NF-κB-mediated transcriptional upregulation of TNFAIP2 by the Epstein–Barr virus oncoprotein, LMP1, promotes cell motility in nasopharyngeal carcinoma

Abstract

Nasopharyngeal carcinoma (NPC), which is closely associated with Epstein-Barr virus (EBV), is a metastasis-prone epithelial cancer. We previously showed that tumor necrosis factor α-induced protein 2 (TNFAIP2) is highly expressed in NPC tumor tissues and is correlated with metastasis and poor survival in NPC patients. However, the underlying mechanism remains unclear. In this study, we demonstrate that the EBV oncoprotein, latent membrane protein 1 (LMP1), can transcriptionally induce TNFAIP2 expression via NF-κB. Quantitative RT-PCR and western blotting revealed that LMP1 induces TNFAIP2 expression through its C-terminal-activating region (CTAR2) domain, which is required for transduction of NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) signaling. Inhibition of NF-κB activation or depletion of p65 (a component of NF-κB) by RNA interference abolished the LMP1-induced expression of TNFAIP2, whereas ectopic expression of p65 was sufficient to induce TNFAIP2 expression. Luciferase reporter assays showed that LMP1 transcriptionally induces TNFAIP2 expression through a newly identified NF-κB-binding site within the TNFAIP2 promoter (-3,869 to -3,860 bp). Immunohistochemical analysis of NPC biopsy specimens further revealed a significant correlation between the protein levels of TNFAIP2 and activated p65 (R=0.689, P<0.001), indicating that our findings are clinically relevant. Immunofluorescence microscopy and co-immunoprecipitation assays showed that TNFAIP2 associates with actin and is involved in the formation of actin-based membrane protrusions. Furthermore, transwell migration assays demonstrated that TNFAIP2 contributes to LMP1-induced cell motility. Collectively, these findings provide novel insights into the regulation of TNFAIP2 and its role in promoting NPC tumor progression.

LMP1 Promotes Expression of Insulin-Like Growth Factor 1 (IGF1) To Selectively Activate IGF1 Receptor and Drive Cell Proliferation

“…LMP1 is capable of increasing cell motility and promoting metastasis (5,44). In agreement with these observations, LMP1 expression increased Rat1 cell migration by roughly 3-fold compared to pBabe vector control cells in a transwell assay (Fig.…”

Microarray Expression Profiling of Long Non-Coding RNAs Involved in Nasopharyngeal Carcinoma Metastasis

“…The correlation between these pathways and multiple diseases including NPC has been proved by previous studies. Among which, apoptosis [33,34,35], p53 [36,37] and NF-κB [38,39] have been reported to be closely related to NPC pathogenesis.…”

Knockdown of TNFAIP1 inhibits growth and induces apoptosis in osteosarcoma cells through inhibition of the nuclear factor-κB pathway

“…It has been reported that NF-κB-mediated transcriptional upregulation of TNFAIP2 by the Epstein-Barr virus oncoprotein, LMP1, promotes cell motility in NPC (20). However, few studies have shown that TNFAIP1 inhibits the transcriptional activities of NF-κB (25).…”

“…Furthermore, TNFAIP1 was found to be downregulated by miR-372/-373 and participates in cell apoptosis and proliferation via the NF-κB pathway (18,19). In addition, TNFAIP2 was found to promote tumor progression in nasopharyngeal carcinoma (NPC) (20), while knockdown of TNFAIP2 was found to markedly reduce the migration and invasion of NPC cells (15). The present study also showed that knockdown of TNFAIP1 repressed cell proliferation and invasion, and induced cell apoptosis in OS cells, which is supported by data that TNFAIP2 can mediate the inhibitory effects of retinoic acid on endometrial cancer cell growth, invasion and apoptosis escape (21), suggesting TNFAIP1/2 as a potential target for retinoic acid in acute promyelocytic leukemia (22).…”