Correlates of anti-EBV EBNA1 IgA positivity among unaffected relatives from nasopharyngeal carcinoma multiplex families.

BACKGROUND: To determine whether non-viral nasopharyngeal carcinoma (NPC) risk factors might be associated with (and mediated through) Epstein-Barr virus (EBV) serological responses linked to NPC risk, we evaluated predictors of risk of anti-EBNA1 IgA seropositivity and other markers among unaffected relatives from a large NPC family study in Taiwan. METHODS: Multivariate logistic regression conditioned on family was used to examine the associations between sociodemographic, dietary, lifestyle, and occupational variables and risk of anti-EBV EBNA1 IgA positivity, anti-VCA IgA, and anti-DNase positivity. RESULTS: Among 2393 unaffected relatives from 319 multiplex families, 1180 (49.3%) were anti-EBV EBNA1 IgA seropositive. None of the associations with anti-EBNA1 IgA were statistically significant, except for being 31-50 years of age (vs <30, adjusted ORs 0.51-0.57). For one or more EBV serological markers, there were suggestive associations for older age, GuangDong firm salted fish, betel use, current alcohol use, and male gender. CONCLUSION: Overall, we found little evidence to suggest that non-viral NPC risk factors significantly alter EBV serological patterns, suggesting that non-viral NPC risk factors act through pathways independent of EBV serological responses.

Linkage analysis localises a Kartagener syndrome gene to a 3.5 cM region on chromosome 15q24-25.

BACKGROUND: Primary ciliary dyskinesia (PCD) is a genetic disorder caused by ciliary immotility/dysmotility due to ultrastructural defects of the cilia. Kartagener syndrome (KS), a subtype of PCD, is characterised by situs inversus accompanying the typical PCD symptoms of bronchiectasis and chronic sinusitis. In most cases, PCD is transmitted as an autosomal recessive trait, but its genetic basis is unclear due to extensive genetic heterogeneity. METHODS: In a genome-wide search for PCD loci performed in 52 KS families and in 18 PCD families with no situs inversus present (CDO, ciliary dysfunction-only), the maximal pairwise LOD score of 3.36 with D15S205 in the KS families indicated linkage of a KS locus to the long arm of chromosome 15. In the follow-up study, 65 additional microsatellite markers encompassing D15S205 were analysed. RESULTS: A maximal pairwise LOD score of 4.34 was observed with D15S154, further supporting linkage of the KS, but not the CDO, families to 15q24-25. Analysis of heterogeneity and haplotypes suggested linkage to this region in 60% of KS families. CONCLUSIONS: Reinforced by the results of multipoint linkage, our analyses indicate that a major KS locus is localised within a 3.5 cM region on 15q, between D15S973 and D15S1037.

Evidence of a substantial genetic basis for IgG2 levels in families with aggressive periodontitis.

IgG2 is elevated in localized but not in generalized aggressive periodontitis (AgP). Exposure to pathogenic bacteria is essential for disease. Immune responses are dominated by IgG2 reactive with bacterial surface carbohydrates. We used variance component analyses to assess IgG2 heritability and determine whether genes that influence IgG2 are the same genes that influence disease susceptibility. We studied 17 Caucasian and 43 African American families with two or more localized or generalized AgP-affected members (274 subjects with IgG2 measurements). Only 16% of the variance in IgG2 was attributable to age, race, and smoking. Even with the addition of localized AgP, the model still explained only 19% of IgG2 variance. By contrast, heritability of IgG2 levels was estimated to be 38% and highly significant (P = 0.0006), demonstrating a substantial genetic basis. Bi-trait variance component analyses of IgG2 and quantitative measures of AgP indicate that different genes appear to control IgG2 levels and disease susceptibility.

Factors associated with delay in the diagnosis of oral cancer.

