Nasopharyngeal carcinoma (NPC). I. Types of cultures derived from tumour biopsies and non-tumorous tissues of Chinese patients with special reference to lymphoblastoid transformation

Nasopharyngeal Carcinoma Cell Lines: Reliable Alternatives to Primary Nasopharyngeal Cells?

Nasopharyngeal carcinoma (NPC) is a type of cancer that originates from the mucosal lining of the nasopharynx and can invade and spread. Although contemporary chemoradiotherapy effectively manages the disease locally, there are still challenges with locoregional recurrence and distant failure. Therefore, it is crucial to have a deeper understanding of the molecular basis of NPC cell movement in order to develop a more effective treatment and to improve patient survival rates. Cancer cell line models are invaluable in studying health and disease and it is not surprising that they play a critical role in NPC research. Consequently, scientists have established around 80 immortalized human NPC lines that are commonly used as in vitro models. However, over the years, it has been observed that many cell lines are misidentified or contaminated by other cells. This cross-contamination leads to the creation of false cell lines that no longer match the original donor. In this commentary, we discuss the impact of misidentified NPC cell lines on the scientific literature. We found 1159 articles from 2000 to 2023 that used NPC cell lines contaminated with HeLa cells. Alarmingly, the number of publications and citations using these contaminated cell lines continued to increase, even after information about the contamination was officially published. These articles were most commonly published in the fields of oncology, pharmacology, and experimental medicine research. These findings highlight the importance of science policy and support the need for journals to require authentication testing before publication.

Efficient Translation of Epstein-Barr Virus (EBV) DNA Polymerase Contributes to the Enhanced Lytic Replication Phenotype of M81 EBV

Epstein-Barr virus (EBV) is linked to the development of both lymphoid and epithelial malignancies worldwide. The M81 strain of EBV, isolated from a Chinese patient with nasopharyngeal carcinoma (NPC), demonstrates spontaneous lytic replication and high-titer virus production in comparison to the prototype B95-8 EBV strain. Genetic comparisons of M81 and B95-8 EBVs were previously been performed in order to determine if the hyperlytic property of M81 is associated with sequence differences in essential lytic genes. EBV SM is an RNA-binding protein expressed during early lytic replication that is essential for virus production. We compared the functions of M81 SM and B95-8 SM and demonstrate that polymorphisms in SM do not contribute to the lytic phenotype of M81 EBV. However, the expression level of the EBV DNA polymerase protein was much higher in M81- than in B95-8-infected cells. The relative deficiency in the expression of B95-8 DNA polymerase was related to the B95-8 genome deletion, which truncates the BALF5 3' untranslated region (UTR). Similarly, the insertion of bacmid DNA into the widely used recombinant B95-8 bacmid creates an inefficient BALF5 3' UTR. We further showed that the while SM is required for and facilitates the efficient expression of both M81 and B95-8 mRNAs regardless of the 3' UTR, the BALF5 3' UTR sequence is important for BALF5 protein translation. These data indicate that the enhanced lytic replication and virus production of M81 compared to those of B95-8 are partly due to the robust translation of EBV DNA polymerase required for viral DNA replication due to a more efficient BALF5 3' UTR in M81.IMPORTANCE Epstein-Barr virus (EBV) infects more than 90% of the human population, but the incidence of EBV-associated tumors varies greatly in different parts of the world. Thus, understanding the connection between genetic polymorphisms from patient isolates of EBV, gene expression phenotypes, and disease is important and may help in developing antiviral therapy. This study examines potential causes of the enhanced lytic replicative properties of M81 EBV isolated from a nasopharyngeal carcinoma (NPC) patient and provides new evidence for the role of the BALF5 gene 3' UTR sequence in DNA polymerase protein expression during lytic replication. Variation in the gene structure of the DNA polymerase gene may therefore contribute to lytic virus reactivation and pathogenesis.

