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Aim: To investigate the role of AHR in nasopharyngeal carcinoma (NPC) and explore the relationship between Epstein–Barr virus (EBV) infection and the AHR pathway. Methods: The effect of LMP1 on the expression of AHR was analyzed using real-time PCR and western blot. Proliferation and migration of cells were assessed using CCK8 and Transwell analysis. Results: EBV infection downregulated the expression of AHR in NPC cells, possibly through activation of the ERK pathway by LMP1 thereby accelerating AHR proteasomal degradation following translocation to the nucleus. Cell proliferation, migration and autophagy are promoted by activating the AHR pathway. Conclusion: In NPC cells, LMP1 increases the phosphorylation of ERK, which may activate the AHR pathway. This article describes the role of a virus, the Epstein–Barr virus (EBV), in the development of a type of cancer that affects the throat called nasopharyngeal carcinoma (NPC). One of the proteins made by the virus, called latent membrane protein 1 (LMP1), is thought to play a role in the development of NPC. We investigate how LMP1 may cause NPC. We found that LMP1 was linked to higher levels of two genes, CYP1A1 and CYP1B1, which are targets of a receptor called the aryl hydrocarbon receptor (AHR). This may be linked to the movement of AHR to the cell's control center, where it can play a role in the development of cancer. This article suggests a pathway for how EBV may cause NPC. [ABSTRACT FROM AUTHOR]

EBV-associated gastric carcinoma (EBVaGC) is a specific subgroup of gastric carcinoma, and the multifunctional transcriptional factor NF-κB may contribute to its tumorigenesis. In this study, we comprehensively characterized NF-κB signaling in EBVaGC using qRT-PCR, western blot, immunofluorescence assays, ELISA, and immunohistochemistry staining. NF-κB-signaling inhibitors may inhibit the growth of EBVaGC cells and induce significant apoptosis. IκBα is a key regulatory molecule, and repression of IκBα can contribute to aberrant NF-κB activation. Overexpression of LMP1 and LMP2A in the EBV-negative GC cell line SGC7901 could inhibit the expression of IκBα and induce NF-κB activation. These findings indicate that the canonical NF-κB signal is constitutively activated and plays an important role in EBVaGC tumorigenesis. [ABSTRACT FROM AUTHOR]

Highlights • The relative expression of miR-BART16 is higher in EBVaGC tissues than cell lines. • Overexpression of miR-BART16 could reduce the LMP1 mRNA and protein levels. • Inhibition the endogenous miR-BART16 increases the LMP1 mRNA and protein level. • BART16 has a vital role on cell proliferation in EBV-associated gastric carcinoma. Abstract Epstein–Barr virus (EBV) is a ubiquitous oncogenic herpesvirus associated with various human tumors. Latent membrane protein (LMP) 1 is considered a key oncoprotein in some EBV-associated tumors, while it is absent in EBV-associated gastric carcinoma (EBVaGC). In the present study, we did not detect the mRNA or the protein expression of LMP1 in 10 EBVaGC tissue samples, but we found that miRNA-BART16 was more abundantly expressed in EBVaGC primary tissues than in cell lines. It has been reported that EBV-encoded miRNA-BART16 can target the 3′-untranslated regions of LMP1 and negatively regulate its expression. When a BART16 inhibitor or mimics were transfected into EBVaGC cell lines, both mRNA and protein levels were changed compared with those in controls. We further investigated the role of miRNA-BART16 in EBVaGC. According to the CCK8 assay, the proliferation of GT38 and GT39 cells increased after treatment with a miRNA-BART16 inhibitor. At the same time, the BART16 inhibitor caused increased accumulation of G2/M phase cells by bromodeoxyuridine and propidium iodide staining analysis. In addition, no obvious difference was observed in apoptosis after treatment with an inhibitor or mimics using annexin V staining. Our findings highlight the viral role of EBV-encoded miRNA-BART16 in regulating oncogenic LMP1 expression and a negative association with the proliferation of EBVaGC. [ABSTRACT FROM AUTHOR]

• LMP1 and LMP2A inhibit the expression of COX-2 in EBVaGC. • TRAF2 is involved in the inhibitory effect of LMP1/2A on COX-2. • LMP1 also down-regulates COX-2 by reducing phosphorylation of ERK. Epstein-Barr virus-associated gastric cancer (EBVaGC) accounts for nearly 10% of gastric cancer. Cyclooxygenase-2 (COX-2) plays a crucial role in cancer progression. However, there is no experimental study on the regulation mechanism of EBV on COX-2 in EBVaGC. To understand more about the tumorigenic mechanism of EBVaGC, the study investigated the role of EBV encode latent membrane protein LMP1 and LMP2A in the regulation of COX-2. The expression of COX-2 was examined in EBVaGC and EBV negative gastric cancer (EBVnGC) cell lines. The plasmids were transfected in SGC7901 to overexpress LMP1/2A. Small interfering RNA (si-RNA) targeting LMP1/2A in GT38 and targeting TRAF2 in SGC7901 were used to detect the expression of COX-2. Furthermore, si-ERK1/2 and the MEK inhibitor PD0325901 were used to investigate whether p-ERK participate in the regulation of COX-2 in SGC7901. The overexpression of LMP1 or LMP2A in SGC7901 down-regulates both COX-2 and TRAF2 expression, and knockdown of LMP1 or LMP2A in GT38 resulted in a certain recovery of COX-2 and TRAF2 expression. Moreover, si-TRAF2 indicated that a sharp down-regulation of COX-2. And the decrease of p-ERK also mediates the inhibitory effect of LMP1 on COX-2. In summary, overexpression of LMP1 and LMP2A inhibits COX-2, which is mediated by a decrease of TRAF2, and p-ERK is involved in the inhibition of COX-2 by LMP1 in gastric cancer. [ABSTRACT FROM AUTHOR]

• The miR-146a expression is higher in EBV-positive than EBV-negative cells, but the CXCR4 expression has an opposite pattern. • The miR-146a inhibits the expression of CXCR4 in a dose- and time-dependent manner. • The miR-146a could suppress cell proliferation, cell migration and promote cell apoptosis by targeting CXCR4. • LMP1 could up-regulate the miR-146a expression and down-regulate the CXCR4 expression in EBV-associated cells. Epstein–Barr virus (EBV), the first human tumor virus to have been discovered, sustains an asymptomatic lifelong infection in ∼95% of the world's population. Reportedly, EBV infection induces the expression of specific cellular microRNAs (miRNAs), such as miR-155, miR-146a, miR-21, which can contribute to the persistence of latently infected cells. In this study, we investigated whether C-X-C chemokine receptor type 4 (CXCR4) is a cellular target of human miR-146a. We also investigated the role of miR-146a and CXCR4 in EBV-associated cells. The results indicate that miR-146a is more abundantly expressed in EBV-positive than in EBV-negative cells. MiR-146a down-regulated CXCR4 expression in a dose- and time-dependent manner. Phenotypic experiments detected miR-146a mimics that could suppress cell proliferation and cell migration and promote cell apoptosis by targeting CXCR4. In addition, miR-146a mimics suppressed cell survival by decreasing the population of G0/G1 phase cells. Latent membrane protein (LMP)1, an importance oncoprotein, can stimulate miR-146a and inhibit the CXCR4 expression. Our findings indicate that LMP1–miR-146a–CXCR4 axis functions as a regulator in the EBV-associated cells. [ABSTRACT FROM AUTHOR]