Etiology of nasopharyngeal carcinoma: a review

Epstein-Barr Virus BRLF1 Induces PD-L1 Expression in Nasopharyngeal Carcinoma Cells

Nasopharyngeal carcinoma (NPC) is a specific human malignancy with unique geographic distribution and genetic backgrounds. Although early treatment with radio-chemotherapy has been proven effective for NPC therapy, its therapeutic efficacy substantially diminishes in the late stages of this malignancy. In the tumor microenvironment of NPC, PD-L1 has been demonstrated as a critical factor in impairing T cell activation. As an etiological role for NPC development, it is found that Epstein-Barr virus (EBV) latent proteins upregulated PD-L1 expression. However, whether EBV lytic protein affects PD-L1 expression remains unclear. In this study, through monitoring the mRNA expression pattern of lytic genes and PD-L1 in EBV-positive NPC cell line NA, EBV immediately-early gene BRLF1(Rta) was found to have the potential for PD-L1 activation. Furthermore, we identified that Rta expression enhanced PD-L1 expression in mRNA and protein levels through quantitative real-time polymerase chain reaction and western blotting analysis. The luciferase reporter assay revealed that Rta expression enhanced PD-L1 promoter activity. We also demonstrated that Rta-induced PD-L1 expressions could impair interleukin 2 secretion of T cells, and this mechanism may be through ERK activation. These results displayed the importance of EBV Rta in PD-L1 expression in NPC and may give an alternative target for NPC therapy.

The Application of Emodin Treatment on Nasopharyngeal Carcinoma Therapy

Nasopharyngeal carcinoma (NPC) is a malignancy prevailing in Taiwan, Hong Kong, Southern China, Southeast Asia, and North Africa. Although early-stage NPC responds well to the primary treatment of radio-chemotherapy, the mortality rate of advanced NPC remains high. Therefore, developing new therapies for nasopharyngeal carcinoma is an urgent task. Emodin is an anthraquinone derivative mainly found in Rheum palmatum. Emodin has been found to possess many anti-cancer functions against various types of cancers, but they are less discussed in the treatment of NPC. This review organized the different studies about the anti-NPC activity of emodin and discussed the potential and challenges of emodin treatment in NPC therapy.

Systematic review of how racialized health inequities are addressed in Epidemiologic Reviews articles (1979-2021): a critical conceptual and empirical content analysis and recommendations for best practices

Critical analysis of the determinants of current and changing racialized health inequities, including the central role of racism, is an urgent priority for epidemiology, for both original research studies and epidemiologic review articles. Motivating our systematic overview review of Epidemiologic Reviews articles is the critical role of epidemiologic reviews in shaping discourse, research priorities, and policy relevant to the social patterning of population health. Our approach was first to document the number of articles published in Epidemiologic Reviews (1979-2021; n = 685) that either: (1) focused the review on racism and health, racial discrimination and health, or racialized health inequities (n = 27; 4%); (2) mentioned racialized groups but did not focus on racism or racialized health inequities (n = 399; 59%); or (3) included no mention of racialized groups or racialized health inequities (n = 250; 37%). We then conducted a critical content analysis of the 27 review articles that focused on racialized health inequities and assessed key characteristics, including (1) concepts, terms, and metrics used regarding racism and racialized groups (notably only 26% addressed the use or nonuse of measures explicitly linked to racism; 15% provided explicit definitions of racialized groups); (2) theories of disease distribution guiding (explicitly or implicitly) the review's approach; (3) interpretation of findings; and (4) recommendations offered. Guided by our results, we offer recommendations for best practices for epidemiologic review articles for addressing how epidemiologic research does or does not address ubiquitous racialized health inequities.

EBV-associated diseases: Current therapeutics and emerging technologies

EBV is a prevalent virus, infecting >90% of the world's population. This is an oncogenic virus that causes ~200,000 cancer-related deaths annually. It is, in addition, a significant contributor to the burden of autoimmune diseases. Thus, EBV represents a significant public health burden. Upon infection, EBV remains dormant in host cells for long periods of time. However, the presence or episodic reactivation of the virus increases the risk of transforming healthy cells to malignant cells that routinely escape host immune surveillance or of producing pathogenic autoantibodies. Cancers caused by EBV display distinct molecular behaviors compared to those of the same tissue type that are not caused by EBV, presenting opportunities for targeted treatments. Despite some encouraging results from exploration of vaccines, antiviral agents and immune- and cell-based treatments, the efficacy and safety of most therapeutics remain unclear. Here, we provide an up-to-date review focusing on underlying immune and environmental mechanisms, current therapeutics and vaccines, animal models and emerging technologies to study EBV-associated diseases that may help provide insights for the development of novel effective treatments.

Association Between Traditional Herbal Diet and Nasopharyngeal Carcinoma Risk: A Prospective Cohort Study in Southern China

Introduction

Prospective evidence for herbal diet and nasopharyngeal carcinoma (NPC) development is absent. We therefore evaluated the associations of herbal soup and herbal tea with NPC in a prospective cohort study in southern China.

Methods

Based on an NPC screening cohort established in 2008-2015, information on herbal diet consumption, potential confounding factors, and Epstein-Barr virus (EBV) antibody levels were collected from 10,179 individuals aged 30-69 years in Sihui city, southern China. Cox regression models were performed to examine herbal diet with NPC risk, and logistic regression models were used to examine herbal diet with EBV reactivation.

Results

During a median of 7.54 years of follow-up, 69 participants developed NPC. Herbal soup consumption was associated with decreased NPC risk, with HRs of 0.31 (95% confidence interval (CI): 0.15-0.62) for the highest intake frequency and 0.29 (95% CI: 0.16-0.51) for a longer duration. However, herbal tea was not significantly associated. Moreover, we identified herbal soup was inversely associated with EBV seropositivity among all the participants at baseline, with the adjusted ORs being 0.78 (95% CI: 0.65-0.93) for immunoglobulin A antibodies against EBV capsid antigens (VCA-IgA) and 0.76 (95% CI: 0.64-0.91) for nuclear antigen 1 (EBNA1-IgA) in those with the highest frequency and 0.70 (95% CI: 0.59-0.84) for VCA-IgA and 0.64 (95% CI: 0.54-0.77) for EBNA1-IgA in those with the longer duration. Inverse associations were also observed in non-NPC individuals.

Conclusions

With inhibition of EBV reactivation by plants, herbal soup could significantly decrease the risk of NPC in endemic areas.

Design of InnoPrimers-Duplex Real-Time PCR for Detection and Treatment Response Prediction of EBV-Associated Nasopharyngeal Carcinoma Circulating Genetic Biomarker

Nasopharyngeal carcinoma (NPC) is an epithelial tumor with high prevalence in southern China and Southeast Asia. NPC is well associated with the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) 30 bp deletion by having its vital role in increased tumorigenicity and decreased immune recognition of EBV-related tumors. This study developed an InnoPrimers-duplex qPCR for detection of NPC blood circulating LMP1 30 bp deletion genetic biomarker for early diagnosis and treatment response prediction of NPC patients. The analytical and diagnostic evaluation and treatment response prediction were conducted using NPC patients' whole blood (WB) and tissue samples and non-NPC cancer patients and healthy individuals' WB samples. The assay was able to detect as low as 20 ag DNA per reaction (equivalent to 173 copies) with high specificity against broad reference microorganisms and archive NPC biopsy tissue and FNA samples. The diagnostic sensitivity and specificity were 83.3% and 100%, respectively. The 30 bp deletion genetic biomarker was found to be a good prognostic biomarker associated with overall clinical outcome of NPC WHO type III patients. This sensitive and specific assay can help clinicians in early diagnosis and treatment response prediction of NPC patients, which will enhance treatment outcome and lead to better life-saving.

