A 3q+ marker chromosome in EBV-carrying nasopharyngeal carcinomas

Epstein-Barr virus BALF3 mediates genomic instability and progressive malignancy in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a head and neck cancer prevalent throughout Southern China and Southeast Asia. Patient death following relapse after primary treatment remains all too common but the cause of NPC relapse is unclear. Clinical and epidemiological studies have revealed the high correlation among NPC development, Epstein-Barr virus (EBV) reactivation and host genomic instability. Previously, recurrent EBV reactivation was shown to cause massive genetic alterations and enhancement of tumor progression in NPC cells and these may be required for NPC relapse. Here, EBV BALF3 has the ability to induce micronuclei and DNA strand breaks. After recurrent expression of BALF3 in NPC cells, genomic copy number aberrations, determined by array-based comparative genomic hybridization, had accumulated to a significant extent and tumorigenic features, such as cell migration, cell invasion and spheroid formation, increased with the rounds of induction. In parallel experiments, cells after highly recurrent induction developed into larger tumor nodules than control cells when inoculated into NOD/SCID mice. Furthermore, RNA microarrays showed that differential expression of multiple cancer capability-related genes and oncogenes increased with recurrent BALF3 expression and these changes correlated with genetic aberrations. Therefore, EBV BALF3 is a potential factor that mediates the impact of EBV on NPC relapse.

Deciphering the molecular genetic basis of NPC through molecular, cytogenetic, and epigenetic approaches

Nasopharyngeal carcinoma (NPC) is consistently associated with EBV infection and prevalence in southern China and Southeast Asia. In addition to EBV, the development of NPC involves cumulative genetic and epigenetic changes influenced by predisposing genetic factors and environmental carcinogens. Over the past two decades, knowledge of genetic and epigenetic alterations of NPC has rapidly accumulated. Multiple chromosomal abnormalities (e.g. copy number changes on chromosomes 3p, 9p, 11q, 12p, and 14q), gene alterations (e.g. p16 deletion and LTBR amplification), and epigenetic changes (e.g. RASSF1A and TSLC1 methylation) have been identified by various genome-wide approaches, such as allelotyping, CGH, and microarray analysis. In this review, we will discuss the critical genetic events that contribute to the initiation and progression of NPC. Studies on the precancerous lesions and in vitro immortalized nasopharyngeal epithelial cell models provide important evidence for the involvement of genetic alterations and EBV infection in early development of this cancer. A hypothetical model describing the role of EBV latent infection and multiple genetic changes in NPC tumorigenesis is proposed.

The progress on genetic analysis of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a rare malignancy in most parts of the world, but is one of the most common cancers in Southeast Asia. Both genetic and environmental factors contribute to the tumorigenesis of NPC, most notably the consumption of certain salted food items and Epstein-Barr virus infection. This review will focus on the current progress of the genetic analysis of NPC (genetic susceptibilities and somatic alterations). We will review the current advances in genomic technologies and their shaping of the future direction of NPC research.

Molecular cytogenetic characterization of nasopharyngeal carcinoma cell lines and xenografts by comparative genomic hybridization and spectral karyotyping

Nasopharyngeal carcinoma (NPC) cell lines and xenografts represent valuable models for functional and therapeutic studies on this common malignancy in Southeast Asia. The karyotypic information in most NPC cell lines and xenografts, however, remains largely unclear to date. We have characterized the chromosomal aberrations in six commonly used human NPC cell lines and xenografts using the molecular cytogenetic technique of comparative genomic hybridization (CGH). Genomic imbalances identified in cell lines were further correlated with structural abnormalities indicated from spectral karyotyping (SKY) analysis. CGH revealed consistent overrepresentations of 8q (six out of six cases) with a smallest overlapping region identified on 8q21.1 approximately q22. Other common gains included 7p (4/6 cases), 7q (4/6 cases), 12q (4/6), and 20q (4/6 cases), where minimal overlapping regions were suggested on 7p15 approximately p14, 7q11.2 approximately q21, and 12q22 approximately q24.1. Common losses were detected on 3p12 approximately p21 (4/6 cases) and 11q14 approximately qter (4/6 cases). Although SKY analysis on cell lines revealed predominantly unbalanced rearrangements, reciprocal translocations that involved chromosome 2 [i.e., t(1;2), t(2;3), and t(2;4)] were suggested. Furthermore, SKY examination illustrated additional breakpoints on a number of apparently balanced chromosomes. These breakpoints included 3p21, 3q26, 5q31, 6p21.1 approximately p25, 7p14 approximately p22, and 8q22. Our finding of regional gains and losses and breakpoints represents information that may contribute to NPC studies in vitro.

