Clinical and molecular characteristics and treatment outcomes of advanced right-colon, left-colon and rectal cancers: data from 1180 patients in a phase III trial of panitumumab with an extended biomarker panel.

BACKGROUND: Primary tumour location (PTL) is being adopted by clinicians to guide treatment decisions in metastatic colorectal cancer (mCRC). Here we test PTL as a predictive marker for panitumumab efficacy, and examine its relationship with an extended biomarker profile. We also examine rectal tumours as a separate location. PATIENTS AND METHODS: mCRC patients from the second-line PICCOLO trial of irinotecan versus irinotecan/panitumumab (IrPan). PTL was classified as right-PTL, left-PTL or rectal-PTL. PTL was assessed as a predictive biomarker for IrPan effect in RAS-wild-type (RAS-wt) patients (compared with irinotecan alone), then tested for independence alongside an extended biomarker profile (BRAF, epiregulin/amphiregulin (EREG/AREG) and HER3 mRNA expression). RESULTS: PTL data were available for 1180 patients (98.5%), of whom 558 were RAS-wt. High HER3 expression was independently predictive of panitumumab overall survival improvement, but PTL and EREG/AREG were not. IrPan progression-free survival (PFS) improvement compared with irinotecan was seen in left-PTL [hazard ratio (HR) = 0.61, P = 0.002) but not right-PTL (HR = 0.98, P = 0.90) (interaction P = 0.05; RAS/BRAF-wt interaction P = 0.10), or in rectal-PTL (HR = 0.82, P = 0.20) (interaction P = 0.14 compared with left-PTL; RAS/BRAF-wt interaction P = 0.04). Patients with right-PTL and high EREG/AREG or HER3 expression, had IrPan PFS improvement (high EREG/AREG HR = 0.20, P = 0.04; high HER3 HR = 0.33, P = 0.10) compared with irinotecan. Similar effect was seen for rectal-PTL patients (high EREG/AREG HR = 0.44, P = 0.03; high HER3 HR = 0.34, P = 0.05). CONCLUSIONS: RAS-wt patients with left-PTL are more likely to have panitumumab PFS advantage than those with right-PTL or rectal-PTL. However, an extended biomarker panel demonstrated significant heterogeneity in panitumumab PFS effect within a tumour location. AREG/EREG and HER3 mRNA expression identifies patients with right-PTL or rectal-PTL who achieve similar PFS effect with panitumumab as left-colon patients. Testing could provide a more reliable basis for clinical decision making. Further validation and development of these biomarkers is required to optimise routine patient care. CLINICAL TRIAL REGISTRATION: ISRCTN identifier: ISRCTN93248876.

Is there a causal relationship between vitamin D and melanoma risk? A Mendelian randomization study.

BACKGROUND: Several preclinical studies have identified the antiproliferative effects of 25-hydroxyvitamin D [25(OH)D; vitamin D]. Ultraviolet radiation (UVR) is essential for vitamin D synthesis yet increases the risk of melanoma. Observational studies on the association of vitamin D levels with melanoma risk have reported inconclusive results, and are difficult to interpret owing to the potential confounding from the dual role of UVR. OBJECTIVES: To determine whether there is a causal association between genetically predicted 25(OH)D concentrations and melanoma using a Mendelian randomization (MR) approach. METHODS: We performed MR using summary data from a large genome-wide association study (GWAS) meta-analysis of melanoma risk, consisting of 12 874 cases and 23 203 controls. Five single nucleotide polymorphisms associated with 25(OH)D concentration - rs12785878, rs10741657, rs2282679, rs6013897 and rs116970203 - were selected as instrumental variables. An inverse variance weighted method was used to access the evidence for causality. MR results from the melanoma meta-analysis were combined with results from an MR study based on a melanoma risk GWAS using UK Biobank data. RESULTS: A 20 nmol L-1 decrease in 25(OH)D was not associated with melanoma risk [odds ratio (OR) 1·06, 95% confidence interval (CI) 0·95-1·19]. Results from the UK Biobank were concordant with this, with meta-analysis of our and UK Biobank-derived MR causal estimates showing no association (OR 1·02, 95% CI 0·92-1·13 for a 20 nmol L-1 decrease). CONCLUSIONS: The results suggest that vitamin D levels may not be causally associated with the risk of melanoma. What's already known about this topic? Antitumour activity of vitamin D has been identified in preclinical studies. Observational studies link vitamin D deficiency with an increased risk of a range of cancers. There is a growing public interest for vitamin D supplementation. Observational studies of melanoma are fraught with difficulties because while higher ultraviolet radiation levels increase vitamin D levels, such exposure is also associated with increased melanoma risk. Results from observational studies are inconclusive regarding the effect of vitamin D on melanoma risk. What does this study add? Using Mendelian randomization, an approach to causal inference, which is analogous to a natural randomized controlled trial, we found no causal association between vitamin D levels and melanoma.