Interplay between Epstein-Barr virus infection and environmental xenobiotic exposure in cancer

Epstein-Barr virus (EBV) is a herpesvirus associated with lymphoid and epithelial malignancies. Both B cells and epithelial cells are susceptible and permissive to EBV infection. However, considering that 90% of the human population is persistently EBV-infected, with a minority of them developing cancer, additional factors are necessary for tumor development. Xenobiotics such as tobacco smoke (TS) components, pollutants, pesticides, and food chemicals have been suggested as cofactors involved in EBV-associated cancers. In this review, the suggested mechanisms by which xenobiotics cooperate with EBV for carcinogenesis are discussed. Additionally, a model is proposed in which xenobiotics, which promote oxidative stress (OS) and DNA damage, regulate EBV replication, promoting either the maintenance of viral genomes or lytic activation, ultimately leading to cancer. Interactions between EBV and xenobiotics represent an opportunity to identify mechanisms by which this virus is involved in carcinogenesis and may, in turn, suggest both prevention and control strategies for EBV-associated cancers.

Association of Epstein-Barr virus infection with peripheral immune parameters and clinical outcome in advanced nasopharyngeal carcinoma

The purpose of this study was to investigate the association of Epstein-Barr virus (EBV) with peripheral blood immune cell counts and clinical outcomes in advanced nasopharyngeal carcinoma (NPC) patients. In a retrospective design, 146 patients with NPC at stage IV were enrolled in this study. The association of EBV status with peripheral blood immune cell counts, distant metastases, and long-term survival in patients with advanced NPC were determined. Eighty-seven (59.6%) of all patients were positive for EBV. Compared with patients with normal NK cell count, patients with lower NK cell count showed a significantly lower EBV viral load (median: 614.0 vs. 2190.0 copies/mL, P = 0.024). EBV-positive patients showed a significantly higher incidence of liver metastasis than EBV-negative patients (32.6% vs. 23.7%, P = 0.021). Multi-variant regression analysis showed that EBV infection was independently associated with liver metastasis (OR: 2.33, P = 0.043). EBV positive patients showed a significantly worse PFS (P = 0.001) and OS (P = 0.001) than EBV negative patients. Multivariate Cox regression analysis revealed that EBV infection was independently associated with a worse PFS (HR: 1.94, P = 0.003), and OS (HR: 2.12, P = 0.014) in advanced NPC. In conclusion, EBV infection is associated with a high risk of liver metastasis and is also an independent negative predictor for PFS and OS in patients with advanced NPC. EBV infection is associated with lower CD8% and higher NK%, while lower NK cell count is associated with lower EBV viral load.

A significant role of transcription factors E2F in inflammation and tumorigenesis of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant tumor from head and neck with characteristics in remarkable geographic and racial distribution worldwide, which has the important features of vigorous proliferation and inflammatory cells infiltration. By analyzing the expression profile data of NPC, we found that the E2F-related gene sets were highly enriched in NPC tissues. E2F transcription factor family is an important cycle regulator, which can promote the malignant proliferation and tumorigenesis. Here, we showed that E2Fs accelerated malignant phenotypes of NPC cells. RNA sequencing revealed that E2Fs can significantly up-regulate the inflammatory pathways in NPC cells. E2F1, as a transcription factor, can active the transcription activity of IL-6 promoter, and modulate macrophage function through a microenvironment manner. Thus, this study characterized a significant role of E2Fs in inflammation and tumorigenesis of NPC, which provided a promising anti-tumor target in NPC, since E2Fs are highly expressed and activated in NPC.

Association Between LMP-1, LMP-2, and miR-155 Expression as Potential Biomarker in Nasopharyngeal Carcinoma Patients: A Case/Control Study in Vietnam

Background: Epstein-Barr virus (EBV) infection and microRNA-155 (miR-155) are considered etiological factors that contribute to nasopharyngeal carcinoma (NPC). The regulation of miR-155 expression induced by EBV infection has been reported to be important in NPC tumorigenesis. Aims: This study was designed to explore the relationships among the expression levels of miR-155, LMP-1 (latent membrane protein-1), and LMP-2 (latent membrane protein-2) in tumor and nontumor specimens of Vietnamese NPC patients. The study was also designed to investigate the association between miR-155 expression and LMP-1 and LMP-2 expression in Vietnamese NPC patients. Materials and Methods: Ninety-three NPC biopsy samples and 100 noncancerous swab specimens were collected from patients and analyzed by real-time reverse transcriptase polymerase chain reaction. Results: LMP-1, LMP2, and miR-155 were significantly upregulated in 76.34%, 67.74%, and 75.27% of NPC samples, respectively, with decreased expression observed in the control group (p < 0.0001). Moreover, the statistical analysis showed that there was a close association between LMP-1 and LMP-2 expression and miR-155 expression in the NPC samples. Conclusion: miR-155 expression was upregulated and significantly associated with the expression of LMP-1 and LMP-2, in Vietnamese NPC cases.

Molecular Screening of Nasopharyngeal Carcinoma: Detection of LMP-1, LMP-2 Gene Expression in Vietnamese Nasopharyngeal Swab Samples

Objective:

This study aimed to characterize the expression of LMP-1, LMP-2 in clinical swab samples in order to find out the potential molecular based biomarker for NPC diagnosis and screening, which could offer a chance in development of rapid method for NPC diagnosis in Vietnamese population.

Materials and Methods:

A total of 93 nasopharyngeal carcinoma swab samples and 100 healthy nasopharyngeal swab samples were collected to evaluate LMP-1, LMP-2 expression by Real-time reversed PCR.

Results:

we figured out the significant association between the expression of LMP-1 (counting for 48.39%), LMP-2 (counting for 39.78%) and NPC. No LMP-1 expression was observed, and only 1 of 100 specimens was detected with LMP-2 positive in healthy samples. In the combination of LMP-1 (+) and/or LMP-2 (+), the frequency of positive was 53.76%, greater than each gene expression. Additionally, sensitivity, specificity, positive predictive value, negative predictive value of assay were 99.00%, 98.04%, 69.72%, and 77.02%, respectively. Additionally, the LMP-2 expression level was 5.50 times higher in NPC samples than non-cancerous samples.

Conclusion:

Our results indicated the molecular invasive method based on the expression of LMP-1, LMP-2 in swab samples would be a promising supplement in NPC diagnosis, screening in the near future in Vietnam.

Higher incidence of nasopharyngeal carcinoma in some regions in the world confers for interplay between genetic factors and external stimuli

Nasopharyngeal carcinoma (NPC) is a rare variety of head and neck cancers. The risk factors include three major causes: genetic factors, viral infection, and environmental and dietary factors. The types of NPC show strong ethnic and geographic variations. The keratinizing and non-keratinizing types are prevalent in the lower incidence regions like North America and Europe; whereas the undifferentiated type is mostly found in the regions with higher incidences like China, North Africa, Arctic, and Nagaland of North-East India. These suggest a possible major role of the internal genetic factors for generation and promotion of this disease. Viral infections might accelerate the process of carcinogenesis by helping in cellular proliferation and loss of apoptosis. Diet and other environmental factors promote these neoplastic processes and further progression of the disease occurs.