Spontaneous lytic replication and epitheliotropism define an Epstein-Barr virus strain found in carcinomas

The Epstein-Barr virus (EBV) is found in a variety of tumors whose incidence greatly varies around the world. A poorly explored hypothesis is that particular EBV strains account for this phenomenon. We report that M81, a virus isolated from a Chinese patient with nasopharyngeal carcinoma (NPC), shows remarkable similarity to other NPC viruses but is divergent from all other known strains. M81 exhibited a reversed tropism relative to common strains with a reduced ability to infect B cells and a high propensity to infect epithelial cells, which is in agreement with its isolation from carcinomas. M81 spontaneously replicated in B cells in vitro and in vivo at unusually high levels, in line with the enhanced viral replication observed in NPC patients. Spontaneous replication and epitheliotropism could be partly ascribed to polymorphisms within viral proteins. We suggest considering M81 and its closely related isolates as an EBV subtype with enhanced pathogenic potential.

Immunisation of common marmosets with vaccinia virus expressing Epstein-Barr virus (EBV) gp340 and challenge with EBV

Epstein-Barr virus (EBV) is the cause of infectious mononucleosis and is associated with a variety of life-threatening diseases in humans. Therefore the development of an effective vaccine is an important objective. Many of the initial studies of vaccine efficacy analyse the ability of vaccine preparations to prevent the induction of lymphomas in cottontop tamarins by the B95-8 strain of EBV. We used a vaccinia virus recombinant expressing gp340, vMA1, tested previously in the cotton-top tamarin, to evaluate a common marmoset model in which the challenge virus, M81, resembles more closely the wild-type strains of EBV in the general population than does the standard B95-8 strain. We characterised the M81 strain of EBV with respect to the sequence of its gp340/220 gene and in regard to the presence of a region deleted in B95-8. Replication of the challenge virus in the group vaccinated with vMA1 was decreased when compared to control groups.

Analysis of the tumorigenic potential of common marmoset lymphoblastoid cells expressing a constitutively activated c-myc gene

The respective roles of Epstein-Barr virus (EBV) and c-myc in the pathogenesis of endemic Burkitt's lymphoma (BL) are unclear. In order to help resolve the question whether constitutive expression of the c-myc gene in an EBV-immortalised B cell is sufficient to induce a tumorigenic phenotype, B cells from a common marmoset (Callithrix jacchus) were immortalised with EBV, transfected with a constitutively activated c-myc gene and inoculated into the host animals. Despite the cell line transfected with c-myc displaying enhanced growth characteristics, in vitro and in vivo experiments demonstrated that this was not sufficient to induce a tumorigenic phenotype. This supports our previous findings with EBV-immortalised human B cells transfected with an activated c-myc gene (Hotchin et al., 1990).

Establishment of Epstein-Barr virus (EBV)-associated nuclear antigen (EBNA)-positive nasopharyngeal carcinoma hybrid cell line (NPC-KT)

Primary nasopharyngeal carcinoma (NPC) cells were fused to hypoxanthine-guanine phosphoribosyltransferase (HGPRT)-defective cells derived from adenoid tissues using Sendai virus. Some of the fused cells developed into epithelial-like hybrid cells in a selective HAT medium. The hybrid cells (NPC-KT) were Epstein-Barr virus (EBV)-associated nuclear antigen (EBNA)-positive cells. There have been no reports on the establishment of EBNA-positive epithelial cell lines derived from NPC. Thus, the epithelial-like hybrid cells might serve as an in vitro model for studying the biologic activity of NPC-associated EBV.

A culture method giving substantial yields of normal nasopharyngeal epithelial cells for work with Epstein-Barr virus

A culture method, utilising a feeder layer of lethally irradiated 3T3 fibroblasts and medium supplemented with hydrocortisone, cholera toxin, and epidermal growth factor, has been elaborated for the in vitro growth of normal human nasopharyngeal epithelial cells. This method allowed the cells to be grown in vitro for periods of up to 146 days, very considerably longer than in previously reported studies, and ensured that the cultures remained largely free from contaminating human fibroblasts. It was found possible to subculture the nasopharyngeal epithelial cells through numerous passages both by dispersing monolayers into single cell suspensions and by transferring coverslip monolayers of the cells to individual Petri dishes. By combining these two methods, at least 50 replicate epithelial cultures could be produced from each tissue sample, thus providing for the first time cultured nasopharyngeal epithelial cells in quantities suitable for extensive experiments with Epstein-Barr virus.