Development and external validation study of a melanoma risk prediction model incorporating clinically assessed naevi and solar lentigines.

BACKGROUND: Melanoma risk prediction models could be useful for matching preventive interventions to patients' risk. OBJECTIVES: To develop and validate a model for incident first-primary cutaneous melanoma using clinically assessed risk factors. METHODS: We used unconditional logistic regression with backward selection from the Australian Melanoma Family Study (461 cases and 329 controls) in which age, sex and city of recruitment were kept in each step, and we externally validated it using the Leeds Melanoma Case-Control Study (960 cases and 513 controls). Candidate predictors included clinically assessed whole-body naevi and solar lentigines, and self-assessed pigmentation phenotype, sun exposure, family history and history of keratinocyte cancer. We evaluated the predictive strength and discrimination of the model risk factors using odds per age- and sex-adjusted SD (OPERA) and the area under curve (AUC), and calibration using the Hosmer-Lemeshow test. RESULTS: The final model included the number of naevi ≥ 2 mm in diameter on the whole body, solar lentigines on the upper back (a six-level scale), hair colour at age 18 years and personal history of keratinocyte cancer. Naevi was the strongest risk factor; the OPERA was 3·51 [95% confidence interval (CI) 2·71-4·54] in the Australian study and 2·56 (95% CI 2·23-2·95) in the Leeds study. The AUC was 0·79 (95% CI 0·76-0·83) in the Australian study and 0·73 (95% CI 0·70-0·75) in the Leeds study. The Hosmer-Lemeshow test P-value was 0·30 in the Australian study and < 0·001 in the Leeds study. CONCLUSIONS: This model had good discrimination and could be used by clinicians to stratify patients by melanoma risk for the targeting of preventive interventions. What's already known about this topic? Melanoma risk prediction models may be useful in prevention by tailoring interventions to personalized risk levels. For reasons of feasibility, time and cost many melanoma prediction models use self-assessed risk factors. However, individuals tend to underestimate their naevus numbers. What does this study add? We present a melanoma risk prediction model, which includes clinically-assessed whole-body naevi and solar lentigines, and self-assessed risk factors including pigmentation phenotype and history of keratinocyte cancer. This model performs well on discrimination, the model's ability to distinguish between individuals with and without melanoma, and may assist clinicians to stratify patients by melanoma risk for targeted preventive interventions.

Associations of pigmentary and naevus phenotype with melanoma risk in two populations with comparable ancestry but contrasting levels of ambient sun exposure.

BACKGROUND: People at high risk of developing melanoma are usually identified by pigmentary and naevus phenotypes. OBJECTIVE: We examined whether associations of these phenotypes with melanoma risk differed by ambient sun exposure or participant characteristics in two population-based, case-control studies with comparable ancestry but different ambient sun exposure. METHODS: Data were analysed from 616 cases and 496 controls from the Australian Melanoma Family Study and 2012 cases and 504 controls from the Leeds (UK) case-control study. Questionnaire, interview and dermatological skin examination data were collected using the same measurement protocols. Relative risks were estimated as odds ratios using unconditional logistic regression, adjusted for potential confounders. RESULTS: Hair and skin colour were the strongest pigmentary phenotype risk factors. All associations of pigmentary phenotype with melanoma risk were similar across countries. The median number of clinically assessed naevi was approximately three times higher in Australia than Leeds, but the relative risks for melanoma associated with each additional common or dysplastic naevus were higher for Leeds than Australia, especially for naevi on the upper and lower limbs. Higher naevus counts on the head and neck were associated with a stronger relative risk for melanoma for women than men. The two countries had similar relative risks for melanoma based on self-reported naevus density categories, but personal perceptions of naevus number differed by country. There was no consistent evidence of interactions between phenotypes on risk. CONCLUSIONS: Classifying people at high risk of melanoma based on their number of naevi should ideally take into account their country of residence, type of counts (clinical or self-reported), body site on which the naevus counts are measured and sex. The presence of naevi may be a stronger indicator of a genetic predisposition in the UK than in Australia based on less opportunity for sun exposure to influence naevus development.

Next-generation sequencing identifies germline MRE11A variants as markers of radiotherapy outcomes in muscle-invasive bladder cancer.