Occupational exposure to wood dust and risk of nasopharyngeal cancer: A systematic review and meta-analysis

INTRODUCTION

Nasopharyngeal cancer (NPC) is one of the most commonly occurring cancers in some regions. While wood dust is a confirmed human carcinogen, its association with NPC remains uncertain due to inconsistent findings in the related studies. We performed the first systematic review and meta-analysis on the epidemiological evidence to examine the association between occupational exposure to wood dust and the risk of NPC.

METHODS

In this meta-analysis study, the PubMed and Scopus databases were searched for English-language publications. seven case-control studies were included in the pooled analysis.

RESULTS

These studies were published between 1991 and 2016. The heterogeneity across the studies was significant (P = 0.06, I² = 50.4%). The results of the random effects model meta-analysis showed that there was a direct relationship between occupational exposure to wood dust and NPC (OR = 1.5 95% CI: 1.09-2.07). Among different histological subtypes of NPC, there was a significantly increased risk for the nonkeratinizing carcinoma following wood dust exposure (OR = 1.68, 95%CI: 1.03-2.74). We found no evidence of publication bias across studies according to the result of the Egger's test (P of bias = 0.073).

CONCLUSIONS

This meta-analysis suggests that occupational exposure to wood dust can be associated with an increased risk of the nonkeratinizing carcinoma of the histological subtypes of nasopharyngeal cancer.

Smoking can increase nasopharyngeal carcinoma risk by repeatedly reactivating Epstein-Barr Virus: An analysis of a prospective study in southern China

Background

The association between smoking and nasopharyngeal carcinoma (NPC) is still uncertain. The aim of this study was to validate smoking effect on NPC and explore if smoking can induce NPC by persistently reactivating EBV in long‐term based on a prospective cohort design.

Methods

A NPC screening cohort with 10 181 eligible residents in Sihui city, southern China was conducted from 2008 to 2015. The smoking habit was investigated through the trained interviewers and EBV antibodies (VCA‐IgA, EBNA1‐IgA) as screening markers were tested periodically. New NPC cases were identified through local cancer registry. Cox's regression model was used to estimate the adjusted hazard ratios (aHRs) of smoking on NPC incidence. In the non‐NPC participants, the associations between smoking and EBV seropositivity in different periods were assessed by logistic regression and generalized estimating equations (GEE).

Results

With a median of 7.54 years, 71 NPCs were diagnosed ≥1 year after recruitment. Compared with never smokers, the aHRs of developing NPC among ever smokers were 3.00 (95%CI: 1.46‐6.16). Stratified by sex, the HRs of ever smoking were 2.59 (95%CI: 1.07‐6.23) for male and 3.75 (95%CI: 1.25‐11.20) for female, respectively. Among the non‐NPC individuals, ever smoking was not only associated with EBV seropositivity at baseline, but also in the 3‐5 years of follow up, with adjusted odds ratios (aORs) of 1.68 (95%CI: 1.29‐2.18) for VCA‐IgA and 1.92 (95%CI: 1.42‐2.59) for EBNA1‐IgA. Among the smokers who were tested EBV antibodies at least twice, the similar results were obtained using GEE.

Conclusion

Smoking could significantly increase the long‐term risk of NPC in southern China, partly by persistently reactivating EBV.

Perspective: Contribution of Epstein-Barr virus (EBV) Reactivation to the Carcinogenicity of Nasopharyngeal Cancer Cells

Nasopharyngeal carcinoma (NPC) is a squamous cell carcinoma derived from the epithelium of the post-nasal cavity, with a unique geographic and ethnic distribution. Epstein–Barr virus (EBV) is an etiological agent of NPC, but how it contributes to carcinogenesis is not completely clear. Although it is thought that EBV latency participates in the development of NPC, increasing evidence reveals that the lytic cycle also plays an important role in the carcinogenic process. In this review, we summarize our recent studies on how EBV reactivation causes genomic instability and accelerates tumorigenesis in epithelial cells. The roles of three lytic genes, namely, BRLF1, BGLF5 and BALF3, in this process are also introduced. Moreover, blocking EBV reactivation using natural compounds may help delay the progression of NPC tumorigenesis. These studies provide a new insight into NPC carcinogenesis and raise the possibility that inhibition of EBV reactivation may be a novel approach to prevent the relapse of NPC.

Detection of Epstein-Barr virus Genome in Squamous Cell Carcinomas of the Larynx

Epstein-Barr virus (EBV) is a B-lymphotropic virus with a tumorigenic potential. EBV infection has been recognized as the main cause of nasopharyngeal carcinoma and Burkitt's lymphoma. The aim of our study was to determine the incidence of EBV in squamous cell carcinomas of the larynx. We employed for our analysis a sensitive polymerase chain reaction (PCR) assay, followed by restriction fragment length polymorphism (RFLP) for further confirmation of the specificity of the PCR-amplification reaction. Our analysis revealed that 9 of 27 (33%) specimens harbored the EBV genome in the tumor tissue while only 4 (15%) specimens from adjacent normal tissue exhibited evidence of EBV infection. Three were EBV positive for both normal and tumor tissue. No association has been found with disease stage, histological differentiation and nodes at pathology. The relatively high incidence of EBV in the tumor tissue (33%) of patients with laryngeal cancer, as compared to the low (15%) incidence of the virus genome detected in the adjacent normal tissue of the patients, indicates a probable role of EBV in the development of the disease.

Triterpenoids from Ganoderma lucidum inhibit the activation of EBV antigens as telomerase inhibitors

Nasopharyngeal carcinoma (NPC) is a malignant disease that threatens the health of humans. To find effective agents for the inhibition of Epstein-Barr virus (EBV) infection, which is associated with NPC, a phytochemical investigation of Ganoderma lucidum was carried out in the present study. Five triterpenoids were identified, including ganoderic acid A (compound 1), ganoderic acid B (compound 2), ganoderol B (compound 3), ganodermanontriol (compound 4), and ganodermanondiol (compound 5), on the basis of spectroscopic analysis. An inhibition of EBV antigens activation assay was implemented to elucidate the triterpenoids from G. lucidum and potentially prevent NPC. All the triterpenoids showed significant inhibitory effects on both EBV EA and CA activation at 16 nmol. At 3.2 nmol, all the compounds moderately inhibited the activation of the two antigens. The activity of telomerase was inhibited by these triterpenoids at 10 µM. Molecular docking demonstrated that compound 1 was able to inhibit telomerase as a ligand. In addition, the physicochemical properties of these compounds were calculated to elucidate their drug-like properties. These results provided evidence for the application of these triterpenoids and whole G. lucidum in the treatment of NPC.

Epstein-Barr virus BRLF1 induces genomic instability and progressive malignancy in nasopharyngeal carcinoma cells

Nasopharyngeal carcinoma (NPC) is a serious health problem in China and Southeast Asia. Relapse is the major cause of mortality, but mechanisms of relapse are mysterious. Epstein-Barr virus (EBV) reactivation and host genomic instability (GI) have correlated with NPC development. Previously, we reported that lytic early genes DNase and BALF3 induce genetic alterations and progressive malignancy in NPC cells, implying lytic proteins may be required for NPC relapse. In this study, we show that immediate early gene BRLF1 induces chromosome mis-segregation and genomic instability in the NPC cells. Similar phenomenon was also demonstrated in 293 and zebrafish embryonic cells. BRLF1 nuclear localization signal (NLS) mutant still induced genomic instability and inhibitor experiments revealed that BRLF1 interferes with chromosome segregation and induces genomic instability by activating Erk signaling. Furthermore, the chromosome aberrations and tumorigenic features of NPC cells were significantly increased with the rounds of BRLF1 expression, and these cells developed into larger tumor nodules in mice. Therefore, BRLF1 may be the important factor contributing to NPC relapse and targeting BRLF1 may benefit patients.

