Familial aggregation of nasopharyngeal carcinoma and other malignancies. A clinicopathologic description

Familial aggregation of nasopharyngeal carcinoma in Taiwan

BACKGROUND

The incidence of nasopharyngeal carcinoma (NPC) is higher in Chinese than in Caucasian populations. Genetic, viral, and lifestyle factors may explain these ethnic differences in the incidence of NPC. In the present study, we examined the familial aggregation, heritability, and relative risks (RRs) of NPC using a nationwide database in Taiwan.

METHODS

A population-based family study was conducted using the Taiwan National Health Insurance Research Database. Participants included all individuals (N=23,422,955) registered with that database in 2013; of these, 17,653 had NPC. Among them, 47.45%, 57.45%, 47.29%, and 1.51% had a parent, child, sibling, and twin, respectively, with NPC.

RESULTS

Among the approximately 23 million Taiwan NHI beneficiaries in 2013, the relative risks (RRs) (95% confidence intervals) for NPC were 34.46 (5.12-231.77) for twins of the patients, 9.23 (6.34-13.43) for siblings, 3.80 (2.97-4.86) for parents, 3.74 (2.60-5.37) for offspring, and 1.78 (1.16-2.74) for spouses without genetic similarity. The mean age of onset in first-degree relative-affected NPC patients was 35.5years compared to 39.0years for NPC patients without affected first-degree relatives (p≤0.0001). Using a threshold liability model, the accountability for phenotypic variance of NPC was estimated to be 61.3% for genetic factors (heritability), 13.9% for shared environmental factors, and 24.8% for non-shared environmental factors. The probability of a patient with NPC to be sporadic was 82.8%.

CONCLUSION

This population-based analysis suggested a strong familial tendency in the development of NPC. Screening of first-degree relatives of NPC patients is recommended, particularly in endemic regions.

Familial nasopharyngeal carcinomas possess distinguished clinical characteristics in southern China

OBJECTIVE

To compare clinical characteristics between familial nasopharyngeal carcinomas (NPCs) and sporadic NPCs in Guangdong province, China, a high-risk area.

METHODS

Between 1991 and 2001, 993 NPC patients treated at the Cancer Center of Sun Yat-Sen University in Guangdong were randomly selected as probands. Information about NPC among the probands' relatives and other information were obtained from a retrospective review of the patients' medical records. The patients were divided into sporadic NPC, low-frequency familial NPC (one NPC patient in addition to the proband in three generations), and high-frequency familial NPC (2 or more additional NPC patients in three generations) groups. Pathological and clinical characteristics were compared among these groups.

RESULTS

Of the 993 patients, 131 (13.2%) had a familial history of NPC. The average age at diagnosis was the lowest in the high-frequency familial NPC group (39 years; P=0.048). Although the overall survival (OS), distant metastasis-free survival (DMFS), and disease-free survival (DFS) rates did not differ between familial and sporadic NPCs, the locoregional recurrence-free survival (LRFS) rate increased in the order sporadic NPCs, low-frequency familial NPCs, and high-frequency familial NPCs (P=0.009), with 5-year rates of 70%, 83%, and 87%, respectively. Multivariate analysis showed that family history of NPC was an independent favorable prognostic factor for LRFS, with adjusted hazard ratio (aHR) of 0.548, 95% CI (0.342-0.878). The high LRFS for familial NPCs was mainly noted among young, advanced-stage patients who received continuous radiation treatment.

CONCLUSIONS

Genetic factors may play an important role in the etiology of high-frequency familial NPC and underlie the early age of onset and sensitivity to radiotherapy.

Evaluation and integration of genetic signature for prediction risk of nasopharyngeal carcinoma in Southern China

Genetic factors, as well as environmental factors, play a role in development of nasopharyngeal carcinoma (NPC). A number of single nucleotide polymorphisms (SNPs) have been reported to be associated with NPC. To confirm these genetic associations with NPC, two independent case-control studies from Southern China comprising 1166 NPC cases and 2340 controls were conducted. Seven SNPs in ITGA9 at 3p21.3 and 9 SNPs within the 6p21.3 HLA region were genotyped. To explore the potential clinical application of these genetic markers in NPC, we further evaluate the predictive/diagnostic role of significant SNPs by calculating the area under the curve (AUC). Results. The reported associations between ITGA9 variants and NPC were not replicated. Multiple loci of GABBR1, HLA-F, HLA-A, and HCG9 were statistically significant in both cohorts (P_combined range from 5.96 × 10⁻¹⁷ to 0.02). We show for the first time that these factors influence NPC development independent of environmental risk factors. This study also indicated that the SNP alone cannot serve as a predictive/diagnostic marker for NPC. Integrating the most significant SNP with IgA antibodies status to EBV, which is presently used as screening/diagnostic marker for NPC in Chinese populations, did not improve the AUC estimate for diagnosis of NPC.

