The association of squamous cell carcinomas of the nasopharynx with Epstein-Barr virus shows geographical variation reminiscent of Burkitt's lymphoma

Analysis of Epstein-Barr virus latent gene expression in endemic Burkitt's lymphoma and nasopharyngeal carcinoma tumour cells by using quantitative real-time PCR assays

Studies of Epstein-Barr virus (EBV)-positive cell lines have identified several forms of virus latency, but the patterns of virus gene expression in EBV-positive tumour cells appear more variable. However, it is unclear to what extent these differences merely reflect the increased sensitivities of different detection methods. Here, the design and validation of novel real-time RT-PCR assays to quantify relative levels of EBV transcripts are described. When the new assays were used to screen a collection of endemic Burkitt's lymphoma tumours, abundant Qp-driven EBNA1 expression was found, whereas the other latent transcripts (with the exception of LMP2A) were either absent or detectable only at trace levels. Analysis of 12 nasopharyngeal carcinoma biopsies revealed significant levels of EBNA1 and LMP2A transcripts in almost every case but, in contrast to previous reports, LMP1 expression was undetectable. These new quantitative assays may help to provide a clearer picture of EBV gene expression in tumour material.

The enigmatic epidemiology of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) has a unique and complex etiology that is not completely understood. Although NPC is rare in most populations, it is a leading form of cancer in a few well-defined populations, including natives of southern China, Southeast Asia, the Arctic, and the Middle East/North Africa. The distinctive racial/ethnic and geographic distribution of NPC worldwide suggests that both environmental factors and genetic traits contribute to its development. This review aims to summarize the current knowledge regarding the epidemiology of NPC and to propose new avenues of research that could help illuminate the causes and ultimately the prevention of this remarkable disease. Well-established risk factors for NPC include elevated antibody titers against the Epstein-Barr virus, consumption of salt-preserved fish, a family history of NPC, and certain human leukocyte antigen class I genotypes. Consumption of other preserved foods, tobacco smoking, and a history of chronic respiratory tract conditions may be associated with elevated NPC risk, whereas consumption of fresh fruits and vegetables and other human leukocyte antigen genotypes may be associated with decreased risk. Evidence for a causal role of various inhalants, herbal medicines, and occupational exposures is inconsistent. Other than dietary modification, no concrete preventive measures for NPC exist. Given the unresolved gaps in understanding of NPC, there is a clear need for large-scale, population-based molecular epidemiologic studies to elucidate how environmental, viral, and genetic factors interact in both the development and the prevention of this disease.

In nasopharyngeal carcinoma cells, Epstein-Barr virus LMP1 interacts with galectin 9 in membrane raft elements resistant to simvastatin

Nasopharyngeal carcinomas (NPC) are etiologically related to the Epstein-Barr virus (EBV), and malignant NPC cells have consistent although heterogeneous expression of the EBV latent membrane protein 1 (LMP1). LMP1 trafficking and signaling require its incorporation into membrane rafts. Conversely, raft environment is likely to modulate LMP1 activity. In order to investigate NPC-specific raft partners of LMP1, rafts derived from the C15 NPC xenograft were submitted to preparative immunoprecipitation of LMP1 combined with mass spectrometry analysis of coimmunoprecipitated proteins. Through this procedure, galectin 9, a beta-galactoside binding lectin and Hodgkin tumor antigen, was identified as a novel LMP1 partner. LMP1 interaction with galectin 9 was confirmed by coimmunoprecipitation and Western blotting in whole-cell extracts of NPC and EBV-transformed B cells (lymphoblastoid cell lines [LCLs]). Using mutant proteins expressed in HeLa cells, LMP1 was shown to bind galectin 9 in a TRAF3-independent manner. Galectin 9 is abundant in NPC biopsies as well as in LCLs, whereas it is absent in Burkitt lymphoma cells. In subsequent experiments, NPC cells were treated with Simvastatin, a drug reported to dissociate LMP1 from membrane rafts in EBV-transformed B cells. We found no significant effects of Simvastatin on the distribution of LMP1 and galectin 9 in NPC cell rafts. However, Simvastatin was highly cytotoxic for NPC cells, regardless of the presence or absence of LMP1. This suggests that Simvastatin is a potentially useful agent for the treatment of NPCs although it has distinct mechanisms of action in NPC and LCL cells.