Seroprevalence of IgA anti Epstein-Barr virus is high among family members of nasopharyngeal cancer patients and individuals presenting with chronic complaints in head and neck area

Epstein-Barr (EBV) infection and presence of a nasopharyngeal cancer (NPC) case in the family increases the risk of developing NPC. Aberrant anti-EBV immunoglobulin A (IgA) antibodies (EBV-IgA) may be present in the sera of non-cancer individuals and predict NPC. Limited studies report the presence of EBV-IgA antibodies within non-cancer individuals in Indonesia where the disease is prevalent. This study aimed at exploring whether EBV-IgA was found more frequently among first degree relatives of NPC patients and individuals presenting with chronic symptoms in the head and neck area compared to healthy controls. A total of 967 non-cancer subjects were recruited, including 509 family members of NPC cases, 196 individuals having chronic complaints in the head and neck region, and 262 healthy donors of the local blood bank. Sera were analyzed using a standardized peptide-based EBV-IgA ELISA. Overall, 61.6% of all individuals had anti-EBV IgA reactivity equal to or below cut off value (CoV). Seroreactivity above CoV was significantly higher in females (38.7%) compared to males (28.7%) (p = 0.001). Older individuals had more seroreactivity above CoV (42.5%) than the younger ones (26.4%) (p< 0.001). Seroprevalence was significantly higher in family members of NPC patients (41.7%), compared to 32.7% of individuals with chronic head and neck problems (p = 0.028) and 16.4% healthy blood donors (p< 0.001). As conclusion, this study showed a significant higher seroprevalence in healthy family members of NPC cases and subjects presenting with chronic symptoms in the head and neck area compared to healthy individuals from the general community. This finding indicates that both groups have elevated risk of developing NPC and may serve as targets for a regional NPC screening program.

Enhanced aerobic glycolysis of nasopharyngeal carcinoma cells by Epstein-Barr virus latent membrane protein 1

Latent membrane protein 1 (LMP1) is a principal viral oncoprotein in Epstein-Barr virus (EBV)-associated malignancies, including nasopharyngeal carcinoma (NPC), which acts through regulating tumorigenesis and metabolic reprogramming of cancers. In the presence of oxygen, we demonstrated that glucose consumption, lactate production and lactate dehydrogenase (LDH) activity were significantly increased upon LMP1 expression in NPC cells and in a LMP1 variant derived from NPC patients-transformed BALB/c-3T3 cells. The amounts of the α subunit of hypoxia-inducible factor-1 (HIF-1α), a key regulator of aerobic glycolysis, and its targets, pyruvate dehydrogenase kinase 1 (PDK1) and the pyruvate kinase M2 (PKM2) isoform, were also consistently elevated by LMP1. Moreover, in parallel with reductions in the oxygen consumption rate and mitochondrial membrane potential in cells, an augmented extracellular lactate concentration was observed due to LMP1 induction. In conclusion, our results proved facilitation of the Warburg effect by LMP1 through alteration of mitochondrial function in NPC cells.

EBV reactivation as a target of luteolin to repress NPC tumorigenesis

Nasopharyngeal carcinoma (NPC) is a malignancy derived from the epithelial cells of the nasopharynx. Although a combination of radiotherapy with chemotherapy is effective for therapy, relapse and metastasis after remission remain major causes of mortality. Epstein-Barr virus (EBV) is believed to be one of causes of NPC development. We demonstrated previously that EBV reactivation is important for the carcinogenesis of NPC. We sought, therefore, to determine whether EBV reactivation can be a target for retardation of relapse of NPC. After screening, we found luteolin is able to inhibit EBV reactivation. It inhibited EBV lytic protein expression and repressed the promoter activities of two major immediate-early genes, Zta and Rta. Furthermore, luteolin was shown to reduce genomic instability induced by recurrent EBV reactivation in NPC cells. EBV reactivation-induced NPC cell proliferation and migration, as well as matrigel invasiveness, were also repressed by luteolin treatment. Tumorigenicity in mice, induced by EBV reactivation, was decreased profoundly following luteolin administration. Together, these results suggest that inhibition of EBV reactivation is a novel approach to prevent the relapse of NPC.

Functions of microRNA-143 in the apoptosis, invasion and migration of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a common cancer characterized by poor prognosis in areas of Southern China where it is endemic. microRNAs (miRNAs) are a class of naturally occurring small noncoding RNAs, some of which contribute to the initiation and development of cancer. The current study was designed to examine the expression level of miR-143 in NPC tissues. The potential functional targets of miR-143 involved in tumor apoptosis, invasion and migration were also investigated. Reverse transcription-quantitative polymerase chain reaction was used to evaluate the expression levels of miR-143 in clinical NPC specimens. Western blotting was used to explore the expression levels of extracellular signal regulated kinase (ERK)-5, Kirsten rat sarcoma viral oncogene homolog (KRAS), caspase 3 and B-cell lymphoma 2 (Bcl-2) in CNE-2Z cells following transfection with miR-143. Significantly decreased expression levels of miR-143 were observed in NPC tissues in comparison with matched normal nasopharyngeal tissues. Moreover, negative associations of miR-143 with tumor invasion depth, as well as lymph node metastasis were found. The enforced expression of miR-143 induced NPC cell apoptosis in addition to the suppression of growth, migration and invasion. The functions of miR-143 in NPC are mediated, at least in part, by the inhibition of ERK-5 activity and promotion of caspase 3 and KRAS expression. These findings suggest that miR-143 may function as a tumor suppressor in the development and progression of NPC.

Pharyngeal cancer mortality among chemical plant workers exposed to formaldehyde

Objectives: To assess the possible relationship between formaldehyde exposure and mortality risk from pharyngeal cancer (PC), in particular nasopharyngeal cancer (NPC). Methods: Subjects were 7328 workers employed at a plastics-producing plant (1941-1984). Vital status for 98% of the cohort and cause of death for 95% of 2872 deaths were determined. Reconstructed exposures to formaldehyde, particulates and pigment were used to compute several exposure measures. Standardized mortality ratios (SMRs) were computed for several demographic, work history and formaldehyde exposure variables. In a nested case-control study, seven cases of NPC and 15 cases of other PC were matched on race, sex, age and year of birth to four controls from the cohort. Among interviewed subjects, lifetime smoking history was determined using respondents or proxies for all but one control subject. Results: Statistically significant 2.23-fold and fivefold excesses for PC and NPC, respectively, were observed. Fivefold range NPC excesses were observed for both short (B / 1 year) and long-term workers and were concentrated among workers hired during 1947-1956. Only three NPC cases were exposed to formaldehyde for longer than one year, and each had low average intensity of formaldehyde exposure (0.03-0.60 ppm). Only a few exposure measures revealed some evidence of an association with all PC or NPC. For all PC combined, adjustment for smoking and year-of-hire in the case-control study generally corroborated findings from the cohort study. Conclusions: Overall, the pattern of findings suggests that the large, persistent nasopharyngeal and other PC excesses observed among the Wallingford workforce are not associated with formaldehyde exposure, and may reflect the influence of nonoccupational risk factors or occupational risk factors associated with employment outside the Wallingford plant.

