Epstein-Barr virus genotypes associated with nasopharyngeal carcinoma in southern China

Genotypic analysis of Epstein-Barr virus isolates associated with nasopharyngeal carcinoma in Chinese immigrants to the United States

EBV genotypes of first- and second-generation Chinese diagnosed with nasopharyngeal carcinoma in the United States were analyzed by PCR techniques. Previous studies showed a geographical distribution of genotypically distinct sub-types of EBV. Viruses detected at a higher frequency among Chinese NPC patients (Cf) were distinguished from those found in the majority of Caucasian NPC patients (DF) in the United States by polymorphisms in the BamHI F and I regions. Exploiting this distinction, we analyzed the biopsies of Chinese immigrants in the United States for their C/D and F/f genotypes to evaluate the importance of retention of the Cf virus among Chinese NPC patients in a geographical area where the DF virus prevails. This study shows that approximately 45.5 to 50% of first- and second-generation Chinese NPC patients in California harbor the Cf virus, which is present in only 8% of Caucasian NPC patients in California. It is interesting that, while only 48% of the viral isolates from immigrant Chinese to California harbor the "f" variant, 96% harbor the type-C viruses.

Epstein-Barr virus genotypes in NPC biopsies from north Africa

The genotypes of Epstein-Barr virus (EBV) were investigated in North African nasopharyngeal carcinoma (NPC) biopsies, nasopharyngeal chronic inflammation (NCI) biopsies, and saliva of healthy individuals from Algeria and Tunisia where there is an intermediate incidence of NPC. The prevalence of A-type virus in NPC, NCI biopsies and saliva of healthy individuals was found in these regions by means of a PCR assay. Restriction enzyme polymorphism analysis by Southern blotting revealed that all North African EBV variants have a conserved restriction site on BamHI W'-I' and XhoI LMP gene. No additional BamHI enzyme site on the BamHI-F fragment was observed; however, the presence of an extra BamHI site on the BamHI-H fragment giving 2 HI and H2 fragment-like EBV M-ABA strains was found. All EBV strains present in NPC or NCI biopsies at all ages were homogeneous in these polymorphisms and no correlation was observed between the EBV genotypes from NPC patients and clinical stages of the cancer. These characteristics revealed a significant difference between the EBV variants common in Chinese NPC and those in North African NPC.

Identification of integrated Epstein-Barr virus in nasopharyngeal carcinoma using pulse field gel electrophoresis

Integrated Epstein-Barr virus (EBV) was found in 4 of 17 pathologically diagnosed, EBV-positive nasopharyngeal carcinoma (NPC) biopsy samples using pulse field gel electrophoresis (PFGE). The analyses were carried out after digestion of biopsy DNA with rare restriction enzymes such as PacI, which does not cleave EBV due to the absence of the recognition sequence, and ClaI. Employing this technique, EBV integration in IB4, through EcoI, and Namalwa through the terminal repeats, was confirmed. We also established that integration of EBV in AW Ramos was through the terminal repeats. The Raji cell line was also found to harbour integrated virus in addition to episomal DNA. However, the site of integration could not be confirmed, since as the Raji DNA appeared to be heavily methylated and could not be cleaved with CPG rare cutters. As in the Raji cell line, the DNA of EBV in nasopharyngeal-carcinoma (NPC) biopsies also appeared to be methylated.

Nasopharyngeal carcinoma: genetic changes, Epstein-Barr virus infection, or both. A clinical and molecular study of 36 patients

BACKGROUND

The pathogenesis of nasopharyngeal carcinoma has been under intense investigation, especially of its peculiar predominance in southern China. The authors previously reported consistent loss of genetic material on the short arm of chromosome 3 in a few nasopharyngeal carcinoma cases. In this study, the authors examined the genetic changes as well as the presence of Epstein-Barr virus (EBV) genome on 36 nasopharyngeal carcinoma primary biopsy specimens of the undifferentiated type and the correlation of the findings to patients' clinical status.

