Let-7 microRNA-binding-site polymorphism in the 3'UTR of KRAS and colorectal cancer outcome: a systematic review and meta-analysis

There is a small but growing body of literature regarding the predictive utility of a Let-7 microRNA-binding-site polymorphism in the 3′-untranslated region (UTR) of KRAS (KRAS-LCS6) for colorectal cancer outcome, although the results are conflicting. We performed a review and meta-analysis in an attempt to better clarify this relationship. A PubMed search was conducted to identify all studies reporting on KRAS let-7 microRNA-binding site polymorphism (LCS6; rs61764370) and colorectal cancer outcome. Hazard ratios (HR) and corresponding 95% confidence intervals (CI) were extracted or estimated from each manuscript. Log HRs and log CIs were combined across studies using the inverse-variance weight to calculate fixed- and random-effects summary estimates and corresponding 95% CIs for overall and progression-free survival. We did not observe any significant association between overall or progression-free survival, neither when considering all colorectal cancer patients nor for subgroup analyses (metastatic, anti-EGFR [epidermal growth factor receptor] treatment, or KRAS wild type). There was substantial heterogeneity across studies, overall and among subgroups analyzed. We have found no clear evidence to support an association between the KRAS-LCS6 genotype and overall or progression-free survival among colorectal cancer patients, even after conducting subgroup analyses by stage and anti-EGFR treatment status. This information helps to clarify the confusing body of literature regarding the clinical implications of the KRAS-LCS6 genetic variant on colorectal cancer outcomes, indicating that it should not be used at the present time to personalize therapeutic strategies (PROSPERO registration number: CRD42013005325).

Leukocyte-adjusted epigenome-wide association studies of blood from solid tumor patients

Epigenome-wide studies of DNA methylation using blood-derived DNA from cancer patients are complicated by the heterogeneity of cell types within blood and the associated cell lineage specification of DNA methylation signatures. Here, we applied a novel set of analytic approaches to assess the association between cancer case-status and DNA methylation adjusted for leukocyte variation using blood specimens from three case-control cancer studies (bladder: 223 cases, 205 controls; head and neck: 92 cases, 92 controls; and ovarian: 131 cases, 274 controls). Using previously published data on leukocyte-specific CpG loci and a recently described approach to deconvolute subject-specific blood composition, we performed an epigenome-wide analysis to examine the association between blood-based DNA methylation patterns and each of the three aforementioned solid tumor types adjusted for cellular heterogeneity in blood. After adjusting for leukocyte profile in our epigenome-wide analysis, the omnibus association between case-status and methylation was significant for all three studies (bladder cancer: P = 0.047; HNSCC: P = 0.013; ovarian cancer: P = 0.0002). Subsequent analyses revealed that CpG sites associated with cancer were enriched for transcription factor binding motifs involved with cancer-associated pathways. These results support the existence of cancer-associated DNA methylation profiles in the blood of solid tumor patients that are independent of alterations in normal leukocyte distributions. Adoption of the methods developed here will make it feasible to rigorously assess the influence of variability of normal leukocyte profiles when investigating cancer related changes in blood-based epigenome-wide association studies.

High-risk HPV types and head and neck cancer

Although HPV16 has been strongly implicated in oropharyngeal carcinogenesis, the role of other high-risk HPV types in the etiology of head and neck cancer remains unclear. To date, few data exist addressing the nature of the association between antibodies to oncogenic proteins of non-HPV16 HPVs in relation to head and neck cancer. We examined the relationship between multiple HPV types (HPV6, 11, 16, 18, 31, 33, 45, 52, 58) and head and neck squamous cell carcinoma (HNSCC) in a large population-based case-control study (1069 cases and 1107 controls). Serological measures for HPV types included antibodies to L1, E6 and/or E7. In a secondary analysis, we excluded HPV16 seropositive subjects to examine independent associations with other high-risk HPVs. All analyses were adjusted for age, race, sex, education, smoking and alcohol consumption. Statistically significant associations were observed for HPV16, 18, 33 and 52 and risk of HNSCC after mutually adjusting for HPV types. Among HPV16 seronegative subjects, elevated risks of HNSCC were observed for HPV18 E6 (OR = 4.19, 95% CI = 1.26-14.0), HPV33 E6 (OR = 7.96, 95% CI = 1.56-40.5) and HPV52 E7 (OR = 3.40, 95% CI = 1.16-9.99). When examined by tumor type, associations with HPV18 and HPV33 remained statistically significant for oropharyngeal cancer, and HPV52 was associated with oral cancer. In addition, magnitude of associations for HNSCC increased markedly with increasing number of seropositive high-risk HPV infections. High-risk HPV types, other than HPV16, are likely to be involved in the etiology of HNSCC.