Preliminary study of differentiating smears from cancerous and non-cancerous nasopharyngeal tissue using confocal Raman spectroscopy

PURPOSE

Current practice for diagnosing nasopharyngeal carcinoma (NPC) is based on invasive tissue biopsy. This study aims to explore the feasibility of using Raman spectroscopy to differentiate cancerous and non-cancerous nasopharyngeal tissue smears, expecting to realize minimal invasive diagnosis using smears from in vivo mucosa tissue by Raman spectroscopy.

METHODS

Biopsy tissue smears were acquired from 74 patients with pathologically diagnosed nasopharyngeal diseases and measured using confocal Raman spectroscopy.

RESULTS

Both fingerprint region and high wavenumber Raman spectra were acquired with distinguish features. Multivariate statistical analysis was used to differentiate cancerous and non-cancerous groups, achieving a diagnostic sensitivity of 87.2 and specificity of 85.7 % for differentiating NPC from nasopharyngeal non-cancerous smears.

CONCLUSIONS

This work indicates that the method has a unique advantage in microanalysis for tissue smears which may provide a promising minimal invasive (or noninvasive) diagnosing tool for cancer diagnosis.

Inhibitory effects of 3-bromopyruvate in human nasopharyngeal carcinoma cells

Tumor cells depend on aerobic glycolysis for adenosine triphosphate (ATP) production, which is therefore targeted by therapeutic agents. The compound 3-bromopyruvate (3-BrPA), a strong alkylating agent and hexokinase inhibitor, inhibits tumor cell glycolysis and the production of ATP, causing apoptosis. 3-BrPA induces apoptosis of nasopharyngeal carcinoma (NPC) cell lines HNE1 and CNE-2Z, which may be related to its molecular mechanisms. In the present study, we investigated the effects of 3-BrPA on the viability, reactive oxygen species (ROS), apoptosis and other types of programmed cell death in NPC cells in vitro and in vivo. PI staining showed significant apoptosis in NPC cells accompanied by the overproduction of ROS and downregulation of mitochondrial membrane potential (MMP, ΔΨm) by 3-BrPA. However, the ROS scavenger N-acetyl-L-cysteine (NAC) significantly reduced 3-BrPA-induced apoptosis by decreasing ROS and facilitating the recovery of MMP. We elucidated the molecular mechanisms underlying 3-BrPA activity and found that it caused mitochondrial dysfunction and ROS production, leading to necroptosis of NPC cells. We investigated the effects of the caspase inhibitor z-VAD-fmk, which inhibits apoptosis but promotes death domain receptor (DR)-induced NPC cell necrosis. Necrostatin-1 (Nec-1) inhibits necroptosis, apparently via a DR signaling pathway and thus abrogates the effects of z-VAD‑fmk. In addition, we demonstrated the effective attenuation of 3-BrPA-induced necrotic cell death by Nec-1. Finally, animal studies proved that 3-BrPA exhibited significant antitumor activity in nude mice. The present study is the first demonstration of 3-BrPA-induced non-apoptotic necroptosis and ROS generation in NPC cells and provides potential strategies for developing agents against apoptosis‑resistant cancers.

Sibship size, birth order and risk of nasopharyngeal carcinoma and infectious mononucleosis: a nationwide study in Sweden

BACKGROUND

The aetiology of nasopharyngeal carcinoma (NPC) remains enigmatic in endemic and non-endemic areas. Early-life infection with Epstein-Barr virus (EBV) may predispose to NPC development, whereas delayed primary infection with EBV may cause infectious mononucleosis (IM).

METHODS

We used Swedish population and health registers to investigate whether potential indicators of early EBV infection, such as birth order, sibship size, maternal age and paternal age, are related to the subsequent risks for NPC and IM. We conducted two nested case-control studies, one for each health outcome, based on 251 NPC case patients, 11 314 IM case patients and five population control subjects per case matched by birth year and sex. We used conditional logistic regression modelling to estimate odds ratios (ORs) and their 95% confidence intervals (CIs) for NPC and IM.

RESULTS

The multivariate-adjusted ORs of developing NPC increased with number of siblings; the ORs associated with having one, two and three or more siblings, compared with none, were 1.59 (95% CI = 0.97, 2.62), 1.94 (95% CI = 1.17, 3.22), and 2.03 (95% CI = 1.23, 3.35), respectively (Ptrend = 0.006). This increased risk of NPC was explained mainly by having older rather than younger siblings. In contrast, lower risks of IM were observed among individuals with an increasing number of older siblings, younger siblings and total siblings.

CONCLUSIONS

Early-life social environment, possibly related to EBV infection, contributes to NPC pathogenesis in non-endemic areas. This hypothesis is further supported by the clearly contrasting findings between NPC and IM.

EGCG inhibits proliferation, invasiveness and tumor growth by up-regulation of adhesion molecules, suppression of gelatinases activity, and induction of apoptosis in nasopharyngeal carcinoma cells

(-)-Epigallocatechin-3-gallate (EGCG), a major green tea polyphenol, has been shown to inhibit the proliferation of a variety of tumor cells. Epidemiological studies have shown that drinking green tea can reduce the incidence of nasopharyngeal carcinoma (NPC), yet the underlying mechanism is not well understood. In this study, the inhibitory effect of EGCG was tested on a set of Epstein Barr virus-negative and -positive NPC cell lines. Treatment with EGCG inhibited the proliferation of NPC cells but did not affect the growth of a non-malignant nasopharyngeal cell line, NP460hTert. Moreover, EGCG treated cells had reduced migration and invasive properties. The expression of the cell adhesion molecules E-cadherin and β-catenin was found to be up-regulated by EGCG treatment, while the down-regulation of matrix metalloproteinases (MMP)-2 and MMP-9 were found to be mediated by suppression of extracellular signal-regulated kinase (ERK) phosphorylation and AP-1 and Sp1 transactivation. Spheroid formation by NPC cells in suspension was significantly inhibited by EGCG. Oral administration of EGCG was capable of suppressing tumor growth in xenografted mice bearing NPC tumors. Treatment with EGCG was found to elevate the expression of p53 and p21, and eventually led to apoptosis of NPC cells via caspase 3 activation. The nuclear translocation of NF-κB and β-catenin was also suppressed by EGCG treatment. These results indicate that EGCG can inhibit the proliferation and invasiveness, and induce apoptosis, of NPC cells, making it a promising agent for chemoprevention or adjuvant therapy of NPC.

Limb-bud and Heart (LBH) functions as a tumor suppressor of nasopharyngeal carcinoma by inducing G1/S cell cycle arrest

Epstein–Barr virus-encoded latent membrane protein-1 (LMP1) plays a fundamental role in the malignant transformation of nasopharyngeal carcinoma (NPC), although the mechanism is not well understood. Here, we showed that Limb-bud and Heart (LBH) is considerably downregulated in patient NPC tissues. The expression of LBH in biopsies of 40 consecutive NPC patients devoid of initial distant metastasis and treated according to consistent guidelines was also analyzed, and we found the LBH expression level was correlated with some of clinicopathological features, disease-specific survival (DSS), distant metastasis-free survival (DMFS). We further determined that LBH normally induces NPC cell cycle arrest at the G1/S transition, and LBH can suppress the growth of transplanted NPC tumors in vivo by downregulating LMP1-mediated NF-κB transcriptional activity. Transforming growth factor-beta 1 (TGF-β1) normally protects against tumor development by suppressing cell proliferation, but NPC cells acquire resistance to TGF-β1–mediated inhibition. We found that TGF-β1 inhibits NF-κB transcriptional activity and nasopharyngeal epithelial cell proliferation through upregulating LBH expression. These data reveal a previously unknown NPC transformation mechanism and provide a new concept and treatment strategy for LMP1-driven oncogenesis in NPC.

