Detection of Epstein-Barr viral DNA internal repeats in the nasopharyngeal mucosa of Chinese with IgA/EBV-specific antibodies

Epstein-Barr virus facilitates the malignant potential of immortalized epithelial cells: from latent genome to viral production and maintenance

Epstein-Barr virus (EBV) is closely associated with several malignancies, including nasopharyngeal carcinoma. To investigate the EBV activity in tumor development, we tried to establish a malignant model of EBV-infected cells in nude mice. On the basis of the Maxi-EBV system, a human embryonic kidney epithelial cell line (293) with a low malignant potential was used for a stable EBV genome infection. The derived cell line, termed 293-EBV, exhibited obvious morphological transformation and significantly increased growth ability, with the cell cycle redistributed. The clonability and tumorigenicity were also substantially accelerated. In 293-EBV cells, the expression level of the transcription factor NF-kappaB and JNK2 were upregulated. The result suggested that latent membrane protein 1 (LMP1) was an important viral protein responsible for the enhanced malignant potential. Matured and budding virus particles were observed in tumor tissues, confirming the spontaneous reactivation of EBV from latent genome to lytic cycle at the site of tumor development. Primary culture of tumor tissues showed two patterns about the EBV maintenance or not in newly grown cells, and this was dependent on the thickness of the planted tissues. Moreover, the tumor cells lost EBV genome easily when subcultured at low density. Our findings revealed the cell-to-cell contact mechanism, which was required for the EBV maintenance in the tumor cells during the expansion of EBV-infected cells. This mechanism might give an explanation to the phenomenon that EBV genome in epithelial tumor cells becomes easily lost during subculture in vitro. Our results provided further evidence of a function for EBV in the etiology of tumor development.

Cancer trends in China

Cancer is the leading death cause in urban China and the second one in rural China. Lung cancer is the most common cancer, followed by stomach cancer, liver cancer, esophageal cancer and colorectal cancer. Cancer Control Programs in China focus on prevention, early diagnosis and treatment. The prevention program includes an anti-smoking campaign and immunization against hepatitis B for infants and children under the age of 15. Screening for breast and cervix cancers is among efforts for the early detection and treatment. Public education and the promotion of healthy lifestyles have been actively carried out.

Improved Accuracy of Detection of Nasopharyngeal Carcinoma by Combined Application of Circulating Epstein–Barr Virus DNA and Anti-Epstein–Barr Viral Capsid Antigen IgA Antibody

Background: Circulating Epstein–Barr viral (EBV) DNA and anti-EBV capsid antigen IgA (IgA VCA) represent two of the most sensitive peripheral blood markers of nasopharyngeal carcinoma (NPC), but direct comparative studies of these two markers are lacking.

Methods: The sensitivities and specificities of IgA-VCA and EBV DNA for diagnosis of NPC were determined in 139 new cases of NPC and 178 healthy individuals, respectively. EBV DNA was also assessed in 36 healthy family members identified as having false-positive IgA-VCA results at a screening clinic. EBV DNA was measured by a real-time quantitative PCR assay with a detection limit of 60 copies/mL. IgA-VCA was measured by semiquantitative indirect immunofluorescent method; a titer ≥1/10 was taken as positive.

Results: The sensitivities of EBV DNA and IgA-VCA for diagnosis of NPC were 95% (95% confidence interval, 91–98%) and 81% (73–87%), respectively. The combined marker panel had an overall sensitivity (positive result by either marker) of 99%. The concentrations of both markers showed dependence on cancer stage. The specificities of EBV DNA and IgA-VCA were 98% (96–99%) and 96% (91–98%), respectively. Among 36 healthy family members with false-positive IgA-VCA results, three-fourths had undetectable EBV DNA, whereas the others had increased EBV DNA concentrations that were significantly lower than in NPC patients.

Conclusions: For diagnosis of NPC, EBV DNA identifies almost all false-negative IgA-VCA cases and gives a 99% diagnostic sensitivity when combined with IgA-VCA. In the screening setting, EBV DNA identifies three-fourths of false-positive IgA-VCA cases. The selective application of EBV DNA in an IgA-VCA-based screening protocol could improve screening accuracy with only moderate increases in cost.

Entry of viruses through the epithelial barrier: pathogenic trickery

Mucosal surfaces--such as the lining of the gut or the reproductive tract--are the main point of entry for viruses into the body. As such, almost all viruses interact with epithelial cells, and make use of the normal epithelial signalling and trafficking pathways of the host cell. In addition to protein receptors, carbohydrate chains of proteoglycans and epithelial-membrane glycosphingolipids have emerged as a new class of receptors for viral attachment to the host cell.