BACKGROUND: Muscle-invasive bladder cancer (MIBC) can be cured by radical radiotherapy (RT). We previously found tumour MRE11 expression to be predictive of survival following RT in MIBC, and this was independently validated in a separate institute. Here, we investigated germline MRE11A variants as possible predictors of RT outcomes in MIBC, using next-generation sequencing (NGS). PATIENTS AND METHODS: The MRE11A gene was amplified in germline DNA from 186 prospectively recruited MIBC patients treated with RT and sequenced using bar-coded multiplexed NGS. Germline variants were analysed for associations with cancer-specific survival (CSS). For validation as a prognostic or predictive marker, rs1805363 was then genotyped in a cystectomy-treated MIBC cohort of 256 individuals. MRE11A mRNA isoform expression was measured in bladder cancer cell lines and primary tumour samples. RESULTS: Carriage of at least one of six (five novel) rare variants was associated with the worse RT outcome (hazard ratio [HR] 4.04, 95% confidence interval [95% CI] 1.42-11.51, P = 0.009). The single-nucleotide polymorphism (SNP), rs1805363 (minor allele frequency 11%), was also associated with worse CSS (per-allele HR 2.10, 95% CI 1.34-3.28, Ptrend = 0.001) following RT in MIBC, with a gene-dosage effect observed, but no effect seen on CSS in the cystectomy cohort (Ptrend = 0.89). Furthermore, rs1805363 influenced relative MRE11A isoform expression, with increased isoform 2 expression with carriage of the rs1805363 minor A allele. CONCLUSIONS: Germline MRE11A SNP rs1805363 was predictive of RT, but not of cystectomy outcome in MIBC. If successfully validated in an independent RT-treated cohort, this SNP could be a useful clinical tool for selecting patients for bladder-conserving treatment.

A spectrum of susceptibility to rheumatoid arthritis within HLA-DRB1: stratification by autoantibody status in a large UK population.

Previously-proposed rheumatoid arthritis (RA) HLA-DRB1 susceptibility and protective models were compared, based on amino acids at positions 67-74 and autoantibody combinations. 3 657 RA patients and 1 357 controls were studied using logistic regression, with secondary stratification by anti-citrullinated peptide antibodies(ACPA) and rheumatoid factor(RF). Susceptibility models were based on previously defined HLA-DRB1 shared epitope(SE) subgroups. (70)DERAA(74), D(70) and I(67) protective models were compared, adjusting for HLA-DRB1 SE. A hierarchy of risk was observed within the HLA-DRB1 SE, particularly for ACPA-positive and RF-positive RA: HLA-DRB1(*)0401∼(*)0404>(*)0101∼(*)1001 ((*)0404>(*)0101: P=0.0003). HLA-DRB1(*)0401/(*)0404 compound heterozygosity conferred a risk similar to (*)0401 homozygosity (P=0.70). Protective effects of D(70) and I(67) were similar. Predictions of the D(70) model fitted the data better than those of the I(67) model. The protective effect of D(70) showed a gene-dose effect (OR 0.82, 95% CI 0.73-0.92, P=5.8 × 10(-4)), but was only seen in RA patients positive for RF or ACPA. HLA-DRB1 SE alleles were also associated with ACPA-negative, RF-positive RA (OR 1.42 (1.15-1.76), P=0.0012). In conclusion, HLA-DRB1 SE alleles show heterogeneity in RA susceptibility; their major effect appears to be mediated by ACPA positivity, but a significant association of HLA-DRB1 SE with RF-positive, ACPA-negative RA was also observed. D(70) specifically protected against antibody-positive RA.

The determinants of periorbital skin ageing in participants of a melanoma case-control study in the U.K.

BACKGROUND: Skin ageing is said to be caused by multiple factors. The relationship with sun exposure is of particular interest because the detrimental cutaneous effects of the sun may be a strong motivator to sun protection. We report a study of skin ageing in participants of an epidemiological study of melanoma. OBJECTIVES: To determine the predictors of periorbital cutaneous ageing and whether it could be used as an objective marker of sun exposure. METHODS: Photographs of the periorbital skin in 1341 participants were graded for wrinkles, degree of vascularity and blotchy pigmentation and the resultant data assessed in relation to reported sun exposure, sunscreen use, body mass index (BMI), smoking and the melanocortin 1 receptor (MC1R) gene status. Data were analysed using proportional odds regression. RESULTS: Wrinkling was associated with age and heavy smoking. Use of higher sun-protection factor sunscreen was protective (P = 0·01). Age, male sex, MC1R variants ('r', P=0·01; 'R', P=0·02), higher reported daily sun exposure (P=0·02), increased BMI (P=0·01) and smoking (P=0·02) were risk factors for hypervascularity. Blotchy pigmentation was associated with age, male sex, higher education and higher weekday sun exposure (P=0·03). More frequent sunscreen use (P=0·02) and MC1R variants ('r', P=0·03; 'R', P=0·001) were protective. CONCLUSIONS: Periorbital wrinkling is a poor biomarker of reported sun exposure. Vascularity is a better biomarker as is blotchy pigmentation, the latter in darker-skinned individuals. In summary, male sex, sun exposure, smoking, obesity and MC1R variants were associated with measures of cutaneous ageing. Sunscreen use showed some evidence of being protective.

