Genetic Analysis of Epstein-Barr Virus Latent Membrane Protein 1 and Immunohistochemical Expression of Transforming Growth Factor (TGF)-beta1, TGF-betaRII, p21, p16, E2F1, Thymidylate Synthase, and NF-kappaB in Epstein-Barr Virus Encoded RNA-positive Gast

BACKGROUND :Although clinicopathologic differences have been described between Epstein-Barr virus (EBV)-positive and negative gastric adenocarcinomas, the pathogenetic basis for these differences remains unclear. In this study, efforts were made to confirm that expression of EBV-latent membrane protein (LMP1) and immunohistochemical characteristics of EBVpositive gastric adenocarcinomas. METHODS: We investigated genomic deletion, and RNA & protein expression of the EBV-LMP1, as well as immunohistochemical protein expression of transforming growth factor (TGF)-beta1, TGF-bata RII, p21, p16, E2F1, thymidylate synthase, and NF-kappaB in relation to EBV positive gastric adenocarcinoma. RESULTS: A total of 38 Epstein-Barr Virus Encoded RNA-positive and 80 negative gastric carcinomas were examined. A 30 bp DNA deletion in the EBV-LMP1 gene, initiating at codon 342, was detected in 94.4% of EBVpositive cases. By RT-PCR and western blotting, EBV-LMP1 mRNA and protein expressions were absent in all cases, re-gardless of DNA deletion. No significant differences in TGF-bata1, TGF-betaRII, p21, NF-kappaB, E2F1, or thymidylate synthase expression were identified. However, the decreased expression of p16 was found in 84.2% of EBV-positive carcinomas, relative to only 57.5% of EBV-negative tumors (p=0.024). CONCLUSION: EBV-LMP1 DNA deletion, mRNA and protein losses are highly prevalent in EBV-positive gastric adenocarcinoma among Korean patients, along with decreased p16 expression.

Colocalization of Interferon Regulatory Factor 7 (IRF7) with Latent Membrane Protein 1 (LMP1) of Epstein-Barr Virus

Interferon regulatory factor 7 (IRF7) is one of the transcriptional factors for the activation of type I Interferon (IFN) genes. It is known that IRF7 and the latent membrane protein 1 (LMP1) of Epstein-Barr virus (EBV) are highly expressed in EBV type III latency cells, and LMP1 induces mRNA expression of IRF7. In this study, the expression pattern of endogenous IRF7 was observed in several B cell lines with or without EBV infection by immunofluorescence staining. IRF7 was localized in the cytoplasm of EBV-negative B cells and EBV type I latency B cell lines. However, IRF7 was located both in the cytoplasm and nucleus of EBV type III latency cell lines. In the Jijoye cell (type III latency cell), IRF7 was colocalized with LMP1 in the cytoplasm in a capping configuration, and their interaction was confirmed by co-immunoprecipitation of LMP1 and IRF7. This colocalization was confirmed by co-transfection of IRF7 and LMP1 plasmids in EBV-negative B cells. These results suggest that the IRF7 and LMP1 interact with each other, and this may relate to the mechanism whereby LMP1 exerts functional effects in B-lymphocytes.