Immunogenetic aspects of nasopharyngeal carcinoma: I. Differences in HL-A antigen profiles between patients and control groups

Current Status and Future Perspectives about Molecular Biomarkers of Nasopharyngeal Carcinoma

Simple Summary

Nasopharyngeal carcinoma is a serious major public health problem in its endemic countries. Up to 80% of NPC patients with locally advanced disease or distant metastasis at diagnosis were associated with poor prognosis and with median survival less than 4 months. The mortality rate of NPC metastasis is up to 91%. To date, there is no available curative treatment or reliable early diagnosis or prognosis for NPC. Discovery and development of reliable early diagnosis and prognosis biomarkers for nasopharyngeal carcinoma are urgent needed. Hence, we have here listed the potential early diagnosis and prognosis biomarker candidates for nasopharyngeal carcinoma. This review will give an insight to readers on the progress of NPC biomarker discovery to date, as well as future prospective biomarker development and their translation to clinical use.

Abstract

Nasopharyngeal carcinoma (NPC) is an epithelial malignancy that shows a remarkable ethnic and geographical distribution. It is one of the major public health problems in some countries, especially Southern China and Southeast Asia, but rare in most Western countries. Multifactorial interactions such as Epstein–Barr virus infection, individual’s genetic susceptibility, as well as environmental and dietary factors may facilitate the pathogenesis of this malignancy. Late presentation and the complex nature of the disease have led it to become a major cause of mortality. Therefore, an effective, sensitive, and specific molecular biomarker is urgently needed for early disease diagnosis, prognosis, and prediction of metastasis and recurrence after treatment. In this review, we discuss the recent research status of potential biomarker discovery and the problems that need to be explored further for better NPC management. By studying the aberrant pattern of these candidate biomarkers that promote NPC development and progression, we are able to understand the complexity of this malignancy better, hence positing our stands better towards strategies that may provide a way forward to the discovery of more reliable and specific biomarkers for diagnosis and targeted therapeutic development.

The roles of ribosomal proteins in nasopharyngeal cancer: culprits, sentinels or both

Ribosomal protein genes encode products that are essential for cellular protein biosynthesis and are major components of ribosomes. Canonically, they are involved in the complex system of ribosome biogenesis pivotal to the catalysis of protein translation. Amid this tightly organised process, some ribosomal proteins have unique spatial and temporal physiological activity giving rise to their extra-ribosomal functions. Many of these extra-ribosomal roles pertain to cellular growth and differentiation, thus implicating the involvement of some ribosomal proteins in organogenesis. Consequently, dysregulated functions of these ribosomal proteins could be linked to oncogenesis or neoplastic transformation of human cells. Their suspected roles in carcinogenesis have been reported but not specifically explained for malignancy of the nasopharynx. This is despite the fact that literature since one and half decade ago have documented the association of ribosomal proteins to nasopharyngeal cancer. In this review, we explain the association and contribution of dysregulated expression among a subset of ribosomal proteins to nasopharyngeal oncogenesis. The relationship of these ribosomal proteins with the cancer are explained. We provide information to indicate that the dysfunctional extra-ribosomal activities of specific ribosomal proteins are tightly involved with the molecular pathogenesis of nasopharyngeal cancer albeit mechanisms yet to be precisely defined. The complete knowledge of this will impact future applications in the effective management of nasopharyngeal cancer.

Histocompatibility locus antigens regions contribute to the ethnicity bias of Epstein-Barr virus-associated nasopharyngeal carcinoma in higher-incidence populations

Nasopharyngeal carcinoma (NPC) is one the most confusing and rare malignancy in most part of the world with significantly high occurrence in some populations of Southeast Asia, North Africa and Alaska. Apart from the dietary and environmental factors, NPC is well-associated with Epstein-Barr virus (EBV) infection in these ethnic groups. However, the internal molecular mechanism(s) for such association in specific populations is not known till date. Polymorphisms in the genes of histocompatibility locus antigens (HLA) are reported in NPC, but association of any particular polymorphism with ethnicity is not established yet. Here, we report a set of HLA polymorphisms in EBV-infected NPC samples from Northeast Indian population. These polymorphisms might play an important role for the lack of proper immune function against EBV infection and thus, eventually, for NPC generation in endemic populations like those of Northeast India.

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.

Fine-mapping of HLA class I and class II genes identified two independent novel variants associated with nasopharyngeal carcinoma susceptibility

BACKGROUND

Several genome-wide association studies (GWASs) have identified strong associations between genetic variants in the human leukocyte antigen (HLA) region and nasopharyngeal carcinoma (NPC). However, given the complex LD pattern in this region, the causal variants and the underlying mechanism of how genetic variants in HLA contribute to NPC development is yet to be understood.

METHODS

To systematically characterize the HLA variants and their relationship to NPC susceptibility, we fine-mapped the HLA genes based on the GWAS data of 1583 NPC cases and 972 healthy controls, using SNP2HLA with the Pan-Asian panel as references. Stepwise conditional regression was used to identify independent association loci.

RESULTS

Interestingly, the most significant association was the presence of Gln in HLA-A amino acid position 62 (OR = 0.57, P = 1.41 × 10^-16 ). The G allele of rs2894207 located between HLA-B and HLA-C showed protective effect of NPC development (OR = 0.52, P = 2.23 × 10^-13 ). Additionally, amino acid Phe-67 located in the peptide-binding pocket of HLA-DRB1 was identified as a novel functional variant with OR = 0.64 and P = 9.64 × 10^-11 . Another novel variant, Glu-45 in HLA-B pocket B, conferred a protective effect on NPC susceptibility (OR = 0.64, P = 5.23 × 10^-8 ). These four variants explained 2.07% of the phenotypic variance for NPC risk.