Early detection and treatment improve the prognosis for oral cancer. Delays from the onset of symptoms to clinical diagnosis are common. Our aim is to identify factors associated with this delay. Between 1995 and 1998, we interviewed 105 consecutive patients with histologically confirmed oral cancer in Greece. If 21 or more days elapsed from the time the patient noticed major symptoms to a definitive diagnosis, we called it a delay (52% of cases). We used logistic and linear regression to estimate odds ratios of delayed diagnosis and to identify correlates of length of delay, respectively. Former smokers had a 4.3 times greater risk of delayed diagnosis compared with current smokers (95% confidence interval: 1.1-17.1). The length of delay was greater among single patients, non-smokers, or those with stage IV tumors. Clinicians should be advised that delay in the diagnosis of oral cancer occurs frequently, even in individuals who do not smoke heavily.

Family cancer history and susceptibility to oral carcinoma in Puerto Rico.

BACKGROUND: Use of alcohol and tobacco are the major risk factors for cancers of the oral cavity and pharynx in most of the world. A heritable component to oral carcinoma risk also has been suggested, although only limited data are available on familial aggregation of this disease. METHODS: A population-based case-control study of 342 subjects with carcinomas of the oral cavity and pharynx (oral carcinoma) and 521 controls was conducted in Puerto Rico. The relation between family history of carcinomas of the oral cavity, the upper aerodigestive tract (UADT), and other selected sites with risk of oral carcinoma was explored using logistic regression modeling techniques. RESULTS: Risk of oral carcinoma was elevated for subjects reporting a first-degree relative with carcinoma of the oral cavity (odds ratio [OR], 2.5; 95% confidence interval [CI], 0.8-8.0) or any UADT carcinoma (OR, 2.6; 95% CI, 1.4-4.8). The increased risk associated with family history of UADT carcinoma tended to be greatest for subjects with known risk factors (i.e., heavy consumption of alcohol and/or tobacco and infrequent intake of raw fruits and vegetables) and with oral carcinoma diagnoses at ages younger than 65 years. CONCLUSIONS: These findings are consistent with a heritable component to oral carcinoma, although shared lifestyle risk factors may be partially involved.

Mouthwash in the etiology of oral cancer in Puerto Rico.

OBJECTIVES: To determine if the risk of cancers of the mouth and pharynx is associated with mouthwash use in Puerto Rico, an area of relatively high risk. METHODS: Interviews were conducted with 342 cases of oral and pharyngeal cancer registered in Puerto Rico and diagnosed between 1992 and 1995 and with 521 population-based controls regarding mouthwash use and other factors. Mouthwash-related risks were estimated using unconditional logistic regression controlling for potential confounders. RESULTS: The adjusted odds ratio associated with using mouthwash with an alcohol content of 25% or greater was 1.0. Risks were not higher with greater frequency, years of use, or lifetime mouthwash exposure. Among tobacco and alcohol abstainers the odds ratio associated with mouthwash use was 2.8 (CI = 0.8-9.9), in contrast to 0.8 (CI = 0.4-1.7) and 0.9 (CI = 0.6-1.3) among those with light and heavy cigarette smoking/alcohol drinking behaviors, respectively. CONCLUSIONS: There was no overall increased risk of oral cancer associated with mouthwash use. An elevated, but not statistically significant, risk was observed among the small number of subjects who neither smoked cigarettes nor drank alcohol, among whom an effect of alcohol-containing mouthwash would be most likely evident. Our findings indicate the need to clarify the mechanisms of oral carcinogenesis, including the possible role of alcohol-containing mouthwash.

Cambridge Healthtech Institute's Third Annual Conference on human genetic variation. 16-18 October 2000, Philadelphia, Pennsylvania, USA.

A major goal of pharmacogenomics is to identify the human genetic variation that influences susceptibility to complex diseases. Recently, theoretical statistical analyses have suggested that genes for complex diseases may be found by linkage disequilibrium (i.e., association). Single nucleotide polymorphism (SNP) susceptibility alleles for common diseases can occur at high frequencies in various populations and, thus, have a major impact on morbidity and mortality. To be successful, SNP mapping studies require successful teamwork, integrating clinicians, epidemiologists, molecular genetics experts, laboratory automation engineers, bioinformatics and database experts. New statistical methods are also developing rapidly and promise to further increase the power of these studies. A recent conference on human genetic variation provided an opportunity for experts in all of these disciplines to exchange ideas. At present, great technological challenges need to be overcome in order to increase the throughput greatly while lowering cost and still maintaining high accuracy for SNP genotyping. Although this approach is relatively new (at least on the scale now being contemplated), the large payoffs anticipated to accrue from the successful mapping of SNPs in disease genes has led the area to be very strongly supported by both public and private funding sources. The potential payoff for improving disease diagnosis and therapeutic efficacy, with better avoidance of adverse events based on SNP associations, is providing a tremendous incentive to move this effort forward at an ever-accelerating pace.

