Latent membrane protein 2A inhibits expression level of Smad2 through regulating miR‐155‐5p in EBV‐associated gastric cancer cell lines

Abstract

Epstein-Barr virus (EBV) infection is one of the causes of gastric cancer (GC). Besides,previous studies have demonstrated that EBV-encoded latent membrane protein 2A (LMP2A) influences the pathogenesis of EBV-associated gastric cancer (EBVaGC) through regulating several key pathways. In this study, the expression level of Smad2 was observed, which was reduced in EBVaGC cell lines, especially in the presence of LMP2A. Meanwhile, we found that LMP2A promoted the expression of miR-155-5p by activated nuclear factor-κB (NF-κB) signaling. After being treated with NF-κB inhibitor (BAY 11-7082), miR-155-5p sharply decreased. Western blot analysis proved that the overexpression of miR-155-5p could inhibit Smad2. Functional studies showed that the role of miR-155-5p might lead to good prognosis in EBVpositive GC through promoting cell apoptosis and cell cycle arrest, as well as inhibiting tumor proliferation. In addition, p-Smad2 protein was also reduced or induced by overexpression or knockdown, respectively, of miR-155-5p. Immunofluorescence analysis further indicated that LMP2A prevented p-Smad2 from transferring to the nucleus, which played a crucial role in transforming growth factor-β (TGF-β) signaling. In summary, our findings confirmed the relationship between LMP2A and Smad2 and provided a potential regulation of the TGF-β pathway in EBVaGC. K E Y W O R D S LMP2A, miR-155-5p, NF-κB, Smad2, TGF-β signaling pathway 1 | INTRODUCTION Gastric cancer (GC), originating from the gastric mucosa, is a malignant tumor. 1 Evidence shows that GC is caused by multiple factors such as sanitation, food preservation, Helicobacter pylori infection, and Epstein-Barr virus (EBV) infection. 2 EBV was first discovered as an oncogenic virus in humans over 50 years ago. 3 EBV, which adopts both latent and lytic forms of infection, has a high prevalence all over the world, and it is thought that roughly 95% of the world's population presents an asymptomatic life-long infection. 4 EBV is best known as the cause of infectious mononucleosis, a variety of lymphomas, nasopharyngeal carcinoma (NPC), and GC. 4,5 EBV-associated gastric cancer (EBVaGC), detected in approximately 10% of GC cases worldwide, is the monoclonal growth of EBV-infected epithelial cells. 6 EBVaGC belongs to latency type I or II, in which only EBV-encoded RNA, EBV nuclear antigen 1, EBVencoded latent membrane protein 2A (LMP2A) and BART micro-RNAs (miRNAs) are expressed. 7 Plenty of studies have demonstrated that LMP2A might influence genomic features of host DNA, messenger RNA (mRNA), miRNA, and CpG methylation profiles

EBV-Positive Gastric Cancer: Current Knowledge and Future Perspectives

“…It can activate the NF-kB-Survivin pathway (51,52), regulate the expression of cyclin-E and proportion of cells in the S phase (53), mediate Notch signaling, and promote mitochondrial division and cell migration (54). Additionally, it can upregulate miR-155-5p through the NF-kB pathway and inhibit the activation of Smad2 and p-Smad2 (55,56). LMP2A can also initiate gastric cancer by upregulating or downregulating other genes.…”

Epstein-Barr Virus-Encoded Latent Membrane Protein 2A Downregulates GCNT3 via the TGF-β1/Smad-mTORC1 Signaling Axis

“…Cross talk of the TGF-b/Smad and mTORC1 signaling pathways has been reported (37). Our previous experiments demonstrated that LMP2A inhibited Smad2 expression via the NF-κB/miR-155a axis (38). As shown in Fig.…”

Diagnostic value of VDBP and miR‑155‑5p in diabetic nephropathy and the correlation with urinary microalbumin

“…In addition, previous studies found that abundant miRNA expression could be seen in kidney tissues of DN patients, and reported that its expression could reflect the condition of patients to a certain extent, and that miRNA and DN were closely related (8). miR-155-5p is a miRNA that plays an important regulatory role in the development and progression of tumors, and its diagnostic and prognostic value in tumors has also been confirmed (9). Previous study also discovered that miR-155-5p was highly expressed in DN, and it was considered that its expression was tied to the severity of DN patients (10).…”