The LMP1 gene isolated from Russian nasopharyngeal carcinoma has no 30-bp deletion

[Epstein-Barr virus (Herpesviridae: Gammaherpesvirinae: Lymphocryptovirus: Human gammaherpesvirus 4) in Kalmyks and Slavs living in Russia: virus types, LMP1 oncogene variants, and malignancies]

INTRODUCTION

The discovery of the Epstein-Barr virus types (Herpesviridae: Gammaherpesvirinae: Lymphocryptovirus: Human gammaherpesvirus 4) (EBV) - EBV-1 and EBV-2, which have different transforming abilities in vitro, stimulated the study of their prevalence in populations in order to elucidate the relationship with malignant neoplasms.The aims of the work are to study the prevalence of EBV-1 and EBV-2 among representatives of 2 ethnic groups of Russia, Kalmyks and Slavs, sequencing analysis of the LMP1 oncogene in virus isolates, and analysis of the correlation between virus types and the incidence of certain forms of tumors.

MATERIALS AND METHODS

DNA samples were isolated from the biological material of oral swabs obtained from ethnic Kalmyks of the Republic of Kalmykia (RK) (n = 50) and Slavs, residents of the Moscow Region (MR) (n = 40). DNA samples were used to amplify EBV DNA, followed by determination of its concentration per 1 cell of washout, amplification of the LMP1 oncogene in viral samples, their sequencing, and determination of LMP1 protein variants.

RESULTS

It has been established that with the same burden of EBV among representatives of both ethnic groups in the Kalmyk group, the ratio of persons infected with transforming and non-transforming types of the virus was almost the same (EBV-1 - 51%; and EBV-2 - 49%). Meanwhile, in the group of Slavs the transforming EBV-1 type virus dominated (80.6%). The predominance of EBV-1 type in representatives of the Slavs correlated with increased incidence of certain forms of tumors in the population of the MR when compared with similar values in the population of the RK, where both types of the virus were prevalent. Differences between the compared rates of cancer incidence were not statistically significant. Analysis of viral isolates showed a similar set of LMP1 variants in both ethnic groups.

CONCLUSION

In order to establish the influence of EBV types on the incidence of malignant tumors, additional studies involving representatives of various ethnic groups from different geographical regions are needed.

A Systematic Review of Epstein-Barr Virus Latent Membrane Protein 1 (LMP1) Gene Variants in Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is an aggressive tumor with a complex etiology. Although Epstein-Barr virus (EBV) infection is known environmental factor for NPC development, the degree to which EBV naturally infects nasopharyngeal epithelium and the moment when and why the virus actively begins to affect cell transformation remains questionable. The aim of this study was to explore the association between LMP1 gene variability and potential contribution to NPC development. A systematic review was performed through searches of PubMed, Web of Science (WoS) and SCOPUS electronic databases. Additionally, meta-analysis of the difference in the frequency of seven LMP1 gene variants in NPC and control individuals was accomplished. The results from this study give a proof of concept for the association between 30 bp deletion (OR = 3.53, 95% CI = 1.48-8.43) and Xhol loss (OR = 14.17, 95% CI = 4.99-40.20) and NPC susceptibility when comparing biopsies from NPC and healthy individuals. Otherwise, 30 bp deletion from NPC biopsies could not distinguish NPC from EBV-associated non-NPC tumors (OR = 1.74, 95% CI = 0.81-3.75). However, B95-8, China1 and North Carolina variants were uncommon for NPC individuals. Much more efforts remains to be done to verify the biological significance of the differences observed, define so-called "high-risk" EBV variants and make it available for clinical application.

Epstein-Barr virus strains and variations: Geographic or disease-specific variants?

The Epstein-Barr Virus (EBV) is associated with the development of several diseases, including infectious mononucleosis (IM), Burkitt's Lymphoma (BL), Nasopharyngeal Carcinoma, and other neoplasias. The publication of EBV genome 1984 led to several studies regarding the identification of different viral strains. Currently, EBV is divided into EBV type 1 (B95-8 strain) and EBV type 2 (AG876 strain), also known as type A and type B, which have been distinguished based upon genetic differences in the Epstein-Barr nuclear antigens (EBNAs) sequence. Several other EBV strains have been described in the past 10 years considering variations on EBV genome, and many have attempted to clarify if these variations are ethnic or geographically correlated, or if they are disease related. Indeed, there is an increasing interest to describe possible specific disease associations, with emphasis on different malignancies. These studies aim to clarify if these variations are ethnic or geographically correlated, or if they are disease related, thus being important to characterize the epidemiologic genetic distribution of EBV strains on our population. Here, we review the current knowledge on the different EBV strains and variants and its association with different diseases. J. Med. Virol. 89:373-387, 2017. © 2016 Wiley Periodicals, Inc.

