STRUCTURAL AND FUNCTIONAL CHARACT ERISTICS OF THE LMP1 ONCOGENE IN PATIENTS WITH TUMORS ASSOCIATED AND NOT ASSOCIATED WITH THE EPSTEIN-BARR VIRUS.

Epstein-Barr virus (EBV) - the etiological agent of a number of human benign and malignant tumors including infectious mononucleosis (IM), Burkitt lymphoma (BL), Hodgkin (HL) and non-Hodgkin (NLH) lymphomas, nasopharyngeal carcinoma (NPC), and many other tumors. Latent membrane protein 1 (LMPl) encoded by the gene of the same name (LMP I) is the main oncoprotein of EBV. LMP1 is a transmembrane protein capable of activating many signaling pathways and transcription factors of the cells, which leads to its transformation. Molecular analysis of LMP1 of various clinical origins identified many variants with different types of amino acid mutations that influence its biological activity. Since the role of LMPl in the development of NPC is still not fully understood, it is important to find out how LMPl samples from patients with EBV-associated form of NPC differ from those of patients with other tumors also located in the oral cavity (OTOC), but not associated with this virus. Unlike most investigations conducted in endemic regions, the present work is intended to compare the genetic structure and the transforming activity of LMPl variants from NPC and OTOC patients has been carried out in a non-endemic region of Russia, where NPC is rarely diagnosed. The obtained data show structural and functional similarities of LMP1 variants in the two groups of patients and, accordingly, a genetic relationship of EBV strains persisting in these patients. Our work suggests that in non-endemic regions any EBV strain with any structure of LMP1 may become the etiologic agent of NPC. However, based on modem concepts, the cancer can occur only if EBV-infected persons have a unique pattern of HLA associated with a high sensitivity to the development of NPC combined with exposure to harmful environmental factors (chemical or physical carcinogens) and lifestyle.

[Molecular biological properties of the Epstein-Barr virus LMP1 gene: structure, function and polymorphism].

Recent studies indicate that the latent membrane protein 1 (LMP1) encoded by the same name gene of the Epstein-Barr virus (EBV) plays an extremely important role in the pathogenesis of a number of malignant neoplasia. Specifically, LMP1 has the ability to transform human B-lymphocytes in vivo and in vitro and rodent fibroblasts (Rat-1) in vitro. The introduction of the latter into athymic mice leads to tumor development. In addition, expression of the oncoprotein has been often found in EBV-associated tumors at the DNA and constantly at the RNA levels. Having pleiotropic effects, LMP1, participates in the transmission and activation of multiple intracellular signals. It is also involved in the inhibition of key tumor suppressors, has significant influence on proliferation, apoptosis and morphological alteration of the infected cells finally resulting in their transformation. General characteristics of EBV and LMP1 gene as well as functional activity of the encoded LMP1 protein and a brief description of human pathologies associated with the virus have been discussed in this review. The questions concerning the polymorphism LMP1 in EBV-associated pathologies have been also analyzed in details.

[The LMP1 oncogene sequence variations in patients with oral tumours associated or not associated with the Epstein Barr].

The role of the Epstein-Barr virus (EBV), a ubiquitous lymphotropic human herpesvirus type 4, in the etiology of nasopharyngeal carcinoma (NPC) is not fully understood. The mechanism of NPC carcinogenesis, associated with the virus, is also not clear. The objective of present investigation was to carry out comparative analysis of the structure of an LMP1 oncogene of EBV in viral isolates obtained from patients with two types of tumors of the oral cavity: (a) associated (i.e., NPC) and (b) not associated (other tumors of the same anatomical region, OTOC) with EBV. Comparative analysis of C-terminal regions of LMP1 variants that was based on a sequence analysis of LMP1 from tumor, blood and throat washing samples of NPC and OTOC patients showed that all structural characteristics of LMP1 in both groups of patients were genetically similar, and differences found between compared parameters were statistically insignificant. Thus, for the first time it has been revealed that in NPC and OTOC patients in Russia genetically related EBV strains with structurally similar LMP1 variants are persisting that are likely to reflect a polymorphism of the virus circulating in population. The findings allow us to suggest that in non-NPC-endemic regions of the world, which include Russia, the risk of NPC development does not depend on the EBVstrain and its variant of LMP1 so much, but mostly from the genetic predisposition of infected persons to the disease and the exposure to other, as yet unknown agents.

[The influence of point mutations in the Epstein-Barr virus LMP1 oncogene on the cell cytoskeleton and activation of inducible form of NO synthase].

One of the latent proteins encoded by the Epstein-Barr virus (EBV), the latent membrane protein 1 (LMP1), plays a key role in developing of EBV-associated human malignancies. Polymorphism of LMP1 protein is its characteristic feature. Some specific mutations in LMP1 genome have previously been detected in different geographic regions, however, the influence of these mutations on functional activity of LMP1 was not still determined. In this study we demonstrated for the first time the significance of individual point mutations among common ones observed in LMP1 and their combination on activation of the inducible form of nitric oxide synthase (iNOS). In addition, the influence of above mutations localized in the CTAR regions of the LMP1 molecule has also been investigated on structural components of the fibroblasts of the Rat1cell line.

[COX-2 as an early diagnostic marker of virus-associated human malignant neoplasms].