Epstein-Barr virus antibodies and the risk of associated malignancies: review of the literature

Epstein-Barr virus (EBV), a ubiquitous herpes virus that infects 90% of humans by adulthood, is linked to the development of various cancers, including nasopharyngeal carcinoma, gastric cancer, Burkitt lymphoma, non-Hodgkin lymphoma (NHL), and Hodgkin lymphoma. We reviewed the literature published since 1980 regarding an association between antibodies against EBV proteins and the risk of EBV-associated malignancies. Immunoglobulin A antibody levels that are elevated before diagnosis have consistently been associated with the risk of nasopharyngeal carcinoma, and patients with Hodgkin lymphoma have significantly higher immunoglobulin G antibody levels than disease-free controls. However, the link between the immune response to EBV and other EBV-associated malignancies was less clear. Although evidence of an association between the risk of Burkitt lymphoma and immunoglobulin G antibodies was consistent for available studies, the sample sizes were limited. Evidence for a link between antibodies against EBV and risk of either gastric cancer or NHL was inconsistent. Future investigations should account for tumor EBV status because only 7%-10% of gastric tumors and select NHL subtypes are related to EBV infection. Comparing differences in the associations between the humoral immune response to EBV and disease risk across cancers may help elucidate how this ubiquitous virus contributes to distinct tumors globally.

Therapeutic implications of Epstein-Barr virus infection for the treatment of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is highly endemic in certain regions including the People’s Republic of China and Southeast Asia. Its etiology is unique and multifactorial, involving genetic background, epigenetic, and environment factors, including Epstein–Barr virus (EBV) infection. The presence of EBV in all tumor cells, aberrant pattern of antibodies against EBV antigens in patient sera, and elevated viral DNA in patient circulation as well as nasopharyngeal site underline the role of EBV during NPC development. In NPC tumors, EBV expresses latency type II, where three EBV-encoded proteins, Epstein–Barr nuclear antigen 1, latent membrane protein 1 and 2 (LMP1, 2), are expressed along with BamH1-A rightward reading frame 1, Epstein–Barr virus-encoded small nuclear RNAs, and BamH1-A rightward transcripts. Among all encoded proteins, LMP1 plays a central role in the propagation of NPC. Standard treatment of NPC consists of radiotherapy with or without chemotherapy for early stage, concurrent chemoradiotherapy in locally advanced tumors, and palliative systemic chemotherapy in metastatic disease. However, this standard care has limitations, allowing recurrences and disease progression in a certain proportion of cases. Although the pathophysiological link and molecular process of EBV-induced oncogenesis are not fully understood, therapeutic approaches targeting the virus may increase the cure rate and add clinical benefit. The promising results of early phase clinical trials on EBV-specific immunotherapy, epigenetic therapy, and treatment with viral lytic induction offer new options for treating NPC.

Epstein-Barr virus serology as a potential screening marker for nasopharyngeal carcinoma among high-risk individuals from multiplex families in Taiwan

BACKGROUND

Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-associated cancer that is highly treatable when diagnosed early, with 5-year disease-free survival of approximately 90%. However, NPC is typically diagnosed at advanced stages, in which disease-free survival is <50%. There is, therefore, a need for clinical tools to assist in early NPC detection, particularly among high-risk individuals.

METHODS

We evaluated the ability of anti-EBV IgA antibodies to detect incident NPC among high-risk Taiwanese individuals. NPC cases (N = 21) and age- and sex-matched controls (N = 84) were selected. Serum collected before NPC diagnosis was tested for ELISA-based IgA antibodies against the following EBV peptides: EBNA1, VCAp18, EAp138, Ead_p47, and VCAp18 + EBNA1 peptide mixture. The sensitivity, specificity, and screening program parameters were calculated.

RESULTS

EBNA1 IgA had the best performance characteristics. At an optimized threshold value, EBNA1 IgA measured at baseline identified 80% of the high-risk individuals who developed NPC during follow-up (80% sensitivity). However, approximately 40% of high-risk individuals who did not develop NPC also tested positive (false positives). Application of EBNA1 IgA as a biomarker to detect incident NPC in a previously unscreened, high-risk population revealed that 164 individuals needed to be screened to detect 1 NPC and that 69 individuals tested positive per case detected.

CONCLUSIONS

EBNA1 IgA proved to be a sensitive biomarker for identifying incident NPC, but future work is warranted to develop more specific screening tools to decrease the number of false positives.

IMPACT

Results from this study could inform decisions about screening biomarkers and referral thresholds for future NPC early-detection program evaluations.

Mitochondrial DNA haplogroup confers genetic susceptibility to nasopharyngeal carcinoma in Chaoshanese from Guangdong, China

Recent studies have shown association of mtDNA background with cancer development. We analyzed mitochondrial DNA (mtDNA) control region variation of 201 patients with nasopharyngeal carcinoma (NPC) and of 201 normal controls from Chaoshan Han Chinese to discern mtDNA haplogroup effect on the disease onset. Binary logistic regression analysis with adjustment for gender and age revealed that the haplogroup R9 (P = 0.011, OR = 1.91, 95% CI = 1.16-3.16), particularly its sub-haplogroup F1 (P = 0.015, OR = 2.43, 95% CI = 1.18-5.00), were associated significantly with increased NPC risk. These haplogroups were further confirmed to confer high NPC risk in males and/or individuals ≥ 40 years of age, but not in females or in subjects <40 years old. Our results indicated that mtDNA background confers genetic susceptibility to NPC in Chaoshan Han Chinese, and R9, particularly its sub-haplogroup F1, is a risk factor for NPC.

Polymorphisms in human DNA repair genes and head and neck squamous cell carcinoma

Genetic polymorphisms in some DNA repair proteins are associated with a number of malignant transformations like head and neck squamous cell carcinoma (HNSCC). Xeroderma pigmentosum group D (XPD) and X-ray repair cross-complementing proteins 1 (XRCC1) and 3 (XRCC3) genes are involved in DNA repair and were found to be associated with HNSCC in numerous studies. To establish our overall understanding of possible relationships between DNA repair gene polymorphisms and development of HNSCC, we surveyed the literature on epidemiological studies that assessed potential associations with HNSCC risk in terms of gene-environment interactions, genotype-induced functional defects in enzyme activity and/or protein expression, and the influence of ethnic origin on these associations.We conclude that large, well-designed studies of common polymorphisms in DNA repair genes are needed. Such studies may benefit from analysis of multiple genes or polymorphisms and from the consideration of relevant exposures that may influence the likelihood of HNSCC when DNA repair capacity is reduced.

Differential miRNA expression in repeated recurrence of nasopharyngeal carcinoma

Deregulated microRNAs (miRNAs) are known to be involved in the tumorigenesis of nasopharyngeal carcinoma (NPC). However, the role of miRNA expression in tumor recurrence is not yet understood. We found distinctive miRNA expression in repeated recurrent tumors using miRNA microarray, and verified this using quantitative real-time RT-PCR and miRNA in situ hybridization analysis. Computational analysis and immunohistochemistry further revealed that differentially expressed miRNAs may work in concert to modulate a multitude of biological pathways. The results not only indicate differential miRNA expression during tumor relapse, but imply the potential use of miRNAs to classify repeated recurrence of NPC beyond the histological approach.