Detection of Epstein-Barr Virus DNA in well and poorly differentiated nasopharyngeal carcinoma cell lines

Undifferentiated and poorly differentiated nasopharyngeal carcinoma (NPC) were known to be tightly associated with Epstein-Barr Virus (EBV). Its association with well differentiated NPC was also reported. In the present study, the presence of EBV was investigated by nucleic acid hybridization, Polymerase Chain Reaction (PCR), Immunoblot and in situ hybridization in two well differentiated NPC cell lines (CNE-1 and HK-1) and two other poorly differentiated NPC cell line (CNE-2 and CNE-3). Contrary to previous report indicating the absence of EBV in these cell lines, EBV DNA and proteins were present in all cell lines. The detection of EBV became more easily when the investigation was carried out on the nude mice tumor induced by transplantation of each NPC epithelial cell line. The EBV latent membrane protein (LMP1) was found by in situ hybridization to be integrated partly in the chromosomal DNA of these cell lines. The observations indicate that EBV could persist for a long time in the carcinoma cells established directly from well and poorly differentiated tumor biopsies and from transplantable NPC tumor in nude mice.

Carcinoma of the nasopharynx. The significance of lymphocytic infiltration

From 1974 to 1985, 76 patients with nasopharyngeal carcinoma (NPC) received irradiation with curative intent and 14 with palliative intent in our department. Of the 76 patients, 59 presented with UICC stage IV. The 5-year actuarial survival rate was 41% and the relapse-free survival rate (RFS) 45%. The slides were reviewed according to the World Health Organization (WHO) histologic classification, also taking into account the degree of lymphocytic infiltration according to its Cologne modification. Undifferentiated carcinoma and non-keratinizing carcinoma had similar 5-year RFS (47 and 44% respectively). Patients with major lymphocytic infiltration in the tumor presented with younger median age, with smaller primary tumors and with more advanced neck disease than the other patients. There was, however, no obvious association between the degree of lymphatic infiltration in the tumor and the prognosis. Patients with major lymphocytic infiltration had a 5-year RFS of 44%, versus 49% for patients without such infiltration.

Rearranged Epstein-Barr virus genomes and clonal origin in nasopharyngeal carcinoma

Epstein-Barr virus (EBV) is known to be associated with two malignant diseases, nasopharyngeal carcinoma (NPC) and endemic Burkitt's lymphoma. In this study, the genomes of EBV in biopsy specimens from 4 NPC patients in Japan were analyzed using Southern blot hybridization. The NPC tissues of all examined cases contained rearranged EBV genomes whose BamHI H fragments were larger than those of prototype EBV genomes. One of them had a BamHI fragment containing contiguous sequences of BamHI Y and H. A single-sized EBV DNA terminus was observed in these NPC tissues, implying the evolution of the carcinoma from a single EBV-infected cell.

Epstein-Barr virus DNA in nasopharyngeal biopsies

The Epstein-Barr virus (EBV) has been closely associated with the undifferentiated form of nasopharyngeal carcinoma (NPC), which is particularly common in the high risk area in southeast China. We have examined 37 nasopharyngeal biopsies from patients within this high risk area, including 31 cases of undifferentiated NPC and 6 cases of patients with nasopharyngitis, for the presence of EBV DNA. We found that 26 of 31 biopsies from NPC patients were EBV DNA positive; 3 of the 6 biopsies from patients diagnosed with nasopharyngitis were also EBV DNA positive. Southern blot analysis of the DNAs obtained from the EBV genome positive biopsies, digested with EcoRI, showed that all preparations from the NPC tumors had only one band corresponding to the EcoRI A fragment when a BamHI W fragment was used as a probe. However, one tumor had an additional band with a molecular weight larger than EcoRI A. The presence of this novel band could indicate the integration of viral DNA into host cellular DNA. DNA from the same biopsies were restricted with BamHI and PstI restriction enzymes. The data obtained from these experiments suggest that the EBV genomes in both the NPC tumor biopsies and biopsies from nasopharyngitis patients obtained from an endemic area in South China may be similar to each other and to the B95-8 EBV isolate with respect to the BamHI Y region of the EBV genome. The data also demonstrate that infection of normal nasopharyngeal epithelial cells with EBV takes place in patients with nasopharyngitis.

Association of the Epstein-Barr virus with lymphoepithelioma of the thymus

A 30-year-old woman with the histologic diagnosis of lymphoepithelioma of the thymus is reported on. Investigation of Epstein-Barr serology showed evidence of infection, and Southern blot analysis showed the presence of the viral genome in the tumor specimen. The patient achieved complete remission after treatment with combination chemotherapy, autologous bone marrow transplant, and radiotherapy. These findings suggest that lymphoepithelioma of the thymus may have a viral pathogenesis similar to that of nasopharyngeal carcinoma.

The differentiated form of nasopharyngeal carcinoma contains Epstein-Barr virus DNA

Immunologic studies of Epstein-Barr virus (EBV) have implicated EBV in undifferentiated and partially differentiated, non-keratinizing nasopharyngeal carcinoma (NPC). Patients with the well-differentiated, keratinizing form of NPC have EBV serologic patterns similar to those of control populations. In addition, viral DNA has not been detected in the differentiated tumors using viral cRNA probes to DNA immobilized on filters. In this study we have tested for EBV DNA using recombinant DNA probes to Southern blots of DNA from 33 NPC specimens. The 24 undifferentiated and 4 partially differentiated specimens generally contained a relatively high number of EBV genome equivalents, while the 5 well-differentiated NPC all contained detectable EBV, but at low copy number. The viral DNA from one of the well-differentiated specimens was cloned into a cosmid vector. Five recombinant clones representing the fused viral termini were obtained, indicating the presence of episomal, intracellular DNA in the tumor. These findings indicate that all histologic subsets of NPC contain EBV DNA.