Occupational dust exposure and head and neck squamous cell carcinoma risk in a population-based case-control study conducted in the greater Boston area

Head and neck cancers account for an estimated 549,000 global cancer diagnoses each year. While tobacco use, alcohol consumption, and HPV16 infection are considered to be the major risk factors for this disease, occupational risk factors, including exposure to asbestos, have also been described, although dust exposures other than asbestos have been historically understudied. We have investigated the relationship between occupational exposures to five types of dusts, including sawdust, concrete dust, leather dust, metal dust, and chimney soot, and head and neck squamous cell carcinomas (HNSCC) in the greater Boston area. We report findings from a population-based case–control study involving 951 incident HNSCC cases and 1193 controls, frequency matched on age (±3 years), sex, and town/neighborhood of residence. Multivariable logistic regression was used to assess the association between occupational exposure to each type of dust and HNSCC, overall and by primary tumor site. After adjusting for age, sex, race, smoking, alcohol consumption, education, and HPV16 serology, laryngeal carcinoma risk increased for each decade of occupational exposure to sawdust (OR = 1.2, 95% CI: 1.0, 1.3) and metal dust (OR = 1.2, 95% CI: 1.0, 1.4); and HNSCC risk increased for each decade of occupational leather dust exposure (OR = 1.5, 95% CI: 1.2, 1.9). We have provided evidence for an association between occupational sawdust and metal dust and laryngeal squamous cell carcinoma, and leather dust and HNSCC, with increasing risk with longer duration at the exposed occupation.

Occupational asbestos exposure is associated with pharyngeal squamous cell carcinoma in men from the greater Boston area

OBJECTIVES

Asbestos is the name given to a group of naturally occurring silicate mineral fibres that were widely used in industry during the 20th century due to their desirable physical properties. Although use in the USA has fallen over the last three decades, significant exposure in the developing world continues and the burden of disease is considerable. Asbestos is a known risk factor for several malignant diseases, including lung cancer and mesothelioma, and has more recently been implicated in pharyngeal and laryngeal cancer. However, studies of asbestos and cancers of the larynx or pharynx with adequate sample size that control for major head and neck squamous cell carcinoma (HNSCC) risk factors remain relatively sparse.

METHODS

We report findings from a case-control study of 674 incident male HNSCC cases from the greater Boston region and 857 population-based male controls, matched on age (±3 years), sex, and town or neighbourhood of residence. Multivariable logistic regression was used to assess the association between occupational asbestos exposure and HNSCC by primary tumour site.

RESULTS

190 cases (28.2%) and 203 controls (23.7%) reported occupational exposure to asbestos. Occupational asbestos exposure was associated with elevated risk of pharyngeal carcinoma in men (OR 1.41, 95% CI 1.01 to 1.97), adjusted for age, race, smoking, alcohol consumption, education, income and HPV16 serology, with borderline increasing risk for each decade in the exposed occupation (OR 1.10, 95% CI 0.99 to 1.23).

CONCLUSIONS

These observations are consistent with mounting evidence that asbestos is a risk factor for pharyngeal cancer.

The fate is not always written in the genes: epigenomics in epidemiologic studies

Cost-effective, high-throughput epigenomic technologies have begun to emerge, rapidly replacing the candidate gene approach to molecular epidemiology and offering a comprehensive strategy for the study of epigenetics in human subjects. Epigenome-wide association studies (EWAS) provide new opportunities for advancing our understanding of epigenetic changes associated with complex disease states. However, such analyses are complicated by the dynamic nature of DNA methylation. In contrast to genomic studies, where genotype is essentially constant across somatic cells, EWAS present a new set of challenges, largely due to differential DNA methylation across distinct cell types, particularly for studies involving heterogeneous tissue sources, and changes in the epigenetic profile that occur over time. This review describes potential applications of EWAS from the viewpoint of the molecular epidemiologist, along with special considerations and pitfalls involved in the design of such studies.

Blood-based profiles of DNA methylation predict the underlying distribution of cell types: a validation analysis