The principal genetic determinants for nasopharyngeal carcinoma in China involve the HLA class I antigen recognition groove

Nasopharyngeal carcinoma (NPC) is an epithelial malignancy facilitated by Epstein-Barr Virus infection. Here we resolve the major genetic influences for NPC incidence using a genome-wide association study (GWAS), independent cohort replication, and high-resolution molecular HLA class I gene typing including 4,055 study participants from the Guangxi Zhuang Autonomous Region and Guangdong province of southern China. We detect and replicate strong association signals involving SNPs, HLA alleles, and amino acid (aa) variants across the major histocompatibility complex-HLA-A, HLA -B, and HLA -C class I genes (P(HLA-A-aa-site-62) = 7.4 × 10(-29); P (HLA-B-aa-site-116) = 6.5 × 10(-19); P (HLA-C-aa-site-156) = 6.8 × 10(-8) respectively). Over 250 NPC-HLA associated variants within HLA were analyzed in concert to resolve separate and largely independent HLA-A, -B, and -C gene influences. Multivariate logistical regression analysis collapsed significant associations in adjacent genes spanning 500 kb (OR2H1, GABBR1, HLA-F, and HCG9) as proxies for peptide binding motifs carried by HLA- A*11:01. A similar analysis resolved an independent association signal driven by HLA-B*13:01, B*38:02, and B*55:02 alleles together. NPC resistance alleles carrying the strongly associated amino acid variants implicate specific class I peptide recognition motifs in HLA-A and -B peptide binding groove as conferring strong genetic influence on the development of NPC in China.

Familial tendency and risk of nasopharyngeal carcinoma in taiwan: effects of covariates on risk

In the present study, the authors compared the long-term risk of nasopharyngeal carcinoma (NPC) of male participants in an NPC multiplex family cohort with that of controls in a community cohort in Taiwan after adjustment for anti-Epstein-Barr virus (EBV) seromarkers and cigarette smoking. A total of 43 incident NPC cases were identified from the 1,019 males in the NPC multiplex family cohort and the 9,622 males in the community cohort, for a total of 8,061 person-years and 185,587 person-years, respectively. The adjusted hazard ratio was 6.8 (95% confidence interval (CI): 2.3, 20.1) for the multiplex family cohort compared with the community cohort. In the evaluation of anti-EBV viral capsid antigen immunoglobulin A and anti-EBV deoxyribonuclease, the adjusted hazard ratios were 2.8 (95% CI: 1.3, 6.0) and 15.1 (95% CI: 4.2, 54.1) for those positive for 1 EBV seromarker and positive for both seromarkers, respectively, compared with those negative for both EBV seromarkers. The adjusted hazard ratio was 31.0 (95% CI: 9.7, 98.7) for participants who reported a family history of NPC and who were anti-EBV-seropositive compared with individuals without such a history who were anti-EBV-seronegative. The findings suggest that both family history of NPC and anti-EBV seropositivity are important determinants of subsequent NPC risk and that the effect of family history on NPC risk cannot be fully explained by mediation through EBV serologic responses.

Nasopharyngeal carcinoma risk by histologic type in central China: impact of smoking, alcohol and family history