Elevated expression of thyroid hormone receptor alpha 2 (c-erb A- alpha 2) in nasopharyngeal carcinoma

Differential display was used to identify genes differentially expressed between cultured normal nasal epithelial cells and nasopharyngeal carcinoma (NPC) cell lines. A 130 bp cDNA fragment showing homology with thyroid hormone receptor alpha2 (TR-alpha2 or c-erb A-alpha2) was identified in NPC cell lines. Northern blot analysis using the 130 bp cDNA fragment and a TR-alpha2 specific cDNA containing part of the coding region as probes, we were able to detect a 2.7 kb transcript corresponding to that of TR-alpha2 in NPC cell lines but not in normal nasal epithelial cells. RNA in situ hybridization was used to detect TR-alpha2 expression in clinical biopsies obtained from NPC patients and non-tumour controls. TR-alpha2 mRNA was detected in 1 out of 24 (4.2%) normal nasopharynx epithelium biopsies, in 5 out of 27 (18.5%) primary and 15 out of 24 (62.5%) recurrent tumours. The positive rate of TR-alpha2 expression in recurrent NPC biopsies was significantly higher than that in normal nasopharynx epithelium (P<0.00001). The relevance of the elevated expression of TR-alpha2 in the pathogenesis process of NPC was discussed.

Functional evidence for a nasopharyngeal carcinoma tumor suppressor gene that maps at chromosome 3p21.3

Nasopharyngeal carcinoma is a malignancy that is prevalent among populations from Southeast Asia. Epidemiological studies indicate that genetic predisposition, Epstein-Barr virus, and environmental conditions may play a role in determining incidence. Molecular studies have implicated a tumor suppressor gene(s) on the short arm of chromosome 3. In this study we provide functional evidence, via monochromosome transfer, for a tumor suppressor gene(s) activity in chromosome 3p21.3.

Characterization of a new EBV-associated nasopharyngeal carcinoma cell line

Only a few reports exist of cytogenetic studies in nasopharyngeal carcinoma (NPC), probably because of the technical limitations of culturing solid tumors. We established a cell line (cell-666) that was derived from an NPC xenograft growing in athymic nude mice. Epstein-Barr virus (EBV) infection is one of the important etiologic factors of NPC. This cell line has been shown to have the consistent presence of EBV by Epstein-Barr virus encoded RNAs (EBER) in situ hybridization. Furthermore, aberrant methylation of 5'CpG island of p16 gene was detected. Thus, this cell line represents a valuable model for the study of NPC tumorigenecity. The karyotype of this newly established cell line is: 45,X,del(X)(q24),-5der(5)(5pter-->5q31::5q13-->+ ++5q31::5p12-->5pter),der(6;?) (q10;p10),add(7)(p22), + 9, del(11)(q13),add(12)(p13),-14,-18,-21, + 2mar. Fluorescence in situ hybridization analyses were performed using whole chromosome painting probes of chromosomes 5, 6, 11, and 12.

Centromeric breakage as a major cause of cytogenetic abnormalities in oral squamous cell carcinoma

Cytogenetic analysis of short-term explant tumor cultures derived from 11 human oral squamous cell carcinomas (nine from primary tumors and two from nude mouse xenograft cultures) revealed clonal chromosomal aberrations with multiple numerical and structural changes in all tumors. Recurrent breakpoints were located at chromosomal bands 1p13 (five tumors), 11q13 (four tumors), 3q27-29 (three tumors), and 12q13 (three tumors). Four tumors had a homogeneously staining region at band 11q13. Consistent chromosomal losses included 3p, 9p13-pter, and 18q22-qter, each occurring in eight tumors. Gain of material was observed for chromosome arms 3q, 5p, 7p, and 8q. As many as 134 of a total of 218 chromosomal breakpoints (61%) occurred in centromeric regions, often resulting in isochromosomes and unbalanced whole-arm translocations. Using fluorescence in situ hybridization with chromosome-specific centromeric alphoid repeat probes, two whole-arm translocations, der(Xq;11q) and a der(3q;11q), each from a different tumor, were shown to contain juxtaposed centromeric sequences of both participating chromosomes, strongly suggesting that the breakpoints were within the centromeres. We propose that centromeric breakage is an important mechanism for the generation of genetic imbalance in the development of oral squamous cell carcinoma.