CONCLUSION

In summary, by fine-mapping the HLA region in south Chinese population, we reported additional loci missed in the GWAS studies and provided a better understanding of the relationship between HLA and NPC susceptibility.

Systematic Review and Meta-analysis of SNPs from Genome-Wide Association Studies of Head and Neck Cancer

Objective Various genome-wide association studies (GWASs) identified new head and neck cancer (HNC) susceptibility loci, although the evidence has not been systematically summarized. We performed a systematic review and meta-analyses of the GWASs to identify the most commonly reported genetic loci associated with a risk of HNC. Data Sources We searched the PubMed, ISI Web of Science, SCOPUS, and GWAS databases to retrieve eligible studies, in English or Italian, published until June 1, 2017. Review Methods Only GWASs reporting data on the association between single-nucleotide polymorphisms (SNPs) and HNC were included. The quality of included studies was evaluated using the Q-Genie tool. Random-effect meta-analyses were performed considering only SNPs with at least 1 significant result from the included articles, and pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Results Seven studies of case-control design were included in the review. Five studies on nasopharyngeal cancer (NPC) in Chinese, reporting on 27 different SNPs, were included in meta-analyses. Results show that 6 SNPs ( rs2076483, rs2975042, rs9258122, rs29232, and rs9510787) had an increased pooled estimates for A risk alleles (OR [95% CI]: 1.55 [1.36-1.77], 1.90 [1.69-2.14], 1.47 [1.31-1.65], 1.52 [1.32-1.76], and 1.22 [1.13-1.31], respectively) while G risk allele of rs3129055 reported an OR of 1.49 (95% CI, 1.33-1.67). Conclusion Our systematic review identified 5 SNPs located on chromosome 6 ( rs2076483, rs2975042, rs3129055, rs9258122, and rs29232) and 1 ( rs9510787) on chromosome 13 as significantly associated with an increased risk of NPC in Chinese.

Carcinogenesis of nasopharyngeal carcinoma: an alternate hypothetical mechanism

Current proposed mechanisms implicate both early and latent Epstein-Barr virus (EBV) infection in the carcinogenic cascade, whereas epidemiological studies have always associated nasopharyngeal carcinoma (NPC) with early childhood EBV infection and with chronic ear, nose, and sinus conditions. Moreover, most patients with NPC present with IgA antibody titers to EBV capsid antigen (VCA-IgA), which can precede actual tumor presentation by several years. If early childhood EBV infection indeed constitutes a key event in NPC carcinogenesis, one would have to explain the inability to detect the virus in normal nasopharyngeal epithelium of patients at a high risk for EBV infection. It is perhaps possible that EBV resides within the salivary glands, instead of the epithelium, during latency. This claim is indirectly supported by observations that the East Asian phenotype shares the characteristics of an increased susceptibility to NPC and immature salivary gland morphogenesis, the latter of which is influenced by the association of salivary gland morphogenesis with an evolutionary variant of the human ectodysplasin receptor gene (EDAR), EDARV370A. Whether the immature salivary gland represents a more favorable nidus for EBV is uncertain, but in patients with infectious mononucleosis, EBV has been isolated in this anatomical organ. The presence of EBV-induced lymphoepitheliomas in the salivary glands and lungs further addresses the possibility of submucosal spread of the virus. Adding to the fact that the fossa of Rosen Müller contains a transformative zone active only in the first decade of life, one might be tempted to speculate the possibility of an alternative carcinogenic cascade for NPC that is perhaps not dissimilar to the model of human papillomavirus and cervical cancer.

A Genome Wide Study of Copy Number Variation Associated with Nasopharyngeal Carcinoma in Malaysian Chinese Identifies CNVs at 11q14.3 and 6p21.3 as Candidate Loci

Background

Nasopharyngeal carcinoma (NPC) is a neoplasm of the epithelial lining of the nasopharynx. Despite various reports linking genomic variants to NPC predisposition, very few reports were done on copy number variations (CNV). CNV is an inherent structural variation that has been found to be involved in cancer predisposition.

Methods

A discovery cohort of Malaysian Chinese descent (NPC patients, n = 140; Healthy controls, n = 256) were genotyped using Illumina^® HumanOmniExpress BeadChip. PennCNV and cnvPartition calling algorithms were applied for CNV calling. Taqman CNV assays and digital PCR were used to validate CNV calls and replicate candidate copy number variant region (CNVR) associations in a follow-up Malaysian Chinese (NPC cases, n = 465; and Healthy controls, n = 677) and Malay cohort (NPC cases, n = 114; Healthy controls, n = 124).

Results

Six putative CNVRs overlapping GRM5, MICA/HCP5/HCG26, LILRB3/LILRA6, DPY19L2, RNase3/RNase2 and GOLPH3 genes were jointly identified by PennCNV and cnvPartition. CNVs overlapping GRM5 and MICA/HCP5/HCG26 were subjected to further validation by Taqman CNV assays and digital PCR. Combined analysis in Malaysian Chinese cohort revealed a strong association at CNVR on chromosome 11q14.3 (P_combined = 1.54x10^-5; odds ratio (OR) = 7.27; 95% CI = 2.96–17.88) overlapping GRM5 and a suggestive association at CNVR on chromosome 6p21.3 (P_combined = 1.29x10^-3; OR = 4.21; 95% CI = 1.75–10.11) overlapping MICA/HCP5/HCG26 genes.