The role of cigarette smoking, alcohol use, family history of cancer and the interaction of cigarettes and family history in the etiology of Nasopharyngeal carcinoma (NPC) in general and within each histologic type are unclear. We conducted a case-control study among 1,044 Han Chinese patients with NPC and 1,095 Han Chinese cancer-free control subjects. Logistic regression was used to analyze the association between histologic type of NPC and cigarette smoking, alcohol drinking and family history. The results indicated that NPC was significantly associated with cigarette smoking [adjusted odds ratio (OR) = 2.97, 95% confidence interval (CI), 2.38-3.70], and the association exhibited a dose-response relationship for intensity, duration, and cumulative consumption of cigarettes (p(trend) < 0.0001 for intensity, duration and cumulative consumption of cigarettes). Positive family history of cancer led to a significant 12-fold elevated risk of NPC (adjusted OR = 12.95, 95% CI, 7.12-23.54) and acted jointly with cigarettes in contributing to NPC risk (adjusted OR = 56.68, 95% CI, 17.25-186.19). The association of NPC risk with cigarettes was stronger for nonkeratinizing carcinoma than for keratinizing squamous cell carcinoma (KSCC), whereas family history was more closely associated with KSCC. NPC risk was not associated with alcohol consumption. Our study demonstrated that cigarette smoking and family history of cancer could serve independently and jointly as risk factors for etiology of NPC and might affect the risk of histology-specific NPC differently. This knowledge may help facilitate comprehension of NPC etiology in general as well as within each histologic type, and thereby improve prevention efforts.

Haplotype-dependent HLA susceptibility to nasopharyngeal carcinoma in a Southern Chinese population

We have conducted a comprehensive case-control study of a nasopharyngeal carcinoma (NPC) population cohort from Guangxi Province of Southern China, a region with one of the highest NPC incidences on record. A total of 1407 individuals including NPC patients, healthy controls, and their adult children were examined for the human leukocyte antigen (HLA) association, which is so far the largest NPC cohort reported for such studies. Stratified analysis performed in this study clearly demonstrated that while NPC protection is associated with independent HLA alleles, most NPC susceptibility is strictly associated with HLA haplotypes. Our study also detected for the first time that A(*)0206, a unique A2 subtype to South and Southeast Asia is also associated with a high risk for NPC. HLA-A(*)0206, HLA-B(*)3802 alleles plus the A(*)0207-B(*)4601 and A(*)3303-B(*)5801 haplotypes conferred high risk for NPC showing a combined odds ratio (OR) of 2.6 (P<0.0001). HLA alleles that associate with low risk for NPC include HLA-A(*)1101, B(*)27, and B(*)55 with a combined OR of 0.42 (P<0.0001). The overall high frequency of NPC-susceptible HLA factors in the Guangxi population is likely to have contributed to the high-NPC incidence in this region.

Evaluation of nonviral risk factors for nasopharyngeal carcinoma in a high-risk population of Southern China

To understand the role of environmental and genetic influences on nasopharyngeal carcinoma (NPC) in populations at high risk of NPC, we have performed a case-control study in Guangxi Province of Southern China in 2004-2005. NPC cases (n = 1,049) were compared with 785 NPC-free matched controls who were seropositive for IgA antibodies (IgA) to Epstein-Barr virus (EBV) capsid antigen (VCA)-a predictive marker for NPC in Chinese populations. A questionnaire was used to capture exposure and NPC family history data. Risk factors associated with NPC in a multivariant analysis model were the following: (i) a first, second or third degree relative with NPC [attributable risk (AR)= 6%, odds ratio (OR) = 3.1, 95% confidence interval (CI) = 2.0-4.9, p < 0.001]; (ii) consumption of salted fish 3 or more than 3 times per month (AR = 3%, OR = 1.9, 95% CI = 1.1-3.5, p = 0.035); (iii) exposure to domestic wood cooking fires for more than 10 years (AR = 69%, OR = 5.8, 95% CI = 2.5-13.6, p < 0.001); and (iv) exposure to occupational solvents for 10 or less years (AR = 4%, OR = 2.6, 95% CI = 1.4-4.8, p = 0.002). Consumption of preserved meats or a history of tobacco smoking were not associated with NPC (p > 0.05). We also assessed the contribution of EBV/IgA/VCA antibody serostatus to NPC risk-32.2% of NPC can be explained by IgA+ status. However, family history and environmental risk factors cumulatively explained only 2.7% of NPC development in NPC high risk population. These findings should have important public health implications for NPC risk reduction in endemic regions.