EBV latent membrane protein 1 abundance correlates with patient age but not with metastatic behavior in north African nasopharyngeal carcinomas

Background

Undifferentiated nasopharyngeal carcinomas are rare in a majority of countries but they occur at a high incidence in South China and to a lesser extent in North Africa. They are constantly associated with the Epstein-Barr virus (EBV) regardless of patient geographic origin. In North Africa, the distribution of NPC cases according to patient age is bi-modal with a large group of patients being around 50 years old (80%) and a smaller group below 25 years old. We and others have previously shown that the juvenile form of NPC has distinct biological characteristics including a low amount of p53 and Bcl2 in the tumor tissue and a low level of anti-EBV IgG and IgA in the peripheral blood.

Results

To get more insight on potential oncogenic mechanisms specific of these two forms, LMP1 abundance was assessed in 82 NPC patients of both groups, using immuno-histochemistry and semi-quantitative evaluation of tissue staining. Serum levels of anti-EBV antibodies were simultaneously assessed. For LMP1 staining, we used the S12 antibody which has proven to be more sensitive than the common anti-LMP1 CS1-4 for analysis of tissue sections. In all NPC biopsies, at least a small fraction of cells was positively stained by S12. LMP1 abundance was strongly correlated to patient age, with higher amounts of the viral protein detected in specimens of the juvenile form. In contrast, LMP1 abundance was not correlated to the presence of lymph node or visceral metastases, nor to the risk of metastatic recurrence. It was also independent of the level of circulating anti-EBV antibodies.

Conclusion

The high amount of LMP1 recorded in tumors from young patients confirms that the juvenile form of NPC has specific features regarding not only cellular but also viral gene expression.

Global gene expression profile of nasopharyngeal carcinoma by laser capture microdissection and complementary DNA microarrays

A number of genetic and epigenetic changes underlying the development of nasopharyngeal carcinomas have recently been identified. However, there is still limited information on the nature of the genes and gene products whose aberrant expression and activity promote the malignant conversion of nasopharyngeal epithelium. Here, we have performed a genome-wide transcriptome analysis by probing cDNA microarrays with fluorescent-labeled amplified RNA derived from laser capture microdissected cells procured from normal nasopharyngeal epithelium and areas of metaplasia-dysplasia and carcinoma from EBV-associated nasopharyngeal carcinomas. This approach enabled the identification of genes differentially expressed in each cell population, as well as numerous genes whose expression can help explain the aggressive clinical nature of this tumor type. For example, genes indicating cell cycle aberrations (cyclin D2, cyclin B1, activator of S-phase kinase, and the cell cycle checkpoint kinase, CHK1) and invasive-metastatic potential (matrix metalloproteinase 11, v-Ral, and integrin beta(4)) were highly expressed in tumor cells. In contrast, genes underexpressed in tumors included genes involved in apoptosis (B-cell CLL/lymphoma 6, secretory leukocyte protease inhibitor, and calpastatin), cell structure (keratin 7 and carcinoembryonic antigen-related cell adhesion molecule 6), and putative tumor suppressor genes (H-Ras-like suppressor 3, retinoic acid receptor responder 1, and growth arrested specific 8) among others. Gene expression patterns also suggested alterations in the Wnt/beta-catenin and transforming growth factor beta pathways in nasopharyngeal carcinoma. Thus, expression profiles indicate that aberrant expression of growth, survival, and invasion-promoting genes may contribute to the molecular pathogenesis of nasopharyngeal carcinoma. Ultimately, this approach may facilitate the identification of clinical useful markers of disease progression and novel potential therapeutic targets for nasopharyngeal carcinoma.