Conclusion

Our results demonstrated the association of CNVs towards NPC susceptibility, implicating a possible role of CNVs in NPC development.

Heterogeneity revealed through meta-analysis might link geographical differences with nasopharyngeal carcinoma incidence in Han Chinese populations

Background

Nasopharyngeal carcinoma (NPC) is an epithelial malignancy highly prevalent in southern China, and incidence rates among Han Chinese people vary according to geographic region. Recently, three independent genome-wide association studies (GWASs) confirmed that HLA-A is the main risk gene for NPC. However, the results of studies conducted in regions with dissimilar incidence rates contradicted the claims that HLA-A is the sole risk gene and that the association of rs29232 is independent of the HLA-A effect in the chromosome 6p21.3 region.

Methods

We performed a meta-analysis, selecting five single-nucleotide polymorphisms (SNPs) in chromosome 6p21.3 mapped in three published GWASs and four case–control studies. The studies involved 8994 patients with NPC and 11,157 healthy controls, all of whom were Han Chinese.

Results

The rs2517713 SNP located downstream of HLA-A was significantly associated with NPC (P = 1.08 × 10⁻⁹¹, odds ratio [OR] = 0.58, 95 % confidence interval [CI] = 0.55–0.61). The rs29232 SNP exhibited a moderate level of heterogeneity (I² = 47 %) that disappeared (I² = 0 %) after stratification by moderate- and high-incidence NPC regions.

Conclusions

Our results suggested that the HLA-A gene is strongly associated with NPC risk. In addition, the heterogeneity revealed by the meta-analysis of rs29232 might be associated with regional differences in NPC incidence among Han Chinese people. The higher OR of rs29232 and the fact that rs29232 was independent of the HLA-A effect in the moderate-incidence population suggested that rs29232 might have greater relevance to NPC incidence in a moderate-incidence population than in a high-incidence population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1607-0) contains supplementary material, which is available to authorized users.

Is palatal vault height a determinant for nasopharyngeal carcinoma: A hypothesis?

Although environmental and genetic factors are known for nasopharyngeal carcinoma, the present study is an attempt to provide a hypothesis behind the development of NPC with regards to the anatomical factor, the hypothesis being that patients with a deeper palatal vault tend to have a higher risk of developing nasopharyngeal cancers. The objective of this study was to find out the palatal vault height in patients with nasopharyngeal carcinoma and compare it with the palatal vault height in patients with oral carcinomas. The heights of the palatal vault of 20 consecutive patients with nasopharyngeal carcinoma and 20 patients with carcinoma of the oral cavity (except hard palate) as control were recorded. In addition, in patients with carcinoma of the nasopharynx the height of the palate on the CT scans was measured and correlation between these recordings were calculated. The palatal heights of the nasopharyngeal and oral cancer cohorts were compared using independent sample T test. A strong correlation was observed in the nasopharyngeal cancer cohort between the palatal height measured manually and the radiologically measured height on the CT scans (Pearson Correlation Coefficient - 0.633; p=0.003). The difference in the mean heights of the nasopharyngeal and oral cancer cohorts was statistically significant (p<0.001). Nasopharyngeal cancer patients tend to have a higher palatal vault height compared to those with carcinoma of oral cavity other than hard palate. In such palates with a deep vault, there is increased turbulent air flow leading to increased deposition of air-borne virus/carcinogens. Lingering of these agents may ultimately cause carcinoma of the nasopharynx.

Sequence-based typing of HLA-A gene in 930 patients with nasopharyngeal carcinoma in Hunan province, southern China

In this study, we typed 930 cases of nasopharyngeal carcinoma (NPC) and 1134 normal controls recruited from Hunan province, southern China for human leukocyte antigen-A (HLA-A) locus by sequencing exons 2-4. Very significant associations between HLA-A*02:07, HLA-A*11:01 and NPC were established [25.7% vs 16.18%; odds ratio, OR (95% confidence interval, CI) = 1.79 (1.54-2.09), P < 0.0001 and 21.1% vs 30.42%, OR (95% CI) = 0.61 (0.53-0.70), P<0.0001, respectively]. Further analysis of the molecular basis underlying these associations suggests that cysteine (C) at codon 99 of α2-helix of HLA-A protein is probably deleterious and confers risk to NPC. Convincing evidence was uncovered for negative association of a rare allele in southern Chinese populations, HLA-A*31:01, with NPC [0.22% vs 2.12%, OR (95% CI) = 0.1 (0.04-0.28), P < 0.0001]. rs1059449-A, which encodes arginine (R) at codon 56 of α1-helix of HLA-A protein, was postulated to be crucial for such a pattern of negative association with NPC. A subset of NPC cases (N = 632) and normal controls (N=712) were tested for anti-virus capsid antigen (anti-VCA) immunoglobulin A (IgA), very significant difference in seropositivity for anti-VCA IgA was observed between the two groups [67.56% vs 6.46%, OR (95% CI) = 30.16 (21.42-42.46), P < 0.0001]. However, seropositivity for anti-VCA IgA did not correlate with HLA-A allelic typing in both groups.