Cancer patterns in nasopharyngeal carcinoma multiplex families in Taiwan

Genetic and environmental factors have been implicated in the etiology of nasopharyngeal carcinoma (NPC), a tumor known to be closely associated with Epstein-Barr virus (EBV) infection. Studies have reported familial aggregation of NPC and have suggested the possible aggregation of NPC and other cancers. We evaluated familial aggregation of cancer in 358 high-risk families with two or more NPC cases enrolled in a NPC genetics study in Taiwan. Participants were linked to the Taiwan National Cancer Registry to identify incident cancers diagnosed after study enrollment (started in 1996) and before December 31, 2005, or death. In total, 2,870 individuals from the NPC Multiplex Family Study contributed 15,151 person-years over an average of 5.3 years of follow-up. One hundred ten incident cancers were identified. Multiple-primary standardized incidence ratios (MP-SIRs) were computed to evaluate overall cancer risk associated with infectious agents and with other tumors. The overall MP-SIR was 1.3 (95% CI: 1.1-1.6), which was largely explained by an excess in NPC (MP-SIR = 15; 95% CI: 10-23). Exclusion of incident NPC diagnoses led to an overall MP-SIR of 1.0 (95% CI: 0.83-1.3). Similarly, the observed excess risk of cancers associated with infectious agents (MP-SIR = 2.0; 95% CI: 1.5-2.6) was driven by the excess in NPC; exclusion of NPC cases led to a reduced MP-SIR that did not differ from 1.0. Analysis of the largest NPC multiplex family study to date confirms the presence of coaggregation of NPC within families in Taiwan but does not provide evidence for a broader familial syndrome involving NPC and other tumors.

Familial nasopharyngeal carcinoma in Hong Kong: epidemiology and implication in screening

The pathogenetic mechanism of nasopharyngeal carcinoma (NPC) is still unclear. Its familial aggregation, on the other hand, has been well documented by many epidemiological studies. The objective of this study was to evaluate the clinical characteristics of familial NPC in an endemic region. Between March 1994 and November 2005, 1,202 consecutive patients were treated at our institution. Patients were divided into 2 groups according to their family history: group 1 had at least one first-degree relative with NPC at the time of diagnosis, and group 2 did not. There were 125(10.4%) patients in group 1, 66% of them had diseased siblings, 44% had diseased parents and 2% had diseased offspring. The patients in group 1 were on average about 2 years younger than group 2 at diagnosis (47.9 vs. 49.8, P = 0.04). There were also more stage I-II patients in group 1 (38 [corrected] vs. 23%, P < 0.01). Although the 5 year overall survival was also higher with group 1 (79 vs. 69%, P < 0.01), only age, sex, T classification and N classification were found to be significant independent factors but not family history per se (P = 0.10). Similar findings were observed after excluding screen-detected patients from group 1. The high incidence of familial clustering and improved outcomes from early detection highlight the importance of screening among these high risk family members.

Genetic factors leading to chronic Epstein-Barr virus infection and nasopharyngeal carcinoma in South East China: study design, methods and feasibility

Nasopharyngeal carcinoma (NPC) is a complex disease caused by a combination of Epstein-Barr virus chronic infection, the environment and host genes in a multi-step process of carcinogenesis. The identity of genetic factors involved in the development of chronic Epstein-Barr virus infection and NPC remains elusive, however. Here, we describe a two-phase, population-based, case-control study of Han Chinese from Guangxi province, where the NPC incidence rate rises to a high of 25-50 per 100,000 individuals. Phase I, powered to detect single gene associations, enrolled 984 subjects to determine feasibility, to develop infrastructure and logistics and to determine error rates in sample handling. A microsatellite screen of Phase I study participants, genotyped for 319 alleles from 34 microsatellites spanning an 18-megabase region of chromosome 4 (4p15.1-q12), previously implicated by a linkage analysis of familial NPC, found 14 alleles marginally associated with developing NPC or chronic immunoglobulin A production (p = 0.001-0.03). These associations lost significance after applying a correction for multiple tests. Although the present results await confirmation, the Phase II study population has tripled patient enrolment and has included environmental covariates, offering the potential to validate this and other genomic regions that influence the onset of NPC.

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.

A functional variant in the transcriptional regulatory region of gene LOC344967 cosegregates with disease phenotype in familial nasopharyngeal carcinoma