Diagnostic application of Epstein-Barr virus-encoded RNA in situ hybridisation

AIMS

Epstein-Barr virus (EBV) has been implicated in the pathogenesis of nasopharyngeal carcinoma and a range of proliferative lymphoid conditions. In situ hybridisation (ISH) looking for virus-encoded RNA (EBER) transcripts is performed simply using a commercially available probe. We aimed to examine the application of this test in a routine diagnostic setting.

METHODS

In total, 26 cases in which EBV ISH was requested for diagnostic purposes were examined. We looked at the indication for testing, the result and its implication for the final diagnosis.

RESULTS

Cases were classified into three categories: possible nasopharyngeal carcinoma; possible EBV-related lymphoma; and possible immunodeficiency-associated lymphoproliferative disorder. Six of nine cases of possible nasopharyngeal carcinoma were EBV ISH positive (3/3 primary and 3/6 secondary), confirming the diagnosis. Three of 14 possible lymphoma cases were EBV ISH positive which, along with appropriate ancillary tests, assisted in making the diagnoses of Burkitt's lymphoma, lymphomatoid granulomatosis and extranodal NK/T-cell lymphoma of nasal type. All of three immunodeficiency-associated cases were EBV ISH positive. Two of these were post-transplant lymphoproliferative disorders, monomorphic type. The third case was classified as HIV-related polymorphic lymphoproliferative disorder.

CONCLUSIONS

In our experience, EBV ISH is a straightforward and rapid procedure to perform, giving unequivocal results. Used in the appropriate clinicopathological setting it can be a highly useful ancillary diagnostic aid.

Les carcinomes du nasopharynx : de la biologie à la clinique

Nasopharyngeal carcinomas (NPC) are very different from other head and neck cancers because of their specific multifactorial etiology and their geographic distribution. Epstein-Barr Virus (EBV) is implicated in oncogenesis of NPC in association with genetic alterations such as inactivation of the p16/Ink4, p19/ARF, RASSF1 or Blu genes. Tumoral tissues include a very abundant characteristic lymphoid infiltrate. Inflammatory cytokines are produced by both malignant and infiltrating cells. There is no efficient immune response against the tumor. On the opposite, infiltrating lymphocytes might play a role in tumor development. Serological methods and detection of circulating viral DNA are expected to become useful for early detection of relapse and on a longer term for primary screening. NPC are often diagnosed at a late stage because patients may remain asymptomatic for a long time. Computed tomography (CT scan) and magnetic resonance imaging (MRI) are complementary for the initial evaluation. Positron emission tomography (PET) is efficient for the evaluation of treatment efficiency and detection of relapses. Treatment is based on radiotherapy and chemotherapy. Their optimal use needs to be evaluated by phase III trials but positive results have been obtained by concomitant association of radiotherapy and chemotherapy. Targeted therapies are being studied with strategies based on disruption of viral latency, use of replicative adenoviruses or anti-tumor vaccination.

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.

Similar BCL-X but different BCL-2 levels in the two age groups of north African nasopharyngeal carcinomas

Nasopharyngeal carcinomas (NPCs) are consistently associated with the Epstein-Barr virus (EBV). As Bcl-2 and Bcl-X are co-expressed in EBV-transformed B-lymphocytes, we attempted to determine their status in malignant NPC cells. A retrospective series of 100 NPC specimens from untreated Tunisian patients was investigated by immuno-histochemistry. Twenty seven of the patients were below 30 years old and therefore classified in the "juvenile" form of north African NPCs. Bcl-2 and Bcl-X expression was assessed semi-quantitatively using a score based on the percentage of positive cells and staining intensity. Intense Bcl-X expression was detected in malignant cells of 100% biopsy samples with similar scores for patients below 30 years or those aged 30 or over. Bcl-2 was detected in 89% biopsies but its expression differed considerably between the samples. The average Bcl-2 score was much lower for patients under 30 years (4.4+/-1.5 compared to 6.5+/-2 for older patients; P<10(-6)). Multivariate analysis demonstrated that no other clinical parameter, except the primary tumor size, was correlated to the Bcl-2 score. Bcl-X and Bcl-2 are co-expressed in 89% of NPCs whereas their expression is mutually exclusive in other head and neck carcinomas (particularly squamous cell carcinomas, SCC). The constantly high expression of Bcl-X is consistent with it being induced by the EBV protein Epstein-Barr nuclear antigen 1 (EBNA1), as recently reported in a murine model. The contrasted levels of Bcl-2 expression in the two age groups strengthen the hypothesis that these clinical forms result from distinct oncogenic mechanisms.