Human leukocyte antigens and epstein-barr virus-associated nasopharyngeal carcinoma: old associations offer new clues into the role of immunity in infection-associated cancers

Nasopharyngeal carcinoma (NPC) is an Epstein–Barr virus (EBV) associated tumor. In addition to EBV, host genetic factors are believed to be important determinants of NPC risk. Of all genes studies to date, human leukocyte antigen (HLA) genes have shown the most consistent evidence for association with NPC, both from candidate-gene studies and genome-wide association studies (GWAS). In this report we summarize results from recent studies that evaluated the association between HLA and NPC, and discuss whether findings reflect direct causal associations for HLA genes and/or indirect associations that mark causal associations with other genes in the gene-dense major histocompatibility (MHC) region where HLA resides. We also compare GWAS results across cancer sites for which strong hits in the MHC region were observed to generate new hypotheses regarding the role of HLA genes in the development of EBV-associated cancers such as NPC. Of note, we report that MHC associations for EBV-associated cancers (NPC, EBV+ Hodgkin lymphoma) are driven by HLA class I genes. In contrast, MHC associations for other viral-associated cancers (cervical cancer, hepatocellular carcinoma) or other hematopoetic cancers (EBV− Hodgkin lymphoma, leukemia, non-Hodgkin lymphomas) are driven by HLA class II genes, and those for other solid tumors with less clear links to infections (lung, testicular, prostate cancers) are driven by non-HLA genes in the MHC region. Future studies should aim to better understand these patterns.

Familial and large-scale case-control studies identify genes associated with nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is an epithelial malignancy and has a remarkable geographic distribution, which is highly prevalent in southern China, Southeast Asia, and North Africa. Although most of the NPC are sporadic cases, the familial clustering of NPC has been demonstrated worldwide. Accumulating studies have proposed that the etiology of NPC is multi-stage and multi-factorial, involving genetic lesions, Epstein-Barr virus infection, and environmental exposure. Genetic variations result in differences in gene function, which in turn lead to different susceptibility to disease. Many studies have been carried out to dissect the genetic variants that contribute to NPC susceptibility. This article reviews the current progress of genetic studies to identify genes associated with NPC, focusing on the familial linkage and large-scale case-control study designs.

HLA association with nasopharyngeal carcinoma in southern Tunisia

In order to study the association of HLA-A, -B and/or DRB1, DQB1 and the nasopharyngeal carcinoma (NPC), 141 patients affected with NPC were typed for the HLA class I by serology method of microlymphocytotoxicity. Among these patients 101 were genotyped for HLA class II system by the PCR-SSP technique. HLA typing results were compared to those of 116 controls. We found that the HLA-A31 and -A33 antigens were significantly more expressed in patients than in the controls (P = 0.016 and 0.010, respectively) and the HLA-A19 antigen, was significantly more frequent in patients when compared to the controls (P = 0.007). The HLA-DRB1*03 and DRB1*13 alleles were significantly more frequent in patients as compared to the controls. The DRB1*01 allele was expressed with a frequency of 20.69% in the controls whereas it was only detected in 3.96% of the NPC patients. Furthermore, the DQB1*05 allele was expressed at a frequency which was significantly less important in affected patient (P = 0.03), whereas, the DQB1*02 allele was more frequent in patients (P = 0.643 x 10(-4)). Thus our study revealed a significant increase of HLA-A31, A33, A19, B16, B53 and DRB1*03, DRB1*13 and DQB1*02 alleles in our patients. These markers could play a predisposing role in the development of NPC. In contrast, a decrease of HLA-B14, -B35 and DRB1*01 and DQB1*05 alleles was found suggesting a likely protective effect.

MDM2 Promoter SNP309 Is Associated with Risk of Occurrence and Advanced Lymph Node Metastasis of Nasopharyngeal Carcinoma in Chinese Population

PURPOSE

Mouse double minute 2 (MDM2) is a key negative regulator of the p53 activity. Recently, a polymorphism in the MDM2 intronic promoter, SNP309, was shown to influence MDM2 expression and p53 activity. We examined whether the SNP309 was related to the risk of developing nasopharyngeal carcinoma (NPC) among Chinese populations.

EXPERIMENTAL DESIGN

We genotyped the SNP309 in two independent case-control populations in southern China, one is from Guangxi province (including 593 NPC patients and 480 controls) and the other is from Guangdong province (including 239 patients and 286 controls), by PCR direct sequencing. Multivariate logistic regression analysis was used to calculate adjusted odds ratio (OR) and 95% confidence interval (95% CI).

RESULTS

We observed that compared with the TT genotype, the genotypes containing G allele (GT + GG genotype) were associated with significant increased susceptibility to NPC in both Guangxi (OR, 1.43; 95% CI, 1.04-1.91) and Guangdong population (OR, 1.53; 95% CI, 1.00-2.36). When these two sample sets were combined, the OR of the GT + GG genotype developing NPC was 1.45 (95% CI, 1.12-1.85) compared with the TT genotype. Furthermore, compared with the TT genotype, the GT + GG genotype was also significantly associated with the advanced lymph node metastasis (OR, 1.84; 95% CI, 1.09-3.05).

CONCLUSIONS

Our findings suggest that the MDM2 SNP309 may be a risk factor for the occurrence and advanced neck lymph node metastasis of NPC in Chinese population.

