bay-11-7082 and Nasopharyngeal-Neoplasms

The latent membrane protein 1 (LMP1) encoded by EBV is expressed in the majority of EBV-associated human malignancies and has been suggested to be one of the major oncogenic factors in EBV-mediated carcinogenesis. In previous studies we experimentally demonstrated that down-regulation of LMP1 expression by DNAzymes could increase radiosensitivity both in cells and in a xenograft NPC model in mice.. In this study we explored the molecular mechanisms underlying the radiosensitization caused by the down-regulation of LMP1 in nasopharyngeal carcinoma. It was confirmed that LMP1 could up-regulate ATM expression in NPCs. Bioinformatic analysis of the ATM ptomoter region revealed three tentative binding sites for NF-κB. By using a specific inhibitor of NF-κB signaling and the dominant negative mutant of IkappaB, it was shown that the ATM expression in CNE1-LMP1 cells could be efficiently suppressed. Inhibition of LMP1 expression by the DNAzyme led to attenuation of the NF-κB DNA binding activity. We further showed that the silence of ATM expression by ATM-targeted siRNA could enhance the radiosensitivity in LMP1 positive NPC cells.. Together, our results indicate that ATM expression can be regulated by LMP1 via the NF-κB pathways through direct promoter binding, which resulted in the change of radiosensitivity in NPCs.

Topics: Animals; Ataxia Telangiectasia Mutated Proteins; Blotting, Western; Carcinoma; Cell Cycle Proteins; Cell Line, Tumor; Computational Biology; DNA-Binding Proteins; DNA, Catalytic; Electrophoretic Mobility Shift Assay; Female; Flow Cytometry; Humans; Immunochemistry; Mice; Mice, Inbred BALB C; Mice, Nude; Nasopharyngeal Carcinoma; Nasopharyngeal Neoplasms; NF-kappa B; Nitriles; Promoter Regions, Genetic; Protein Binding; Protein Serine-Threonine Kinases; Real-Time Polymerase Chain Reaction; RNA, Small Interfering; Signal Transduction; Sulfones; Tumor Suppressor Proteins; Viral Matrix Proteins; X-Rays

Epstein-Barr virus (EBV) infection in tumor cells is generally restricted to the latent forms of viral infection. Switching the latent form of viral infection into the lytic form may induce tumor cell death. An important nuclear factor, nuclear factor (NF)-kappaB, is thought to play an essential role in EBV lytic infection; high levels of NF-kappaB can inhibit EBV lytic replication. In this study, we tested the effect of inducing EBV lytic replication using two NF-kappaB inhibitors: Bay11-7082 and Z-LLF-CHO, to reveal the possibility of targeting EBV-positive cancer therapy with these two NF-kappaB inhibitors. Our results showed that Bay11-7082 and Z-LLF-CHO reactivated EBV in a dose-dependent manner, thus resulting in EBV-positive 5-8F cell death. In contrast, there was no significant effect on EBV-negative HNE3 cells. When ganciclovir was used in combination with either Bay11-7082 or Z-LLF-CHO to treat 5-8F cells, the cytotoxic effect of the NF-kappaB inhibitor was amplified. The finding indicates that inhibiting the NF-kappaB activity of EBV-positive cells can induce lytic replication of EBV and cause lytic cytotoxicity against these cells.

Topics: Antiviral Agents; Cell Line, Tumor; Cell Nucleus; Cytoplasm; Epstein-Barr Virus Infections; Ganciclovir; Herpesvirus 4, Human; Humans; Nasopharyngeal Neoplasms; NF-kappa B; Nitriles; Oligopeptides; Sulfones; Transcription Factor RelA; Virus Activation