Nasopharyngeal carcinomas: an update

Among the group of head and neck cancers, nasopharyngeal carcinomas (NPC) represent a distinct entity in terms of their epidemiology, clinical presentation, biological markers, carcinogenic risk factors, prognostic factors, treatment and outcome. Undifferentiated NPC (UCNT), the most frequent histological type, is endemic in certain regions, especially in South East Asia. The disease has also been associated with the presence of the Epstein-Barr Virus (EBV). Although NPC is a radiosensitive and chemosensitive tumour, a substantial number of patients develop local recurrence or distant metastases. For patients with locoregional advanced disease, it is well known that conventional radiotherapy is insufficient in terms of both the local control rates and distant metastases. New techniques of radiation and new combined radiotherapy and chemotherapy modalities have been evaluated in numerous clinical trials in recent years. The purpose of this article is to review the current knowledge in terms of the epidemiology, biology, prognosis, management and outcome of patients with NPC.

Epstein-Barr virus-associated carcinomas: facts and fiction

The Epstein-Barr virus (EBV) is associated with several human tumours including lymphoid and epithelial malignancies. Most EBV-associated tumours are rare or occur at higher incidence only in certain geographical regions. The recently reported detection of EBV in gastric, breast, and hepatocellular carcinomas raises the possibility of involvement of the virus in the pathogenesis of common cancers. This article reviews the evidence linking EBV infection to epithelial tumours. It is concluded that at present, there is no convincing evidence to suggest that breast carcinoma and hepatocellular carcinoma are EBV-associated tumours.

Lack of evidence for an association of Epstein-Barr virus infection with breast carcinoma

BACKGROUND

Epstein-Barr virus (EBV) is a ubiquitous human gamma-herpes virus infecting more than 90% of the population worldwide. EBV is associated with certain malignancies (e.g. Burkitt lymphoma, Hodgkin lymphoma and nasopharyngeal carcinoma). Recent studies have raised the possibility that EBV may also be involved in the pathogenesis of breast carcinoma, the most common carcinoma of females. If substantiated, this finding would have major implications regarding prevention and therapy of the disease. The studies published so far have employed diverse methods, however, and the results have been controversial.

METHODS

Using the EBV DNA PCR, EBV DNA in situ hybridisation and in situ hybridisation for the detection of the EBV-encoded RNAs, and using immunohistochemistry for the demonstration of the EBV-encoded nuclear antigen 1, we have studied a series of 59 invasive breast carcinomas for evidence of EBV infection.

RESULTS

EBV-encoded RNA-specific in situ hybridisation and EBV-encoded nuclear antigen 1 immunohistochemistry were negative in all cases. Using the PCR, EBV DNA was detected in four out of 59 cases. These cases were further studied by EBV DNA in situ hybridisation, showing an absence of viral DNA from the tumour cells.

CONCLUSION

These results indicate that breast carcinoma is not an EBV-associated tumour.

Epstein-Barr virus in gastric adenocarcinomas: association with ethnicity and CDKN2A promoter methylation

AIMS

It has been shown previously (by immunohistochemistry) that gastric adenocarcinomas harbouring Epstein-Barr virus (EBV) frequently lose p16 protein. This study aimed to examine the mechanisms of inactivation of the CDKN2A gene and correlate the results with clinicopathological features.

METHODS

Methylation specific polymerase chain reaction was used to detect CDKN2A promoter methylation in gastric adenocarcinomas from American patients. In addition, immunohistochemistry was used to detect the loss of the p16 protein and in situ hybridisation was used to detect the presence of EBV. The tumours were also analysed for the presence of microsatellite instability.