Cloning of a breakpoint cluster region at band 3q27 involved in human non-Hodgkin's lymphoma

In a previous cytogenetic analysis, we showed the recurrence of translocations involving band 3q27 and immunoglobulin gene regions in 20 out of 319 patients with non-Hodgkin's lymphoma (NHL). We report here the molecular cloning of the translocation breakpoint from tumor cells of a patient (LAR) with t(3;14)(q27;q32) and the isolation of DNA probes which identify a major translocation cluster region (MTC) at band 3q27. A DNA library from LAR tumor cells was screened with a JH probe and several clones were identified corresponding either to a somatic rearrangement of JGH genes (V4-D2-J6-C mu clonal rearrangement) or to the t(3;14). Analysis of the t(3;14) breakpoint showed that chromosome 3 material was translocated to an inverted 14q32 VH-containing fragment which was itself translocated to the J3 gene. Chromosome 3-assigned probes were used to investigate local DNA rearrangements in a series of NHL with 3q27 translocations. Rearrangements were detected in 13 of 17 patients including 9 of 11 with t(3;14)(q27;q32), 1 of 2 with t(2;3)(p12;q27), 1 of 2 with t(3;22)(q27;q11), and 2 of 2 NHL with translocations not involving an IG gene, namely, t(3;4)(q27;p11) and t(3;7)(q27;p12). The finding of this MTC should be useful for diagnostic and prognostic studies and for the identification of a novel oncogene at band 3q27 involved in the development of B cell NHL.

Cytogenetic characterization of Epstein-Barr virus-associated T-cell malignancies

Recently, Epstein-Barr virus (EBV) infection has been found not only to be associated with Burkitt lymphoma and nasopharyngeal carcinoma but also with some T-cell malignancies. Cytogenetic studies were performed on four Chinese patients with EBV-associated T-cell neoplasms: three peripheral T-cell lymphomas and one large granular lymphocyte leukemia with coexpression of T-cell antigen. Clonal chromosomal abnormalities were detected in all four patients. Rearrangements of chromosome 7 were observed in three patients: one at 7p22, one at 7q35 or 36, and the remaining one at both sites. The last patient also had a chromosomal abnormality involving 14q11. Trisomy of part of the 1q segment was detected in two patients. The results revealed that the chromosomal abnormalities in these patients were similar to those observed in other T-cell lymphomas. Further studies on more patients are necessary to find out whether there are specific chromosomal aberrations in EBV-associated T-cell neoplasms.

Cytogenetic studies in three xenografted nasopharyngeal carcinomas

Cytogenetics results of three xenografted nasopharyngeal carcinomas (NPC) are reported. One (C15) was almost diploid and had only an isochromosome 1q, trisomy 2, and loss of chromosome X. The two other tumors, C17 and C19, were hypodiploid and had complex karyotypes with some variations. Nonrandom structural abnormalities of chromosomes 1, 3, 8, and 17 were observed. A correlation between a del(17)(p11-12) observed in C17 and loss of both alleles of p53 recently shown in this tumor is emphasized.

Rearrangements of chromosome arm 3q in poorly differentiated nasopharyngeal carcinoma

Cell lines were established from fresh tumor biopsies from two Saudi patients with poorly differentiated nasopharyngeal carcinoma (NPC). Cytogenetic analysis on Giemsa-banded metaphase cells revealed complex, abnormal karyotypes in both patients with modal chromosome numbers of 77 and 52. A der(3)dup(3)(q25-q2?7) or t(3;?)(q27;?) was observed in both cell lines. The rearrangements involving chromosomes X, 1, 4, 6, 7, 8, 12, 13, 15, 17, and 22 in the first patient and 1, 6, and 22 in the second patient could represent clonal evolution.

Measurement of urokinase-type plasminogen activator activity in sera of nasopharyngeal carcinoma patients by an immunocapture assay

The urokinase-type plasminogen activator (uPA) activity in sera of patients suffering from nasopharyngeal carcinoma was examined by a uPA-specific immunocapture assay. The results revealed that the activity levels in the patient sera were significantly higher than that of normal healthy controls. The uPA activity also increased with the staging of the disease and the anti-EBV VCA IgA titre which is a diagnostic test for the disease, although the results were not statistically different. These findings showed that the levels of the enzyme were related to the spread of the disease. In addition, it was demonstrated that the sensitivity of the assay could be increased by using SDS. If the sera were treated with 0.2% sodium dodecyl sulphate (SDS) prior to the assay, higher levels of measureable PA activity were detected.

Cytogenetic characterization of a nasopharyngeal carcinoma cell line and its subline

Cytogenetic results of a nasopharyngeal carcinoma (NPC) cell line NPC-TW039 and its subline NPC-TW039-N1, established from the nude mouse transplant, were reported. This is the third case of NPC presented with banded karyotype, to date, in the literature. A 3q + marker chromosome, with involvement of band q25 similar to that present in the two previously reported cases, was detected in most tumor cells from both cell lines. The structural chromosome abnormalities of NPC-TW039-N1 were similar to its original cell line, NPC-TW039, except that the subline lost one marker chromosome and gained a new one.