LPLUNC1 inhibits nasopharyngeal carcinoma cell growth via down-regulation of the MAP kinase and cyclin D1/E2F pathways

Long-palate, lung and nasal epithelium clone 1 (LPLUNC1) gene expression is relatively tissue specific. It is highly expressed in nontumor nasopharyngeal epithelial tissues, but its expression is reduced in nasopharyngeal carcinoma (NPC), indicating that LPLUNC1 may be associated with the tumorigenesis of NPC. To study the effects of LPLUNC1 on NPC tumorigenesis, a full-length LPLUNC1 expression plasmid was stably transfected into the NPC cell line, 5-8F. Our data indicated that LPLUNC1 inhibited NPC cell proliferation in vitro and tumor formation in vivo. LPLUNC1 also delayed cell cycle progression from G1 to S phase and inhibited the expression of cyclin D1, cyclin-dependent kinase 4 (CDK4) and phosphorylated Rb. To further investigate the molecular mechanisms underlying the suppressive effects of LPLUNC1 on NPC tumorigenesis, cDNA microarray was performed. These studies revealed that LPLUNC1 inhibited the expression of certain mitogen-activated protein (MAP) kinases (MAPK) kinases and cell cycle-related molecules. Western blotting confirmed that the expression of MEK1, phosphorylated ERK1/2, phosphorylated JNK1/2, c-Myc and c-Jun were inhibited by LPLUNC1. Furthermore, the transcriptional activity of AP-1 was down-regulated by LPLUNC1, suggesting that the MAPK signaling pathway is regulated by LPLUNC1. Taken together, the present study indicates that LPLUNC1 delays NPC cell growth by inhibiting the MAPK and cyclin D1/E2F pathways and suggests that LPLUNC1 may represent a promising candidate tumor suppressor gene associated with NPC.

Association of LAPTM4B gene polymorphism with nasopharyngeal carcinoma susceptibility in a Chinese population

Lysosome-associated protein transmembrane-4 beta (LAPTM4B) is a novel cancer-related gene. It has two alleles designated LAPTM4B 1 and LAPTM4B 2. Previous studies have revealed that LAPTM4B polymorphisms contribute to the risk of many cancers. The aim of this study was to investigate the association between different LAPTM4B alleles and the risk of nasopharyngeal carcinoma (NPC), one of the most common cancers in southern China. Using polymerase chain reaction (PCR) in a case-control study, we detected the LAPTM4B genotype in peripheral blood samples from 134 patients with NPC and 327 control subjects. The chi-square test was used to analyze differences of categorical variables and Hardy-Weinberg equilibrium. Odds ratios and 95 % CI were computed using an unconditional logistic regression model. The frequency of allele 2 was 26.87 % in the NPC group, which was not significantly different from that of the control group (27.98 %, P = 0.867). Using the LAPTM4B 1/1 genotype as a reference, we found that the 1/2, 2/2 and 1/2 + 2/2 genotype were also not associated with the risk of NPC. No association was observed between LAPTM4B gene polymorphisms and the risk of NPC adjusted by gender and age. The results of our study indicated that the polymorphism of LAPTM4B gene did not influence the susceptibility of NPC in the Chinese population. Large-scale studies are needed to confirm our findings.

Fractal analysis of two-photon microscopic images for diagnosis of nasopharyngeal cancer

In this study, two-photon microscopy (TPM) was applied to obtain high-resolution, optically sectioned images with cellular morphology information from normal and cancerous nasopharyngeal tissue. Notable difference of nuclear-cytoplasmic ratio was found between these two groups. In particular, fractal dimension (FD) analysis based on TPM images showed good differentiation between normal and cancerous nasopharyngeal tissues. Our results indicate that TPM coupled with FD analysis methods has the potential to extract diagnostic features for label-free histological diagnosis.

Repressing malic enzyme 1 redirects glucose metabolism, unbalances the redox state, and attenuates migratory and invasive abilities in nasopharyngeal carcinoma cell lines

A large amount of nicotinamide adenine dinucleotide phosphate (NADPH) is required for fatty acid synthesis and maintenance of the redox state in cancer cells. Malic enzyme 1(ME1)-dependent NADPH production is one of the three pathways that contribute to the formation of the cytosolic NADPH pool. ME1 is generally considered to be overexpressed in cancer cells to meet the high demand for increased de novo fatty acid synthesis. In the present study, we found that glucose induced higher ME1 activity and that repressing ME1 had a profound impact on glucose metabolism of nasopharyngeal carcinoma(NPC) cells. High incorporation of glucose and an enhancement of the pentose phosphate pathway were observed in ME1-repressed cells. However, there were no obvious changes in the other two pathways for glucose metabolism: glycolysis and oxidative phosphorylation. Interestingly, NADPH was decreased under low-glucose condition in ME1-repressed cells relative to wild-type cells, whereas no significant difference was observed under high-glucose condition. ME1-repressed cells had significantly decreased tolerance to low-glucose condition. Moreover, NADPH produced by ME1 was not only important for fatty acid synthesis but also essential for maintenance of the intracellular redox state and the protection of cells from oxidative stress. Furthermore, diminished migration and invasion were observed in ME1-repressed cells due to a reduced level of Snail protein. Collectively, these results suggest an essential role for ME1 in the production of cytosolic NADPH and maintenance of migratory and invasive abilities of NPC cells.

The synergistic effect of chemical carcinogens enhances Epstein-Barr virus reactivation and tumor progression of nasopharyngeal carcinoma cells

Seroepidemiological studies imply a correlation between Epstein-Barr virus (EBV) reactivation and the development of nasopharyngeal carcinoma (NPC). N-nitroso compounds, phorbols, and butyrates are chemicals found in food and herb samples collected from NPC high-risk areas. These chemicals have been reported to be risk factors contributing to the development of NPC, however, the underlying mechanism is not fully understood. We have demonstrated previously that low dose N-methyl-N’-nitro-N-nitrosoguanidine (MNNG, 0.1 µg/ml) had a synergistic effect with 12-O-tetradecanoylphorbol-13-acetate (TPA) and sodium butyrate (SB) in enhancing EBV reactivation and genome instability in NPC cells harboring EBV. Considering that residents in NPC high-risk areas may contact regularly with these chemical carcinogens, it is vital to elucidate the relation between chemicals and EBV and their contributions to the carcinogenesis of NPC. In this study, we constructed a cell culture model to show that genome instability, alterations of cancer hallmark gene expression, and tumorigenicity were increased after recurrent EBV reactivation in NPC cells following combined treatment of TPA/SB and MNNG. NPC cells latently infected with EBV, NA, and the corresponding EBV-negative cell, NPC-TW01, were periodically treated with MNNG, TPA/SB, or TPA/SB combined with MNNG. With chemically-induced recurrent reactivation of EBV, the degree of genome instability was significantly enhanced in NA cells treated with a combination of TPA/SB and MNNG than those treated individually. The Matrigel invasiveness, as well as the tumorigenicity in mouse, was also enhanced in NA cells after recurrent EBV reactivation. Expression profile analysis by microarray indicates that many carcinogenesis-related genes were altered after recurrent EBV reactivation, and several aberrations observed in cell lines correspond to alterations in NPC lesions. These results indicate that cooperation between chemical carcinogens can enhance the reactivation of EBV and, over recurrent reactivations, lead to alteration of cancer hallmark gene expression with resultant enhancement of tumorigenesis in NPC.