Epstein-Barr viral serology in nasopharyngeal carcinoma patients in the USSR and Cuba, and its value for differential diagnosis of the disease

Serological responses to Epstein-Barr virus (EBV)-associated antigens were studied in nasopharyngeal carcinoma (NPC) patients in 2 countries non-endemic for the disease: the USSR (77 cases) and Cuba (55 cases). Two age- and sex-matched control groups were available, one consisting of patients with other head-and-neck tumours (OHNT) (171 from the USSR and 56 from Cuba), and the other of normal individuals (blood donors) (83 from the USSR and 80 from Cuba). Unlike the control groups, NPC patients from both countries had high levels of IgG and IgA antibodies, similar to those seen in patients from endemic areas. The only difference between NPC patients in the USSR and those in Cuba was lower (2-2.5 fold) anti-VCA IgG and IgA antibody titres. Using one-factor and multi-factor statistical methods the diagnostic value of different titres of EBV-specific IgG and IgA antibodies and their combinations for NPC patients (in the USSR) was evaluated. It was found that with simple mathematical analysis of EBV-specific antibody titres a differential diagnosis of NPC could be made to a significance level of 90%. The data obtained demonstrated the importance and reliability of EBV serology in the diagnosis of NPC in areas of low incidence of the disease.

Replication of Epstein-Barr virus within the epithelial cells of oral "hairy" leukoplakia, an AIDS-associated lesion

We conducted a study to identify the viruses in tissue specimens of oral "hairy" leukoplakia, a lesion that is found in immunosuppressed male homosexuals and that is associated with the subsequent development of the acquired immunodeficiency syndrome. When stained for papillomavirus core antigen, 49 of 67 biopsy specimens (73 per cent) yielded positive results in epithelial-cell nuclei. Electron microscopy showed papillomavirus-like particles in all of 25 specimens, and the herpes-type virus described in a previous report was seen in 23 of the 25 specimens. Three specimens had both types of particle in the same individual epithelial cells. Immunofluorescence for herpes simplex virus, varicella-zoster virus, and cytomegalovirus gave negative results in all cases, but 19 of 20 specimens showed intense nuclear staining in epithelial cells for the viral capsid antigen of Epstein-Barr virus (EBV). DNA hybridization using EBV probes in Southern blots demonstrated EBV DNA in all of 13 specimens and found 200 or more viral DNA molecules per cellular genome in 11 of the 13. The whole EBV genome was also demonstrated in the specimens and found to be in linear virion form. We conclude that EBV replicates within the epithelial cells in hairy leukoplakia.

Persistent Epstein-Barr virus infection and a histiocytic sarcoma in a renal transplant recipient

Lymphomas occurring in renal transplant recipients are mostly large cell non-Hodgkin's lymphomas (B-cell-derived). A sarcoma with all morphologic, immunohistochemical, and ultrastructural characteristics of a tumor of the mononuclear phagocytic system (MPS) developed in a 23-year-old woman 1 year after renal transplantation. Anti-Epstein-Barr-virus antibody titers proved to be exceptionally high, even in pretransplant sera. Tumor-derived cells proved to be positive for Epstein-Barr nuclear antigen (EBNA), and hybridization showed multiple copies of Epstein-Barr virus (EBV)-DNA, suggesting a relationship between this tumor and EBV. More widespread use of immunochemical and histochemical diagnostic techniques might detect more cases, which, until now, have probably been diagnosed as B-cell-derived immunoblastic lymphomas.

Presence of EBV-DNA sequences in nasopharyngeal cells of individuals without IgA-VCA antibodies

Exfoliated nasopharyngeal (NP) cells from 62 normal Cantonese Chinese having IgA/VCA antibodies for more than a year and from 39 similar persons without IgA/VCA antibodies, were tested for the presence of EBV/DNA sequences by spot followed by blot hybridization tests, using the cloned internal repeat of B95-8 viral DNA as probe. Thirteen out of 62 specimens from IgA/VCA-positive (21%) and six out of 39 specimens (15.4%) from IgA/VCA-negative individuals were found to contain EBV/DNA sequences. Forty-six cases (20 IgA/VCA-positive and 26 IgA/VCA-negative) were followed a year later for EBV/DNA sequences and EBV serology. Half of the individuals having EBV/DNA sequences in their exfoliated NP cells in 1981 did not have detectable EBV sequences a year later, and to out of 15 negative individuals became EBV/DNA-positive. There was no obvious correlation between EBV/DNA detectability and EBV serology. (We conclude that the best marker for NPC risk remains the increasing IgA/VCA and/or EA antibody titers.