Epstein-barr virus induction by a serum factor: IV. Ubiquitous occurrence of the factor within vertebrates and its interaction with defined lymphoid cell lines

We have recently reported the existence of a serum factor that induces Epstein-Barr virus antigens in Raji cells (Bauer et al., 1982b, c). Here we demonstrate the ubiquitous presence of this factor in sera of vertebrates of all five classes. Furthermore, we tested 48 EBV-genome-positive lymphoid cell lines of different origins for responsiveness to the serum factor. Only cells from lines of two groups, i.e. Burkitt's lymphoma and EBV-transformed marmoset lines, responded to the factor, whereas human lymphoblastoid cell lines were not induced by the serum factor.

A monoclonal antibody with anti-Burkitt lymphoma specificity. I. Analysis of human haematopoietic and lymphoid cell lines

38-13 is a hybridoma-produced monoclonal rat IgM which appears to define a Burkitt's lymphoma-associated antigen (BLA). In this paper, we described the reactivity of 38-13 with a panel of human haematopoietic and lymphoid cell lines. In indirect immunofluorescence (IF) assays, 15 of 26 Burkitt's lymphoma (BL) lines studied were clearly stained with 38-13 (from 13 to 100% positive cells) by microscope, with varying numbers of heavily labelled cells. In these positive cell lines, fluorescence-activated cell-sorter (FACS) analysis demonstrated that BLA was actually present on all the cells. Positive BL included Epstein-Barr virus (EBV) genome-carrying lines and EBV-negative ones; thus, BLA is not related to the presence of EBV. Most of the 15 BL cells that reacted with 38-13 contained a typical t(8;14) translocation, but had variant translocations such as t(2;8) and t(8;22). The cells were derived from BL patients of different geographical origins and clinical features. Four BL lines were poorly stained and seven were negative with 38-13 in IF assays. The 32 EBV-positive lymphoblastoid cell-lines (LCL) studied were negative. In three line pairs, consisting of a tumor line and an LCL from the same patient, only the BL line was demonstrated to react with 38-13. A series of non-BL cells, including haematopoietic, lymphoid and solid tumor lines, all failed to react with 38-13. Various attempts to modulate the expression of BLA on BL cells were unsuccessful. However, it cannot be ruled out that BLA is actually a transient B-cell differentiation marker.

NADH cytochrome b5 reductase activity in lymphoid cell lines. Expression of the defect in epstein Barr virus transformed lymphoblastoid cell lines from patients with recessive congenital methemoglobinemia

Recessive congenital methemoglobinemia (RCM) is due to the homozygous deficiency of NADH-cytochrome b5 reductase (EC 1.6.2.2.). In type I disease, in which the patients are only methemoglobinemic, the enzyme defect is fully expressed in the erythrocytes, whereas the leukocytes are much less affected. In type II disease, in which the patients are, in addition, mentally retarded, the defect is generalized to all the tissues including cultured fibroblasts. In the present study we have investigated Epstein-Barr virus (EBV) transformed lymphoid cell lines (LCL) derived from patients with both types of cytochrome b5 reductase deficiency and from nondeficient individuals. The total cytochrome b5 reductase activity of the control LCL was found to be similar whatever the LCL origin, except for one lymphoma line (Daudi). The enzyme from the control LCL (c 252/B 95) was found to be immunologically related to the human soluble erythrocyte cytochrome b5 reductase, indicating that it is the product of the same gene: the DIA1 (diaphorase) locus. The LCL derived from one patient with the type I disease and two patients with the type II disease were investigated.l In the former the defect was expressed to a lesser degree than in the cases with mental retardation in which the defect was much pronounced, and involved both the mitochondrial and the microsomal fraction. This indicated that all the subcellular forms of the cytochrome b5 reductase are under the same genetic control. Altogether, these data show that the LCL are a favorable material for studying both types of cytochrome b5 reductase deficiency and for investigating in depth the molecular aspects of this metabolic disease.

Identification of murine endogenous xenotropic retrovirus in cultured multicellular tumour spheroids from nude-mouse-passaged nasopharyngeal carcinoma

After nude-mouse-passage, a carcinoma of the nasopharynx was found to contain a few scattered C-type retrovirus particles. Culture of this nude-mouse-grown material over solid agar allowed the human tumour cells to grow as multicellular spheroids which increased in number by budding and could be subcultured for up to 6 months. Within the spheroids the human tumour cells expressed increased retrovirus replication and large numbers of C-type particles were observed. Treatment with a halogenated pyrimidine further enhanced the virus production. This tissue culture system provided sufficient virus production for the identification of the retrovirus as an endogenous xenotropic murine leukaemia virus and not a human agent.