The review analyzes recent data and current ideas on the enzyme cyclooxygenase 2 (COX-2) as a possible biomarker of virus-associated human malignant neoplasm. Possible mechanisms of COX-2 activation in the cells infected with oncogenic human viruses, such as hepatitis B virus, Epstein-Barr virus, and human papillomavirus are considered in detail.

[LMP1 gene polymorphism in patients with Epstein-Barr virus-negative gastric carcinomas in Russia].

The investigation was undertaken to study the molecular characteristics of Epstein-Barr virus (EBV) LMP1 gene samples amplified from the tumor and intact tissues of patients with EBV-negative forms of gastric carcinoma (GC). The genetic structure of these samples determined by their sequencing was compared with that of the gene samples isolated from the cells of oropharyngeal washing specimens from the same patients with GC, as well as peripheral blood lymphocytes of patients with infectious mononucleosis (IM) and blood donors. The findings suggest that the samples of tumor tissue LMP1 from patients with GC have higher divergence than those from patients with IM and blood donors although no specific variants of the gene for GC were found. Comparison of LMP1 sequences from tumor tissue and cells of oropharyngeal washing specimens from the same patients with EBV-negative GC revealed the common LMP1 variant in 2 cases while they differed in 3 cases. The findings are an initial step in studying the role of EBV in the carcinogenesis of EBV-negative GC that is likely to be established by investigations on representative clinical material, by applying the up-to-date technologies.

Functionally significant mutations in the Epstein-Barr virus LMP1 gene and their role in activation of cell signaling pathways.

Latent membrane protein 1 (LMP1) of the Epstein-Barr virus is a constitutively activated analog of the tumor necrosis factor receptor TNF-R1. LMP1 serves as a viral oncogene able to transform human B-lymphocytes and rodent fibroblasts via activation of numerous cellular signal cascades. Two specific motifs within LMP1 are responsible for interaction of this viral protein with the receptor protein beta-TrCP/HOS SCF of the ubiquitin ligase E3 complex, playing an important role in degradation of numerous cellular proteins including NF-kappaB inhibitor IkappaBalpha. In this study, we demonstrate for the first time the importance of point mutations affecting HOS-recognizing motifs of LMP1 for activation of NF-kappaB, AP1, and PI3K/Akt signaling pathways. It has also been shown that rat fibroblast cell lines (Rat-1) expressing different HOS mutants of LMP1 produce different amounts of reactive nitrogen species. Our data confirm the hypothesis that point mutations in the C-terminal region of the LMP1 cytoplasmic domain can influence the transforming potential of the Epstein-Barr virus.

[Mutations of the Epstein-Barr virus LMP1 gene mutations in Russian patients with lymphoid pathology and healthy individuals].

Epstein-Barr virus (EBV) is an etiological agent of a number of benign and malignant human diseases, such as infectious mononucleosis (IM), Hodgkin's lymphoma (HL), and non-Hodgkin's lymphoma (NHL). EBV latent membrane protein 1 (LMP1) gene (recognized as a viral oncoprotein) of various clinical and geographical origin was found to have different types of amino acid mutations affecting its biological activity. Since there was no information on the strain differences in LMP1 of EBV persisting in Russia, the authors made a sequence analysis of LMP1 samples amplified from the biological materials of Russian patients with IM, HL, and NHL and healthy individuals. The studies have shown that LMP1 variants of Russian origin are a mixed heterogeneous group containing both the earlier characterized and presumably new genetic variants. Among the point amino avid substitutions, the mutations S366T, F106Y, 185L, and E328Q associated with the enhanced transforming activity of a LMP1 molecule and its reduced cytotoxicity. There was no specific association between the certain Russian variants of LMP1 and the specific forms of the disease (IM, HL, and NHL).

[Functional analysis of Epstein-Barr virus latent membrane proteins (LMP1) in patients with limphoproliferative disorders].

Latent membrane protein1 (LMP1) encoded by the LMP1 gene of the Epstein-Barr virus (EBV) is a transmembrane protein, which can activate a number of cellular signal cascades and transcriptional factors leading to cell transformation. In the present study the sequencing of full-length LMP1 variants isolated from Russian patients with Hodgkin's lymphoma (HL), non-Hodgkin's lymphomae (NHL) and infectious mononucleosis (IM) has been carried out. The phylogenetic analysis of obtained sequences revealed dominance of the LMP1 variants belonging to proteins of low-divergent group LMP1-B95.8b characterized by minimal set of mutations. Investigation of biological properties in the Russian representatives of this group revealed that expression of studied LMP1 variants in embryonic kidney 293 cells was accompanied by insignificant increase in transcriptional factor NF-kappaB activation and had minor influence on activation of transcriptional factor AP-1. It was also detected that all investigated low-divergent LMP1 variants expressed in Rat-1 cells induced activation of inducible NO-synthase (iNOS) and intracellular production of nitric oxide (NO). At the same time the level of NO accumulation was lower than that induced by the low-transforming prototype variant LMP1-B95.8. The data obtained indicate that the LMP1 variants, which are the most common among Russian patients with EBV-associated lymphoproliferative diseases, are characterized by minimum number of mutations and rather low ability to activate basic cellular signaling pathways regardless the nature of pathological process, benign (IM) or malignant (HL, NHL). It is suggested that in addition to the modest activation of NF-kappaB and iNOS induction by LMP1 other factors are involved in the cell transformation process.