The enigmatic epidemiology of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) has a unique and complex etiology that is not completely understood. Although NPC is rare in most populations, it is a leading form of cancer in a few well-defined populations, including natives of southern China, Southeast Asia, the Arctic, and the Middle East/North Africa. The distinctive racial/ethnic and geographic distribution of NPC worldwide suggests that both environmental factors and genetic traits contribute to its development. This review aims to summarize the current knowledge regarding the epidemiology of NPC and to propose new avenues of research that could help illuminate the causes and ultimately the prevention of this remarkable disease. Well-established risk factors for NPC include elevated antibody titers against the Epstein-Barr virus, consumption of salt-preserved fish, a family history of NPC, and certain human leukocyte antigen class I genotypes. Consumption of other preserved foods, tobacco smoking, and a history of chronic respiratory tract conditions may be associated with elevated NPC risk, whereas consumption of fresh fruits and vegetables and other human leukocyte antigen genotypes may be associated with decreased risk. Evidence for a causal role of various inhalants, herbal medicines, and occupational exposures is inconsistent. Other than dietary modification, no concrete preventive measures for NPC exist. Given the unresolved gaps in understanding of NPC, there is a clear need for large-scale, population-based molecular epidemiologic studies to elucidate how environmental, viral, and genetic factors interact in both the development and the prevention of this disease.

Variation of the killer cell immunoglobulin-like receptors and HLA-C genes in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is an Epstein-Barrvirus (EBV)-associated malignancy. Previous studies have shown that NPC is associated with specific human leukocyte antigen (HLA) alleles which function in adaptive immunity to present viral and other antigens to the immune system. The role of innate immunity in NPC development is unknown. To determine whether innate immunity is associated with NPC, a case-control study was conducted among 295 Taiwanese NPC cases (99% EBV seropositive) and 252 community controls (29% EBV seropositive). Using high-resolution genotyping, we evaluated the variation of HLA class I alleles and killer cell immunoglobulin-like receptor (KIR) alleles. Located on the surface of natural killer (NK) cells and a subset of T cells, inhibitory KIRs diminish NK cytolysis of target cells upon binding to their HLA class I ligands and activating KIRs are thought to stimulate NK destruction of target cells. Our results suggest that an increasing number of activating KIRs may be associated with increasing NPC risk, particularly in individuals seropositive for anti-EBV antibodies known to be linked to NPC susceptibility (P(trend) = 0.07). Among EBV-seropositive individuals, carriers of > or =5 activating KIRs had a 3.4-fold increased risk of disease (95% confidence interval, 0.74-15.7) compared with individuals with no functional activating KIRs. In contrast, there was no clear evidence of risk associated with increasing numbers of inhibitory KIRs. When evaluating HLA-Cw alleles, we observed that carriers of HLA-Cw*0401 alleles were at a significantly reduced NPC risk (odds ratio, 0.46; 95% confidence intervals, 0.23-0.92), an effect that could not be explained by linkage disequilibrium with other NPC-associated HLA alleles. Our results suggest that KIR-mediated activation may be associated with NPC risk. As this finding is consistent with a recent report examining cervical cancer, a malignancy caused by human papillomavirus, the data raises the possibility that KIRs, and more generally innate immunity, may be involved in the pathogenesis of viral-associated cancers.

Nasopharyngeal carcinoma-susceptibility locus is localized to a 132 kb segment containing HLA-A using high-resolution microsatellite mapping

Nasopharyngeal carcinoma (NPC) is an epithelial tumor uniquely prevalent in southern Chinese. HLA-A2 is associated with NPC. In a previous study, we showed that the genes associated with susceptibility to NPC are primarily located within the HLA-A locus in Taiwanese NPC patients. However, the pathogenic genes causing NPC susceptibility remain unknown. Here, 8 polymorphic microsatellite markers distributed over a 1 megabase region surrounding the HLA-A locus were subjected to genetic analysis for the NPC-susceptibility locus. Statistical studies of associated alleles detected on each microsatellite locus showed that the NPC- susceptibility genes are most likely located between the D6S510 and D6S211 markers within a 132 kb segment containing the HLA-A locus. These results undoubtedly would facilitate the further positional cloning of the NPC-susceptibility locus, which has been elusive for the past 30 years.

Epstein-Barr virus and cancer

EBV was the first human virus to be directly implicated in carcinogenesis. It infects >90% of the world's population. Although most humans coexist with the virus without serious sequelae, a small proportion will develop tumors. Normal host populations can have vastly different susceptibility to EBV-related tumors as demonstrated by geographical and immunological variations in the prevalence of these cancers. EBV has been implicated in the pathogenesis of Burkitt's lymphoma, Hodgkin's disease, non-Hodgkin's lymphoma, nasopharyngeal carcinoma, and lymphomas, as well as leiomyosarcomas arising in immunocompromised individuals. The presence of this virus has also been associated with epithelial malignancies arising in the gastric region and the breast, although some of this work remains in dispute. EBV uses its viral proteins, the actions of which mimic several growth factors, transcription factors, and antiapoptotic factors, to usurp control of the cellular pathways that regulate diverse homeostatic cellular functions. Recent advances in antiviral therapeutics, application of monoclonal antibodies, and generation of EBV-specific CTLs are beginning to show promise in the treatment of EBV-related disorders.