Carcinoembryonic antigen (CEA) in the cancer family syndrome

We present findings on plasma CEA in relatives and spouses from six kindreds manifesting the Cancer Family syndrome. The CEA distributions per se were transformed to square root CEA to correct for skewness and kurtosis. Significant effects of age and duration of smoking were adjusted for by linear regression. Relatives were classified as: 1) cancer patients, 2) individuals at high genetic cancer risk (one or more first-degree relatives affected, and 3) individuals at low genetic cancer risk (no first-degree relatives affected) for statistical comparisons. Unrelated spouses were also classified into corresponding groups according to their directline mate's status. Cancer patients and relatives at high genetic risk had significantly greater mean square root CEA than relatives at low genetic risk, and, surprisingly, unrelated spouses had mean levels of square root CEA which were similar to that in the corresponding cancer risk class of their direct-line mates. Our results suggest the existence of both a genetic and connubial effect on CEA, presumably due to a common environmental agent acting in concert with the degree of genetic predisposition to oncogenesis in this syndrome.

Cytogenetics of malignant epithelial cells and lymphoblastoid cell lines from nasopharyngeal carcinoma

The malignant epithelial cells of nasopharyngeal carcinoma (NPC) and cells of lines derived form the lymphoid cells which infiltrate this tumour have been investigated cytogenetically. Chromosome spreads of lymphoblastoid cells of lines established from 7 different NPC biopsy specimens were examined after banding staining. Banding was also applied to the epithelial tumour cells of 5 further biopsy specimens freed from non-malignant infiltrating cells by passage through nude mice; epithelial cell spreads were obtained by in vivo splindle arrest. Five of the lymphoblastoid lines were found to be diploid, and 2 tetraploid; the karyotypes were essentially normal. The squamous epithelial nature of the cells in the nude-mouse-grown NPC tumours was established by light and electronmicroscopy, and 3 tumours were found to be near-triploid, and 2 near-diploid. The cells of the near-triploid tumours contained grossly abnormal chromosomes but those of the near-diploid tumours showed only relatively minor changes. Although abnormalities were observed which were specific for cells from each individual tumour, no discernible change was common to cells from all the tumours.

Isolation of infectious EB virus from the epithelial tumour cells of nasopharyngeal carcinoma

Evidence of herpesvirus replication has been found by light and electron microscopy in the malignant epithelial cells of two out of six nasopharyngeal carcinomas (NPC) examined directly after growth in nude mice to eliminate non-malignant infiltrating cells. The agent has been identified as EB virus by immunofluorescence tests for EB virus capsid antigen, and has been shown to be biologically active by its ability to infect and transform foetal cord blood lymphocytes. Lymphoblastoid cell lines which express the EB virus nuclear antigen have been established from the transformed foetal lymphocytes, and thus carry the first isolate of the virus from the actual epithelial tumour cells of NPC, in a form suitable for further investigation. The results are discussed in terms of the relationship of EB virus to NPC epithelial cells.

Characterization of a spontaneous undifferentiated carcinoma from an African green monkey (Cercopithecus aethiops)

An adult male African green monkey (Cercopithecus aethiops) with an undifferentiated carcinoma, probably originating from the nasal mucosa, was received from the Akron, Ohio zoo. Cultivation of this tumor in vitro resulted in a mixture of fibroblastic and epithelial cells which was subsequently separated using differential trypsinization. The neoplastic nature of the cultured epithelial cells was verified by their ability to transplant into athymic nude, or antithymocyte serum-treated mice, where poorly differentiated carcinomas were produced, and cultures of the tumors that arose in nude mice were morphologically similar to pretransplantation cultures. Early cultures showed a normal male karyotype characteristic of the species; however, in long-term cultures, a clearly defined, small submetacentric Y chromosome was not observed. Electron microscopic examination of tumor tissue and cultured tumor cells revealed desmosomes and the presence of cytoplasmic (keratin-type) fibrils, which tended to be organized around the nucleus. In addition to the keratin-type fibrils, the cultured tumor cells also contained a large amount of cytoplasmic inclusion material that may represent keratohyalin granules. There was no evidence of a viral association with tumor material or cultured cells. The cultures were susceptible to infection by vesicular stomatitis virus, Herpesvirus hominis type 1, and H. saimiri, but were resistant to the Epstein-Barr virus.

