EBV‐encoded miRNAs target ATM‐mediated response in nasopharyngeal carcinoma

Abstract

Nasopharyngeal carcinoma (NPC) is a highly invasive epithelial malignancy that is prevalent in southern China and Southeast Asia. It is consistently associated with latent Epstein–Barr virus (EBV) infection. In NPC, miR‐BARTs, the EBV‐encoded miRNAs derived from BamH1‐A rightward transcripts, are abundantly expressed and contribute to cancer development by targeting various cellular and viral genes. In this study, we establish a comprehensive transcriptional profile of EBV‐encoded miRNAs in a panel of NPC patient‐derived xenografts and an EBV‐positive NPC cell line by small RNA sequencing. Among the 40 miR‐BARTs, predominant expression of 22 miRNAs was consistently detected in these tumors. Among the abundantly expressed EBV‐miRNAs, BART5‐5p, BART7‐3p, BART9‐3p, and BART14‐3p could negatively regulate the expression of a key DNA double‐strand break (DSB) repair gene, ataxia telangiectasia mutated (ATM), by binding to multiple sites on its 3'‐UTR. Notably, the expression of these four miR‐BARTs represented more than 10% of all EBV‐encoded miRNAs in tumor cells, while downregulation of ATM expression was commonly detected in all of our tested sequenced samples. In addition, downregulation of ATM was also observed in primary NPC tissues in both qRT‐PCR (16 NP and 45 NPC cases) and immunohistochemical staining (35 NP and 46 NPC cases) analysis. Modulation of ATM expression by BART5‐5p, BART7‐3p, BART9‐3p, and BART14‐3p was demonstrated in the transient transfection assays. These findings suggest that EBV uses miRNA machinery as a key mechanism to control the ATM signaling pathway in NPC cells. By suppressing these endogenous miR‐BARTs in EBV‐positive NPC cells, we further demonstrated the novel function of miR‐BARTs in inhibiting Zta‐induced lytic reactivation. These findings imply that the four viral miRNAs work co‐operatively to modulate ATM activity in response to DNA damage and to maintain viral latency, contributing to the tumorigenesis of NPC. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Hepatitis C Virus Mediated Inhibition of miR‐181c Activates ATM Signaling and Promotes Hepatocyte Growth

“…ATM was initially recognized in individuals with ataxia telangiectasia, a neurodegenerative autosomal recessive disorder exhibiting motor neuropathy, immunodeficiency, and cancer predisposition . Several exogenous and endogenous factors regulate the kinase activity of ATM, including microRNAs (miRNAs) …”

“…(12) Several exogenous and endogenous factors regulate the kinase activity of ATM, including microRNAs (miRNAs). (13,14) MicroRNAs are endogenous noncoding short RNA molecules that have been highly conserved during evolution. They generally bind to the 3′ untranslated region (UTR) of mRNAs and regulate many cellular processes, including metabolism, proliferation, differentiation, and apoptosis.…”

MiRNAs in Radiotherapy Resistance of Nasopharyngeal Carcinoma

“…In addition, in vitro animal experiments also indicate that EBV-miR-BART8-3p significantly increased the size of xenografts in nude mice and promotes radioresistance of NPC by regulating the activity of the ATM/ATR signaling pathway [63]. Studies have shown that the other four miRNAs encoded by EBV (BART5-5p, BART7-3p, BART9-3p and BART14-3p) directly target endogenous ATM, and the reduced ATM also helps maintain the virus incubation period [31,64]. MiR-24 expression was found to be decreased in nasopharyngeal carcinoma cells and patients with higher stage nasopharyngeal carcinoma, and this change was associated with the development of radiotherapy resistance [65,66].…”

“…The hallmark of DNA double-strand break (DSB) is phosphorylation of histone H2AX in chromatin to produce γ-H2AX [30]. In eukaryotes, DNA damage is repaired after irradiation through DNA damage response (DDR) [31]. The repair of DNA damage greatly affects the survival of tumor cells, producing the resistance of radiotherapy.…”

“…In addition, the replication and high expression of EBV virus is one of the important factors in the poor prognosis of nasopharyngeal carcinoma. The level of EBV DNA is closely related to local recurrence and distant metastasis after treatment in patients with nasopharyngeal carcinoma [31,59]. EBV infection can induce the expression of a variety of miRNAs including microRNA-21, and scholars have found that Epstein-Barr virus-encoded LMP1 (latent membrane protein 1) can increase miR-21, negatively regulate pro-apoptotic factor procedural cell death 4 (PDCD4) and Fas ligand (Fas-L) increase resistance to cisplatin treatment in nasopharyngeal carcinoma cells [60].…”