Genetic susceptibility to nasopharyngeal carcinoma within the HLA-A locus in Taiwanese

NPC is an epithelial tumor that is highly prevalent among the southern Chinese. Numerous studies have indicated that specific HLA haplotypes and genes within the HLA complex are associated with NPC. As a first effort to localize the gene responsible for susceptibility, the HLA-A, -B, and -A2 subtypes were examined for their association to NPC. Consistent with previous reports, frequencies of HLA-A2 [OR = 2.50, pc = 0.020 (study population); OR = 3.73, pc = 0.0030 (> or =40 years old)] were significantly higher in patients with NPC than in healthy controls. Two-locus analysis indicated that A2(+)B46(+) individuals are at greater risk for NPC than A2(-)B46(-) individuals in both the population studied and the > or =40-year-old group. This, however, may be due to the close linkage of these 2 genes. Moreover, A2(+)B38(+) individuals were at higher risk than A2(-)B38(-) individuals in both the population studied and the > or =40-year-old group; A2 and B38 are not genetically linked. These findings suggest that B38 or B46 alone cannot confer a high risk of NPC but that, in conjunction with A2, B38 or B46 positivity greatly increases risk. None of 5 A2 subtypes identified from studied populations was significantly associated with NPC. Microsatellite marker D6S211, located 97 kb telomeric to HLA-A, was analyzed for its association with NPC. Allele 4 of D6S211 was significantly associated with NPC (OR = 3.97, pc = 0.0042). These results strongly support the hypothesis that genes associated with susceptibility to NPC in the HLA region are within the HLA-A locus.

The aetiology of nasopharyngeal carcinoma

Nasopharyngeal carcinoma is a disease with a remarkable racial and geographical distribution. In most parts of the world it is a rare condition and in only a handful of places does this low risk profile alter. These include the Southern Chinese, Eskimos and other Arctic natives, inhabitants of South-East Asia and also the populations of North Africa and Kuwait.

Nasopharyngeal carcinoma, with emphasis on its relationship to Epstein-Barr virus

Nasopharyngeal carcinoma (NPC) is an epithelial tumor with a distinct geographic distribution and characteristic histologic appearance. It is rare in Europe and North America, but it is among the most common cancers in southern China. Genetic predisposition, environmental factors, and Epstein-Barr virus (EBV) all have been associated with the pathogenesis of this tumor. There is an increasing body of evidence that among all these factors, EBV appears to be the strongest and most consistently related factor. According to the current sensitive in situ hybridization methods for the detection of EBV-encoded small RNAs (EBER), almost 100% of cases of NPC, irrespective of their histologic subtypes, have demonstrable EBERs in the nuclei of the tumor cells. In this review paper, we discuss the predisposing genetic and environmental factors and the role of EBV in the pathogenesis of this tumor with particular emphasis on the role of EBV.

Immune regulation in Epstein-Barr virus-associated diseases

Epstein-Barr virus (EBV) is a member of the human herpesvirus family and, like many other herpesviruses, maintains a lifelong latent association with B lymphocytes and a permissive association with stratified epithelium in the oropharynx. Clinical manifestations of primary EBV infection range from acute infectious mononucleosis to an asymptomatic persistent infection. EBV is also associated with a number of malignancies in humans. This review discusses features of the biology of the virus, both in cell culture systems and in the natural host, before turning to the role of the immune system in controlling EBV infection in healthy individuals and in individuals with EBV-associated diseases. Cytotoxic T cells that recognize virally determined epitopes on infected cells make up the major effector arm and control the persistent infection. In contrast, the options for immune control of EBV-associated malignancies are more restricted. Not only is antigen expression restricted to a single nuclear antigen, EBNA1, but also these tumor cells are unable to process EBV latent antigens, presumably because of a transcriptional defect in antigen-processing genes (such as TAP1 and TAP2). The likelihood of producing a vaccine capable of controlling the acute viral infection and EBV-associated malignancies is also discussed.

HLA A2.1-restricted cytotoxic T cells recognizing a range of Epstein-Barr virus isolates through a defined epitope in latent membrane protein LMP2

Cytotoxic T-lymphocyte (CTL) responses induced by persistent Epstein-Barr virus (EBV) infection in normal B-lymphoid tissues could potentially be directed against EBV-positive malignancies if expression of the relevant viral target proteins is maintained in tumor cells. For malignancies such as nasopharyngeal carcinoma and Hodgkin's disease, this will require CTL targeting against the nuclear antigen EBNA1 or the latent membrane proteins LMP1 and LMP2. Here we analyze in detail a B95.8 EBV-reactivated CTL response which is specific for LMP2 and restricted through a common HLA allele, A2.1. We found that in vitro-reactivated CTL preparations from several A2.1-positive virus-immune donors contained detectable reactivity against A2.1-bearing target cells expressing either LMP2A or the smaller LMP2B protein from recombinant vaccinia virus vectors. Peptide sensitization experiments then mapped the A2.1-restricted response to a single epitope, the nonamer CLGGLLTMV (LMP2A residues 426 to 434), whose sequence accords well with the proposed peptide binding motif for A2.1. Most Caucasian and African virus isolates (whether of type 1 or type 2) were identical in sequence to B95.8 across this LMP2 epitope region, although 2 of 12 such isolates encoded a Leu-->Ile change at epitope position 6. In contrast, most Southeast Asian and New Guinean isolates (whether of type 1 or type 2) constituted a different virus group with a Cys-->Ser mutation at epitope position 1. CTLs raised against the B95.8-encoded epitope were nevertheless able to recognize these variant epitope sequences in the context of A2.1 whether they were provided exogenously as synthetic peptides or generated endogenously in B cells transformed with the variant viruses. A CTL response of this kind could have therapeutic potential in that it is directed against a protein expressed in many EBV-positive malignancies, is reactive across a range of virus isolates, and is restricted through a relatively common HLA allele.

Familial nasopharyngeal carcinoma in patients who are not Chinese

BACKGROUND

Nasopharyngeal carcinoma (NPC) is a malignancy that is prominent in Cantonese Chinese people. It is presumed to result from an interaction of genetic and environmental factors, including the Epstein-Barr virus (EBV). In an attempt to further clarify the pathogenesis of this disease, an evaluation of NPC occurring in racial/ethnic groups not considered susceptible to this disease could be informative.