Activation in vitro by BUdR of a productive EB virus infection in the epithelial cells of nasopharyngeal carcinoma

Material from a nasopharyngeal carcinoma (NCP) has been passaged in athymic (nude) mice to eliminate non-malignant infiltrating cells. The human origin and derivation from NPC malignant epithelial cells of the nude mouse tumours have been confirmed by chromosome examination, electron microscopy showing desmosomes and keratin fibrils, and postive EB virus nuclear antigen (EBNA) testing. Samples of the mouse-grown tumours were cultured and pure monolayers of epithelial cells were obtained which still expressed EBNA and contained desmosomes and keratin; these cultures grew well for about 3 weeks. Extensive electron microscope searches failed to reveal herpes virus particles. In contrast, cultures treated with BUdR showed typical immature and mature herpes virus particles in epithelial, keratin-containing cells, and immunofluorescence tests for virus capsid antigen with a battery of human sera identified this agent as EB virus. EB virus has thus, for the first time, been activated in NPC epithelial cells and shown to be capable of replication in a cell type other than a primate B-lymphocyte.

Immunity to antigens associated with a cell line derived from nasopharyngeal cancer (NPC) in non-Chinese NPC patients

Delayed hypersensibility to antigens derived from four lymphoid cell lines was measured in 27 non-Chinese patients with nasopharyngeal cancer (NPC) and 63 non-NPC cancer patients. Of the NPC patients, 17/27 (63%) had a positive skin test response to antigens derived from HKLY-28, a lymphoid cell line which was developed from an NPC biopsy. Only 10/51 (20%) and 1/13 (8%) patients with solid tumors and hematopoietic malignancies, respectively, had positive skin test responses to HKLY-28. Positive skin tests were found less frequently when extracts from cell lines derived from normal individuals or lymphoma patients were utilized, although NPC patients were more reactive to two of the non-NPC derived cell lines than the controls. The NPC patients in this study also had significantly elevated antibody titers to the Epstein-Barr virus (EBV), capsid antigen (VCA) and early antigen (EA). Titers were highest in the patients with more anaplastic nasopharyngeal carcinomas. The skin test and serologic data are consistent with studies in Chinese patients, indicating that NPC in non-Chinese and Chinese patients is biologically similar.

Lymphoblastoid transformation and kinetics of appearance of viral nuclear antigen (EBNA) in cord-blood lymphocytes infected by Epstein-Barr Virus (EBV)

Human cord-blood lymphocytes were infected with B95.8 Epstein-Barr virus (EBV) before and after separation into B- and T-cell populations. Lymphoblastoid cells exhibiting B-cell characteristics appeared after 2 to 3 days of culture in the total population and in the separated B-cell subpopulation but not in the T-cell subpopulation. EBV nuclear antigen (EBNA) was detected concurrently with the appearance of lymphoblastoid cells. The proportion of EBNA-positive cells corresponded to that of lymphoblastoid cells, and reached 50% after 4 days. EBNA was present only in cells with B-cell markers. These observations indicate that only B-cells are susceptible to EBV infection, that the transformation occurs within a few days and that EBNA is a valid early marker for susceptibility to EBV transformation.

Classification and biological nature of established human hematopoietic cell lines