Smoking and alcohol in the etiology of oral cancer: gender-specific risk profiles in the south of Greece.

Oral and pharyngeal cancer (OC) mortality is very low in Greece, especially among men, compared to other European countries. We conducted a case-control study of OC in Athens, and obtained information on tobacco, alcohol use and other potential risk factors and confounding variables for 110 incident cases and 115 hospital-based controls. We used multivariate logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Tobacco smoking (pack years, P(trend)=0.01) and alcohol use (drinks/week, P(trend)=0.07) were independent risk factors, with a multiplicative effect for combined exposures (OR, 8.3; 95% CI, 2.4-29.1, for >28 alcohol drinks/week and >50 pack years of cigarette smoking). The type of alcoholic beverage also seemed important: drinking ouzo and tsipouro (liquors of high ethanol concentration) was associated with greater increased OC risk than drinking comparable amounts of wine, beer or dark spirits. While alcohol drinking is more common for male cases versus controls, few men reported regularly consuming large quantities of ethanol associated with highest risk of OC in other studies. This may partially explain the low rates of male OC mortality in Greece. Among the 38% of our cases who were women, however, neither smoking nor alcohol drinking frequencies were significantly elevated compared to controls, and so the etiology of OC risk in females requires further investigation.

Associations between serum antibody levels to periodontal pathogens and early-onset periodontitis.

BACKGROUND: The role of antibodies to periodontal microorganisms in the development of periodontal tissue destruction is still unclear. The aim of this study was to investigate the association between serum levels of IgG, IgA, and IgM antibodies to 6 periodontal microorganisms and clinical subtypes of varying severity of early-onset periodontitis (EOP) in young African American adults. METHODS: The study group consisted of 159 African Americans aged 19 to 25 years (mean 22 years) and included 97 cases with EOP and 62 controls with no clinical signs of EOP. These subjects were selected from a nationally representative sample of adolescents who received an oral examination as part of the National Survey of Oral Health of United States Children in 1986-1987. The group was examined clinically a second time 6 years later and blood samples were collected. Serum levels of IgG, IgA, and IgM reactive to Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Campylobacter rectus, Eikenella corrodens, and Fusobacterium nucleatum were assessed. RESULTS: Serum levels of IgG and IgA antibody reactive to P. gingivalis and A. actinomycetemcomitans and IgA antibody to P. intermedia were significantly higher in generalized EOP cases compared to healthy controls. IgM antibody levels did not show any significant associations with EOP for any of the 6 bacterial species tested. There were no significant differences in antibody levels between controls and the 13 subjects in our study who were classified with localized EOP. CONCLUSIONS: The findings suggest that antibodies to P. gingivalis, P. intermedia, and A. actinomycetemcomitans may play a significant role in the pathogenesis of EOP. Substantial longitudinal studies that monitor antibody levels and avidity prior to disease onset, during progression, and following clinical intervention will be necessary to fully understand the role of this component of the immune response in protection versus tissue destruction and the potential use in EOP risk assessment and disease management.

Evidence of a substantial genetic basis for risk of adult periodontitis.