The Epstein-Barr virus latent membrane protein-1 (LMP1) 30-bp deletion and XhoI-polymorphism in nasopharyngeal carcinoma: a meta-analysis of observational studies

BACKGROUND

Epstein-Barr virus (EBV) is considered to be closely associated with nasopharyngeal carcinoma (NPC), in which EBV-encoded latent membrane protein 1 (LMP1) was found to have an oncogenic role. However, the results published on the LMP1 polymorphism are inconsistent. In the present study, we performed a meta-analysis to determine the frequency of the associations and a more precise association between NPC and EBV LMP1 gene variants (30-bp deletion (del)/XhoI-loss).

METHODS

Eligible articles met the inclusion/exclusion criteria and were identified in the following electronic databases: PubMed, ScienceDirect, and SciELO. Consequently, the data of interest were extracted and plotted in a table to calculate the frequency and odds ratio (OR) of the outcomes of interest (30-bp del-LMP1/XhoI-loss) in patients with NPC. Study quality (Newcastle-Ottawa Scale (NOS)), publication bias, and heterogeneity were assessed.

RESULTS

Thirty-one observational studies were included with a total of 2,846 individuals (NPC, n = 1,855; control, n = 991). The risk of bias in relation to study quality evaluated by NOS was considered low. The pooled estimate of the frequency of 30-bp del-LMP1 and XhoI-loss in patients with NPC was 77% (95% confidence interval (CI): 72 to 82) and 82% (95% CI: 71 to 92), respectively. There was an association between 30-bp del-LMP1 and NPC susceptibility (OR = 2.86, 95% CI: 1.35 to 6.07, P = 0.00). Similarly, there was an association between XhoI-loss and NPC (OR = 8.5, 95% CI: 1.7 to 41, P = 0.00). However, when we analyze the co-existence of the 30-bp del-LMP1 and XhoI-loss in patients with NPC, there was no association (OR = 1.09, 95% CI: 0.06 to 18.79, P = 0.002).

CONCLUSIONS

Our results suggest an association between the 30-bp del-LMP1 and XhoI-loss with NPC susceptibility. However, our data should be interpreted with caution because the sample size was small, and there was heterogeneity between the studies. Thus, future studies are needed with adjusted estimates to simultaneously evaluate multiple factors involved in the development of NPC.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42014013496 .

Carboxy-terminal sequence variation of LMP1 gene in Epstein-Barr-virus-associated mononucleosis and tumors from Serbian patients

Seven strains of Epstein-Barr virus (EBV) are defined based on C-terminal sequence variations of the latent membrane protein 1 (LMP1). Some strains, especially those with a 30-bp deletion, are thought to be related to tumorigenic activity and geographical localization. The aims of the study were to determine the prevalence of different LMP1 strains and to investigate sequence variation in the C-terminal region of LMP1 in Serbian isolates. This study included 53 EBV-DNA-positive plasma and tissue block samples from patients with mononucleosis syndrome, renal transplantation, and tumors, mostly nasopharyngeal carcinoma. The sequence of the 506-bp fragment of LMP1 C terminus was used for phylogenetic analyses and identification of LMP1 strains, deletions, and mutations. The majority of isolates were non-deleted (66%), and the rest had 30-bp, rare 69-bp, or yet unknown 27-bp deletions, which were not related to malignant or non-malignant isolate origin. However, the majority of 69-bp deletion isolates were derived from patients with nasopharyngeal carcinoma. Less than five 33-bp repeats were found in the majority of non-deleted isolates (68.6%), whereas most 69-bp deletion isolates (75%) had five or six repeats. Serbian isolates were assigned to four LMP1 strains: B95-8 (32.1%), China 1 (24.5%), North Carolina (NC; 18.9%), and Mediterranean (Med; 24.5%). In NC isolates, three new mutations unique for this strain were identified. EBV EBNA2 genotypes 1 and 2 were both found, with dominance of genotype 1 (90.7%). This study demonstrated noticeable geographical-associated characteristics in the LMP1 C terminus of investigated isolates.