METHODS

A white family with NPC occurring in three siblings was investigated and information was gleaned from literature on other reports of familial NPC in non-Chinese families.

RESULTS

In the family being investigated, another genetically determined disease, hemophilia, was identified. Radiation early in life was noted to be a possible risk factor for NPC in the proband. A review of familial NPC in the white population revealed that in contrast to sporadic NPC, which is usually of the well-differentiated type, familial NPC usually is poorly differentiated.

CONCLUSIONS

Familial NPC offers an important opportunity to investigate the etiology of this disease. With newer laboratory techniques to investigate pathogenetic mechanisms, detailed evaluations of non-Chinese NPC families may become increasingly important.

The molecular basis for reactivity of anti-Cw1 and anti-Cw3 alloantisera with HLA-B46 haplotypes

HLA haplotypes containing the HLA-B46 allele react with both anti-Cw1 and anti-Cw3 alloantisera, a pattern of reactivity defined as the Cw11 antigen and postulated to involve either a distinctive Cw11 allele or a duplicated HLA-C locus. From serological characterization of CIR cells transfected with B46 cDNA we now demonstrate that the anti-Cw3 reactivity with these haplotypes is solely due to the B46 molecule and not to an HLA-C molecule. Furthermore, isolation and characterization of HLA-C mRNA from cells expressing B46 strongly suggest that anti-Cw1 reactions are directed against the product of a conventional Cw1 allele. The antigenic cross-reactivities of B46 with B62 and Cw3 correlate with its chimaeric primary structure, which is identical to that of B62, except in the alpha 1 helix where it is identical to both Cw3 and Cw1. The structure, distribution and genetic linkage of B46 indicate it is of recent, Asian origin and is the result of a gene conversion, involving Cw1 as the donor gene and B62 as the recipient. These results demonstrate that the Cw11 antigen neither corresponds to a novel HLA-C allele nor a duplicated HLA-C locus, but to a combination of epitopes contributed by linked Cw1 and B46 alleles. The nucleotide sequence we previously and erroneously attributed to a distinct Cw11 allele is now demonstrated to encode Cw8. Isolation of the cDNA clone with this sequence from a library made from a cell homozygous for the B46 haplotype was probably an artefact of contamination.

HLA antigens and bronchogenic carcinoma in the Greek population

The distribution of HLA antigens was studied in 85 Greek patients with bronchogenic carcinoma. Fifty-seven specific HLA antisera were used to determine 27 HLA-A and B antigens, with the two-stage standard NIH microlymphocytotoxicity assay. The results were compared with those in a control group, consisting of 400 healthy individuals. In the whole group of patients there was a significantly higher frequency of HLA-AW19 and HLA-A29 (p less than 0.003 and p less than 0.006 respectively) and a lower frequency of HLA-A2 and HLA-A3 (p less than 0.014 and p less than 0.006 respectively) than in the control population. In patients with squamous cell carcinoma there was a significantly higher frequency of HLA-AW19 and lower frequency of HLA-A2 (p less than 0.02 and p less than 0.05 respectively). In small cell carcinoma patients there was a significantly lower frequency of HLA-A3 (p less than 0.04) than among the controls. In patients with adenocarcinoma no significant change of HLA antigen frequencies was observed when compared to the controls.

Diet, living conditions and nasopharyngeal carcinoma in Tunisia--a case-control study

We conducted a case-control study of nasopharyngeal carcinoma (NPC) in Tunisia, on diet, dietary patterns and life style, the characteristics of which had been defined by an anthropological study. Eighty incident cases, diagnosed in Tunisia between November 1986 and November 1987, were each matched for sex, age and place of residence to 2 controls. The subjects were asked for dietary data referring to the year preceding the diagnosis of NPC and, with help of their families, during childhood and after weaning. After adjustment for an empirical living conditions score, the following food items were found to be associated with an increased risk for NPC: preserved spiced meat (quaddid), basic stewing preparation (mixture of red and black pepper, garlic, oil, caraway and coriander), and harissa (red pepper, olive oil, garlic, caraway, salt) taken with bread as a snack during childhood and youth. Moreover, subjects who had been directly weaned from mother's milk on to an adult diet were found to be at higher risk for NPC.

Linkage of a nasopharyngeal carcinoma susceptibility locus to the HLA region

The frequency of nasopharyngeal carcinoma is nearly 100-fold higher in southern Chinese than in most European populations. Earlier studies have suggested that an increased risk of nasopharyngeal carcinoma is associated with specific haplotypes in the HLA region: relative risks slightly over twofold were found for haplotypes A2, Bw46 and the antigen B17. We now report a linkage study based on affected sib pairs which suggests that a gene closely linked to the HLA locus confers a greatly increased risk of nasopharyngeal carcinoma. The maximum likelihood estimate is of a relative risk of approximately 21. The relationship between this suspected disease susceptibility gene (or genes) and known viral and environmental aetiological factors remains to be elucidated.