The potential influence of underlying differences in relative leukocyte distributions in studies involving blood-based profiling of DNA methylation is well recognized and has prompted development of a set of statistical methods for inferring changes in the distribution of white blood cells using DNA methylation signatures. However, the extent to which this methodology can accurately predict cell-type proportions based on blood-derived DNA methylation data in a large-scale epigenome-wide association study (EWAS) has yet to be examined. We used publicly available data deposited in the Gene Expression Omnibus (GEO) database (accession number GSE37008), which consisted of both blood-derived epigenome-wide DNA methylation data assayed using the Illumina Infinium HumanMethylation27 BeadArray and complete blood cell (CBC) counts among a community cohort of 94 non-diseased individuals. Constrained projection (CP) was used to obtain predictions of the proportions of lymphocytes, monocytes and granulocytes for each of the study samples based on their DNA methylation signatures. Our findings demonstrated high consistency between the average CBC-derived and predicted percentage of monocytes and lymphocytes (17.9% and 17.6% for monocytes and 82.1% and 81.4% for lymphocytes), with root mean squared error (rMSE) of 5% and 6%, for monocytes and lymphocytes, respectively. Similarly, there was moderate-high correlation between the CP-predicted and CBC-derived percentages of monocytes and lymphocytes (0.60 and 0.61, respectively), and these results were robust to the number of leukocyte differentially methylated regions (L-DMRs) used for CP prediction. These results serve as further validation of the CP approach and highlight the promise of this technique for EWAS where DNA methylation is profiled using whole-blood genomic DNA.

Gastric reflux is an independent risk factor for laryngopharyngeal carcinoma

BACKGROUND

Gastric reflux can reach into the upper airway, inducing cellular damage in the epithelial lining. This condition is believed to be a risk factor for development of laryngopharyngeal squamous cell carcinoma (LPSCC), although the literature is conflicting.

METHODS

To better clarify this relationship, we assessed the association of self-reported heartburn history and medication use among 631 patients with LPSCCs and 1234 control subjects (frequency-matched on age, gender, and town of residence) enrolled as part of a population-based case-control study of head and neck squamous cell carcinoma in the greater Boston area.

RESULTS

After adjusting for age, gender, race, smoking, alcohol consumption, HPV16 seropositivity, education, and body mass index, subjects reporting a history of frequent heartburn and who were neither a heavy smoker nor heavy drinker had a significantly elevated risk of LPSCCs [OR, 1.78; 95% confidence interval (CI), 1.00-3.16]. Among those with a history of heartburn, there was an inverse association between antacid use and LPSCCs relative to those never taking heartburn medication (OR, 0.59; 95% CI, 0.38-0.93) that remained consistent when analyzed by smoking/drinking status, HPV16 status, or by primary tumor site.

CONCLUSIONS

Our data show that gastric reflux is an independent risk factor for squamous cancers of the pharynx and larynx. Further studies are needed to clarify the possible chemopreventive role of antacid use for patients with gastric reflux.

IMPACT

Elucidation of additional risk factors for head and neck cancer can allow for risk stratification and inform surveillance of high-risk patients.

Abstract 3627: Occupational asbestos exposure is associated with head and neck cancer

Asbestos describes a group of naturally occurring silicate mineral fibers that were frequently used in industry during the 20th century due to their desirable flame retardant and tensile properties. Although use has fallen over the last three decades, exposure continues and the burden of disease is considerable. The primary routes of exposure to the fibers include inhalation and ingestion. Asbestos is a known risk factor for several malignant respiratory diseases, including lung cancer and mesothelioma, and has more recently been implicated in pharyngeal and laryngeal cancer. However, studies of asbestos and cancers of the larynx or pharynx with adequate sample-size and control for other risk factors for head and neck squamous cell carcinoma (HNSCC) such as smoking and drinking habit remain somewhat sparse. We report findings from a case-control study consisting of 934 incident HNSCC cases from the greater Boston region and 1180 population-based controls, frequency matched on age (+/- 3 years), sex, and town or neighborhood of residence. Study subjects completed a self-administered questionnaire that provided detailed data on history of asbestos exposure, sociodemographics and personal characteristics, alcohol and tobacco use, personal and family cancer history, and other relevant dietary, occupational, residential and medical exposures. Occupational asbestos exposure was dichotomized as exposed or never exposed based on self reported occupation data. Multivariate unconditional logistic regression was used to assess the association between asbestos exposure and HNSCC, overall and by primary tumor site and smoking history. A total of 217 cases (23.2%) and 226 controls (19.2%) reported an occupational exposure to asbestos. We observed a borderline association of asbestos exposure and laryngopharyngeal cancer (OR = 1.23, 95% CI: 0.95-1.59), adjusted for age, sex, race, smoking, alcohol consumption, and education. After stratifying by smoking history, a significant association was observed between asbestos exposure and laryngopharyngeal cancer among ever-smokers (OR = 1.36, 95% CI: 1.00-1.84). These observations are consistent with the mounting evidence that asbestos is a risk factor for pharyngeal and laryngeal cancer.