Nasopharyngeal carcinoma is a common malignancy in Southeast Asian countries, and genetic background is a well-known component of the complexity underlying its tumorigenic process. We have mapped a nasopharyngeal carcinoma susceptibility locus to chromosome 4p15.1-q12 in a previous linkage study on nasopharyngeal carcinoma pedigrees. In this study provided in this communication, we screened all the genes in this region, with a focus on exons, promoters, and the exon-intron boundary to identify nasopharyngeal carcinoma-associated mutations or functional variants. Importantly, we found a novel gene (LOC344967) with a single nucleotide polymorphism -32G/A in the promoter region. This gene is a member of the acyl CoA thioesterase family that plays an important role in fatty acid metabolism and is involved in the progression of various types of tumors. The -32A variant was found cosegregated with the disease phenotype in the nasopharyngeal carcinoma pedigrees that we previously used for the linkage study. Moreover, this -32A variant creates an activator protein (AP-1)-binding site in the transcriptional regulatory region of LOC344967, which significantly enhanced the binding of AP-1 to the promoter region and the transcription activity of the promoter in vivo. Furthermore, the expression of LOC344967 was significantly up-regulated at both mRNA and protein levels in nasopharyngeal carcinoma cells sharing the -32G/A genotype compared with nasopharyngeal carcinoma cells with the -32G/G genotype. Collectively, these results provide evidence that the -32A variant is a functional sequence change and may be related to nasopharyngeal carcinoma susceptibility in the families studied.

Familial clustering of nasopharyngeal carcinoma in a non-endemic geographical region. Report of two Hungarian cases and a review of the literature

The aim of this study was to investigate the familial clustering of nasopharyngeal carcinoma (NPC) in a non-endemic geographical region on the basis of two case reports and a review of the literature. Following an upper respiratory infection, NPC (WHO type III) was detected in a 57-year-old female (Case 1) who presented with nasal symptoms and a year later in her 36-year-old son (Case 2) who presented with enlarged lymph nodes. After a full diagnostic work-up, cT2a cN0 cM0 (stage IIA; Case 1) and cT2a cN2 cM0 (stage III; Case 2) disease were identified, and telecobalt irradiation was administered to both patients. The mother achieved complete remission and has been disease-free during a 14-year follow-up period. After initial complete remission, the son experienced regional (cervical) and base of the skull relapses within 2 years, which were treated unsuccessfully by means of radical neck dissection, a second course of radiotherapy and chemotherapy. Epstein-Barr virus (EBV) was detected in pathology sections from both patients. The authors review 20 additional well-documented cases of familial clustering of NPC in non-endemic geographical regions from the English language literature. This clinical entity typically has WHO type III histology; it may occur following an upper respiratory tract infection, and EBV-related serological titers were elevated in all 20 investigated cases. No consequent promoting factors were identified. The present two cases and the review of the literature strongly suggest that familial clustering of NPC in non-endemic geographical areas may be related to EBV infections. The difference in outcome of our two cases may be explained by the fact that the disease in Case 2 was diagnosed 1 year later than that in Case 1 and hence at a more advanced stage.

Evaluation of Risk Factors for Nasopharyngeal Carcinoma in High-Risk Nasopharyngeal Carcinoma Families in Taiwan

A study of nasopharyngeal carcinoma (NPC) families with two or more affected members was conducted in Taiwan (265 families with 2,444 individuals, 502 affected and 1,942 unaffected) to determine the association between NPC and potential etiologic factors in NPC high-risk families. Similar to results from a previous case-control study in Taiwan, Guangdong salted fish consumption during childhood, exposure to wood, and betel nut consumption were all associated with elevated NPC risk using conditional logistic regression, although these associations were not as strong as in the case-control study possibly due to shared environment among family members. Risk associated with cumulative wood exposure and salted fish consumption before age 10 was stronger in families with early NPC age-onset [odds ratio (OR(wood)), 5.10; 95% confidence interval (95% CI), 1.50-17.34; OR(fish), 3.94; 95% CI, 1.47-10.55] or three or more affected members (OR(wood), 4.41; 95% CI, 1.58-12.30; OR(fish), 4.27; 95% CI, 1.10-16.47). In contrast, a tendency for elevated risk was noted for betel nut use in late age-onset families (OR, 2.44; 95% CI, 1.16-5.13) and the CYP2E1 c2 allele in families with less than three affected members (OR, 2.06; 95% CI, 1.04-3.35). Risk estimates associated with these exposures were similar when the analyses were restricted to EBV-seropositive subjects. To better adjust for degree of relationship among family members and residual genetic correlations, we also calculated ORs using a variance components model. The results from the two methods were similar indicating that the risk estimates from conditional logistic regression were unbiased.

Familial risk and clustering of nasopharyngeal carcinoma in Guangdong, China

BACKGROUND

Previous studies have suggested that genetic susceptibility may play an important role in the etiology of nasopharyngeal cancer (NPC). However, to date, few large-scale studies have been conducted on familial risk and clustering of NPC in a high-risk area of China.

