Genetic susceptibility to head and neck cancer: interaction between nutrition and mutagen sensitivity

The Association between Carotenoids and Head and Neck Cancer Risk

Head and neck cancer (HNC) includes oral cavity cancer (OCC), pharyngeal cancer (PC), and laryngeal cancer (LC). It is one of the most frequent cancers in the world. Smoking and alcohol consumption are the typical well-known predictors of HNC. Human papillomavirus (HPV) is an increasing etiological factor for oropharyngeal cancer (OPC). Moreover, food and nutrition play an important role in HNC etiology. According to the World Cancer Research Fund and the American Institute for Cancer Research, an intake of non-starchy vegetables and fruits could decrease HNC risk. The carotenoids included in vegetables and fruits are well-known antioxidants which have anti-mutagenic and immune regulatory functions. Numerous studies have shown the relationship between carotenoid intake and a lower HNC risk, but the role of carotenoids in HNC risk is not well defined. The goal of this review is to present the current literature regarding the relationship between various carotenoids and HNC risk.

Alcohol drinking and head and neck cancer risk: the joint effect of intensity and duration

BACKGROUND

Alcohol is a well-established risk factor for head and neck cancer (HNC). This study aims to explore the effect of alcohol intensity and duration, as joint continuous exposures, on HNC risk.

METHODS

Data from 26 case-control studies in the INHANCE Consortium were used, including never and current drinkers who drunk ≤10 drinks/day for ≤54 years (24234 controls, 4085 oral cavity, 3359 oropharyngeal, 983 hypopharyngeal and 3340 laryngeal cancers). The dose-response relationship between the risk and the joint exposure to drinking intensity and duration was investigated through bivariate regression spline models, adjusting for potential confounders, including tobacco smoking.

RESULTS

For all subsites, cancer risk steeply increased with increasing drinks/day, with no appreciable threshold effect at lower intensities. For each intensity level, the risk of oral cavity, hypopharyngeal and laryngeal cancers did not vary according to years of drinking, suggesting no effect of duration. For oropharyngeal cancer, the risk increased with durations up to 28 years, flattening thereafter. The risk peaked at the higher levels of intensity and duration for all subsites (odds ratio = 7.95 for oral cavity, 12.86 for oropharynx, 24.96 for hypopharynx and 6.60 for larynx).

CONCLUSIONS

Present results further encourage the reduction of alcohol intensity to mitigate HNC risk.

Risk Prediction Models for Head and Neck Cancer in the US Population From the INHANCE Consortium

Head and neck cancer (HNC) risk prediction models based on risk factor profiles have not yet been developed. We took advantage of the large database of the International Head and Neck Cancer Epidemiology (INHANCE) Consortium, including 14 US studies from 1981-2010, to develop HNC risk prediction models. Seventy percent of the data were used to develop the risk prediction models; the remaining 30% were used to validate the models. We used competing-risk models to calculate absolute risks. The predictors included age, sex, education, race/ethnicity, alcohol drinking intensity, cigarette smoking duration and intensity, and/or family history of HNC. The 20-year absolute risk of HNC was 7.61% for a 60-year-old woman who smoked more than 20 cigarettes per day for over 20 years, consumed 3 or more alcoholic drinks per day, was a high school graduate, had a family history of HNC, and was non-Hispanic white. The 20-year risk for men with a similar profile was 6.85%. The absolute risks of oropharyngeal and hypopharyngeal cancers were generally lower than those of oral cavity and laryngeal cancers. Statistics for the area under the receiver operating characteristic curve (AUC) were 0.70 or higher, except for oropharyngeal cancer in men. This HNC risk prediction model may be useful in promoting healthier behaviors such as smoking cessation or in aiding persons with a family history of HNC to evaluate their risks.

Age at start of using tobacco on the risk of head and neck cancer: Pooled analysis in the International Head and Neck Cancer Epidemiology Consortium (INHANCE)

BACKGROUND

Tobacco use is a well-established risk factor for head and neck cancer (HNC). However, less is known about the potential impact of exposure to tobacco at an early age on HNC risk.

METHODS

We analyzed individual-level data on ever tobacco smokers from 27 case-control studies (17,146 HNC cases and 17,449 controls) in the International Head and Neck Cancer Epidemiology (INHANCE) consortium. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using random-effects logistic regression models.

RESULTS

Without adjusting for tobacco packyears, we observed that younger age at starting tobacco use was associated with an increased HNC risk for ever smokers (OR<10 years vs. ≥30 years: 1.64, 95% CI: 1.35, 1.97). However, the observed association between age at starting tobacco use and HNC risk became null after adjusting for tobacco packyears (OR<10 years vs. ≥30 years: 0.97, 95% CI: 0.80, 1.19). In the stratified analyses on HNC subsites by tobacco packyears or years since quitting, no difference in the association between age at start and HNC risk was observed.

CONCLUSIONS

Results from this pooled analysis suggest that increased HNC risks observed with earlier age at starting tobacco smoking are largely due to longer duration and higher cumulative tobacco exposures.

Joint effects of intensity and duration of cigarette smoking on the risk of head and neck cancer: A bivariate spline model approach

OBJECTIVES

This study aimed at re-evaluating the strength and shape of the dose-response relationship between the combined (or joint) effect of intensity and duration of cigarette smoking and the risk of head and neck cancer (HNC). We explored this issue considering bivariate spline models, where smoking intensity and duration were treated as interacting continuous exposures.

MATERIALS AND METHODS

We pooled individual-level data from 33 case-control studies (18,260 HNC cases and 29,844 controls) participating in the International Head and Neck Cancer Epidemiology (INHANCE) consortium. In bivariate regression spline models, exposures to cigarette smoking intensity and duration (compared with never smokers) were modeled as a linear piecewise function within a logistic regression also including potential confounders. We jointly estimated the optimal knot locations and regression parameters within the Bayesian framework.

RESULTS

For oral-cavity/pharyngeal (OCP) cancers, an odds ratio (OR) >5 was reached after 30 years in current smokers of ∼20 or more cigarettes/day. Patterns of OCP cancer risk in current smokers differed across strata of alcohol intensity. For laryngeal cancer, ORs >20 were found for current smokers of ≥20 cigarettes/day for ≥30  years. In former smokers who quit ≥10  years ago, the ORs were approximately halved for OCP cancers, and ∼1/3 for laryngeal cancer, as compared to the same levels of intensity and duration in current smokers.

CONCLUSION

Referring to bivariate spline models, this study better quantified the joint effect of intensity and duration of cigarette smoking on HNC risk, further stressing the need of smoking cessation policies.