Citation Format: Scott M. Langevin, Mattie H. O'Sullivan, Jennifer L. Valerio, Kate M. Applebaum, Melissa Eliot, Michael D. McClean, Karl T. Kelsey. Occupational asbestos exposure is associated with head and neck cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3627. doi:10.1158/1538-7445.AM2013-3627

Smokeless tobacco and risk of head and neck cancer: evidence from a case-control study in New England

Current studies suggesting that smokeless tobacco use increases the risk of head and neck cancer are hampered by small numbers. Consequently, there remains uncertainty in the magnitude and significance of this risk. We examined the relationship between smokeless tobacco use and head and neck squamous cell carcinoma (HNSCC) in a population-based case-control study with 1,046 cases and 1,239 frequency-matched controls. Logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals (95% CI), adjusting for age, gender, race, education level, cigarette smoking, and alcohol consumption. A nonsignificant elevated association between having ever used smokeless tobacco and HNSCC risk (OR = 1.20, 95% CI: 0.67-2.16) was observed. Individuals who reported 10 or more years of smokeless tobacco use had a significantly elevated risk of HNSCC (OR = 4.06, 95% CI: 1.31-12.64), compared to never users. In an analysis restricted to never cigarette smokers, a statistically significant association was observed between ever use of smokeless tobacco and the risk of HNSCC (OR = 4.21, 95% CI: 1.01-17.57). These findings suggest that long-term use of smokeless tobacco increases the risk of HNSCC.

Abstract 4240: A novel approach to adjust for immune cell distribution in blood-based epigenome-wide association studies of cancer

Epigenome-wide association studies (EWAS) promise to advance our understanding of epigenetic variation in cancer and are made possible by the recent emergence of cost-effective high-throughput technologies. Blood is the most widely available source of genomic DNA that can be used for study of cancer-associated alterations in DNA methylation (DNAm). These analyses are complicated by the heterogeneity of blood, which represents multiple cell types with unique DNAm signatures. Shifts in immune profile could confound results since altered leukocyte numbers are common in response to exposures or disease. We applied a novel approach to blood-based EWAS, adjusting for leukocyte composition estimated by epigenetic deconvolution of blood. Normal human peripheral blood leukocytes (n = 47) were isolated by magnetic activated cell sorting and purity was confirmed by fluorescence activated cell sorting. DNAm was interrogated using the Infinium HumanMethylation27 BeadArray (Illumina) on the sorted leukocyte samples and peripheral blood samples from 3 independent case-control studies of bladder cancer (223 cases, 205 controls), head and neck squamous cell carcinoma (HNSCC; 92 cases, 92 controls), and ovarian cancer (131 cases, 274 controls). Differentially methylated loci associated with leukocyte lineage were identified using a series of linear mixed effects models fit to the DNAm data for each of the 26,486 autosomal CpGs for the sorted leukocytes, yielding an F-statistic for each locus. The subject-specific leukocyte distribution (vector ω) was estimated using constrained projections, as previously described by Houseman et al (2012). Several regression parameters were estimated: βj, representing the association of case-status and DNAm at CpG j, unadjusted for ω; αj, representing the corresponding association adjusted for ω, and Γ, the association of case-status and ω. Γ, β and α were each adjusted for age, sex and smoking for bladder cancer and HNSCC, and age for ovarian cancer. Statistical inference was achieved by permutation, where null distributions were obtained by permuting case-status with respect to DNAm values and other covariates, using an omnibus test adjusted for multiple-comparisons, constructed by comparing the observed average F-statistic across all CpGs to the corresponding quantity obtained from the permutation distribution. After adjusting for leukocyte composition (α), the association between DNAm and case-status was significant for all 3 studies (bladder cancer: p = 0.047; HNSCC: p = 0.013; ovarian cancer: p = 0.0002). Subsequent analyses revealed that cancer-associated pathways were overrepresented among significant loci. These results indicate cancer-specific variation in DNAm of peripheral blood, independent of immune cell shifts. Further research is indicated for elucidation of mechanisms driving these observations.

Citation Format: Scott M. Langevin, E. A. Houseman, William P. Accomando, Devin C. Koestler, Brock C. Christensen, Heather H. Nelson, Margaret R. Karagas, Carmen J. Marsit, John K. Wiencke, Karl T. Kelsey. A novel approach to adjust for immune cell distribution in blood-based epigenome-wide association studies of cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4240. doi:10.1158/1538-7445.AM2013-4240

Periodontal disease and mouthwash use are risk factors for head and neck squamous cell carcinoma

PURPOSE

The purpose of this study was to examine associations between oral hygiene, including history of periodontal disease and mouthwash use, and risk of head and neck squamous cell carcinoma (HNSCC).

METHODS

We measured history of oral hygiene and dental care on 513 HNSCC cases and 567 controls from a population-based study of HNSCC. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (95% CI).

RESULTS

Periodontal disease was associated with a slightly elevated risk of HNSCC (OR = 1.09, 95% CI: 1.02, 1.16). Using any type of mouthwash at least once per day was associated with increased risk compared to never using mouthwash (OR = 1.11, 95% CI: 1.02, 1.20). HNSCC was associated with frequent use of non-alcoholic mouthwash compared to using any kind of mouthwash rarely or never (OR = 1.24, 95% CI: 1.05, 1.47).