METHODS

The authors examined the DNA from tumor tissue and from matched blood leukocytes of 36 patients who suffered from nasopharyngeal carcinoma by the restriction fragment length polymorphism analysis. The genotyping for EBV was carried out by polymerase chain reaction using primers complementary to both types of EBV and probes specific to EBNA-2A (EBV-A) or EBNA-2B (EBV-B).

RESULTS

A consistent deletion at two specific locus of the short arm of chromosome 3 was observed in all informative cases. The authors also found that EBV genome, especially type A, was present in 35 of 36 cases. In the remaining one case, EBV-B was detected.

CONCLUSIONS

As the same tumor tissue was used for both genetic and viral studies in each case, the results may represent sequential genetic lesions in the pathogenesis and/or summation of genetic events. Moreover, 7 of 32 informative tumors were from patients of early staging (Stages I and II), which suggests the genetic changes may occur in the early development of nasopharyngeal carcinoma. Difference in allele frequency in specific locus was also noted between Asian and white patients for the first time.

Epstein-Barr virus (EBV) gene expression in EBV-positive peripheral T-cell lymphomas

Epstein-Barr virus (EBV) DNA has been detected in peripheral T-cell lymphomas. In this study, analysis of the EBV termini indicated that the infection was clonal and nonpermissive. Analysis of viral expression detected the processed, spliced mRNAs representing EBNA1, LMP1, LMP2, and BamHI A transcripts in all EBV-positive peripheral T-cell lymphomas. The LMP1 protein was detected by immunofluorescence in a single specimen. In contrast, neither the EBNA2 protein nor the spliced EBNA2 mRNA were detected. These data indicate that EBV-infected T-cell lymphomas are clonal expansions of a single EBV-infected cell with a pattern of gene expression which is distinct from that detected in Burkitt's lymphomas or posttransplant lymphomas but similar to viral expression in nasopharyngeal carcinomas.

Familial clusters of nasopharyngeal carcinoma and salivary gland carcinomas in Greenland natives

BACKGROUND

Nasopharyngeal carcinoma (NPC) and anaplastic salivary gland carcinoma (SGC), both associated with Epstein-Barr virus (EBV), are common among Inuit from Greenland, Canada, and Alaska. Because immigrant studies have shown that factors acting early in life are important for the development of NPC, the authors interviewed new patients in Greenland with either NPC or SGC about their lifestyles during childhood and additional cases in their families.

METHODS

On admission, new patients from Greenland with either NPC or SGC were interviewed about childhood life-style, family size, and other cases of NPC or SGC within the family. Additional cases were confirmed by review of the medical records concerning these patients.

RESULTS

During the 11 years from 1980 through 1990, 17 of 63 (27%) cases in Greenland were found in familial clusters among first-degree relatives. There were no differences in the life-styles of multiple-case families and single-case families.

CONCLUSIONS

The high rate of familial clusters among natives of Greenland is of interest because EBV is believed to play a role in the origin of these two diseases similar to that of Marek disease in neurolymphomatosis of chickens. Therefore, the familial clustering of NPC and SGC may indicate that an enhanced oncogenic potential of an EBV strain may occur more frequently in Greenland than in other parts of the world.

Emergence of non-major-histocompatibility-complex-restricted lytic CD8+ cells in the blood of nasopharyngeal carcinoma patients

A large body of evidence has suggested that the Epstein-Barr virus (EBV) is strongly associated with undifferentiated nasopharyngeal carcinoma. Immunologically, this neoplasia is characterized by the absence of anti-EBV circulating cytotoxic T lymphocytes (CTL), despite a high number of peripheral activated CD8+ cells, as previously determined in our laboratory. In order to determine whether the absence of anti-EBV CTL is related to a reduced number of circulating anti-EBV effector cells, we attempted to expand these hypothetical specific T cells by induction of proliferation with recombinant interleukin-2 (rIL-2), in the, absence of any stimulator cells. Optimal conditions for stimulation of peripheral blood lymphocytes (PBL) of nasopharyngeal patients were obtained with 100 U/ml rIL-2 during 10 days of culture. PBL treated with rIL-2 induced a selective expansion of CD8+ cells and generated a potent cytotoxicity towards autologous or HLA-compatible lymphoblastoid cell lines, used as target cells in a chromium-release thest. However, this cytolysis was non-MHC-restricted, since, the monoclonal antibodies anti-(HLA class I) and anti-(HLA class II) were inefficient in inhibiting this cytotoxicity. Interestingly, purified CD8+ cells acquired the capacity for non-MHC-restricted cytolysis.