Shared and Study-specific Dietary Patterns and Head and Neck Cancer Risk in an International Consortium

BACKGROUND

A few papers have considered reproducibility of a posteriori dietary patterns across populations, as well as pattern associations with head and neck cancer risk when multiple populations are available.

METHODS

We used individual-level pooled data from seven case-control studies (3844 cases; 6824 controls) participating in the International Head and Neck Cancer Epidemiology consortium. We simultaneously derived shared and study-specific a posteriori patterns with a novel approach called multi-study factor analysis applied to 23 nutrients. We derived odds ratios (ORs) and 95% confidence intervals (CIs) for cancers of the oral cavity and pharynx combined, and larynx, from logistic regression models.

RESULTS

We identified three shared patterns that were reproducible across studies (75% variance explained): the Antioxidant vitamins and fiber (OR = 0.57, 95% CI = 0.41, 0.78, highest versus lowest score quintile) and the Fats (OR = 0.80, 95% CI = 0.67, 0.95) patterns were inversely associated with oral and pharyngeal cancer risk. The Animal products and cereals (OR = 1.5, 95% CI = 1.1, 2.1) and the Fats (OR = 1.8, 95% CI = 1.4, 2.3) patterns were positively associated with laryngeal cancer risk, whereas a linear inverse trend in laryngeal cancer risk was evident for the Antioxidant vitamins and fiber pattern. We also identified four additional study-specific patterns, one for each of the four US studies examined. We named them all as Dairy products and breakfast cereals, and two were associated with oral and pharyngeal cancer risk.

CONCLUSION

Multi-study factor analysis provides insight into pattern reproducibility and supports previous evidence on cross-country reproducibility of dietary patterns and on their association with head and neck cancer risk. See video abstract at, http://links.lww.com/EDE/B430.

Screening pathogenic genes in oral squamous cell carcinoma based on the mRNA expression microarray data

Oral squamous cell carcinoma (OSCC) is one of the most common malignancies and its survival rate has barely improved over the past few decades. The purpose of this study was to screen pathogenic genes of OSCC via microarray analysis. The mRNA expression microarray datasets (GSE2280 and GSE3524) were downloaded from the Gene Expression Omnibus (GEO) database. In GSE2280, there were 22 OSCC samples without metastasis and 5 OSCC samples with lymph node metastasis. In GSE3524, there were 16 OSCC samples and 4 normal tissue samples. The differentially expressed genes (DEGs) in OSCC samples with lymph node metastasis compared with those without metastasis (named as DEGs-1), and the DEGs in OSCC samples compared with normal tissue samples (named as DEGs-2), were obtained via limma package. The Database for Annotation, Visualization and Integrated Discovery (DAVID) was used to perform the functional enrichment analyses of DEGs-1 and DEGs-2. The miRNA-gene pairs of overlaps among DEGs were screened out with the TargetScan database, and the miRNA-gene regulated network was constructed by Cytoscape software. A total of 233 and 410 DEGs were identified in the sets of DEGs-1 and DEGs-2, respectively. DEGs-1 were enriched in 188 Gene Ontology (GO) terms and 8 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, and DEGs-2 were enriched in 228 GO terms and 6 KEGG pathways. In total, 126 nodes and 135 regulated pairs were involved in the miRNA-gene regulated network. Our study indicated that transglutaminase 2 (TGM2) and Islet 1 (ISL1) may be biomarkers of OSCC and their metastases. Moreover, it provided some potential pathogenic genes (e.g. P2RY2 and RAPGEFL1) in OSCC.

Mouthwash use and cancer of the head and neck: a pooled analysis from the International Head and Neck Cancer Epidemiology Consortium

Most mouthwashes contain alcohol, a known cause of head and neck cancer (oral cavity, pharynx, larynx), likely through the carcinogenic activity of acetaldehyde, formed in the oral cavity from alcohol. We carried out a pooled analysis of 8981 cases of head and neck cancer and 10 090 controls from 12 case-control studies with comparable information on mouthwash use in the International Head and Neck Cancer Epidemiology Consortium. Logistic regression was used to assess the association of mouthwash use with cancers of the oral cavity, oropharynx, hypopharynx, and larynx, adjusting for study, age, sex, pack-years of tobacco smoking, number of alcoholic drinks/day, and education. Compared with never users of mouthwash, the odds ratio (OR) of all head and neck cancers was 1.01 [95% confidence interval (CI): 0.94-1.08] for ever users, based on 12 studies. The corresponding ORs of cancer of the oral cavity and oropharynx were 1.11 (95% CI: 1.00-1.23) and 1.28 (95% CI: 1.06-1.56), respectively. OR for all head and neck cancer was 1.15 (95% CI: 1.01-1.30) for use for more than 35 years, based on seven studies (P for linear trend=0.01), and OR 1.31 (95% CI: 1.09-1.58) for use more than one per day, based on five studies (P for linear trend <0.001). Although limited by the retrospective nature of the study and the limited ability to assess risks of mouthwash use in nonusers of tobacco and alcohol, this large investigation shows potential risks for head and neck cancer subsites and in long-term and frequent users of mouthwash. This pooled analysis provides the most precise estimate of the association between mouthwash use and head and neck cancer.

Dietary fiber intake and head and neck cancer risk: A pooled analysis in the International Head and Neck Cancer Epidemiology consortium

The possible role of dietary fiber in the etiology of head neck cancers (HNCs) is unclear. We used individual-level pooled data from ten case-control studies (5959 cases and 12,248 controls) participating in the International Head and Neck Cancer Epidemiology (INHANCE) consortium, to examine the association between fiber intake and cancer of the oral cavity/pharynx and larynx. Odds Ratios (ORs) and their 95% Confidence Intervals (CIs) were estimated using unconditional multiple logistic regression applied to quintile categories of non-alcohol energy-adjusted fiber intake and adjusted for tobacco and alcohol use and other known or putative confounders. Fiber intake was inversely associated with oral and pharyngeal cancer combined (OR for 5th vs. 1st quintile category = 0.49, 95% CI: 0.40-0.59; p for trend <0.001) and with laryngeal cancer (OR = 0.66, 95% CI: 0.54-0.82, p for trend <0.001). There was, however, appreciable heterogeneity of the estimated effect across studies for oral and pharyngeal cancer combined. Nonetheless, inverse associations were consistently observed for the subsites of oral and pharyngeal cancers and within most strata of the considered covariates, for both cancer sites. Our findings from a multicenter large-scale pooled analysis suggest that, although in the presence of between-study heterogeneity, a greater intake of fiber may lower HNC risk.