CONCLUSIONS

Our results support an association between periodontal disease and HNSCC. Our data suggest that mouthwash use is associated with HNSCC, but we noted no difference between the effects of alcohol-containing and non-alcoholic mouthwashes.

Regular dental visits are associated with earlier stage at diagnosis for oral and pharyngeal cancer

PURPOSE

Oral and pharyngeal cancer patients diagnosed at an advanced stage experience increased morbidity and mortality relative to those with localized disease. The aim of this study was to assess the impact of dental insurance status and regularity of dental visits on early detection of oral and pharyngeal cancer.

METHODS

We examined the relationship of dental insurance and frequency of dental visits with stage at diagnosis among 441 oral and pharyngeal cancer cases from a population-based study of head and neck cancer. Ordinal logistic regression models were used to assess the association with stage, and tumor (T) and nodal (N) classification.

RESULTS

Never or rarely going to the dentist was associated with being diagnosed at higher stage for oral and pharyngeal cancer (cumulative OR = 2.28, 95 % CI: 1.02-5.10) and oral cancer (cumulative OR = 9.17, 95 % CI: 2.70-31.15) compared to those going to the dentist at least annually. Oral and pharyngeal cancer patients who went to the dentist infrequently (cumulative OR = 1.82, 95 % CI: 1.09-3.05) or rarely/never (cumulative OR = 3.24, 95 % CI: 1.59-6.57) were diagnosed with a higher T classification compared with those who went at least annually.

CONCLUSIONS

Receipt of regular dental examinations at least annually may reduce the public health burden of oral and pharyngeal cancer by facilitating earlier detection of the disease.

Peripheral blood immune cell methylation profiles are associated with nonhematopoietic cancers

BACKGROUND

Blood leukocytes from patients with solid tumors exhibit complex and distinct cancer-associated patterns of DNA methylation. However, the biologic mechanisms underlying these patterns remain poorly understood. Because epigenetic biomarkers offer significant clinical potential for cancer detection, we sought to address a mechanistic gap in recently published works, hypothesizing that blood-based epigenetic variation may be due to shifts in leukocyte populations.

METHODS

We identified differentially methylated regions (DMR) among leukocyte subtypes using epigenome-wide DNA methylation profiling of purified peripheral blood leukocyte subtypes from healthy donors. These leukocyte-tagging DMRs were then evaluated using epigenome-wide blood methylation data from three independent case-control studies of different cancers.

RESULTS

A substantial proportion of the top 50 leukocyte DMRs were significantly differentially methylated among head and neck squamous cell carcinoma (HNSCC) cases and ovarian cancer cases compared with cancer-free controls (48 and 47 of 50, respectively). Methylation classes derived from leukocyte DMRs were significantly associated cancer case status (P < 0.001, P < 0.03, and P < 0.001) for all three cancer types: HNSCC, bladder cancer, and ovarian cancer, respectively and predicted cancer status with a high degree of accuracy (area under the curve [AUC] = 0.82, 0.83, and 0.67).

CONCLUSIONS

These results suggest that shifts in leukocyte subpopulations may account for a considerable proportion of variability in peripheral blood DNA methylation patterns of solid tumors.

IMPACT

This illustrates the potential use of DNA methylation profiles for identifying shifts in leukocyte populations representative of disease, and that such profiles may represent powerful new diagnostic tools, applicable to a range of solid tumors.

Peripheral blood DNA methylation profiles are indicative of head and neck squamous cell carcinoma: an epigenome-wide association study

Head and neck cancer accounts for an estimated 47,560 new cases and 11,480 deaths annually in the United States, the majority of which are squamous cell carcinomas (HNSCC). The overall 5 year survival is approximately 60% and declines with increasing stage at diagnosis, indicating a need for non-invasive tests that facilitate the detection of early disease. DNA methylation is a stable epigenetic modification that is amenable to measurement and readily available in peripheral blood. We used a semi-supervised recursively partitioned mixture model (SS-RPMM) approach to identify novel blood DNA methylation markers of HNSCC using genome-wide methylation array data for peripheral blood samples from 92 HNSCC cases and 92 cancer-free control subjects. To assess the performance of the resultant markers, we constructed receiver operating characteristic (ROC) curves and calculated the corresponding area under the curve (AUC). Cases and controls were best differentiated by a methylation profile of six CpG loci (associated with FGD4, SERPINF1, WDR39, IL27, HYAL2 and PLEKHA6), with an AUC of 0.73 (95% CI: 0.62-0.82). After adjustment for subject age, gender, smoking, alcohol consumption and HPV16 serostatus, the AUC increased to 0.85 (95% CI: 0.76-0.92). We have identified a novel blood-based methylation profile that is indicative of HNSCC with a high degree of accuracy. This profile demonstrates the potential of DNA methylation measured in blood for development of non-invasive applications for detection of head and neck cancer.

