fluorouracil weekly. Successive generations of xenografts yielded a highly malignant EBVaGC cell line, SNU-4th, which displays properties of CSCs and mainly consists of CD44+ CD24- cells. In SNU-4th cells, an EBV-encoded circRNA, ebv-circLMP2A, expression increased and plays crucial roles in inducing and maintaining stemness phenotypes through targeting miR-3908/TRIM59/p53 axis. Additionally, high expression of ebv-circLMP2A is significantly associated with metastasis and poor prognosis in patients with EBVaGC. These findings not only provide evidence for the existence of CSCs in EBVaGC and elucidate the pathogenic mechanism of ebv-circLMP2A in EBVaGC, but also provide a promising therapeutic target for EBVaGC.

Improving pathological early diagnosis and differential biomarker value for hepatocellular carcinoma via RNAscope technology.

BACKGROUND: The diagnostic and prognostic values of glypican3 (GPC3) and glutamine synthetase (GS) proteins in hepatocellular carcinoma (HCC) have been reported, but their specificity and sensitivity remain low. Here, we applied RNAscope to improve HCC early pathological and differential diagnosis by estimating GPC3 and GS mRNAs. METHODS: We performed RNAscope and immunohistochemistry (IHC) to detect GPC3 and GS biomarkers on the tissue sections of 194 cases, including high- and low-grade liver dysplastic nodules; highly, moderately, and poorly differentiated HCCs; intrahepatic cholangiocarcinomas (ICCs); metastatic HCC; and carcinomas from other organs. RESULTS: The results showed that all the cases that were negative for GPC3 by RNAscope were also negative for this protein by IHC. The use of RNAscope assay improved the GPC3 and GS specificity and sensitivity by 20-30%. Hence, HCC shows early recognition and upgrades the metastatic HCC differentiation by 23% compared with IHC (p = 0.0001, 0.0064). Meanwhile, all liver cirrhosis, cholangiocytes and non-HCC samples were negative for GPC3 and GS except lymphocytes in lymphomas, and 2 (8.3%) out of the 24 ICC samples but not in the cancer cells. CONCLUSION: RNAscope for GPC3 and GS panel was highly specific and sensitive for the pathological identification of dysplastic nodules, early stages of HCCs, and would differentiate them from HCCs and metastatic tumors compared with IHC.

Identification of virus-encoded circular RNA.

Circular RNAs (circRNAs) are a novel class of non-coding RNA molecules in eukaryotic organisms that have potentially important roles in gene regulation. Nevertheless, whether viruses can encode circRNA is still uncertain. To examine whether large genome DNA viruses can generate circRNA during the infection of human cells, we performed RNA sequencing of ribosomal RNA-depleted total RNA from Epstein-Barr virus (EBV)-infected cell lines, including SNU-719, AGS-EBV, C666-1 and Akata. We identified an EBV-encoded circRNA, ebv_circ_RPMS1, that consists of the head-to-tail splicing of exons 2-4 from the RPMS1 gene. Furthermore, we demonstrated that ebv_circ_RPMS1 was localized in both cytoplasm and nuclei. Given that circRNAs shape gene expression by titrating microRNAs, regulating transcription and/or interfering with splicing, we identified a novel viral regulator of host and/or viral gene expression.