Antibodies to Epstein-Barr virus-specific DNase in patients with nasopharyngeal carcinoma and control groups

Serum samples from 154 patients with nasopharyngeal carcinoma (NPC), 374 with other cancers, 1,000 normal controls from Government Employees' Clinic Center (GECC), and 3,642 individuals of various ethnic-dialect groups living in high-risk areas for NPC were collected and the concentration of antibodies to Epstein-Barr virus (EBV)-specific DNase activity was determined. Taking a serum sample where 1 ml will neutralize two or more units of the DNase activity as positive, 2-4 units as low level, 4-6 units as medium level, and more than 6 units as a high level of antibody, 90.3% of the NPC patients contained significant amounts of antibodies to EBV-specific DNase activity and most of those had high levels of the antibody. In contrast, only 11% of sera from patients with cancers other than NPC contained antibodies to EBV-specific DNase activity, and high levels were very rare (2.1%). The difference in positive rates between these two groups is highly significant according to the chi 2 test (P less than 0.001). The positive rate of this antibody in the control group (GECC) was 5.3% with 0.0%, 0.8%, and 4.5% having high, medium, and low levels of antibodies, respectively. Again, the difference in positive rates between the GECC group and the NPC group is statistically significant (P less than 0.001). Taken separately, the positive rates of anti-EBV DNase activity in the three high-risk groups were 11.7%, 13.0%, and 13.1%. No significant difference in age distribution for the levels of this antibody was observed in the control GECC group or the three high-risk groups. However, the positive rates of the three high-risk groups are more than twice those of the GECC group (11.7% approximately 13.1% vs 5.3%). This ratio coincides with the ratio of the probability of developing NPC in high-risk groups compared to that of the GECC group (also more than two times). The significance of this coincidence is discussed.

Nasopharyngeal carcinoma in Israel: epidemiology and Epstein-Barr virus-related serology

Epidemiological, histological and serological characteristics of nasopharyngeal carcinoma (NPC) were investigated. Included were 25 patients aged 10-70 with male to female ratio 2:1. Among 23 Jewish patients, 18 were of Asian-African (AA) and five of European (Eur) descent; two were Arabs (Ar). The dominant histological type among AA patients was undifferentiated carcinoma (UCNT) and among Eur squamous cell carcinoma (SCC). Elevated IgG and IgA antibodies to Epstein-Barr (EBV) viral capsid, early and nuclear antigens were observed in patients, as compared to 34 healthy controls matched by age, sex and ethnic origin. Although not statistically significant, antibodies to EBV were elevated in AA, as compared to Eur patients. No significant differences in IgG and IgA antibodies to Herpes simplex, Cytomegalo and Varicella-zoster viruses were demonstrated among patients and controls. The study suggests that NPC in Israel, as elsewhere, is associated with EBV and genetic or environmental factors may influence the prevalence of NPC among certain ethnic groups.

Human leukocyte antigen associated with endometrial carcinoma with a new classification of endometrial carcinoma based on its etiology

To elucidate the relationship between endometrial carcinoma and the constitution, HLA antigen typing (A-locus, 13; B-locus, 20; C-locus, 6; DR-locus, 9) was investigated in 74 patients with endometrial carcinoma. A significant increase in two HLA antigens, Cw7 and DRw8, was demonstrated, but there was no intimate correlation between Cw7 or DRw8 and the three complications commonly associated with endometrial carcinoma--diabetes mellitus, obesity, and hypertensive disease. On the basis of these results, a new classification of endometrial carcinoma was proposed as follows: type A is positive Cw7 or DRw8 group; type B is negative for Cw7 and DRw8 and positive for the complications mentioned; type C is negative for Cw7 and DRw8, negative for the complications mentioned, and positive for DR 5; type D is a non-A, non-B, and non-C type.

Presence of in vivo-activated T-cells expressing HLA-DR molecules and IL-2 receptors in peripheral blood of patients with nasopharyngeal carcinoma

Epstein-Barr Virus (EBV) is associated with two malignant diseases, African Burkitt's Lymphoma (BL) and Undifferentiated Nasopharyngeal Carcinoma (UNPC). North Africa is a geographical area with a high incidence of NPC. Our purpose in this study was to explore cell-mediated immunity of peripheral blood lymphocytes (PBL) from patients with UNPC and DNPC. We found an elevated percentage of OKT8 cells and of large granular lymphocytes (LGL) (30-35% HNK-I-positive cells) compared to PBL from healthy matched individuals. PBL from NPC patients contained 35% HLA-DR-positive and 30% Interleukin-2 (IL-2) receptor-positive circulating lymphocytes. PBL from NPC patients exhibited a normal proliferative response to phytohemagglutinin (PHA) and Concanavalin A (Con A) and an increased response to pokeweed mitogen (PWM). Natural killer (NK) activity towards K562 cells was low in our patients who, in addition, exhibited no lytic activity against HLA-matched EBV-transformed B cells. This lack of cytotoxicity against an EBV-transformed B-cell line cannot be explained by an impairment of IL-2 secretion, and is probably a result of the presence of high numbers of OKT8 suppressor T cells.

Irradiation of nasopharyngeal carcinoma: correlations with treatment factors and stage

Eighty patients with nasopharyngeal carcinoma were treated with radiotherapy in the Radiation Center at the University of Louisville from January 1955 to December 1980. Among the patients were 70 whites, nine blacks and one Chinese; their ages ranged from eight to 82 years. There was a 40% recurrence rate within the nasopharynx, and a 29% recurrence rate within neck nodes. The five year survival and relapse-free survival rates of the entire group were 36 and 33%, respectively. Forty-nine patients died of cancer, four patients died of intercurrent disease and eight patients were lost to follow-up. Nineteen patients are alive and free of disease. Factors considered in this study included tumor and nodal status, the presence of cranial neuropathy, the size and area irradiated, and dose delivered. Primary site relapse was not demonstrated to be dependent on T group or nodal status, but was likely to be related to inadequacy of original treatment volume and dose. A higher survival was noted with our lymphoepithelioma category (p = .056).