Smokeless Tobacco Use and the Risk of Head and Neck Cancer: Pooled Analysis of US Studies in the INHANCE Consortium

Previous studies on smokeless tobacco use and head and neck cancer (HNC) have found inconsistent and often imprecise estimates, with limited control for cigarette smoking. Using pooled data from 11 US case-control studies (1981-2006) of oral, pharyngeal, and laryngeal cancers (6,772 cases and 8,375 controls) in the International Head and Neck Cancer Epidemiology (INHANCE) Consortium, we applied hierarchical logistic regression to estimate odds ratios and 95% confidence intervals for ever use, frequency of use, and duration of use of snuff and chewing tobacco separately for never and ever cigarette smokers. Ever use (versus never use) of snuff was strongly associated with HNC among never cigarette smokers (odds ratio (OR) = 1.71, 95% confidence interval (CI): 1.08, 2.70), particularly for oral cavity cancers (OR = 3.01, 95% CI: 1.63, 5.55). Although ever (versus never) tobacco chewing was weakly associated with HNC among never cigarette smokers (OR = 1.20, 95% CI: 0.81, 1.77), analyses restricted to cancers of the oral cavity showed a stronger association (OR = 1.81, 95% CI: 1.04, 3.17). Few or no associations between each type of smokeless tobacco and HNC were observed among ever cigarette smokers, possibly reflecting residual confounding by smoking. Smokeless tobacco use appears to be associated with HNC, especially oral cancers, with snuff being more strongly associated than chewing tobacco.

Epidemiological evidence on environmental tobacco smoke and cancers other than lung or breast

We reviewed 87 epidemiological studies relating environmental tobacco smoke (ETS) exposure to risk of cancer other than lung or breast in never smoking adults. This updates a 2002 review which also considered breast cancer. Meta-analysis showed no significant relationship with ETS for nasopharynx cancer, head and neck cancer, various digestive cancers (stomach, rectum, colorectal, liver, pancreas), or cancers of endometrium, ovary, bladder and brain. For some cancers (including oesophagus, colon, gall bladder and lymphoma) more limited data did not suggest a relationship. An increased cervix cancer risk (RR 1.58, 95%CI 1.29-1.93, n = 17 independent estimates), reducing to 1.29 (95%CI 1.01-1.65) after restriction to five estimates adjusting for HPV infection or sexual activity suggests a causal relationship, as do associations with nasosinus cancer observed in 2002 (no new studies since), and less so kidney cancer (RR 1.33, 95%CI 1.04-1.70, n = 6). A weaker association with total cancer (RR 1.13, 95%CI 1.03-1.35, n = 19) based on heterogeneous data is inconclusive. Inadequate confounder control, recall bias, publication bias, and occasional reports of implausibly large RRs in individual studies contribute to our conclusion that the epidemiological evidence does not convincingly demonstrate that ETS exposure causes any of the cancers studied.

Natural vitamin C intake and the risk of head and neck cancer: A pooled analysis in the International Head and Neck Cancer Epidemiology Consortium

Evidence of associations between single nutrients and head and neck cancer (HNC) is still more limited and less consistent than that for fruit and vegetables. However, clarification of the protective mechanisms of fruit and vegetables is important to our understanding of HNC etiology. We investigated the association between vitamin C intake from natural sources and cancer of the oral cavity/pharynx and larynx using individual-level pooled data from ten case-control studies (5,959 cases and 12,248 controls) participating in the International Head and Neck Cancer Epidemiology (INHANCE) consortium. After harmonization of study-specific exposure information via the residual method, adjusted odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were estimated using unconditional multiple logistic regression models on quintile categories of 'non-alcohol energy-adjusted' vitamin C intake. In the presence of heterogeneity of the estimated ORs among studies, we derived those estimates from generalized linear mixed models. Higher intakes of vitamin C were inversely related to oral and pharyngeal (OR = 0.54, 95% CI: 0.45-0.65, for the fifth quintile category versus the first one, p for trend<0.001) and laryngeal cancers (OR = 0.52, 95% CI: 0.40-0.68, p for trend = 0.006), although in the presence of heterogeneity among studies for both sites. Inverse associations were consistently observed for the anatomical subsites of oral and pharyngeal cancer, and across strata of age, sex, education, body mass index, tobacco, and alcohol, for both cancer sites. The inverse association of vitamin C intake from foods with HNC may reflect a protective effect on these cancers; however, we cannot rule out other explanations.

Vitamin E intake from natural sources and head and neck cancer risk: a pooled analysis in the International Head and Neck Cancer Epidemiology consortium

BACKGROUND

Evidence for the possible effect of vitamin E on head and neck cancers (HNCs) is limited.

METHODS

We used individual-level pooled data from 10 case-control studies (5959 cases and 12 248 controls) participating in the International Head and Neck Cancer Epidemiology (INHANCE) consortium to assess the association between vitamin E intake from natural sources and cancer of the oral cavity/pharynx and larynx. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using unconditional logistic regression models applied to quintile categories of non-alcohol energy-adjusted vitamin E intake.

RESULTS

Intake of vitamin E was inversely related to oral/pharyngeal cancer (OR for the fifth vs the first quintile category=0.59, 95% CI: 0.49-0.71; P for trend <0.001) and to laryngeal cancer (OR=0.67, 95% CI: 0.54-0.83, P for trend <0.001). There was, however, appreciable heterogeneity of the estimated effect across studies for oral/pharyngeal cancer. Inverse associations were generally observed for the anatomical subsites of oral and pharyngeal cancer and within covariate strata for both sites.

CONCLUSION

Our findings suggest that greater vitamin E intake from foods may lower HNC risk, although we were not able to explain the heterogeneity observed across studies or rule out certain sources of bias.

Carotenoid intake and head and neck cancer: a pooled analysis in the International Head and Neck Cancer Epidemiology Consortium

Food and nutrition play an important role in head and neck cancer (HNC) etiology; however, the role of carotenoids remains largely undefined. We explored the relation of HNC risk with the intake of carotenoids within the International Head and Neck Cancer Epidemiology Consortium. We pooled individual-level data from 10 case-control studies conducted in Europe, North America, and Japan. The analysis included 18,207 subjects (4414 with oral and pharyngeal cancer, 1545 with laryngeal cancer, and 12,248 controls), categorized by quintiles of carotenoid intake from natural sources. Comparing the highest with the lowest quintile, the risk reduction associated with total carotenoid intake was 39 % (95 % CI 29-47 %) for oral/pharyngeal cancer and 39 % (95 % CI 24-50 %) for laryngeal cancer. Intakes of β-carotene equivalents, β-cryptoxanthin, lycopene, and lutein plus zeaxanthin were associated with at least 18 % reduction in the rate of oral and pharyngeal cancer (95 % CI 6-29 %) and 17 % reduction in the rate of laryngeal cancer (95 % CI 0-32 %). The overall protective effect of carotenoids on HNC was stronger for subjects reporting greater alcohol consumption (p < 0.05). The odds ratio for the combined effect of low carotenoid intake and high alcohol or tobacco consumption versus high carotenoid intake and low alcohol or tobacco consumption ranged from 7 (95 % CI 5-9) to 33 (95 % CI 23-49). A diet rich in carotenoids may protect against HNC. Persons with both low carotenoid intake and high tobacco or alcohol are at substantially higher risk of HNC.