RESULTS

Eleven (10%) of 107 tumours harboured EBV in the malignant cells. In gastric cancers without EBV, 32% exhibited CDKN2A promoter methylation and 26% had p16 protein loss. In contrast, 91% of the tumours containing EBV had CDKN2A promoter methylation (p = 0.0003) and 90% showed p16 protein loss (p = 0.0001). The presence of EBV was also associated with male sex (p = 0.03) and was more common in tumours from Texas Hispanics than from non-Hispanic whites or African-Americans (p = 0.01). EBV was not associated with microsatellite instability, histological subtype, stage, or grade of the tumour, or age or survival time of the patient.

CONCLUSIONS

The presence of EBV in gastric adenocarcinomas is strongly associated with CDKN2A inactivation by promoter methylation. In addition, these findings suggest that there are ethnic differences in tumour virology and pathogenesis.

Differences in EBNA2 and LMP-1 carboxy terminal region sequences of Epstein-Barr virus type A between the tumors in a multiple cancer patient

Using PCR, type A Epstein-Barr virus (EBV) infection was demonstrated in a squamous cell carcinoma of the maxilla (in a 52-year-old man) and the tongue of the same patient 18 years later (at the age of 70). Furthermore, at the age of 72, this patient developed an EBV-infected anaplastic large cell lymphoma. Analysis of the terminal regions of the EBV genome revealed a monoclonal proliferation of EBV-infected lymphoma cells. However, sequence analysis of the EBV revealed a slight difference in the EBNA2 regions between the virus-infected lymphoma and the squamous cell carcinomas. The mutations at 48991 (G-->T) and 48998 (C-->A) were demonstrated in the lymphoma. Although the squamous cell carcinoma of the tongue occurred after an interval of 18 years, the mutation site in the carcinomas was the same, 49137 (A-->G), as compared with B95-8 strain EBV EBNA2. The mutations at 48991 and at 49137 were associated with amino acid changes, Arg-->Met and Thr-->Ala, respectively, but the alteration at 48998 was a silent mutation. Thirty-bp deletion in the LMP-1 carboxy terminal region was demonstrated in the virus-infected lymphoma, but not in the squamous cell carcinomas. On the other hand, HTLV-1 proviral DNA (tax, gag and env) was not detected in the lymphoma, nor was HPV demonstrated in the squamous cell carcinomas, although Okinawa is known as an HTLV-1 and HPV prevalence region. The T-cell receptor beta gene rearrangement was demonstrated in the lymphoma, but the t(2;5) fusion transcript was not detected using PCR. Cytogenetic analysis of the lymphoma cells showed a complex hypertriploid karyotype with 76XY. The type A EBV infection might play a role in the carcinogenesis of the tumors of our patient. Interestingly, the infected virus genome sequences, the EBNA2 and LMP-1 regions, which were closely associated with carcinogenesis in the squamous cell carcinomas and the lymphoma, showed slight differences.

Epstein-Barr virus infection and human malignancies

The Epstein-Barr virus (EBV) is a herpes virus which establishes a life-long persistent infection in over 90% of the human adult population world-wide. Based on its association with a variety of lymphoid and epithelial malignancies, EBV has been classified as a group 1 carcinogen by the International Agency for Research on Cancer. In this article we discuss the evidence supporting an aetiological role for EBV in the pathogenesis of human tumours. The biology of EBV infection will be described with special emphasis on viral transforming gene products. A brief survey of EBV-associated tumours is followed by a discussion of specific problems. Evidence is presented which suggests that failures of the EBV-specific immunity may play a role in the pathogenesis of EBV-associated tumours also in patients without clinically manifest immunodeficiencies. Finally, the timing of EBV infection in the pathogenesis of virus-associated malignancies is discussed. There is good evidence that EBV infection precedes expansion of the malignant cell populations in some virus-associated tumours. However, this is clearly not always the case and for some of these tumours there are indications that clonal genetic alterations may occur prior to EBV infection. Thus, whilst there is good evidence to suggest that EBV is a human carcinogen, its precise role(s) in the development of virus-associated human tumours requires clarification.