The NP9 protein encoded by the human endogenous retrovirus HERV-K(HML-2) negatively regulates gene activation of the Epstein-Barr virus nuclear antigen 2 (EBNA2)

Epstein-Barr virus (EBV) is a human tumour virus that efficiently growth-transforms primary human B-lymphocytes in vitro. The viral nuclear antigen 2 (EBNA2) is essential for immortalisation of B-cells and stimulates viral and cellular gene expression through interaction with DNA-bound transcription factors. Like its cellular homologue Notch, it associates with the DNA-bound repressor RBPJκ (CSL/CBF1) thereby converting RBPJκ into the active state. For instance, both EBNA2 and Notch activate the cellular HES1 promoter. In EBV-transformed lymphocytes, the RNA of the NP9 protein encoded by human endogenous retrovirus HERV-K(HML-2) Type 1 is strongly up-regulated. The NP9 protein is detectable both in EBV-positive Raji cells, a Burkitt's lymphoma cell line, and in IB4, an EBV-transformed human lymphoblastoid cell line. NP9 binds to LNX that forms a complex with the Notch regulator Numb. Therefore, the function of NP9 vis-à-vis Notch and EBNA2 was analysed. Here, we show that NP9 binds to EBNA2 and negatively affects the EBNA2-mediated activation of the viral C- and LMP2A promoters. In contrast, NP9 did neither interfere in the activation of the HES1 promoter by Notch nor the induction of the viral LMP1 promoter by EBNA2. In an electrophoretic mobility shift analysis, NP9 reduced the binding of EBNA2 to DNA-bound RBPJκ by about 50%. The down-regulation of EBNA2-activity by NP9 might represent a cellular defence mechanism against viral infection or could, alternatively, represent an adaptation of the virus to prevent excessive viral protein production that might otherwise be harmful for the infected cell.

Epstein-Barr virus genetic variation in Vietnamese patients with nasopharyngeal carcinoma: full-length analysis of LMP1

Genetic variation in tumor virus genes and its impact on function might contribute to the understanding of geographic differences in risks for virus-associated tumors. This is particularly true for the genes known to contribute to the biology of the tumor. It is has been proposed that Epstein-Barr virus (EBV) gene variation has a role in the high risk of nasopharyngeal carcinoma (NPC) in South-East Asia. NPC is among the five most common cancers in Vietnam. EBV-NPC cells always express EBV nuclear antigen 1 (EBNA1) and also frequently latent membrane protein 1 and 2 (LMP1 & LMP2). To investigate EBV gene variation in Vietnamese NPC patients we analyzed the full length of LMP1 gene including its promoter region, and the N-termini of both EBNA1 and LMP2A genes from five NPC biopsies. We detected two EBV variants V1 and V2 based on the LMP1 nucleotide sequence pattern compared with the prototype B95-8 and some available sequences including Chinese variants. The V1 variant shows strong similarity to a variant dominant in Southern China (China 1), while the V2 variant is similar to a Thai variant SEA 2 and partly identity with GD1 in the C-terminus. The promoter region and transmembrane domain of the SEA 2-like samples contained some specific differences compared with previously published variants. In contrast, analysis of EBNA1 N- and LMP2A N-termini only revealed minor changes. Our findings reinforces that the polymorphisms of whole LMP1 sequence should be considered in future EBV molecular epidemiology studies in different geographic populations.

Polymorphism analysis of Epstein-Barr virus isolates of nasopharyngeal carcinoma biopsies from Tunisian patients