Evaluation of human leukocyte antigen-A (HLA-A), other non-HLA markers on chromosome 6p21 and risk of nasopharyngeal carcinoma

BACKGROUND

The association between human leukocyte antigen (HLA) genes (located in the Major Histocompatibility Complex [MHC] region of chromosome 6p21) and NPC has been known for some time. Recently, two genome-wide association studies (GWAS) conducted in Taiwan and China confirmed that the strongest evidence for NPC association was mapped to the MHC region. It is still unclear, however, whether these findings reflect direct associations with Human Leukocyte Antigen (HLA) genes and/or to other genes in this gene-rich region.

METHODS

To better understand genetic associations for NPC within the MHC region of chromosome 6, we conducted an evaluation that pooled two previously conducted NPC case-control studies in Taiwan (N = 591 cases and N = 521 controls). PCR-based genotyping was performed for 12 significant SNPs identified within 6p21 in the Taiwan NPC GWAS and for the HLA-A gene (exons 2 and 3).

FINDINGS

After confirming homogeneity between the two studies, pooled odds ratios (OR) and 95% confidence intervals (CI) were estimated by logistic regression. We found that HLA-A (p-trend = 0.0006) and rs29232 (within the GABBR1 gene; p-trend = 0.005) were independent risk factors for NPC after adjustment for age, gender, study and each other. NPC risk was highest among individuals who were homozygous for the HLA-A*0207 risk allele and carriers of the rs29232 risk allele (A).

CONCLUSION

Our study suggests that most of the SNPs significantly associated with NPC from GWAS reflect previously identified HLA-A associations. An independent effect of rs29232 (GABBR1), however, remained, suggesting that additional genes within this region might be associated with NPC risk.

Seroreactivity against Epstein-Barr virus (EBV) among first-degree relatives of sporadic EBV-associated nasopharyngeal carcinoma in Indonesia

Epstein-Barr virus (EBV) infection and family history are significant risk factors associated with undifferentiated nasopharyngeal carcinoma. The presence of aberrant immunoglobulin A (IgA) antibodies against specific EBV antigens in healthy individuals can be predictive of the disease. Very limited reports explored the EBV IgA antibody presence within families of sporadic cases of nasopharyngeal carcinoma. This study aimed to determine whether EBV IgA was observed more frequently among family members of sporadic cases of nasopharyngeal carcinoma compared to community controls and evaluated the non-viral factors as determinants of antibody level. First-degree relatives of nasopharyngeal carcinoma patients (n = 520) and case-matched community controls (n = 86) were recruited. Sera from all individuals were tested in standardized peptide-based EBV IgA ELISA. Data on demographic variables and other exogenous factors were collected using a questionnaire through face-to-face interviews. A similar frequency of EBV IgA (cut-off value/CoV 0.354) was observed in the first-degree relatives of cases and in community controls (41.2% vs. 39.5%, P = 0.770). However, with a higher antibody level (OD(450)  = 1.000; about three times standard CoV), the relatives showed significantly higher frequency (36.9% vs. 14.7%, P = 0.011). When adjusted for all exogenous factors, the strongest factors associated with seropositivity are being a father (odds ratio/OR = 4.36; 95% confidence interval/CI = 1.56-12.21) or a sibling (OR = 1.89; 95% CI = 1.06-3.38) of a case of nasopharyngeal carcinoma. The higher level of EBV IgA seroreactivity in first-degree relatives of sporadic cases of nasopharyngeal carcinoma compared to the general population supports the use of EBV IgA ELISA for screening among family members.

Nasopharyngeal carcinoma in Indonesia: epidemiology, incidence, signs, and symptoms at presentation

Among all head and neck (H&N) cancers, nasopharyngeal carcinoma (NPC) represents a distinct entity regarding epidemiology, clinical presentation, biological markers, carcinogenic risk factors, and prognostic factors. NPC is endemic in certain regions of the world, especially in Southeast Asia, and has a poor prognosis. In Indonesia, the recorded mean prevalence is 6.2/100 000, with 13 000 yearly new NPC cases, but otherwise little is documented on NPC in Indonesia. Here, we report on a group of 1121 NPC patients diagnosed and treated at Dr. Cipto Mangunkusumo Hospital, Jakarta, Indonesia between 1996 and 2005. We studied NPC incidence among all H&N cancer cases (n=6000) observed in that period, focusing on age and gender distribution, the ethnic background of patients, and the disease etiology. We also analyzed most prevalent signs and symptoms and staging of NPC patients at first presentation. In this study population, NPC was the most frequent H&N cancer (28.4%), with a male-to-female ratio of 2.4, and was endemic in the Javanese population. Interestingly, NPC appeared to affect patients at a relatively young age (20% juvenile cases) without a bimodal age distribution. Mostly, NPC initiated in the fossa of Rosenmuller and spreaded intracranially or locally as a mass in the head. Occasionally, NPC developed at the submucosal level spreading outside the anatomic limits of the nasopharynx. At presentation, NPC associated with hearing problems, serous otitis media, tinnitus, nasal obstruction, anosmia, bleeding, difficulty in swallowing and dysphonia, and even eye symptoms with diplopia and pain. The initial diagnosis is difficult to make because early signs and symptoms of NPC are not specific to the disease. Early-age Epstein-Barr virus (EBV) infection combined with frequent exposure to environmental carcinogenic co-factors is suggested to cause NPC development. Undifferentiated NPC is the most frequent histological type and is closely associated with EBV. Expression of the EBV-encoded latent membrane protein 1(LMP1) oncogene in biopsy material was compared between NPC patients of <30 years old and those of ≥30 years old, matched for sex and tumor stage. Higher LMP1 expression in patients of <30 years old was observed, which was related to more locoregional progressivity. Increased medical awareness of prevailing early stage signs and symptoms coupled to use of EBV-related diagnostic tumor markers may lead to down-staging and timely treatment to improve survival of patients with this aggressive disease.

Genetic predisposition factors and nasopharyngeal carcinoma risk: a review of epidemiological association studies, 2000-2011: Rosetta Stone for NPC: genetics, viral infection, and other environmental factors

While infection with Epstein-Barr virus (EBV) is known to be an essential risk factor for the development of nasopharyngeal carcinoma (NPC), other co-factors including genetic factors are thought to play an important role. In this review, we summarize association studies conducted over the past decade to evaluate the role of genetic polymorphisms in NPC development. A review of the literature identified close to 100 studies, including 3 genome-wide association studies (GWAS), since 2000 that evaluated genetic polymorphisms and NPC risk in at least 100 NPC cases and 100 controls. Consistent evidence for associations were reported for a handful of genes, including immune-related HLA Class I genes, DNA repair gene RAD51L1, cell cycle control genes MDM2 and TP53, and cell adhesion/migration gene MMP2. However, for most of the genes evaluated, there was no effort to replicate findings and studies were largely modest in size, typically consisting of no more than a few hundred cases and controls. The small size of most studies, and the lack of attempts at replication have limited progress in understanding the genetics of NPC. Moving forward, if we are to advance our understanding of genetic factors involved in the development of NPC, and of the impact of gene-gene and gene-environment interations in the development of this disease, consortial efforts that pool across multiple, well-designed and coordinated efforts will most likely be required.