BACKGROUND: A few previous studies have suggested that risk for adult periodontitis (AP) has a genetic (heritable) component. We estimated genetic and environmental variances and heritability for gingivitis and adult periodontitis using data from twins reared together. METHODS: One hundred seventeen (117) pairs of adult twins (64 monozygotic [MZ] and 53 dizygotic [DZ] pairs) were recruited. Probing depth (PD), attachment loss (AL), plaque, and gingivitis (GI) were assessed on all teeth by two examiners. Measurements were averaged over all sites, teeth, and examiners. Extent of disease in subjects was defined at four thresholds: the percentage of teeth with AL > or = 2, AL > or = 3, PD > or = 4, or PD > or = 5 mm. Genetic and environmental variances and heritability were estimated using path models with maximum likelihood estimation techniques. RESULTS: MZ twins were more similar than DZ twins for all clinical measures. Statistically significant genetic variance was found for both the severity and extent of disease. AP was estimated to have approximately 50% heritability, which was unaltered following adjustments for behavioral variables including smoking. In contrast, while MZ twins were also more similar than DZ twins for gingivitis scores, there was no evidence of heritability for gingivitis after behavioral covariates such as utilization of dental care and smoking were incorporated into the analyses. CONCLUSIONS: These results confirm previous studies and indicate that approximately half of the variance in disease in the population is attributed to genetic variance. The basis for the heritability of periodontitis appears to be biological and not behavioral in nature.

Confirmation of linkage of Van der Woude syndrome to chromosome 1q32: evidence of association with STR alleles suggests possible unique origin of the disease mutation.

Van der Woude syndrome (VWS) is an autosomal dominant craniofacial disorder with high penetrance and variable expression. Its clinical features are variably expressed, but include cleft lip and/or cleft palate, lip pits and hypodontia. All VWS families studied to date map the disease gene to a < 2 cM region of chromosome 1q32, with no evidence of locus heterogeneity. The aim of this study is to refine the localization of the VWS gene and to further assess possible heterogeneity. We analyzed four multiplex VWS families. All available members were clinically assessed and genotyped for 19 short tandem repeat markers on chromosome 1 in the VWS candidate gene region. We performed two-point and multipoint limit of detection (LOD) score analyses using a high penetrance autosomal dominant model. All families showed positive LOD scores without any recombination in the candidate region. The largest two-point LOD score was 5.87. Our assay method for short tandem repeat (STR) markers provided highly accurate size estimation of marker allele fragment sizes, and therefore enabled us to determine the specific alleles segregating with the VWS gene in each of our four families. We observed a striking pattern of STR allele sharing at several closely linked loci among our four Caucasian VWS families recruited at three different locations in the US. These results suggest the possibility of a unique origin for a mutation responsible for many or most cases of VWS.

Linkage disequilibrium of interleukin-1 genetic polymorphisms with early-onset periodontitis.

BACKGROUND: Genetic polymorphisms at interleukin (IL)-1alpha and IL-1beta were recently suggested to be associated with severity of adult periodontitis. We evaluated whether these polymorphisms might also be associated with early-onset periodontitis (EOP) in 28 African American families and 7 Caucasian American families with 2 or more affected members. METHODS: Genomic DNA from peripheral blood was amplified, followed by restriction endonuclease digestion and acrylamide gel electrophoresis to distinguish alleles of different fragment sizes. Genetic epidemiological methods suitable for family data were used that are robust to false-positive findings due to mismatching of cases and controls or mixed subpopulations of different ethnic or geographic origin. The 2 major EOP subtypes, localized juvenile periodontitis (LJP), and generalized early-onset periodontitis (G-EOP, encompassing rapidly progressive periodontitis and generalized juvenile periodontitis), were analyzed both separately and together. RESULTS: We obtained highly significant evidence of linkage disequilibrium for both African American and Caucasian G-EOP subjects. A similar trend was noted for LJP. The IL- alleles associated with high risk of EOP had been suggested previously to be correlated with low risk for severe adult periodontitis. Disequilibrium with G-EOP was equally strong for smoking and non-smoking subjects. IL-1alpha and IL-1beta polymorphisms were in strong disequilibrium with each other in Caucasians, but not in African Americans. Haplotype analyses evaluating both polymorphisms simultaneously indicated that the IL-1beta variant is likely to be most important for EOP risk. Sibpair linkage analyses, by contrast, provided only marginal support for a gene of very major effect on EOP risk attributable to these IL-1 polymorphisms. CONCLUSIONS: Recent theoretical analyses indicate that our findings are most consistent with an interpretation of EOP as a complex, oligogenic disorder, with IL-1 genetic variation contributing an important but not exclusive influence on disease risk.