Carotenoid Intake from Natural Sources and Head and Neck Cancer: A Systematic Review and Meta-analysis of Epidemiological Studies

Because of their role as antioxidants, the intake of carotenoids has been hypothesized to reduce the risk of head and neck cancer (HNC). We conducted a systematic review and meta-analysis of the epidemiological studies to investigate whether the intake of specific carotenoids from dietary sources, as well as combined carotenoids, is associated with the risk of HNC according to cancer subsites. A comprehensive literature search of the Medline and Scopus databases was conducted. Sixteen articles were identified from the literature search, of which 15 were case-control studies and one prospective cohort study. The risk reduction associated with β-carotene equivalents intake was 46% (95% CI, 20%-63%) for cancer of oral cavity and 57% (95% CI, 23%-76%) for laryngeal cancer. Lycopene and β-cryptoxanthin also reduced the risk for laryngeal cancer; the ORs for the highest category compared with the lowest one of carotenoid intake were 50% (95% CI, 11%-72%) and 59% (95% CI, 49%-67%), respectively. Lycopene, α-carotene, and β-cryptoxanthin were associated with at least 26% reduction in the rate of oral and pharyngeal cancer (95% CI, 2%-44%). Our systematic review and meta-analysis on dietary carotenoids intake and HNC showed carotenoids to act protectively against HNC, in relation to most of single nutrients and subsites.

Risk factors for head and neck cancer in young adults: a pooled analysis in the INHANCE consortium

BACKGROUND

Increasing incidence of head and neck cancer (HNC) in young adults has been reported. We aimed to compare the role of major risk factors and family history of cancer in HNC in young adults and older patients.

METHODS

We pooled data from 25 case-control studies and conducted separate analyses for adults ≤ 45 years old ('young adults', 2010 cases and 4042 controls) and >45 years old ('older adults', 17700 cases and 22 704 controls). Using logistic regression with studies treated as random effects, we estimated adjusted odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

The young group of cases had a higher proportion of oral tongue cancer (16.0% in women; 11.0% in men) and unspecified oral cavity / oropharynx cancer (16.2%; 11.1%) and a lower proportion of larynx cancer (12.1%; 16.6%) than older adult cases. The proportions of never smokers or never drinkers among female cases were higher than among male cases in both age groups. Positive associations with HNC and duration or pack-years of smoking and drinking were similar across age groups. However, the attributable fractions (AFs) for smoking and drinking were lower in young when compared with older adults (AFs for smoking in young women, older women, young men and older men, respectively, = 19.9% (95% CI=9.8%, 27.9%), 48.9% (46.6%, 50.8%), 46.2% (38.5%, 52.5%), 64.3% (62.2%, 66.4%); AFs for drinking=5.3% (-11.2%, 18.0%), 20.0% (14.5%, 25.0%), 21.5% (5.0%, 34.9%) and 50.4% (46.1%, 54.3%). A family history of early-onset cancer was associated with HNC risk in the young [OR=2.27 (95% CI=1.26, 4.10)], but not in the older adults [OR=1.10 (0.91, 1.31)]. The attributable fraction for family history of early-onset cancer was 23.2% (8.60% to 31.4%) in young compared with 2.20% (-2.41%, 5.80%) in older adults.

CONCLUSIONS

Differences in HNC aetiology according to age group may exist. The lower AF of cigarette smoking and alcohol drinking in young adults may be due to the reduced length of exposure due to the lower age. Other characteristics, such as those that are inherited, may play a more important role in HNC in young adults compared with older adults.

Folate intake and the risk of oral cavity and pharyngeal cancer: a pooled analysis within the International Head and Neck Cancer Epidemiology Consortium

There are suggestions of an inverse association between folate intake and serum folate levels and the risk of oral cavity and pharyngeal cancers (OPCs), but most studies are limited in sample size, with only few reporting information on the source of dietary folate. Our study aims to investigate the association between folate intake and the risk of OPC within the International Head and Neck Cancer Epidemiology (INHANCE) Consortium. We analyzed pooled individual-level data from ten case-control studies participating in the INHANCE consortium, including 5,127 cases and 13,249 controls. Odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were estimated for the associations between total folate intake (natural, fortification and supplementation) and natural folate only, and OPC risk. We found an inverse association between total folate intake and overall OPC risk (the adjusted OR for the highest vs. the lowest quintile was 0.65, 95% CI: 0.43-0.99), with a stronger association for oral cavity (OR = 0.57, 95% CI: 0.43-0.75). A similar inverse association, though somewhat weaker, was observed for folate intake from natural sources only in oral cavity cancer (OR = 0.64, 95% CI: 0.45-0.91). The highest OPC risk was observed in heavy alcohol drinkers with low folate intake as compared to never/light drinkers with high folate (OR = 4.05, 95% CI: 3.43-4.79); the attributable proportion (AP) owing to interaction was 11.1% (95% CI: 1.4-20.8%). Lastly, we reported an OR of 2.73 (95% CI:2.34-3.19) for those ever tobacco users with low folate intake, compared with nevere tobacco users and high folate intake (AP of interaction =10.6%, 95% CI: 0.41-20.8%). Our project of a large pool of case-control studies supports a protective effect of total folate intake on OPC risk.

Nutrient-based dietary patterns and the risk of head and neck cancer: a pooled analysis in the International Head and Neck Cancer Epidemiology consortium

BACKGROUND

The association between dietary patterns and head and neck cancer has rarely been addressed.

PATIENTS AND METHODS

We used individual-level pooled data from five case-control studies (2452 cases and 5013 controls) participating in the International Head and Neck Cancer Epidemiology consortium. A posteriori dietary patterns were identified through a principal component factor analysis carried out on 24 nutrients derived from study-specific food-frequency questionnaires. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were estimated using unconditional logistic regression models on quintiles of factor scores.