Expression of cytokine and chemokine genes in Epstein-Barr virus-associated nasopharyngeal carcinoma: comparison with Hodgkin's disease

Nasopharyngeal carcinoma (NPC) and Hodgkin's disease (HD) are characterized by their association with Epstein-Barr virus (EBV) and the presence of an intense lymphoid stroma, consisting of T lymphocytes and other reactive cells. In both entities, the tumour cells express viral proteins known to provide target epitopes for cytotoxic T-cells (CTLs), yet in vivo, the tumour cells appear to escape CTL recognition. A comparative in situ hybridization study of cytokine and chemokine gene expression in NPC and HD has been undertaken, focusing on cytokines which are known to be inducible by EBV in vitro. Hodgkin and Reed-Sternberg (HRS) cells expressed interleukin (IL)-6, IL-8, and IL-10, and the thymus and activation regulated chemokine (TARC) in 15/22, 0/22, 5/22, and 16/21 cases, respectively. In NPC, the epithelial tumour cells showed expression of IL-6 in 3/43 cases and of IL-8 in 2/40 cases. There was no detectable expression of IL-10 and TARC in these cases. These data confirm that HRS cells frequently express cytokine and chemokine genes and suggest that this may enable HRS cells to modulate the immune response in their microenvironment and to escape CTL detection. In contrast, NPC tumour cells show only rare expression of IL-6 and IL-8 and no detectable expression of IL-10 and TARC. Thus, the results suggest that the mechanisms employed by the EBV-positive tumour cells to escape immune recognition and destruction differ between HD and NPC.

Epstein-Barr virus infection and human malignancies

The Epstein-Barr virus (EBV) is a herpes virus which establishes a life-long persistent infection in over 90% of the human adult population world-wide. Based on its association with a variety of lymphoid and epithelial malignancies, EBV has been classified as a group 1 carcinogen by the International Agency for Research on Cancer. In this article we discuss the evidence supporting an aetiological role for EBV in the pathogenesis of human tumours. The biology of EBV infection will be described with special emphasis on viral transforming gene products. A brief survey of EBV-associated tumours is followed by a discussion of specific problems. Evidence is presented which suggests that failures of the EBV-specific immunity may play a role in the pathogenesis of EBV-associated tumours also in patients without clinically manifest immunodeficiencies. Finally, the timing of EBV infection in the pathogenesis of virus-associated malignancies is discussed. There is good evidence that EBV infection precedes expansion of the malignant cell populations in some virus-associated tumours. However, this is clearly not always the case and for some of these tumours there are indications that clonal genetic alterations may occur prior to EBV infection. Thus, whilst there is good evidence to suggest that EBV is a human carcinogen, its precise role(s) in the development of virus-associated human tumours requires clarification.

Epstein-Barr virus infection and human malignancies

The Epstein-Barr virus (EBV) is a herpes virus which establishes a life-long persistent infection in over 90% of the human adult population world-wide. Based on its association with a variety of lymphoid and epithelial malignancies, EBV has been classified as a group 1 carcinogen by the International Agency for Research on Cancer. In this article we discuss the evidence supporting an aetiological role for EBV in the pathogenesis of human tumours. The biology of EBV infection will be described with special emphasis on viral transforming gene products. A brief survey of EBV-associated tumours is followed by a discussion of specific problems. Evidence is presented which suggests that failures of the EBV-specific immunity may play a role in the pathogenesis of EBV-associated tumours also in patients without clinically manifest immunodeficiencies. Finally, the timing of EBV infection in the pathogenesis of virus-associated malignancies is discussed. There is good evidence that EBV infection precedes expansion of the malignant cell populations in some virus-associated tumours. However, this is clearly not always the case and for some of these tumours there are indications that clonal genetic alterations may occur prior to EBV infection. Thus, whilst there is good evidence to suggest that EBV is a human carcinogen, its precise role(s) in the development of virus-associated human tumours requires clarification.