METHODS

In the current study, 2252 patients with NPC who were treated at the Cancer Center of Sun Yat-Sen University in Guangdong Province, China, were identified as probands. Family histories of NPC and other malignancies were observed in first-degree relatives (FDRs) and second-degree relatives, and other information was obtained through interviews. One thousand nine hundred and three Cantonese families were selected for further investigation. To assess familial aggregation, the authors used standardized incidence ratios (SIRs) to measure the risk of NPC for FDRs and compared the observed number of cases with the number predicted by population-based frequencies in the Cantonese population of Hong Kong.

RESULTS

The current analysis indicated that families with > or = 3 relatives who had NPC were distributed predominantly among a high-risk subgroup of the Cantonese population in Guangdong Province and that the frequency of these families was 0.68%. An SIR of 2.09 (95% confidence interval [CI], 1.80-2.40) was observed among 13,833 FDRs in the high-risk subgroup, and a significantly elevated risk for NPC was observed in FDRs of probands with early age of onset (age < 40 years; SIR, 9.01 [95% CI, 6.10-13.30]). Furthermore, decreased risks of hepatic, lung, esophageal, gastric, and breast carcinoma, as well as malignancy of all sites, were observed among FDRs of probands with NPC when Hong Kong and Shanghai populations were used as reference groups.

CONCLUSIONS

NPC tends to aggregate in Cantonese families in Guangdong Province, and the malignancies in these families appear to be site specific, with no excess of any other malignancy.

Familial nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) has a striking geographical and ethnical distribution. It occurs with high frequency in southern China and Southeast Asia. Family clustering was also observed in NPC and a typical family with 15 NPC cases was introduced in this paper. Epidemiological and genetic studies have been carried out in the previous decades and vast information was accumulated for familiar NPC, in terms of risk factors, inheritance mode, and involvement of gene polymorphisms. The major findings in this field were summarized. Furthermore, future directions leading to understanding the genetic mechanism of the familial form of NPC was also discussed.

Definition of three minimal deleted regions by comprehensive allelotyping and mutational screening of FHIT,p16(INK4A), and p19(ARF) genes in nasopharyngeal carcinoma

BACKGROUND

Recurrent deletion on a chromosomal location in tumor cells can be detected by frequent allelic loss and generally is considered to be an indication of the existence of a tumor suppressor gene (TSG) in the region. In the current study, using fluorescent-labeled, high-density microsatellite markers for allelotyping, the authors pinpointed three minimal deleted regions (MDRs) and screened mutations of putative TSGs on chromosomes 3, 9, and 11 in nasopharyngeal carcinoma (NPC) cases occurring in Taiwan.

METHODS

A total of 133 informative microsatellite markers were used on chromosomes 3, 9, and 11 with an average marker density of 4 centimorgans (cM) for the allelotyping of genomic DNAs isolated from NPC tissues and their corresponding lymphocytes in 48 patients. The correlation between allelic loss and the clinicopathologic parameters of NPC tissues was examined. In addition, putative TSGs including FHIT, p16(INK4a), and p19(ARF) were selected for mutation screening to investigate their potential participation in NPC tumorigenesis.

RESULTS

Of 3787 informative allelotyping data, 25 frequent allelic losses (or loss of heterozygosity [LOH]) in 13 cytogenetic loci were identified based on a deletion frequency that was greater than the average of allelic loss on that particular chromosome. Several significant associations were determined after statistical analysis of the correlation between allelic loss and clinicopathologic parameters. The allelic losses by D9S318 and D11S1304 were associated with N2/N3 (P = 0.035 and P = 0.005, respectively), and those by D9S905 and D11S1304 were associated with grouped American Joint Committee on Cancer (AJCC) Stage III/IV samples (P = 0.022 and P = 0.017, respectively) of NPC tissues. In addition, three MDRs were revealed on 3p25.3-24.1 (< 19 cM), 3p23-21.31 (< 9 cM), and 11q22.1-23.2 (< 8 cM). To examine somatic mutations in previously reported TSGs located near these frequent LOH loci, three candidate genes, p16(INK4a), p19(ARF), and FHIT, were analyzed. Point mutations in the coding region of FHIT and in the intron 1 splicing acceptor site of both p16(INK4a) and p19(ARF) were detected in NPC cell lines. Sequence analysis of both p16(INK4a) and p19(ARF) transcripts revealed that the point mutation resulted in skipping of exon 2 and the generation of shorter transcripts.