Many studies suggest that the focal distribution of nasopharyngeal carcinoma (NPC) may be influenced not only by host genetics, diet and environments but also by interplay with Epstein-Barr virus (EBV) genetics. Specific EBV gene variants (the A and C types, the BamHI f configuration, a C terminal 30 bp deletion and a N terminal loss of an XhoI site in the BNLF1 gene) have been explored in high incidence areas in southern Asian NPC patients. In contrast, in Tunisia where NPC represents the most frequent type of Head and Neck cancer the distribution of these polymorphisms remains poorly investigated. In order to characterize the epidemiology of EBV variants in Tunisian NPC patients, we have investigated the A or B type of the EBV nuclear antigen (EBNA)2 gene, the C or D type of the BamHI W1/I1 region, the F/f variants of the BamHI F region and the presence or the absence of the XhoI site, 30 bp deletion and Taq1 site in the BNLF1 gene in 47 NPC biopsies, 12 being younger than 30 and 35 older than 30. Our results show a unique genetic profile of the tumor EBV strains regarding the A and D types, the prototype F and retention of the XhoI restriction site in the N terminal region of BNLF1 gene. With regard to the C terminal region of this gene, four genetic profiles were detected: (1) the occurrence of the 30 bp deletion in association with the Taq1 site in 39 cases (83%), (2) the presence of the Taq1 site by itself in 5 cases, (3) the occurrence of the 30 bp deletion by itself in 2 cases and (4) the occurrence of a new deletion of 81 bp covering the 30 bp deletion in association with the Taq1 site in one case. With the exception of the 81 bp deletion, which has not been previously described in the literature, the summarized results have shown the same genetic profile in Tunisian NPC tumor isolates as tumor isolates from other North African and Mediterranean countries. Hence, the observed EBV polymorphisms are not fully specific of to the Tunisian NPCs. Nevertheless, the notion of a divergence between North African and Asian tumor EBV isolates is reinforced by this study.

The 30-bp deletion of Epstein-Barr virus latent membrane protein-1 gene has no effect in nasopharyngeal carcinoma

OBJECTIVE

The specific 30-bp deletion of the Epstein-Barr virus (EBV)-derived latent membrane protein-1 gene has been suggested to be associated with the pathogenesis of nasopharyngeal carcinoma (NPC) and a more aggressive phenotype of some EBV-associated malignancies.

METHODS

The authors conducted a retrospective cohort study. Between 1995 and 2001, 542 patients who had received complete courses of radiotherapy followed by at least 3 years of follow up were enrolled. Patients were divided into two groups according to the presence or absence of the 30-bp deletion in their tumor samples.

RESULTS

A total of 446 (82.3%) patients were found to feature the 30-bp deletion, whereas 88 (16.2%) did not. Interestingly, dual infection was found in eight (1.5%) patients. No statistical significance was found in age, gender, NPC-presenting stage, radiosensitivity, and pathologic classification between the two groups. The actuarial 5-year overall survival rate and the distant metastasis-free rate for the 30-bp deletion and nondeletion group were not statistically different (61.3% vs. 65.4% and 68.1% vs. 73.1%; P = .132 and .135, respectively). In multivariate analysis, older age, nasopharyngeal recurrence, advanced tumor stage, and the development of distant metastasis were shown to be poorer prognosticators for overall survival, whereas the presence of 30-bp deletion was not. For distant metastasis, only advanced tumor stage was shown to be a poor prognosticator, whereas other variables, including the presence of 30-bp deletion, had no statistical significance.

CONCLUSIONS

In this retrospective cohort, we have demonstrated that this specific 30-bp sequence deletion might be only the predominant variant rather than an NPC phenotype-associated polymorphism. Additionally, dual infection is a rare but possible phenomenon in the endemic NPC tumors.

Epstein-Barr virus latent membrane protein 1 (CAO) up-regulates VEGF and TGF alpha concomitant with hyperlasia, with subsequent up-regulation of p16 and MMP9

EBV latent membrane protein 1 (LMP1) is an oncoprotein frequently expressed in nasopharyngeal carcinoma. We have generated transgenic mice expressing the nasopharyngeal carcinoma-derived CAO strain of LMP1 and LMP1 of the B95-8 strain, using the viral ED-L2 promoter for epithelial expression. LMP1(CAO) and LMP1(B95-8) induce transforming growth factor alpha expression and epidermal hyperplasia. However, levels of total epidermal growth factor receptor (EGFR) decline with the appearance of phosphorylated EGFR products, suggesting that the negative feedback loop upon EGFR expression is intact or that there is faster turnover at these early stages of carcinogenesis. In the L2LMP1(CAO) mice, increased levels of vascular endothelial growth factor are also seen at an early stage in the skin. As the phenotype worsens, with increasing hyperplasia and vascularization leading to keratoacanthoma, p16(INK4a) and matrix metalloproteinase 9 expression is induced. The lesions can progress spontaneously to carcinoma. Carcinoma cell lines developed from these mice show high levels of total and phosphorylated EGFR. These data show that the induction of signaling through EGFR by LMP1 is an early event in carcinogenesis and that any inhibition upon EGFR expression is lifted during progression. Furthermore, expression of LMP1 is not sufficient to inhibit induction of p16(INK4a) in response to abnormal proliferation. These data are consistent with the cooperative effects seen between LMP1 and loss of the INK4a locus in transgenic mice and with the frequency of loss of this locus in EBV-associated nasopharyngeal carcinoma.