Mutagen sensitivity of nasopharyngeal cancer patients

Primary nasopharyngeal carcinomas (NPCs) may be of various types, including squamous cell carcinomas, undifferentiated carcinomas, and lymphoepitheliomas. Tumor initiation has been linked to the Epstein-Barr virus and, in some geographical regions, to alimentary factors. Possible hereditary components for the appearance of NPCs have not yet been clearly identified. In this study, genetic sensitivity to the genotoxic effects of carcinogenic xenobiotics as an endogenous risk factor of tumor initiation was investigated. The single cell microgel electrophoresis assay was used to quantify chemically-induced DNA damage in lymphocytes of 30 NPC patients and 30 non-tumor donors. The xenobiotics investigated were N'-nitrosodiethylamine, sodium dichromate, and nickel sulphate, with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and dimethyl sulfoxide (DMSO) as positive and negative controls, respectively. The extent of DNA migration in the solvent control cultures was not significantly different between the two groups (1.2+/-0.5 mean Olive tail moment and standard deviation of 30 individuals for NPC patients; 1.1+/-0.4 for non-tumor donors). With constant exposure and electrophoretic conditions, genotoxic effects of varying degrees were induced by the different xenobiotics in tumor and non-tumor patients (nickel sulphate: 7.1+/-2.5 for NPC patients and 5.9+/-1.6 for non-tumor donors; sodium dichromate: 18.1+/-5.3 for NPC patients and 16.2+/-5.4 for non-tumor donors; MNNG: 47.8+/-13.3 for NPC patients and 52.7+/-13.6 for non-tumor donors). Only N'-nitrosodiethylamine proved to induce significantly more DNA migration in lymphocytes of tumor patients (9.8+/-3.1) as compared to non-tumor patients (8.2+/-2.3). Although for sodium dichromate the degree of DNA migration did not significantly differ, variability in migration patterns proved to be lower in the tumor group. Mutagen sensitivity of NPC patients was shown to be elevated for a selected xenobiotic, whereas a general elevation of DNA fragility was not present. Further studies on mutagen sensitivity as an endogenous risk factor influencing the susceptibility of patients at the time of first diagnosis of nasopharyngeal carcinomas are warranted.

Nasopharyngeal carcinoma: clinical assessment and review of 176 cases

OBJECTIVE

The objective of this study was to delineate salient disease characteristics and to determine factors associated with survival in a series of patients with nasopharyngeal carcinoma (NPC).

STUDY DESIGN

To address our research objective, we used a retrospective cohort study design and a sample of patients who presented for evaluation and management of NPC. Demographic data, medical history, radiographic findings, staging, and histology were recorded. Treatment and follow-up information were ascertained. Survival data and descriptive statistics were calculated. Multivariate analyses identified risk factors associated with survival rates for all World Health Organization (WHO) types.

RESULTS

The sample comprised 123 men and 53 women (n = 176) of which 70% were white and 23% were Asian. A neck mass was the initial symptom in 49% of patients. In 99% of cases, radiation therapy was the primary treatment mode. WHO types 1 and 3 were most common. Overall 5-year disease-free survival rate was 45.5%. Age, use of tobacco or ethanol, and number of presenting symptoms were statistically associated with decreased survival rate in WHO 1 (squamous cell) tumors. Male gender and total number of presenting symptoms were associated with decreased survival rate for WHO 2 and 3 (nonkeratinizing or undifferentiated) tumors.

CONCLUSIONS

Being attuned to the presenting signs of NPC may lead to a more expedient diagnosis. The differing risk factors associated with WHO 1 tumors become clear in this predominantly white population.

Epstein-Barr virus infection in the pathogenesis of nasopharyngeal carcinoma

The association of nasopharyngeal carcinoma (NPC) with the Epstein-Barr virus (EBV) was firmly established as early as 1973. Nevertheless, the role for the virus in the pathogenesis of NPC is still controversial. In this article, the evidence implicating EBV in the development of NPC is reviewed, focusing on the cellular site of EBV persistence, the association of the virus with different NPC histotypes, the tumour cell phenotype in the context of viral latent gene expression, and the possible role of the lymphoid stroma.

Occupational exposure to formaldehyde and wood dust and nasopharyngeal carcinoma

OBJECTIVES

To investigate whether occupational exposures to formaldehyde and wood dust increase the risk of nasopharyngeal cancer (NPC).