Over 200 established human hematopoietic cell lines of normal and malignant origin have been investigated by morphological and functional parameters. Employing morphology as the overriding parameter four types of lines were identified. (1) Lymphoblastoid cell lines, derived from normal and neoplastic hematopoietic tissue, were characterized by the wide morphologic flexibility of individual lymphoblastoid cells, constant association with Epstein-Barr virus (EBV), polyclonal derivation, differentiation for immunoglobulin production (secretion) and their diploids. (2) Lymphoma cell lines. This type of line was established at a high frequency from Burkitt's lymphoma and rarely from other types of lymphoma, but never from patients without malignancy or with non-lymphoma malignancies. Important characteristics were morphologic stereotypia within each line, monoclonal derivation, common but not obligatory association with EBV, variability in the expression of Ig synthesis (no production, or membrane bound Ig, or secretion) and aneuploidy. (3) Myeloma cell lines could only rarely be obtained from patients with myeloma. The basis for classification of these lines is their production of Ig identical to the myeloma protein in vitro. Other important distinguishing features were: plasma cell morphology, absence of EBV and aneuploidy. (4) The leukemia cell line (MOLT 4) was the only line with T-cell characteristics and was easily distinguished from the other types. Important characteristics were a typical surface ultrastructure, absence of EBV and absence of immunoglobulin production, Individual lymphoblastoid lines were in principle identical whereas each line of the other three types had its own characteristic profile. The phenotypic characteristics of the lymphoblastoid lines were very stable during prolonged serial cultivation. Only in a few cases were secondary chromosomal, functional or morphologic alterations noted. We conclude that EBV-carrying lymphoblastoid lines can be obtained from non-neoplastic precursor cells from healthy as well as from diseased individuals. Lymphoma, myeloma and leukemia lines are only obtained from the respective neoplastic tissue but generally at a low frequency. With the exception of Burkitt's lymphoma, malignant hematopoietic tissue and leukemia frequently give rise to established cell lines in vitro of the lymphoblastoid type rather than lines derived from the neoplastic cells;

Direct evidence for the presence of Epstein-Barr virus DNA and nuclear antigen in malignant epithelial cells from patients with poorly differentiated carcinoma of the nasopharynx

A well-differentiated squamous cell carcinoma and three poorly differentiated carcinomas of the nasopharynx were analyzed for the presence of Epstein-Barr virus DNA by hybridization with radioactive complementary RNA. The well-differentiated carcinoma contained no detectable Epstein-Barr virus DNA, whereas the three anaplastic carcinomas contained 41, 16, and 14 viral genome equivalents per cell. The anaplastic carcinomas were heavily infiltrated with lymphocytes and other non-neoplastic cells. All four tumors were successfully passaged in nude (thymusless) mice. Mouse cell admixture in the heterotransplanted tumors was estimated by analysis of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and varied between 25% and 80%. After two passages in nude mice, the carcinoma that was negative for Epstein-Barr virus DNA remained negative, while the three anaplastic carcinomas retained their viral DNA. After correction for mouse cell admixture, the latter tumors were found to contain about 80, 55, and 160 Epstein-Barr virus genome equivalents per human cell. The virus-determined nuclear antigen was localized in the large carcinoma cell clusters in all three mouse-passaged tumors positive for the viral DNA, but other virus-determined antigens were not detected, indicating the absence of virus induction. In contrast to the original tumor biopsies, the nude-mouse-passaged tumors showed virtually no lymphocytic infiltration. It is concluded that the Epstein-Barr virus DNA found in biopsies of human nasopharyngeal carcinomas is localized in the neoplastic cells.

Anti-Epstein Barr virus antibody in nasopharyngeal carcinoma

A retrospective study of anti-Epstein Barr virus (anti-EBV titers) in the sera of 400 patients with nasopharyngeal carcinoma (NPC) in Taiwan according to the clinical staging system of American Joint Committee is reported. Of NPC patients, 60% were seropositive (> 1:1640), while such values occurred only in 17.7, 10.9 and 20.6% respectively of normal adults, inflammatory diseases of the nose and throat, and head and neck tumor patients other than NPC (control groups). The geometric mean titer was 1:404 in NPC patients, and 1:116, 1:80 and 1:125 respectively in the three control groups. When 321 patients were staged, the seropositive rate increased successively from 12.5% in Stage I to 77.2% in Stage IV. Statistically, Stage I NPC patients had the same titer as the three control groups and a highly significant difference in chi-square tests from those in other stages. Radiotherapy did not influence the anti-EBV titers much; however, there was a definite decrease of titers in patients 7–18 months postradiotherapy. Thirty patients with recurrent disease and 28 patients with distant metastases demonstrated high positive titers and high geometric mean titers falling between those in Stage III and Stage IV. The correlation between EBV and NPC is discussed.