RESULTS

We identified three major dietary patterns named 'animal products and cereals', 'antioxidant vitamins and fiber', and 'fats'. The 'antioxidant vitamins and fiber' pattern was inversely related to oral and pharyngeal cancer (OR=0.57, 95% CI 0.43-0.76 for the highest versus the lowest score quintile). The 'animal products and cereals' pattern was positively associated with laryngeal cancer (OR=1.54, 95% CI 1.12-2.11), whereas the 'fats' pattern was inversely associated with oral and pharyngeal cancer (OR=0.78, 95% CI 0.63-0.97) and positively associated with laryngeal cancer (OR=1.69, 95% CI 1.22-2.34).

CONCLUSIONS

These findings suggest that diets rich in animal products, cereals, and fats are positively related to laryngeal cancer, and those rich in fruit and vegetables inversely related to oral and pharyngeal cancer.

DNA repair and mutagen sensitivity of epithelial cells and lymphocytes in oropharyngeal cancer

Tobacco-associated nitrosamines are known carcinogens causing DNA damage in epithelial cells of the head and neck. A matched case-control study was performed to evaluate the sensitivity of patients with squamous cell cancer (SCC) of the oropharynx, and controls to tobacco-associated nitrosamines. Quantitative DNA repair was evaluated following a period of 15 and 30 min. Fresh biopsies from 100 male donors of macroscopically healthy oropharyngeal cells and lymphocytes (50 SCC patients and 50 controls) were incubated with N-nitrosodiethylamine (NDEA), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) or N-nitrosonornicotine (NNN). DNA damage in epithelial cells and lymphocytes was assessed using the comet assay. Following incubation with NDEA, cells underwent a period of DNA repair. All of the nitrosamines caused equivalent genotoxic damage in mucosal cells and lymphocytes of the two groups. Lymphocyte DNA repair capacity in the control group (26.8 and 37.1% after 15 and 30 min) was comparable to the tumor group (23.6 and 40.6%). However, epithelial cell DNA repair capacity of carcinoma patients was significantly reduced to 17.1% (15 min) and 23% (30 min) compared to the DNA repair of the control group (36.2%, 15 min and 46.0%, 30 min). Mutagen sensitivity was comparable in patients and controls. Thus, reduced epithelial cell DNA repair capacity of tumor patients is a possible endogenous risk factor for the development of head and neck squamous cell cancer.

Dietary influences on mutagenesis--where is this field going?

Early studies on dietary mutagenesis were mostly observational, with large numbers of potential dietary mutagens being identified from every conceivable dietary source. These included known dietary carcinogens such as aflatoxin B1 and benzo[a]pyrene, and hitherto unrecognized dietary mutagens, such as the pyrolysis products formed during the heating of proteinaceous materials (heterocyclic amines). The 1993 evaluation of 2-amino-3-methyl-3H-imidazo(4,5-j)quinoline as a probable human carcinogen by the International Agency for Research on Cancer was a landmark, as this was done in the absence of specific human carcinogenicity data, and strongly influenced by mutagenicity test data. In the 21st century, the field has moved from the identification of more and more mutagens, to molecular epidemiologic approaches that not only show a mutagenic effect but also seek to link it to a dietary (or environmental) cause. Effects of diet in stimulating chronic inflammation may lead to reactive species and thereby mutation as a secondary consequence, while dietary deficiencies and nutrient imbalances may be strong sources of mutagenesis. Recognition of the roles of nutrients in cell signaling processes and control of microRNAs suggest major influences on gene expression, in the absence of permanent DNA changes. Genome-wide association studies have highlighted new pathways such as JAK/STAT signaling that profoundly influence genomic instability and responses to dietary mutagens. With improved methodologies for DNA sequencing and epigenetic changes, it is time to apply more sophisticated approaches to recognizing and proving the role of diet as a primary modulator of mutagenesis in humans.

Coffee and tea intake and risk of head and neck cancer: pooled analysis in the international head and neck cancer epidemiology consortium

BACKGROUND

Only a few studies have explored the relation between coffee and tea intake and head and neck cancers, with inconsistent results.

METHODS

We pooled individual-level data from nine case-control studies of head and neck cancers, including 5,139 cases and 9,028 controls. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI), adjusting for potential confounders.

RESULTS

Caffeinated coffee intake was inversely related with the risk of cancer of the oral cavity and pharynx: the ORs were 0.96 (95% CI, 0.94-0.98) for an increment of 1 cup per day and 0.61 (95% CI, 0.47-0.80) in drinkers of >4 cups per day versus nondrinkers. This latter estimate was consistent for different anatomic sites (OR, 0.46; 95% CI, 0.30-0.71 for oral cavity; OR, 0.58; 95% CI, 0.41-0.82 for oropharynx/hypopharynx; and OR, 0.61; 95% CI, 0.37-1.01 for oral cavity/pharynx not otherwise specified) and across strata of selected covariates. No association of caffeinated coffee drinking was found with laryngeal cancer (OR, 0.96; 95% CI, 0.64-1.45 in drinkers of >4 cups per day versus nondrinkers). Data on decaffeinated coffee were too sparse for detailed analysis, but indicated no increased risk. Tea intake was not associated with head and neck cancer risk (OR, 0.99; 95% CI, 0.89-1.11 for drinkers versus nondrinkers).

CONCLUSIONS

This pooled analysis of case-control studies supports the hypothesis of an inverse association between caffeinated coffee drinking and risk of cancer of the oral cavity and pharynx.

IMPACT

Given widespread use of coffee and the relatively high incidence and low survival of head and neck cancers, the observed inverse association may have appreciable public health relevance.