Various 30 and 69 bp deletion variants of the Epstein-Barr virus LMP1 may arise by homologous recombination in nasopharyngeal carcinoma of Tunisian patients

Nasopharyngeal carcinoma (NPC) occurs with a striking geographic distribution, it is endemic in certain areas of Southeast Asia and North Africa. NPC is tightly linked to Epstein-Barr virus (EBV), however, only a small subset of EBV genes are expressed, among them the latent membrane protein 1 (LMP1). LMP1 is considered as the main EBV oncoprotein and its 30 bp deleted-variant has been reported to be more prevalent in biopsies of NPC. We have assessed the 30 bp deletion and the XhoI polymorphisms of the BNLF1 gene in 30 peripheral bloods of NPC patients and 62 nasopharyngeal biopsies, 42 being confirmed as undifferentiated nasopharyngeal carcinoma and 20 are normal nasopharyngeal epithelium cells. Our results show that 100% of individuals retained the XhoI restriction site. A rare NPC variant, having a 69 bp deletion in the C-terminus region of the BNLF1 gene, covering the 30 bp deletion, was found in two NPC biopsies. The deleted 30 and 69 bp deleted-variants are significantly (p = 0.006) more frequent in NPC (71.42%) than in control biopsies (52%). In peripheral blood of NPC patients, the deleted-variants (47%) are also lower than in tumor tissues (p = 0.0004), suggesting that the deletion could be associated with a risk of tumor genesis. Direct repeats, located at the extremities of the 30 and 69 bp deletions, should be involved in this process. We propose that other deletions could be found since another similar direct repeat is present at the vicinity of the former ones.

Nucleotide sequences and functions of the Epstein-Barr virus latent membrane protein 1 genes isolated from salivary gland lymphoepithelial carcinomas

Epstein-Barr virus (EBV) infection is associated with salivary gland lymphoepithelial carcinoma (SLEC) and nasopharyngeal carcinoma (NPC). EBV is a ubiquitous herpes virus world wide, but EBV-associated SLEC and NPC are prevalent in restricted regions such as south areas of China, Southeastern Asia and Greenland (Eskimos). To examine whether particular EBV variants play roles in the development of SLEC and NPC, we isolated the complete EBV LMP1 genes from 12 paraffin-embedded biopsy samples of SLECs isolated from China, Taiwan and Russia, and compared these LMP1 genes with those of NPC (CAO) and the prototype B95-8 EBV. Nucleotide sequence analysis showed that SLECs LMP1 is more similar to that of CAO than that of prototype B95-8. The analysis also identified several conserved (67-100%) variations in SLEC-LMP1 and CAO-LMP1 distinct from B95-8-LMP1. These included 10-amino acid deletion, 5-amino acid deletion and 12-single amino acid variations. A SLEC-LMP1 gene with the aforementioned conserved variations inhibited the growth of an embryonic kidney cell line (293T), highly activated the NF-kappaB pathway, and these activities were equivalent to those of B95-8 and CAO. These findings suggest that the biological functions of SLEC-LMP 1 are similar to those of B95-8-LMP1 and CAO-LMP1, and that these amino acid variations including the well-known 10-aa deletion did not affect these two prominent activities. While the present results could not uncover functional differences between SLEC-LMP1 and B95-8-LMP1, the nucleotide sequences and the molecular clone of LMP1 directly isolated from SLEC patients will be a useful tool to identify the high-pathogenic EBV strain(s), associated with SLEC and NPC.