CONCLUSIONS

High-density allelotyping permitted the discovery of 3 MDRs on 3p25.3-24.1 (< 19 cM), 3p23-21.31 (< 9 cM), and 11q22.1-23.2 (< 8 cM) and a correlation was determined between allelic loss and clinicopathologic parameters of NPC tissues. More important, one somatic mutation in NPC cell lines on the intron 1/exon 2 splicing acceptor site of the INK4a/ARF locus was found to result in exon 2 skipping both p16(INK4a) and p19(ARF) transcripts, which presumably inactivates the functions of both the p16(INK4a) and p19(ARF) proteins.

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.

Epstein-barr virus-associated malignancies: epidemiologic patterns and etiologic implications

Epstein-Barr virus (EBV), a ubiquitous B-lymphotrophic herpesvirus, has been found in the tumor cells of a heterogeneous group of malignancies (Burkitt's lymphoma, lymphomas associated with immunosuppression, other non-Hodgkin's lymphomas, Hodgkin's disease, nasopharyngeal carcinoma, gastric adenocarcinoma, lymphoepithelioma-like carcinomas, and immunodeficiency-related leiomyosarcoma). As the epidemiologic characteristics of these cancers have not been considered together, this review seeks to relate their incidence patterns and risk factors to EBV biology and virus-host interaction in an attempt to help elucidate factors involved in EBV-related carcinogenesis. We include a brief review of EBV virology and primary infection to provide a biologic context for considering the epidemiology, summarize the most salient epidemiologic features of each malignancy, synthesize epidemiologic data by risk factor to uncover commonalities and informative contrasts across the diseases, and propose hypotheses regarding etiologic mechanisms, based on the possible effect of the risk factors at various stages in the viral life cycle.

Human helicase gene SKI2W in the HLA class III region exhibits striking structural similarities to the yeast antiviral gene SKI2 and to the human gene KIAA0052: emergence of a new gene family

Helicases are essential enzymes for life because DNA replication, DNA repair, recombination, transcription, RNA splicing and translation all involve more than one helicase to unwind DNA or RNA. We have discovered, cloned and partially characterized a novel human helicase gene, SKI2W. The human SKI2W is located between the RD and RP1 genes in the class III region of the major histocompatibility complex (MHC) on chromosome 6, a genomic region associated with many malignant, genetic and autoimmune diseases. Derived amino acid sequence of human SKI2W showed an open reading frame for 1246 residues. It contains consensus sequences for structural motifs of an RNA helicase with a DEVH box. It has a leucine zipper motif that may be important for protein dimerization, and an RGD motif close to the N-terminus that might serve as a ligand for integrin or cell adhesion molecules. SKI2W shares a striking and extensive similarity to the yeast Ski2p that is involved in the inhibition of translation of poly(A) negative [poly(A)-] RNA, and plays an important role in antiviral activities. Human SKI2W fusion protein expressed in insect cells using a baculovirus vector has ATPase activity. The human SKI2W protein and the yeast Ski2p share extensive sequence similarities to another putative human protein KIAA0052, suggesting the presence of a new gene family that may be involved in translational regulation of cellular and viral RNA.

Multiple occurrence of carcinoma in the upper aerodigestive tract associated with esophageal cancer: reference to smoking, drinking and family history

Smoking and drinking habits as well as family history were examined in 143 men with esophageal cancer, including 30 who had associated second cancers of the upper aerodigestive tract (UADT) and 113 who did not. The risk of second cancers of UADT associated with the main lesions of the esophagus was evaluated, using odds ratios (ORs). As a result, the ORs of second cancers for current smoking and drinking were 5.3 and 7.6 respectively. The ORs significantly increased to 12.7 and 14.7 in heavy smokers and in heavy drinkers respectively. Furthermore, the risk of second cancer also significantly increased (8-fold) in patients who had close relatives with UADT cancer, compared to those without family history of any cancer. However, there were no differences in smoking or drinking habits regardless of family history. Our data thus suggest that a family history of UADT cancer as well as heavy smoking and drinking are clearly associated with multiple occurrence of UADT cancer. Therefore, careful and frequent examination for appearance of any second lesions are required for patients in these high-risk groups.