METHODS

A multicentered, population based case-control study was carried out at five cancer registries in the United States participating in the National Cancer Institute's SEER program. Cases (n=196) with a newly diagnosed NPC between 1987 and 1993, and controls (n=244) selected over the same period from the general population through random digit dialing participated in structured telephone interviews which inquired about suspected risk factors for the disease, including a lifetime history of occupational and chemical exposure. Histological type of cancer was abstracted from clinical records of the registries. Potential exposure to formaldehyde and wood dust was assessed on a job by job basis by experienced industrial hygienists who were blinded as to case or control status.

RESULTS

For formaldehyde, after adjusting for cigarette use, race, and other risk factors, a trend of increasing risk of squamous and unspecified epithelial carcinomas was found for increasing duration (p=0.014) and cumulative exposure (p=0.033) but not for maximum exposure concentration. The odds ratio (OR) for people cumulatively exposed to >1.10 ppm-years was 3.0 (95% confidence interval (95% CI) 1.3 to 6.6) compared with those considered unexposed. In analyses limited to jobs considered definitely exposed, these trends became stronger. The associations were most evident among cigarette smokers. By contrast, there was no association between potential exposure to formaldehyde and undifferentiated and non-keratinising carcinomas. There was little evidence that exposure to wood dust increased risk of NPC, as modest crude associations essentially disappeared after control for potential exposure to formaldehyde.

CONCLUSIONS

These results support the hypothesis that occupational exposure to formaldehyde, but not wood dust, increases risk of NPC. This association seems to be specific to squamous cell carcinomas. Established cohorts of workers exposed to formaldehyde and wood dust should continue to be monitored for NPC and other respiratory cancers. Future studies of NPC should take into account histological type in assessing risk from environmental and host factors.

Presentation and epidemiology of nasopharyngeal carcinoma in Jordan

A retrospective study, which highlights some of the aspects of nasopharyngeal carcinoma (NPC) as seen in a large hospital for 20 years in Jordan, was performed. Collected data showed that NPC accounted for one per cent of all malignant tumours during the period. The present series showed an age range from six to 89 years old with a mean of 39.5 years. There was a bimodal peak at presentation at 16 to 20 and 46 to 50 years. A high incidence of childhood NPC was also noticed (two per cent of all childhood malignant tumours). The difficulty in early diagnosis urges for better awareness of the tumour especially among general practitioners. The tumour is still detected at an advanced stage with 34 per cent metastasis most frequently to bone. The study stresses the importance of full ENT examination in cases of persistent middle ear disease, recurrent or persistent nasal symptoms or headache, or neck swelling; and routine bone scanning for all cases with NPC. There is a need for prospective studies of the causal relationship of NPC to environmental factors including Epstein-Barr (EB) virus as well as occupational and domestic hazards.

Epstein-Barr virus expression within keratinizing nasopharyngeal carcinoma

Three stages of maturation can be seen in keratinizing nasopharyngeal carcinomas. These stages are similar morphologically to basal cells, intermediate and superficial squamous cells seen in normal squamous epithelium. Taking advantage of such a diverse tumour cell population, 10 keratinizing nasopharyngeal carcinoma (NPC) were examined by in situ hybridization for the presence of latent Epstein-Barr Virus (EBV) using EBV encoded RNAs (EBERs) and by immunohistology for the presence of EBV early antigen-diffuse (EA-D) and the 350/220 kd membrane glycoprotein of the EBV. The basal cell-like tumour cells are mainly infected latently with the virus; viral replication was found in isolated intermediate squamous cells, whilst superficial squamous cells are largely depleted of all the viral markers. We used a control series of nonkeratinizing nasopharyngeal carcinomas composed of undifferentiated and poorly differentiated tumour cells and EBV latency was present in these tumours. Viral replication was detected by RT-PCR, in the undifferentiated tumours but viral replication was not seen by immunohistology. The possible relationship between EBV life cycle in these tumours and tumour cell differentiation is discussed in the light of these findings.