Cytogenetics of undifferentiated nasopharyngeal carcinoma xenografts from southern Chinese

Three undifferentiated nasopharyngeal carcinoma (NPC) tumour lines were successfully established from fresh biopsy material injected s.c. into athymic mice and passaged for many generations. These xenografts were found to be free of infiltrating lymphoid cells and remained undifferentiated up to passage 30. They were designated NPC/HK2117 (Xeno-1), NPC/HK1915 (Xeno-2) and NPC/HK1530 (Xeno-3), respectively. Passage 16 from Xeno-1, passage 1 from Xeno-2 and passage 14 from Xeno-3 were studied cytogenetically using G-banding with the trypsin-Giemsa method. Two xenografts were hyperdiploid with chromosome modal numbers ranging from 49 to 76, and one was hypodiploid with modal numbers ranging from 28 to 38. Five marker chromosomes have been identified with involvement of chromosomes 1, 3, 11, 12 and 17. Marker chromosomes derived from chromosomes 12q, 1q and 3q were consistent in one of the 2 xenografts successfully G-banded, and chromosomes 12, 11 and 17 were consistent in another. Three out of the 6 markers involve 12q13----qter. An abnormal chromosome 3 with most of the p arm deleted was also observed.

Establishment and characterization of three transplantable EBV-containing nasopharyngeal carcinomas

Three transplantable nasopharyngeal carcinoma (NPC) tumors, designated C15, C17 and C18, have been obtained and characterized. C15, derived from a primary NPC tumor, has been propagated in nude mice for 30 passages. C17 and C18, derived from metastatic NPC tissue, have been passaged 10 times. Desmosomes, present in every case, provided confirmation of the epithelial origin of all 3 tumors. The Epstein-Barr virus (EBV) genome is contained in C15, C18 and C17 tumor cells with 30, 12 and 3 copies, respectively. The Epstein-Barr virus nuclear antigen (EBNA) was stained by the classical anti-complement immunofluorescence (ACIF) technique. Fluorescence intensity was strong in C15, moderate in C18, and hardly detectable in C17 cells. No expression of the EA and VCA antigens was detected. Flow cytometry analysis performed on monocellular suspensions showed the absence of detectable CR2 molecules (the EBV receptor on B lymphocytes) in all 3 tumors, and the constitutive expression of HLA class-II antigens in C15 and C17 cells. IL-1 activity was demonstrated in the supernatant of C15 and C17 cells cultivated in vitro for 3 days. These data confirm that the constitutive synthesis of MHC class-II molecules and the release of IL-1-like activities are frequent features of NPC cells. These characteristics could be of importance in relation with the T-cell infiltrate found in NPC primary tumors.

Nasopharyngeal carcinoma. Brief review

Nasopharyngeal carcinoma has a well-defined geographic distribution, primarily affecting persons from southern China and Southeast Asia. Environmental factors are numerous and appear to have a secondary role, mainly in the promotion of the neoplastic process. Relationship with the Epstein-Barr virus is indicated by the identification of viral genome copies within the cells and by a persistent host antibody response with restricted specificity for nasopharyngeal malignancies. The World Health Organization has recently adopted a histologic classification categorized into three subtypes according to the degree of epithelial differentiation, keratinization, and stromal lymphocytic infiltration. The tumor expands locally to contiguous structures, spreads through the cervical lymphatics following the jugular chain, and eventually metastasizes to the skeleton and liver. Primary management consists of radiation therapy to cervicofacial fields and usually offers adequate palliation, with a five-year median survival of 67 percent for stage I and 17 percent for stage IV disease.

Persistent Epstein-Barr virus infection associated with monosomy 7 or chromosome 3 abnormality in childhood myeloproliferative disorders

This report deals with myeloproliferative disorders associated with chronic, persistent Epstein-Barr virus (EBV) infection and with monosomy 7 and aberrations concerning chromosomes 3 and 5. Altogether five children were affected, their age ranging from 1 to 4 years at time of clinical diagnosis. Principal symptoms were: hepatomegaly, splenomegaly, recurring upper respiratory tract infection and anaemia. The serum IgG level remained persistently increased. Anti EBV antibody concentrations were measured over a period of 9 months to 6 years, demonstrating persistently increased concentrations of IgG antibodies to viral capsid antigen (VCA) and against early antigen (EA). In three patients IgA antibodies were also studied and were found to be elevated. Within 2-5 years two children developed chronic myelomonocytic leukaemia from the chronic myeloproliferative syndrome. A third patient who initially was diagnosed as chronic myelomonocytic leukaemia developed acute leukaemia within a period of 12 months. A fourth patient with myeloproliferative syndrome went into spontaneous remission after an observation period of 2 years. A fifth patient, the only one with translocation t(3;5)(q27;q33), displayed symptoms and a clinical course that can best be characterized as juvenile chronic myelocytic leukaemia. The clinical, haematological, serological and cytogenetic findings may be related.