Genotypic analysis of Epstein-Barr virus associated with nasopharyngeal carcinoma of Japanese patients

Types and certain genetic markers were studied for Epstein-Barr virus present in 10 specimens of nasopharyngeal carcinoma (NPC) from Japanese patients. The type 1 virus was predominant in our NPC specimens, as in the general Japanese population, and the type 2 virus was found only in one NPC specimen. The type C variant, which lacks the BamHI site between the BamHI-W1* and -I1* regions, appeared to be common among Japanese strains as in those in Southern China. The type f variant which has an extra BamHI site in the BamHI-F region and has been shown to be strongly associated with NPC in Southern China was found in only one NPC specimen. This virus strain was also the only type 2 virus among our specimens. The present study, therefore, does not show any specific association of the type f variant with NPC in Japan.

Analysis of Epstein-Barr virus in localized nasopharyngeal carcinoma tumors

BACKGROUND

An f variant of Epstein-Barr virus (EBV) appears associated with nasopharyngeal carcinoma (NPC) in Southern Chinese. Early diagnosis of the tumor allows the detection of some localized tumors.

METHODS

A polymerase chain reaction (PCR) assay for genotyping EBV was used to evaluate the presence of the virus in NPC biopsies of local tumors of eight Chinese patients.

RESULTS

The f variant was detected in the nasopharynx of seven of eight patients. The f variant was present in equal frequency in the "normal" and tumor regions.

CONCLUSIONS

Examination of localized NPC tumors by the PCR genotyping assay revealed EBV was present on the tumor side of the nasopharynx in greater quantities than the "normal" side in seven of eight patients studied. Concurrent infection with both the prototype F and f variant was observed in two of the eight patients investigated.

EBV strain variation: geographical distribution and relation to disease state

The strains of Epstein-Barr virus (EBV) were characterized in epithelial and lymphoid malignancies from geographic regions with high or low incidence. The predominant strains in nasopharyngeal carcinoma (NPC) from regions with elevated incidence were EBV type 1 in southeast Asia and Mediterranean Africa. In Alaskan Eskimos, a distinct variant of EBV type 2 was found in NPC and carcinoma of the parotid gland. This strain contained polymorphisms characteristic of the Asian EBV type 1. The strains prevalent in southeast Asia and Mediterranean Africa were also found in NPC which developed in caucasian Americans. These variants were not detected in lymphomas which developed in central Africa, Mediterranean Africa, or continental United States. These results suggest that distinct EBV strains predominate in geographic areas with elevated incidence of NPC. The detection of these distinct strains in epithelial tumors from areas of low incidence may reflect an epithelial cell tropism or pathogenicity.

Infectious agents in the etiology of esophageal cancer

Extensive epidemiological and experimental studies have suggested that some chemical agents, nutritional deficiencies, and physical factors are associated with the development of esophageal cancer (EC). Recent evidence also suggests an etiologic role of certain microorganisms in esophageal carcinogenesis either by producing carcinogens or promotors or by acting directly on the host cells. The mutagenic and carcinogenic effects of several fungi and bacteria isolated from the grains and foodstuffs in high-risk areas have been shown by in vitro and in vivo studies. Certain viruses, e.g., human papillomavirus, herpes simplex virus, cytomegalovirus, and Epstein-Barr virus, have been implicated in the pathogenesis of a variety of human cancers, and all of them are known to produce tumors in animals and cell transformation in vitro. These viruses also have been shown to infect the esophageal epithelium. Therefore, although many of the key issues of their mechanisms of action are unclear as yet, they should be considered potential etiologic agents of EC. The present review summarizes the data available on the etiology of EC, emphasizing the current evidence implicating an etiologic role of microorganisms in the pathogenesis of this malignancy.