Allergies and risk of head and neck cancer

BACKGROUND

Individuals with allergies have a heightened Th2 (T helper 2) immunity, which may provide advantages in controlling tumor growth. Inverse associations have been reported among individuals with allergies and risk of brain and pancreatic cancers.

METHODS

We examined the relationship between allergies and risk of head and neck squamous cell carcinoma (HNSCC) in a population-based case-control study with 1,014 cases and 1,193 frequency-matched controls. Logistic regression models were used to estimate odds ratios (OR) and 95 % confidence intervals (95 % CI) controlling for age, sex, race, smoking history, alcohol consumption, and education. In addition, in a subset of the population, models were adjusted for HPV16 status.

RESULTS

Individuals with allergies had a 19 % lower risk of HNSCC (OR = 0.81, 95 % CI = 0.67-0.98). Associations with allergies were stronger for laryngeal (OR = 0.66, 95 % CI = 0.45-0.97) and oropharyngeal (OR = 0.73, 95 % CI = 0.57-0.92) cancers, while no association was observed for oral cavity cancers (OR = 0.98, 95 % CI = 0.76-1.26). History of asthma was not associated with overall HNSCC, but the association was statistically significant for oropharyngeal cancer (OR = 0.67, 95 % CI = 0.44-0.99). HPV16 status did not confound or modify the associations with allergies.

CONCLUSIONS

Elevated Th2 immunity in individuals with history of allergies and asthma may reduce the risk of HNSCC. Additional research into related mechanisms may provide new insights into how to treat HNSCC.

IMPACT

These findings may provide new insight into biological pathways that could lead to a better understanding of the etiology of this disease.

Abstract 5022: Immune biology drives cancer specific methylation profiles in blood

Blood leukocytes from patients with solid tumors exhibit complex and distinct cancer-associated patterns of DNA methylation. However, the biological mechanisms underlying these patterns remain poorly understood. Since epigenetic biomarkers offer significant clinical potential for cancer detection, we sought to address a mechanistic gap in recently published works, hypothesizing that this variation is in large part due to shifts in leukocyte populations. To discern differentially methylated regions (DMRs) among leukocyte subtypes, we assessed epigenome-wide DNA methylation in sorted, purified, healthy human peripheral blood leukocyte subtypes. Performing a targeted analysis of leukocyte DMRs from epigenome-wide blood methylation data in three independent case-control studies of different cancers revealed that leukocyte DMRs predict case status with a high degree of accuracy (area under the curve = 0.82, 0.83, and 0.67, forhead and neck squamous cell carcinoma (HNSCC), ovarian, and bladder cancer, respectively). These results demonstrate that blood-derived differences in DNA methylation patterns in patients with solid tumors are largely attributable to systematic differences in the DMRs that define specific, known leukocyte sub-populations, suggesting that the unique epigenetic signatures in blood from solid tumor patients arise as a result of immune responses represented by shifts in leukocyte populations.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5022. doi:1538-7445.AM2012-5022

In utero exposures, infant growth, and DNA methylation of repetitive elements and developmentally related genes in human placenta

BACKGROUND

Fetal programming describes the theory linking environmental conditions during embryonic and fetal development with risk of diseases later in life. Environmental insults in utero may lead to changes in epigenetic mechanisms potentially affecting fetal development.

OBJECTIVES

We examined associations between in utero exposures, infant growth, and methylation of repetitive elements and gene-associated DNA in human term placenta tissue samples.

METHODS

Placental tissues and associated demographic and clinical data were obtained from subjects delivering at Women and Infants Hospital in Providence, Rhode Island (USA). Methylation levels of long interspersed nuclear element-1 (LINE-1) and the Alu element AluYb8 were determined in 380 placental samples from term deliveries using bisulfite pyrosequencing. Genomewide DNA methylation profiles were obtained in a subset of 184 samples using the Illumina Infinium HumanMethylation27 BeadArray. Multiple linear regression, model-based clustering methods, and gene set enrichment analysis examined the association between birth weight percentile, demographic variables, and repetitive element methylation and gene-associated CpG locus methylation.

RESULTS

LINE-1 and AluYb8 methylation levels were found to be significantly positively associated with birth weight percentile (p = 0.01 and p < 0.0001, respectively) and were found to differ significantly among infants exposed to tobacco smoke and alcohol. Increased placental AluYb8 methylation was positively associated with average methylation among CpG loci found in polycomb group target genes; developmentally related transcription factor binding sites were overrepresented for differentially methylated loci associated with both elements.

