Infection with the Epstein-Barr virus (EBV) is a strong predisposing factor in the development of nasopharyngeal carcinoma (NPC). Many viral gene products including EBNA1, LMP1, and LMP2 have been implicated in NPC tumorigenesis, although the de novo control of these viral oncoproteins remains largely unclear. The recent discovery of EBV-encoded viral microRNA (miRNA) in lymphoid malignancies has prompted us to examine the NPC-associated EBV miRNA. Using large-scale cloning analysis on EBV-positive NPC cells, two novel EBV miRNA, now named miR-BART21 and miR-BART22, were identified. These two EBV-encoded miRNA are abundantly expressed in most NPC samples. We found two nucleotide variations in the primary transcript of miR-BART22, which we experimentally confirmed to augment its biogenesis in vitro and thus may underline the high and consistent expression of miR-BART22 in NPC tumors. More importantly, we determined that the EBV latent membrane protein 2A (LMP2A) is the putative target of miR-BART22. LMP2A is a potent immunogenic viral antigen that is recognized by the cytotoxic T cells; down-modulation of LMP2A expression by miR-BART22 may permit escape of EBV-infected cells from host immune surveillance. Taken together, we demonstrated that two newly identified EBV-encoded miRNA are highly expressed in NPC. Specific sequence variations on the prevalent EBV strain in our locality might contribute to the higher miR-BART22 expression level in our NPC samples. Our findings emphasize the role of miR-BART22 in modulating LMP2A expression, which may facilitate NPC carcinogenesis by evading the host immune response.

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.

Pulmonary lymphoepithelioma-like carcinoma (LELC) is a subtype of non-small cell lung cancer (NSCLC) characterized by marked lymphocytic infiltration and association with Epstein–Barr virus (EBV). The molecular basis underlying the disease remains unclear. We sought to study the molecular landscape by multiple approaches including whole genomic sequencing, capture-based targeted sequencing, fluorescent in situ hybridization and immunohistochemistry. Tumor cells from 57 EBV-positive pulmonary LELCs were isolated by careful microdissection prior to genomic sequencing. Integrated analysis revealed a distinct genomic landscape of low TP53 mutation rate (11%), low incidence of known drivers in the RTK/RAS/RAF (11%) and PI3K/AKT/mTOR pathways (7%), but enriched for loss-of-function mutations in multiple negative regulators of the NF-κB pathway. High level programmed cell death ligand-1 (PD-L1) expression was shown with 47% and 79% of the cases showing positive PD-L1 immunoreactivity at ≥50% and ≥1% tumor proportion score, respectively. Subsets of the patients with actionable fibroblast growth factor receptor 3 (FGFR3) aberrations (4%) and mismatch repair deficiency (4%) were potentially eligible for precision medicine. Pulmonary LELC showed a distinct genomic landscape, different from major NSCLC subtypes but resembled that of EBV-associated nasopharyngeal carcinoma. Our work facilitated the understanding of molecular basis underlying pulmonary LELC to explore potential therapeutic options.

A common GC polymorphism within miRNA-146a precursor region (rs2910164) has been associated with the risk of various cancers despite the underlying mechanism is unclear. In the current study, we aimed to examine the role of rs2910164 in the pathogenesis and predisposition to nasopharyngeal carcinoma (NPC). The GC polymorphism in 233 NPC patients, 173 matched controls and 3613 healthy elderly subjects in our locality were first determined using melting temperature (T(m))-shift allele-specific genotyping method. Results in our case-control study indicated that CC genotype was associated with the risk effect of NPC (adjusted odds ratio of GC + GG vs. CC, 0.49; 95% confidence interval, 0.35-0.69; P < 0.0001). Using real-time polymerase chain reaction (PCR) assay, we subsequently revealed that expressions of both miR-146a and its passenger strand (miR-146a*C or miR-146a*G) were increased in NPC samples (P < 0.001), albeit expression of miR-146a was not linked to the genotype. Furthermore, miR-146a*C in NPC was significantly increased in CC genotype (CC vs. GC, P = 0.038). Finally, we demonstrated by co-immunoprecipitation and luciferase reporter assays that all three miR-146a precursor-derived mature miRNAs interacted with Argonaute2 (Ago2) protein complex and could function as gene silencers. Taken together, our results showed that the variant C in rs2910164 was associated with the predisposition of NPC in Chinese population. This polymorphism may influence the risk of NPC by producing active mature miR-146a*C that regulate distinct set of target genes. These findings may enrich our understanding of how miRNA single nucleotide polymorphism affect NPC pathogenesis, and may have potential implications to improve NPC treatment in the future.

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