Genome Instability and Bleomycin Sensitivity Test

Procjena individualne osjetljivosti na mutagene često je dio istraživanja u epidemiološkim studijama koje prate pojavnost zloćudnih bolesti u populacijama. Posljedica djelovanja mutagena u genomu izloženih osoba jest nastanak osoba jest nastanak određene, manje ili veće, količine oštećenja, uvjetovane individualnim razlikama u osjetljivosti. Viša razina takve genomske nestabilnosti znači opasnost (rizik) od razvoja zloćudnih bolesti. Interindividualne razlike u odgovoru na mutagene obično se povezuju i s promijenjenom (većinom smanjenom) sposobnosti (kapacitetom) za popravak DNA. Citogenetičke studije su pokazale da je genom tumorskih stanica nestabilniji od normalnih, a time i skloniji akumuliranju oštećenja, bilo da je nestabilnost uzrokovana nasljeđem, izloženošću ili kombinacijom tih dvaju učinaka. U oboljelih ispitanika utvrđena je povećana učestalost kromatidnih i kromosomskih aberacija naspram normalne populacije te sklonost razvoju određenih vrsta neoplazija. U praćenju povezanosti promijenjenog odgovora i pojavnosti tumora služe nam različiti biomarkeri. Kao indirektni pokazatelji uspješnosti popravka DNA često se rabe testovi osjetljivosti na mutagene u kulturama limfocita periferne krvi. Jedan od takvih testova je i bleomicinski test. Radiomimetik i citostatik, a po strukturi glikopeptid, bleomicin se u stanici prevodi u aktivni oblik sposoban cijepati molekulu DNA što uzrokuje brojne jednolančane i dvolančane lomove. Kao jednostavna i jeftina metoda, zasniva se na utvrđivanju ukupnog broja jednolančanih lomova u kromosomima limfocita uzgajanih u staničnoj kulturi koji su u uvjetima in vitro tijekom kasne G2-faze staničnog ciklusa bili izloženi bleomicinu. Ovaj revijalni rad daje pregled utjecaja raznih faktora na rezultate samog testa i pokazuje njegovu široku primjenu u proučavanju genomske nestabilnosti koju najčešće uzrokuje kombinacija raznih faktora.

Current topics in the epidemiology of oral cavity and oropharyngeal cancers

Oral cancer incidence rates rose dramatically during the twentieth century in the United States and Europe, especially among individuals under the age of 60 years. Although influenced by age, sex, and country of origin, incidence trends were most strongly affected by elevated risk among individuals born after approximately 1915. This cohort effect was indicative of strong behavioral influences on oral cancer risk. In this article, associations between oral cancer risk and established behavioral risk factors including alcohol and tobacco use are reviewed. Additionally, possible associations between oral cancer risk and oral hygiene, diet, nutritional status, and sexual behavior as well as the influence of genetic factors on oral cancer risk are considered. Special emphasis is placed on evaluating possible risk differences in individuals above and below the age of 45 and in users and nonusers of alcohol and tobacco.

The role of folates in squamous cell carcinoma of the head and neck

The primary objective of this review is to explore the hypothesis that folate insufficiency may be important in the pathogenesis of squamous cell carcinomas of the head and neck (SCCHN) and that folate repletion may be an effective component of chemoprevention. The main results are that folate insufficiency disrupts DNA global and specific gene methylation patterns such that the activity of certain tumor suppressor genes such as p16 and possibly p53 may be lost. Folate pool imbalance and impaired repair mechanisms may contribute to DNA instability and strand breaks. Sensitive methods exist for identification of individuals with folate insufficiency in contrast to the relatively insensitive conventional serum or red cell folate assays with broad "normal" ranges. The impact of folate supplementation can thus be quantified. Folate imbalance may result from alterations in folate cellular uptake by the reduced folate carrier (RFC) and/or the folate receptor (FR) and polymorphisms in enzymes important in folate retention such as folylpolyglutamate synthetase and in folate modification such as methylene tetrahydrofolate reductase (MTHFR). Known predisposing factors for SCCHN such as alcohol and tobacco carcinogens may influence folate balance. Folate supplementation may reduce primary or secondary risk of cancer. Formal studies of folate sufficiency in persons at risk for or diagnosed and treated for SCCHN are needed to define the role of folate supplementation in the prevention of these cancers.

Descriptive epidemiology and risk factors for head and neck cancer

Although more common in developing countries, over 11,000 deaths will occur in the United States from head and neck cancer in 2004. Squamous cell carcinomas account for the vast majority of cases in the United States and the majority of these are related to exposure to tobacco and alcohol. Newer data suggest a genetic contribution. This group is the focus of primary and secondary preventative efforts.

Differential susceptibility to chromatid breaks induced by bleomycin in sub-fertile and fertile bovines

The rate of chromatid breaks was studied in cows with a history of sub-fertility by means of a test based on measurement of the average of breaks induced in lymphocytes of peripheral blood cultures. Fourteen female specimens were divided into two groups: fertile and sub-fertile. Peripheral blood lymphocytes were cultured and prepared for cytogenetic analysis. Two types of culture were established for each animal to evaluate the response of peripheral blood lymphocyte cultures to the genotoxic effects of bleomycin. The first culture did not receive bleomycin treatment (spontaneous chromosome aberrations). Our results showed that median breaks per cell (b/c) (+/-semirange) for spontaneous culture of the fertile and sub-fertile animals and bleomycin sensitivity assay for fertile and sub-fertile animals were 0.00+/-0.06, 0.02+/-0.03, 0.08+/-0.05 and 0.22+/-0.09, respectively. There was no significant difference (P>0.05) in the chromosomal breakage in lymphocytes not exposed to bleomycin; however, in comparing the number of chromatid breaks per cell in cultures treated with bleomycin, the sub-fertile group showed a significantly higher (P<0.05) level than the fertile group. These findings have implications both for identifying cattle with less than optimum fertility as well as for providing potential avenues to study the origins of sub-fertility.

Diet and oral, pharyngeal, and esophageal cancer

Cancers of the upper digestive tract, including those arising in the oral cavity, pharynx, and esophagus, present a significant public health problem worldwide. These cancers are associated with high morbidity and mortality, and identification of protective factors is very important. A number of epidemiological studies have examined the association between vegetables, fruits, carotene, vitamin A, vitamin C, and vitamin E and oral, pharyngeal, and esophageal cancers. The results of 35 epidemiological studies, including one prospective cohort study, one nested case-control study, two randomized controlled trials, nine population-based case-control studies, and 22 hospital-based case-control studies, in addition to in vitro and animal studies, were examined to determine whether the criteria for causal assumption were satisfied for a protective role of these dietary components against development of oral, pharyngeal, and esophageal cancers. There is enough evidence to point to a preventive role of vegetable intake, including green vegetables, cruciferous vegetables, and yellow vegetables, total fruit intake, and citrus fruit intake. Yellow fruits are likely to be protective. Carotene, vitamin C, and vitamin E are protective, most likely in combination with each other and other micronutrients. The role of vitamin A is not clear because of conflicting findings in the studies reviewed.