CONCLUSIONS

Our results suggest that repetitive element methylation markers, most notably AluYb8 methylation, may be susceptible to epigenetic alterations resulting from the intrauterine environment and play a critical role in mediating placenta function, and may ultimately inform on the developmental basis of health and disease.

Abstract A37: Peripheral blood DNA methylation profiles are predictive of head and neck squamous cell carcinoma

Head and neck cancer accounts for an estimated 47,560 new cases and 11,480 deaths annually in the United States, the majority of which are squamous cell carcinomas (HNSCC). The overall 5-year survival is approximately 60% and declines with increasing stage at diagnosis, indicating a need for non-invasive tests that facilitate the detection of early disease. DNA methylation is a stable epigenetic modification that is amenable to measurement and readily available in peripheral blood. DNA methylation profiles are commonly altered in tumor tissue, including HNSCC. We applied a semi-supervised recursively partitioned mixture model (SS-RPMM) approach to identify novel blood DNA methylation markers of HNSCC using genome-wide methylation array data (26,486 autosomal CpG loci) for peripheral blood samples from 92 HNSCC cases and 92 cancer-free controls. Subjects were randomly split into training (n = 92) and testing (n = 92) sets, stratified by case-control status to ensure an equal distribution of cases and controls between sets. A series of mixed effects models were fit to the training data only and CpG loci were ranked according to absolute t-statistic. The top M loci were selected to train a classifier, where M was chosen using a nested cross-validation procedure, which was then fit to the testing data. To assess the performance of the resultant markers in the testing data, we constructed receiver operating characteristic (ROC) curves and calculated the corresponding area under the curve (AUC). Cases and controls were best differentiated by a methylation profile of 6 CpG loci (associated with FGD4, SERPINF1, WDR39, IL27, HYAL2 and PLEKHA6), resulting in 4 classes, with an AUC of 0.73 (95% CI: 0.62–0.82). After adjustment for subject age, gender, smoking, alcohol consumption and HPV16 serostatus, the AUC increased to 0.85 (95% CI: 0.76–0.92). There was no significant difference in stage at diagnosis, tumor site or HPV-16 serostatus for cases by class. We have identified a novel blood-based methylation profile that is predictive of HNSCC with a high degree of accuracy. Although not yet adequate for use in clinical settings, this profile demonstrates the potential of DNA methylation measured in blood for development of non-invasive applications for detection of head and neck cancer.

Citation Information: Cancer Prev Res 2011;4(10 Suppl):A37.

Female hormonal and reproductive factors and head and neck squamous cell carcinoma risk

Men are much more likely than women to develop head and neck squamous cell carcinoma (HNSCC), a discrepancy that is insufficiently explained by gender differences in smoking and alcohol consumption. It has been hypothesized that differential hormonal exposures may account for some of this risk but thus far the literature on female reproductive factors and HNSCC risk has been sparse. To address the association of HNSCC with female hormonal and reproductive factors, a case-control study was conducted on 149 women with head and neck cancer and 158 controls. After adjusting for potential confounding, postmenopausal women using female hormones for more than 5 years showed a borderline protective effect for HNSCC (adjusted OR = 0.47, 95% CI: 0.20-1.08), with a borderline trend across duration of use categories (P = 0.06). There was no association of HNSCC with age at menarche, hysterectomy/oophorectomy status, oral contraceptive use, history of fertility medication, or number of pregnancies, parity, or age at first pregnancy or live birth. The findings of this study do not support a link between HNSCC and reproductive factors, although the borderline association with HRT warrants further investigation.

The influence of aging, environmental exposures and local sequence features on the variation of DNA methylation in blood

In order to properly comprehend the epigenetic dysregulation that occurs during the course of disease, there is a need to characterize the epigenetic variability in healthy individuals that arises in response to aging and exposures, and to understand such variation within the biological context of the DNA sequence. We analyzed the methylation of 26,486 autosomal CpG loci in blood from 205 healthy subjects, using three complementary approaches to assess the association between methylation, age or exposures, and local sequence features, such as CpG island status, repeat sequences, location within a polycomb target gene or proximity to a transcription factor binding site. We clustered CpGs (1) using unsupervised recursively partitioned mixture modeling (RPMM) and (2) bioinformatically-informed methods, and (3) also employed a marginal model-based (non-clustering) approach. We observed associations between age and methylation and hair dye use and methylation, where the direction and magnitude was contingent on the local sequence features of the CpGs. Our results demonstrate that CpGs are differentially methylated dependent upon the genomic features of the sequence in which they are embedded, and that CpG methylation is associated with age and hair dye use in a CpG context-dependent manner in healthy individuals.

