SNHG8 Promotes the Progression of Epstein-Barr Virus-Associated Gastric Cancer via Sponging miR-512-5p and Targeting TRIM28.

Changyan Zou,Changyan Zou,Jinrong Liao,Tao Huang,Tao Huang,Xiongwei Zheng,Xiandong Lin,Xiandong Lin,Keyu Lin,Huamei Lin,Huamei Lin,Dan Hu,Dan Hu,Xingguan Luo,Lurong Zhang,Lurong Zhang,Ying Su,Ying Su

doi:10.3389/fonc.2021.734694

Abstract

SNHG8, a family member of small nucleolar RNA host genes (SNHG), has been reported to act as an oncogene in gastric carcinoma (GC). However, its biological function in Epstein–Barr virus (EBV)-associated gastric cancer (EBVaGC) remains unclear. This study investigated the role of SNHG8 in EBVaGC. Sixty-one cases of EBVaGC, 20 cases of non-EBV-infected gastric cancer (EBVnGC), and relative cell lines were studied for the expression of SNHG8 and BHRF1 (BCL2 homolog reading frame 1) encoded by EBV with Western blot and qRT-PCR assays. The relationship between the expression levels of SNHG8 and the clinical outcome in 61 EBVaGC cases was analyzed. Effects of overexpression or knockdown of BHRF1, SNHG8, or TRIM28 on cell proliferation, migration, invasion, and cell cycle and the related molecules were determined by several assays, including cell proliferation, colony assay, wound healing assay, transwell invasion assay, cell circle with flow cytometry, qRT-PCR, and Western blot for expression levels. The interactions among SNHG8, miR-512-5p, and TRIM28 were determined with Luciferase reporter assay, RNA immunoprecipitation (RIP), pull-down assays, and Western blot assay. The in vivo activity of SNHG8 was assessed with SNHG8 knockdown tumor xenografts in zebrafish. Results demonstrated that the following. (1) BHRF1 and SNHG8 were overexpressed in EBV-encoded RNA 1-positive EBVaGC tissues and cell lines. BHRF1 upregulated the expressions of SNHG8 and TRIM28 in AGS. (2) SNHG8 overexpression had a significant correlation with tumor size and vascular tumor thrombus. Patients with high SNHG8 expression had poorer overall survival (OS) compared to those with low SNHG8 expression. (3) SNHG8 overexpression promoted EBVaGC cell proliferation, migration, and invasion in vitro and in vivo, cell cycle arrested at the G2/M phase via the activation of BCL-2, CCND1, PCNA, PARP1, CDH1, CDH2 VIM, and Snail. (4) Results of dual-luciferase reporter assay, RNA immunoprecipitation, and pull-down assays indicated that SNHG8 sponged miR-512-5p, which targeted on TRIM28 and promoted cancer malignant behaviors of EBVaGC cells. Our data suggest that BHRF1 triggered the expression of SNHG8, which sponged miR-512-5p and upregulated TRIM28 and a set of effectors (such as BCL-2, CCND1, CDH1, CDH2 Snail, and VIM) to promote EBVaGC tumorigenesis and invasion. SNHG8 could be an independent prognostic factor for EBVaGC and sever as target for EBVaGC therapy.

Highlights

Epstein–Barr virus (EBV), belonging to the herpes virus family [1, 2], is a causative virus for many malignancies including nasopharyngeal carcinoma (NPC) and Burkitt lymphoma [3,4,5]
We have reported that small nucleolar RNA host gene 8 (SNHG8) was a key regulator of EBVpositive GC (EBVaGC) by an integrative analysis of lncRNA and mRNA expression [21]
Western blot assays (WB) show that the expression levels of BFRF1 and tripartite motif-containing 28 (TRIM28) were much higher in AGS/EBV-encoded small ribonucleic acid 1 (BHRF1) cells than those in AGS/NC cells (Figure 1E). qRT-polymerase chain reaction (PCR) assays revealed that the expression of BHRF1, SNHG8, and TRIM28 was much higher in the AGS/BHRF1 group than in the AGS/NC group (Figure 1F)

Summary

Introduction

Epstein–Barr virus (EBV), belonging to the herpes virus family [1, 2], is a causative virus for many malignancies including nasopharyngeal carcinoma (NPC) and Burkitt lymphoma [3,4,5]. Dysregulations of lncRNAs are associated with a variety of cancer malignant behaviors, such as cell migration, invasion, metastasis, gene transcription, and tumorigenesis [13, 14]. SNHG8, located on 4q26 and encoding small nucleolar RNAs (snoRNAs), was detected in multiple malignant tumors, including non-small-cell lung cancer, hepatocellular carcinoma [10, 15], and pancreatic adenocarcinoma [11, 16]. LncRNAs, as oncogenes or tumor suppressors, are directly involved in tumorigenesis, cell cycle arrest, apoptosis, epithelial to mesenchymal transition (EMT), cell migration, invasion metastasis, and chemoresistance via activating the JAK2/STAT3 pathway or Wnt/b-catenin signaling [17,18,19,20].

Methods

Results

Conclusion