Food mutagens

Several lines of evidence indicate that diet and dietary behaviors can contribute to human cancer risk. One way that this occurs is through the ingestion of food mutagens. Sporadic cancers result from a gene-environment interactions where the environment includes endogenous and exogenous exposures. In this article, we define environment as dietary exposures in the context of gene-environment interactions. Food mutagens cause different types of DNA damage: nucleotide alterations and gross chromosomal aberrations. Most mutagens begin their action at the DNA level by forming carcinogen-DNA adducts, which result from the covalent binding of a carcinogen or part of a carcinogen to a nucleotide. However the effect of food mutagens in carcinogenesis can be modified by heritable traits, namely, low-penetrant genes that affect mutagen exposure of DNA through metabolic activation and detoxification or cellular responses to DNA damage through DNA repair mechanisms or cell death. There are some clearly identified (e.g., aflatoxin) and suspected (e.g., N-nitrosamines, polycyclic aromatic hydrocarbons or heterocyclic amines) food mutagens. The target organs for these agents are numerous, but there is target-organ specificity for each. Mutagenesis however is not the only pathway that links dietary exposures and cancers. There is growing evidence that epigenetic factors, including changes in the DNA methylation pattern, are causing cancer and can be modified by dietary components. Also DNA damage may be indirect by triggering oxidative DNA damage. When considering the human diet, it should be recognized that foods contain both mutagens and components that decrease cancer risk such as antioxidants. Thus nutritionally related cancers ultimately develop from an imbalance of carcinogenesis and anticarcinogenesis. The best way to assess nutritional risks is through biomarkers, but there is no single biomarker that has been sufficiently validated. Although panels of biomarkers would be the most appropriate, their use as a reflection of target-organ risk remains to be determined. Also even when new biomarkers are developed, their application in target organs is problematic because tissues are not readily available. For now most biomarkers are used in surrogate tissues (e.g., blood, urine, oral cavity cells) that presumably reflect biological effects in target organs. This article reviews the role of food mutagens in mutagenesis and carcinogenesis and how their effects are modified by heritable traits and discusses how to identify and evaluate the effects of food mutagens.

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.

Genomic instability in head and neck cancer patients

BACKGROUND

In the normal host, there are a variety of cellular systems that ensure the accurate replication and repair of DNA. Recent evidence suggests that there are individual variations in the ability to preserve the genome. Certain individuals have defects in these checkpoints and have an inherent genomic instability. They are susceptible to the accumulation of DNA damage and are prone to carcinogenesis. This article examines the role of genomic instability in the development of head and neck cancer.

RESULTS

Patients with either the chromosomal instability syndromes or the Li-Fraumeni syndrome have marked defects in either DNA repair or apoptosis. These patients are prone to have head and neck neoplasms develop. Head and neck cancer patients also have a diminished ability to repair DNA damage compared with the "normal" population. Abnormalities have been identified in mutagen sensitivity, the expression of DNA mismatch repair enzymes, the expression of p53, and telomerase activity when head and neck cancer patients are compared with controls.

CONCLUSION

Subpopulations exist who have increased genomic instability. These individuals are at an increased risk for the accumulation of DNA mutations and the development of head and neck cancer. More research is needed to identify specific mechanisms of genomic instability and to further define the importance of this phenomenon.

DNA content as a prognostic marker in patients with oral leukoplakia

BACKGROUND

Oral leukoplakia may develop into squamous-cell carcinoma, which has a poor prognosis. Risk factors for oral carcinoma have been identified, but there are no reliable predictors of the outcome in individual patients with oral leukoplakia.

METHODS

We identified 150 patients with oral leukoplakia that was classified as epithelial dysplasia and measured the nuclear DNA content (ploidy) of the lesions to determine whether DNA ploidy could be used to predict the clinical outcome. Biopsy specimens obtained at annual follow-up visits were graded histologically and classified with respect to DNA content in a blinded fashion. Disease-free survival was assessed in relation to DNA ploidy and the histologic grade. The mean duration of follow-up was 103 months (range, 4 to 165).

RESULTS

Among 150 patients with verified epithelial dysplasia, a carcinoma developed in 36 (24 percent). Of the 150 patients, 105 (70 percent) had diploid (normal) lesions, 20 (13 percent) had tetraploid (intermediate) lesions, and 25 (17 percent) had aneuploid (abnormal) lesions at the time of the initial diagnosis. A carcinoma developed in 3 of the 105 patients with diploid lesions (3 percent), as compared with 21 of the 25 patients with aneuploid lesions (84 percent), yielding a negative predictive value of 97 percent with respect to the diploid lesions and a positive predictive value of 84 percent with respect to the aneuploid lesions. Carcinoma developed in 12 of 20 patients with tetraploid lesions (60 percent). The mean time from the initial assessment of the DNA content to the development of a carcinoma was 35 months (range, 4 to 57) in the group with aneuploid lesions and 49 months (range, 8 to 78) in the group with tetraploid lesions (P=0.02). The cumulative disease-free survival rate was 97 percent among the group with diploid lesions, 40 percent among the group with tetraploid lesions, and 16 percent among the group with aneuploid lesions (P<0.001).

CONCLUSIONS

The DNA content in cells of oral leukoplakia can be used to predict the risk of oral carcinoma.

Diet, genetic susceptibility and carcinogenesis

At least six types of gene-environment interactions (GEI) have been proposed (Kouhry and Wagener, 1993). In the first type, neither the environmental exposure (EE) nor the genetic risk factor (GRF) have any effect by themselves, but interaction between them causes disease. This is the case of phenylalanine exposure and the phenylketonuria genotype. Type 2 is a situation in which the GRF has no effect on disease in the absence of exposure, but exacerbates the effects of the latter. This is the most important type of GEI in relation to metabolic susceptibility genes and human carcinogenesis. The third type is the converse of the second (EE is ineffective per se, but enhances the effect of GRF). Type 4 occurs when both FE and GRF increase the risk for disease, but the combination is interactive or synergistic: an example is the interaction between Xeroderma Pigmentosum and LWV radiation. Types 5 and 6, according to the classification proposed by Kouhry, refer to cases in which the GRF is protective. The model of GEI that is emerging as the most important in chemical carcinogenesis refers to metabolic susceptibility genes. The general population can be divided into subgroups depending on their susceptibility to the action of carcinogens, based on their ability to metabolize such compounds to electrophilic, reactive metabolites (which form adducts with DNA), or, respectively, electrophobic metabolites that are excreted. The present contribution is a short review of the relevant literature, with particular emphasis on some polymorphisms involved in dietary exposures. In addition, the practical implications of genetic testing in this field are discussed.

Squamous carcinoma of the head and neck: molecular mechanisms and potential biomarkers

Squamous cell carcinoma (SCC) of the head and neck remains a major health problem worldwide. Recent advances in cell biology suggest that cancer results from the accumulation of specific genetic mutations, many of which have now been identified. These mutations can cause the activation of genes that promote cellular proliferation or inhibit cell death (oncogenes), or they may inactivate genes that inhibit proliferation or promote cell death (tumour suppressor genes). Although there is no known set sequence of events leading to the formation of SCC of the head and neck, there is evidence that many of the genomic mutations implicated in other forms of cancer have an aetiological role in these tumours. Certain viruses, notably Epstein-Barr virus and some types of human papillomaviruses, are causally related to some head and neck cancers. There is now the prospect of using molecular markers to achieve earlier diagnosis and to aid in the prediction of both tumour behaviour and likely responses to particular treatment modalities.