Reducing the burden of oral and pharyngeal cancers.

In the United States, oral and pharyngeal cancers continue to result in significant morbidity and mortality. Dental professionals play a pivotal role in all facets of controlling the burden of oral and pharyngeal cancer-from efforts to prevent its occurrence, to ensuring that oral cancers are detected at the earliest possible stage, to treating these cancers, and to ensuring maximum quality of life and function for oral and pharyngeal cancer survivors. Individually and by making linkages within the community and beyond, dentists can help patients modify their risk of these cancers and can take steps to screen for them, thereby potentially improving survival and function of those who develop oral cancer. Creative partnerships between community dentists and academic and other research centers will help move knowledge of the biological processes involved in carcinogenesis and innovations in treatment into clinical practice. Partnerships between dental and medical professionals may also help efforts to reduce the morbidity related to oral and pharyngeal cancers. Local, state and national multidisciplinary initiatives are emerging that focus more broadly on risk factor control or oral and pharyngeal cancer issues. These many forms of cooperative approaches offer excellent opportunities to make a significant impact on reducing the incidence of and in treating these debilitating and disfiguring malignancies.

Scientific progress in understanding oral and pharyngeal cancers.

Oral and pharyngeal cancers result from a complex interaction between genetic susceptibility and behavioral factors. Improved understanding of the underlying genetic events has led to insights about how oral and pharyngeal cancers develop and suggests promising new treatments. Tobacco and alcohol consumption are associated with most oral and pharyngeal cancers. Dental professionals' efforts to modify their patients' tobacco and alcohol use and to detect oral lesions at an early stage, together with scientific advances, will help reduce the impact of these cancers.

Genome scan for teratogen-induced clefting susceptibility loci in the mouse: evidence of both allelic and locus heterogeneity distinguishing cleft lip and cleft palate.

Nonsyndromic clefting of the lip and palate in humans has a highly complex etiology, with both multiple genetic loci and exposure to teratogens influencing susceptibility. Previous studies using mouse models have examined only very small portions of the genome. Here we report the findings of a genome-wide search for susceptibility genes for teratogen-induced clefting in the AXB and BXA set of recombinant inbred mouse strains. We compare results obtained using phenytoin (which induces cleft lip) and 6-aminonicotinamide (which induces cleft palate). We use a new statistical approach based on logistic regression suitable for these categorical data to identify several chromosomal regions as possible locations of clefting susceptibility loci, and we review candidate genes located within each region. Because cleft lip and cleft palate do not frequently co-aggregate in human families and because these structures arise semi-independently during development, these disorders are usually considered to be distinct in etiology. Our data, however, implicate several of the same chromosomal regions for both forms of clefting when teratogen-induced. Furthermore, different parental strain alleles are usually associated with clefting of the lip versus that of the palate (i.e., allelic heterogeneity). Because several other chromosomal regions are associated with only one form of clefting, locus heterogeneity also appears to be involved. Our findings in this mouse model suggest several priority areas for evaluation in human epidemiological studies.

Phenotypic variation in Waardenburg syndrome: mutational heterogeneity, modifier genes or polygenic background?

We have identified 11 mutational changes in the PAX3 gene in patients with type 1 Waardenburg syndrome (WS1) including three in the paired domain, six within or immediately adjacent to the homeodomain and two previously described polymorphic variants in exons 2 and 6. The affected members of one family carried substitutions involving two base pairs separated by one unaltered codon. Two of the deleterious mutations were identical and three others were identical to previously reported mutations. A comparison of clinical findings in families carrying substitutions in the same codon failed to reveal conspicuous similarities. Although subtle mutation-specific effects may well exist, allelic heterogeneity clearly cannot account for within family variation. However, the striking concordance of a pair of monozygotic twins with Waardenburg syndrome (WS) and previous reports of similar pairs indicate that phenotypic variation in WS has a genetic basis. If the genetic effects are mediated by oligogenic epistasis, as studies in the mouse suggest, it may ultimately be possible to predict clinically relevant aspects of the Waardenburg phenotype.