Direct detection of Epstein-Barr virus in peripheral blood and comparison of Epstein-Barr virus genotypes present in direct specimens and lymphoblastoid cell lines established from nasopharyngeal carcinoma patients and healthy carriers in Hong Kong

By means of a PCR assay, EBV was demonstrated directly in peripheral blood of previously infected individuals. The virus was detected in approximately 80% of specimens from EBV-seropositive individuals, but not in cord-blood lymphocytes by this method. When virus present in peripheral blood was compared to that observed directly in NPC biopsies or throat washings, it was distinct from that seen in biopsies in 4/15 cases (27%) and from that seen in throat washes in 1/22 cases (5%). The throat-wash virus differed from the biopsy virus in 3/20 cases (15%). The prototype F virus was found in 7/10 LCLs (70%) established from NPC patients' peripheral blood, but was only detected in 2/9 specimens (22%) directly analyzed by the PCR assay. This finding suggests selective isolation of prototype F EBV in spontaneous LCLs established from NPC patients.

Expression of beta-2-microglobulin by nasopharyngeal carcinoma

Serum beta-2-microglobulin (beta 2M) levels of 274 Chinese patients with different stages of nasopharyngeal carcinoma at presentation and that of 35 patients who developed distant metastases post-treatment were assayed. beta 2M level was found to increase with advancing stage of disease, with statistically significant differences among early-stage, advanced-stage, and metastatic disease. Elevated pre-treatment beta 2M levels were expressed more frequently by tumours with lower degree of histological differentiation. The sensitivity of serum beta 2M for diagnosis of nasopharyngeal carcinoma, however, is low.

Detection of distinct Epstein-Barr virus genotypes in NPC biopsies from southern Chinese and Caucasians

Using the polymerase chain reaction (PCR) to analyze paraffin sections from 12 Caucasian patients, we detected only the prototype F Epstein-Barr virus (EBV) in 10 specimens from patients with nasopharyngeal carcinoma (NPC). This is in contrast to the higher frequency of association of "f" variants in NPC biopsies from Southern Chinese. The results of EBV genotyping support evidence that the EBV strains associated with NPC in the Southern Chinese population differ from those found in Caucasians. DNA sequencing confirmed that a simple point mutation is responsible for the restriction-fragment-length polymorphism which distinguishes the prototype F virus from the "f" variant.

Detection and prevalence of the "f" variant of Epstein-Barr virus in southern China

The "f" variant of Epstein-Barr virus (EBV) may have an association with the development and/or maintenance of nasopharyngeal carcinoma (NPC) among Southern Chinese. This variant is detected at a higher frequency among individuals with elevated IgA antibody levels against EBV capsid antigen who have no detectable NPC and in NPC patients as compared to healthy individuals or patients who are in remission for NPC for over 3 years. Conversion or replacement of the f variant by the prototype BamHI F virus usually occurs by 3 to 4 years after radiotherapy. By 5 years post-therapy the majority of people in remission for NPC no longer harbor the f variant in their oropharynx. Eradication of this f variant, however, does not appear essential for maintenance of a disease-free state since several patients harboring this variant were in remission for NPC for up to 21 years. The virus strain detected directly in the nasopharynx is not always identical to that seen in the oropharynx. Dual infection was commonly observed in throat washings of NPC patients although the biopsy from tumors harbored unique strains of EBV.

An Epstein-Barr virus-producer line Akata: establishment of the cell line and analysis of viral DNA

An Epstein-Barr virus (EBV)-producer line, designated Akata, was established from a Japanese patient with Burkitt's lymphoma. The Akata line possessed the Burkitt's-type chromosome translocation, t(8q- ; 14q+), and was derived from the tumor cell. Akata cells produced a large quantity of transforming virus upon treatment of cells with anti-immunoglobulin antibodies (Takada, 1984). Southern blot analysis of viral DNA indicated that the Akata EBV is nondefective and more representative of wild-type viruses. Akata cells should be useful as a source of EBV.