Biochemical characterisation of the proteins encoded by the DiGeorge critical region 6 (DGCR6) genes

The DiGeorge critical region 6 (DGCR6) gene exists in two highly homologous copies (DGCR6 and DGCR6L) on chromosome 22q11 and is deleted in patients with velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS). The DGCR6 mRNA levels are increased in metastatic mammary tumour cells and regulate the expression of neighbouring genes at the 22q11 region. Newly developed monoclonal antibodies detected predominantly nuclear phosphoproteins of approximately 25 kDa, with low expression levels in the cytoplasm. Both proteins have half-lives of about 2.5 h. Exogenously expressed DGCR6 and DGCR6L migrated with slightly different mobility in SDS-gels in accordance with two immunoreactive bands observed for the endogenous proteins. DGCR6 is found at low levels in primary human fibroblasts or peripheral blood mononuclear cells, while tumour cells, B-cells transformed by EBV as well as activated normal human T cells, contain elevated levels of the proteins. The proteins are differentially expressed in mammalian tissues, with high protein levels in heart, liver and skeletal muscle. These observations are important as some patients with DGCR6 syndrome exhibit a T-cell deficiency and/or cardiac malformations. As the DGCR6 protein(s) influence gene expression in trans, we analysed the influence of DGCR6/DGCR6L on the Epstein-Barr virus-encoded oncoproteins EBNA2 and EBNA3c in the activation of the viral LMP1 promoter, as well as LMP1-mediated activation of NFkB, but found no effect in either setting.

Prevalence of LMP-1 gene in tonsils and non-neoplastic nasopharynxes by nest-polymerase chain reaction in Taiwan

BACKGROUND

The purpose of this study was to investigate the frequency of Epstein-Barr virus (EBV) latent membrane protein-1 (LMP-1) in tonsils and non-neoplastic nasopharynxes in Taiwan.

METHODS

Nest-polymerase chain reaction (nest-PCR) was used to examine the presence of LMP-1 gene in lymphoid hyperplasia from non-neoplastic tonsillar and nasopharyngeal tissues and in tonsillar cancers.

RESULTS

In 152 cases, 64 biopsy tissues were obtained from lymphoid hyperplasia of nasopharynxes, 57 from tonsillectomy of non-neoplastic tonsils, and 31 from tonsillar cancers. LMP-1 was detected in 43.4% of the study group. Nineteen (29.7%) and 29 (50.9%) lymphoid hyperplasias from normal nasopharynxes and tonsils, respectively, and 18 (58.1%) biopsies from tonsillar cancers had positive LMP-1. The 30-base pair (bp) deleted variant was detected in 89.5% and 82.8% of normal nasopharynxes and tonsils, respectively, and in 66.7% of biopsies from tonsillar cancers (p =.198).

CONCLUSION

This study found that the 30-bp variant was the predominant type of LMP-1 from a healthy population in Taiwan.

Amino acid changes in functional domains of latent membrane protein 1 of Epstein-Barr virus in nasopharyngeal carcinoma of southern China and Taiwan: prevalence of an HLA A2-restricted 'epitope-loss variant'

Full-length sequences of the Epstein-Barr virus (EBV) gene for latent membrane protein (LMP)-1 from 22 nasopharyngeal carcinoma (NPC) biopsy specimens and 18 non-neoplastic counterparts (NPI) were determined. Relative to the B95-8 strain, the amino acid sequences of the toxic-signal and transformation domains were changed variably in NPC and NPI specimens; in contrast, no change was observed in the NF-kappaB (nuclear factor kappaB) activation domain. HLA typing revealed that 47 % of NPC and 31 % of NPI specimens were HLA A2-positive. A major A2-restricted epitope within LMP-1 (residues 125-133) was analysed. At residue 126, a change of L-->F was detected in 91 % (20/22) of NPC and 67 % (12/18) of NPI specimens. In addition, a deletion at residue 126 was detected in one NPC sample from Taiwan. At residue 129, a change of M-->I was observed in all samples, regardless of whether they were NPC or NPI. The changes in this peptide between NPC and NPI specimens, including mutation and deletion, are statistically significant (P<0.05). A recent report indicated that this variant sequence is recognized poorly by epitope-specific T cells. Genotyping results indicated that 96 % of NPC and 67 % of NPI samples carried a type A virus. By scanning the entire sequence of LMP-1, eight distinct patterns were identified. Detailed examination of these patterns revealed that type A strains are more prevalent in NPC than in NPI specimens and are marked by the loss of an XhoI site, the presence of a 30 bp deletion and the presence of a mutated, A2-restricted, T cell target epitope sequence. These results suggest that an EBV strain carrying an HLA A2-restricted 'epitope-loss variant' of LMP-1 is prevalent in NPC in southern China and Taiwan.

