RESUMEN
Epstein-Barr virus (EBV) was the first oncovirus found to encode microRNAs. In EBV-associated gastric cancer (EBVaGC), EBV-encoded BamHI-A rightward transcript microRNAs (BARTs) are highly expressed. However, the role of BARTs in EBVaGC remains obscure. In this study, we found that EBV-miR-BART12 (miR-BART12) inhibits cell proliferation and migration. Zinc finger protein SNAI1 (Snail) is an important epithelial-mesenchymal transition (EMT) inducer, and overexpression of Snail is closely associated with cancer metastasis. Here, we report that Snail expression in EBVaGC cells is lower than in EBV-negative gastric cancer (EBVnGC) cells. A dual luciferase reporter assay showed that miR-BART12 targets Snail directly by interacting with its 3'-UTR. A CHX chase assay revealed that miR-BART12 accelerates the degradation of Snail. Furthermore, we found that miR-BART12 can regulate the expression of EMT-related genes. Flow cytometry analysis showed that transfection with miR-BART12 induced G2/M phase arrest and promoted cell apoptosis. In summary, the results of our study have suggested a new mechanism by which BARTs can repress cell proliferation and migration in gastric cancer.
Asunto(s)
Infecciones por Virus de Epstein-Barr/patología , Herpesvirus Humano 4/fisiología , MicroARNs/metabolismo , ARN Viral/metabolismo , Factores de Transcripción de la Familia Snail/metabolismo , Neoplasias Gástricas/patología , Apoptosis , Ciclo Celular , Línea Celular Tumoral , Movimiento Celular , Proliferación Celular , Transición Epitelial-Mesenquimal/genética , Infecciones por Virus de Epstein-Barr/genética , Infecciones por Virus de Epstein-Barr/metabolismo , Infecciones por Virus de Epstein-Barr/virología , Regulación Neoplásica de la Expresión Génica , Humanos , MicroARNs/genética , FN-kappa B/genética , FN-kappa B/metabolismo , ARN Viral/genética , Transducción de Señal , Factores de Transcripción de la Familia Snail/genética , Neoplasias Gástricas/genética , Neoplasias Gástricas/metabolismo , Neoplasias Gástricas/virologíaRESUMEN
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 EBV-positive 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-ß (TGF-ß) signaling. In summary, our findings confirmed the relationship between LMP2A and Smad2 and provided a potential regulation of the TGF-ß pathway in EBVaGC.