MicroRNA-137 promoter methylation is associated with poorer overall survival in patients with squamous cell carcinoma of the head and neck

BACKGROUND

The overall 5-year survival rate of approximately 60% for head and neck cancer patients has remained essentially unchanged over the past 30 years. MicroRNA-137 (miR-137) plays an essential role in cell-cycle control at the G1/S-phase checkpoint. However, the aberrant miR-137 promoter methylation observed in squamous cell carcinoma of the head and neck (SCCHN) suggests a tumor-specific molecular defect that may contribute to disease progression.

METHODS

The goal of this study was to assess, in formalin-fixed, paraffin-embedded tumor tissue, the association between miR-137 promoter methylation and survival (both overall and disease free) and with prognostic factors including stage, tumor size, lymph node positivity, tumor grade, and surgical tumor margin positivity.

RESULTS

The promoter methylation status of miR-137 was ascertained by methylation-specific polymerase chain reaction and detected in 11 of 67 SCCHN patients (16.4%), with no significant differences according to site (oral cavity, pharynx, larynx). Methylation of the miR-137 promoter was significantly associated with overall survival (hazard ratio, 3.68; 95% confidence interval, 1.01-13.38) but not with disease-free survival or any of the prognostic factors evaluated.

CONCLUSIONS

The results of this study indicate that miR-137 is methylated in tumor tissue from pharyngeal and laryngeal squamous cancers, in addition to oral squamous cell carcinoma, and that miR-137 promoter methylation has potential utility as a prognostic marker for SCCHN.

Determinants of head and neck cancer survival by race

BACKGROUND

Several factors contribute to the documented racial disparity in head and neck cancer, among which are socioeconomic status, access to care, and biologic factors.

METHODS

Clinical characteristics of 87 African-American patients with head and neck cancer and a random sample of 261 white patients matched on age and smoking dose were associated with outcome.

RESULTS

Black patients with cancers of the oral cavity and larynx were more likely diagnosed with advanced stages than whites, after adjusting for socioeconomic and insurance status and other confounding factors. There was a significant difference in relapse-free survival between blacks and whites with tumors of the larynx (hazard ratio [HR] = 3.36, 95% confidence interval [CI]: 1.62-7.00), but not with tumors of the oral cavity or pharynx.

CONCLUSIONS

Differences in disease outcome may be attributed to a combination of tumor stage, socioeconomic status, and access to health care. The inclusion of biologic markers such as human papillomavirus (HPV) status is needed in future studies to further evaluate racial disparities in head and neck cancer outcomes.

The impact of health insurance status on the survival of patients with head and neck cancer

BACKGROUND

In 2006, it was estimated that 47 million people in the United States are without insurance. Studies have shown that patients who are uninsured or are insured by Medicaid are more likely to present with more advanced cancer. The objective of this study was to examine whether cancer recurrence and mortality of patients diagnosed with squamous cell carcinoma of the head and neck are associated with insurance status, after adjusting for known cancer risk factors. The main outcome measures were overall survival and relapse-free survival.

METHODS

Retrospective cohort of patients with a biopsy-proven primary squamous cell carcinoma of the oral cavity, pharynx, or larynx diagnosed or treated at the University of Pittsburgh Medical Center between 1998 and 2007. Patients were stratified by their insurance status, including private insurance, uninsured/Medicaid, Medicare disability (Medicare under age 65), and Medicare 65 years + . Covariates included age, gender, race, smoking status, alcohol consumption, anatomic tumor site, treatment, stage at diagnosis, and occupational prestige score. Cox proportional hazards regression was used to estimate the effect of insurance status on overall survival, relapse-free survival, tumor stage, and lymph node involvement.

RESULTS

A total of 1231 patients were included in the analysis. Patients with Medicaid/uninsured (hazard ratio [HR], 1.50; 95% confidence interval [CI], 1.07-2.11) and Medicare disability (HR, 1.69; 95% CI, 1.16-2.48) had significantly lower overall survival compared with patients with private insurance; the result was independent of variables known to affect outcome, such as alcohol and tobacco use. For all squamous cell carcinoma of the head and neck (SCCHN) cancer sites, Medicaid and uninsured patients were significantly more likely to present with an advanced stage tumor at diagnosis (odds ratio [OR] = 2.94; 95% CI, 1.72-5.01) and to present with at least 1 positive lymph node (OR = 1.84; 95% CI, 1.16-2.90) compared with patients with private insurance.

CONCLUSIONS

Patients with Medicaid/uninsured and Medicare disability were at increased risk of death after a diagnosis of SCCHN when compared with patients with private insurance, after adjustment for age, gender, race, smoking, alcohol use, site, socioeconomic status, treatment, and cancer stage.