Induced genome instability as a potential screening test for cancer susceptibility?

The variety of mutations associated with carcinogenesis, along with variations in penetrance and environmental factors, complicate the genetic screening for cancer predisposition. It is proposed here that the detection of inherent genome instability as determined by increased mutagen susceptibility may enhance the identification of populations at risk for cancer. In support for this hypothesis, our analysis reveals a strong association between mutagen-induced chromosomal instability in peripheral blood lymphocytes and the propensity for cancers of oral cavity, pharynx, larynx, and lung. DNA instability in response to a variety of mutagens identifies patients with gastrointestinal, brain, endocrine, breast, skin, and hematologic tumors as well as individuals with cancer family syndromes. Induced genome instability therefore appears to be strongly linked to cancer predisposition, and prospective studies may yield a screening test utilizing a panel of mutagens to better identify populations at risk.

Cancer of the tongue in patients less than forty

INTRODUCTION

It is the opinion of many surgeons that the biologic potential of cancer that develops in young people is different compared with older patients. Prior reports on small series of patients addressing this issue have inadequate statistical power to resolve the question.

METHODS

By use of the techniques of meta-analysis, patients less than 40 years old who had undergone treatment of squamous cell carcinoma (SCC) of the oral tongue were examined. Twenty-eight patients who were encountered in the Department of Otolaryngology, University of Pittsburgh School of Medicine, and 94 patients were identified in the literature for a total of 122 patients <40 years old. A control group of 150 patients, aged 40 years and older treated for SCC of the oral tongue between 1982 and 1994 was identified.

RESULTS

Three-year disease-free survival in the group of patients aged less than 40 was 53.3% compared with 3-year disease free survivorship of 55.0% in the older cohort of patients.

CONCLUSION

These data strongly suggest that the outcomes of treatment for SCC of the oral tongue in young patients are similar compared with patients older than 40 with similar extent of disease.

The impact of molecular genetics on oral health paradigms

As a result of our increased understanding of the human genome, and the functional interrelationships of gene products with each other and with the environment, it is becoming increasingly evident that many human diseases are influenced by heritable alterations in the structure or function of genes. Significant advances in research methods and newly emerging partnerships between private and public sector interests are creating new possibilities for utilization of genetic information for the diagnosis and treatment of human diseases. The availability and application of genetic information to the understanding of normal and abnormal human growth and development are fundamentally changing the way we approach the study of human diseases. As a result, the issues and principles of medical genetics are coming to bear across all disciplines of health care. In this review, we discuss some of the potential applications of human molecular genetics for the diagnosis and treatment of oral diseases. This discussion is presented in the context of the ongoing technological advances and conceptual changes that are occurring in the field of medical genetics. To realize the promise of this new molecular genetics, we must be prepared to foresee the possibilities and to incorporate these newly emergent technologies into the evolving discipline of dentistry. By using examples of human conditions, we illustrate the broad application of this emerging technology to the study of simple as well as complex genetic diseases. Throughout this paper, we will use the following terminology: Penetrance--In a population, defined as the proportion of individuals possessing a disease-causing genotype who express the disease phenotype. When this proportion is less than 100%, the disease is said to have reduced or incomplete penetrance. Polymerase chain reaction (PCR)--A technique for amplifying a large number of copies of a specific DNA sequence flanked by two oligonucleotide primers. The DNA is alternately heated and cooled in the presence of DNA polymerase and free nucleotides, so that the specified DNA segment is denatured, hybridized with primers, and extended by DNA polymerase. MIM--Mendelian Inheritance in Man catalogue number from V. McKusick's Mendelian Inheritance in man (OMIM, 1998).

Upper airway complications of smoking

Tobacco smoke has a myriad of acute and chronic effects on the upper airway. These problems can range from aggravating inflammatory reactions to life threatening malignancies. Cessation of smoking is the key to successful resolution of many upper airway complaints. An increased awareness of these disease processes can improve early diagnosis and appropriate treatment. A better awareness of these processes may facilitate physicians in counseling patients about smoking.

Family history of cancer, mutagen sensitivity, and increased risk of head and neck cancer

To evaluate individual cancer susceptibility, 170 previously untreated patients with pathologically-confirmed squamous cell carcinoma of the oral cavity, pharynx, and larynx, and 175 age- and sex-matched health controls were investigated for the occurrence of cancer in first-degree relatives along with other established risk factors for head and neck cancer. More than 54% of these subjects were assayed for mutagen sensitivity by quantifying in-vitro bleomycin-induced chromosomal breaks within peripheral blood lymphocytes. After adjusting for age, gender, education, family income, tobacco and alcohol consumption, the odds ratio associated with three or more first-degree relatives with cancer at any site was 3.79 (95% CI 0.9-15.9) with a linearly-increased trend in risk (P = 0.040). Significantly elevated risk was found to be associated with a history of cancer within siblings (OR = 2.61, 1.2-5.6, P = 0.014). Patients with a family cancer history and mutagen sensitivity were at greatest risk (OR = 7.88, 2.5-25.3, P = 0.005), indicating an additive interactive effect. The findings suggested that genetic familial influence is important in the causation of head and neck cancer.

p53 overexpression in oral mucosa in relation to smoking

The tumour-suppressor protein p53 is mutated in many head and neck squamous cell carcinomas (HNSCCs). In this immunohistochemical study, similar numbers of p53-overexpressing cells were uniformly distributed throughout normal oral epithelium, irrespective of different smoking habits or the presence of an adjacent HNSCC. In a previous study, an increased number of proliferating cells were observed in normal oral mucosa from (ex)-smoking individuals and the present observations indicate that overexpression of p53 does not play a role in this increase. In contrast, focally overexpressed p53 occurred more frequently (p<0.05) in the tumour-adjacent normal mucosa (TAM) from smoking HNSCC patients (50 per cent) than in that from non-smoking HNSCC patients (20 per cent). This increase in focal p53 overexpression might represent an early alteration in the development of HNSCC, but it could not be detected in mucosa from healthy smokers. This indicates that besides the abuse of tobacco, other environmental and/or genetic factors must contribute to the presence of p53-positive clusters in TAM. Abuse of alcohol, an additional factor in these HNSCC patients, together with the abuse of tobacco, might play a role in the development of the p53-positive clusters.