Detection of wild type and deleted latent membrane protein 1 (LMP1) of Epstein-Barr virus in clinical biopsy material

The latent membrane protein 1 (LMP1) of Epstein-Barr virus (EBV) is one of two postulated viral oncogenic proteins. Sequence variations, and in particular a 30 base pair deletion variant called CAO, may define different disease populations. We developed a panel of rat monoclonal antibodies (MAb) specific for the non-wild type LMP1 and compared the presence of the antibody staining with LMP1 DNA sequence analysis on clinical samples of nasopharyngeal carcinoma, peripheral T-cell lymphoma (PTCL), Hodgkin's disease, lymphoblastoid cell lines (LCL) from normal volunteers, and patients with nasopharyngeal carcinoma. The results demonstrate specificity of the monoclonal cocktail for detecting the non-wild type LMP1 and the ability to sub-differentiate between the mediterranean type of LMP1 and the CAO-LMP1. Double immunofluorescence on paraffin material using the traditional CS1-4 monoclonal antibodies and the CAO-cocktail revealed no dual population of cells in the biopsy material from the Asian region.

Interaction of Epstein-Barr Virus Latent Membrane Protein 1 with SCFHOS/β-TrCP E3 Ubiquitin Ligase Regulates Extent of NF-κB Activation

The Epstein-Barr virus latent membrane protein 1 (LMP1) is pivotal in the transforming activity of this virus. We found that the common LMP1-95-8 variant interacts with Homologue of Slimb (HOS), a receptor for the SCFHOS/betaTrCP ubiquitin-protein isopeptide ligase (E3) via one canonical and one cryptic HOS recognition site. These sites are mutated or deleted in the tumor-derived LMP1-Cao variant, which did not bind to HOS. Mutations within these sites on LMP1-95-8 abrogated HOS binding and increased transforming activity of LMP1. HOS did not regulate stability of LMP1-95-8 unless it was mutated to bear additional lysine residues near the cryptic motif. LMP1 proteins that could not bind to HOS exhibited an increased ability to induce IkappaB degradation and NF-kappaB-mediated transcription without further increase in activation of IkappaB kinases. Expression of LMP1-95-8 reduced the levels of endogenous HOS available to interact with phosphorylated IkappaBalpha. Degradation of IkappaBalpha and dose dependence of NF-kappaB activation by LMP1-95-8 were promoted by co-expression of HOS. Our data suggest that LMP1-95-8 is a pseudo-substrate of SCFHOS/betaTrCP E3 ubiquitin ligase and that interaction between LMP1 and HOS restricts the extent of LMP1-induced NF-kappaB signaling. We discuss the potential role of this mechanism in transforming and cytostatic effects of LMP1 variants in cells and Epstein-Barr virus-associated tumors.

Mutational events in LMP1 gene of Epstein-Barr virus in salivary gland lymphoepithelial carcinomas

It is still unknown what kinds of roles Epstein-Barr virus (EBV) infection that are highly specific to salivary gland lymphoepithelial carcinomas (LECs) play in their tumorigenesis. To clarify the significance of EBV in LECs, we paid particular attention to the LMP1 gene, which is responsible for triggering several pathways for activating transcription factors. Sixty-one cases of EBV positive LECs confirmed by PCR and in-situ hybridization were collected from various areas of the world and studied immunohistochemically for latent membrane protein-1. Furthermore, PCR for the LMP1 carboxyl (C)-terminus region was performed, and the PCR products were sequenced for detection of other mutational events. LMP1 gene products were immunohistochemically demonstrated in 51% of the cases, while PCR amplification of the LMP1 gene was successful in 41 cases (67%). Among them, a 30 bp deletion in the C-terminus of the LMP1 gene, which had been shown to be characteristic to EBV in Chinese nasopharyngeal carcinomas, was found in 20 cases (32%). Most of them were from Guangzhou, Chengdu and Taiwan, while most of the cases from Shanghai and other areas exhibited no 30 bp deletion. In addition, several point mutations including codon 338 of LMP1 were commonly shared by the cases with or without the 30 bp deletion. These results indicate that there are 2 major genomic variations of EBV infecting salivary gland LECs. The frequent mutational events in the C-terminus in addition to the 30 bp deletion also seem to be critical for the pathogenesis because such mutational events may possibly promote cellular proliferation.