Melanoma sentinel node biopsy and prediction models for relapse and overall survival.

BACKGROUND: To optimise predictive models for sentinal node biopsy (SNB) positivity, relapse and survival, using clinico-pathological characteristics and osteopontin gene expression in primary melanomas. METHODS: A comparison of the clinico-pathological characteristics of SNB positive and negative cases was carried out in 561 melanoma patients. In 199 patients, gene expression in formalin-fixed primary tumours was studied using Illumina's DASL assay. A cross validation approach was used to test prognostic predictive models and receiver operating characteristic curves were produced. RESULTS: Independent predictors of SNB positivity were Breslow thickness, mitotic count and tumour site. Osteopontin expression best predicted SNB positivity (P=2.4 × 10⁻7), remaining significant in multivariable analysis. Osteopontin expression, combined with thickness, mitotic count and site, gave the best area under the curve (AUC) to predict SNB positivity (72.6%). Independent predictors of relapse-free survival were SNB status, thickness, site, ulceration and vessel invasion, whereas only SNB status and thickness predicted overall survival. Using clinico-pathological features (thickness, mitotic count, ulceration, vessel invasion, site, age and sex) gave a better AUC to predict relapse (71.0%) and survival (70.0%) than SNB status alone (57.0, 55.0%). In patients with gene expression data, the SNB status combined with the clinico-pathological features produced the best prediction of relapse (72.7%) and survival (69.0%), which was not increased further with osteopontin expression (72.7, 68.0%). CONCLUSION: Use of these models should be tested in other data sets in order to improve predictive and prognostic data for patients.

Power, validity, bias and robustness of family-based association analysis methods in the presence of linkage for late onset diseases.

This simulation-based report compares the performance of five methods of association analysis in the presence of linkage using extended sibships: the Family-Based Association Test (FBAT), Empirical Variance FBAT (EV-FBAT), Conditional Logistic Regression (CLR), Robust CLR (R-CLR) and Sibship Disequilibrium Test (SDT). The two tests accounting for residual familial correlation (EV-FBAT and R-CLR) and the model-free SDT showed correct test size in all simulated designs, while FBAT and CLR were only valid for small effect sizes. SDT had the lowest power, while CLR had the highest power, generally similar to FBAT and the robust variance analogues. The power of all model-dependent tests dropped when the model was misspecified, although often not substantially. Estimates of genetic effect with CLR and R-CLR were unbiased when the disease locus was analysed but biased when a nearby marker was analysed. This study demonstrates that the genetic effect does not need to be extreme to invalidate tests that ignore familial correlation and confirms that analogous methods using robust variance estimation provide a valid alternative at little cost to power. Overall R-CLR is the best-performing method among these alternatives for the analysis of extended sibship data.

Immunoblotting using multiple antigens is essential to demonstrate the true risk of Helicobacter pylori infection for gastric cancer.

BACKGROUND: Enzyme-linked immunosorbent assays (ELISAs) for detection of Helicobacter pylori infection, using IgG antibodies, may significantly underestimate the association with gastric cancer. AIM: To compare associations between H. pylori and cardia (CGC) and noncardia gastric cancer (NCGC) using ELISA and immunoblotting and determine the effect of atrophic gastritis on detection. METHODS: Nested case-control study within the Melbourne Collaborative Cohort Study. Helicobacter pylori antibodies were detected in subjects with CGC (n = 18), NCGC (n = 34) and controls (n = 69 and 134 respectively) using ELISA (pylori DTect) and immunoblot (Helicoblot 2.1). Pepsinogen I levels were measured using ELISA. RESULTS: Using ELISA, H. pylori-positivity in the CGC group was 33% vs. 35% in controls [odds ratio (OR = 0.9, 95% CI: 0.3-2.7)], while that in the NCGC group was 79% vs. 63% in controls [OR = 2.3 (95% CI: 0.9-5.8)]. Based on immunoblotting, H. pylori-positivity in the CGC group was 44% vs. 39% in their controls [OR = 1.2 (95% CI: 0.4-3.4)], while that in the NCGC group was 94% vs. 63% in controls [OR = 10.6 (95% CI: 2.4-47.4)]. Pepsinogen I levels in the NCGC cases and controls showed the lowest median level (4 ng/mL) to be in subjects negative by ELISA but positive by immunoblotting. CONCLUSION: Immunoblotting improves the accuracy of H. pylori studies involving gastric cancer.

Family based studies and genetic epidemiology: theory and practice.

Family based studies have underpinned many successes in uncovering the causes of monogenic and oligogenic diseases. Now research is focussing on the identification and characterisation of genes underlying common diseases and it is widely accepted that these studies will require large population based samples. Population based family study designs have the potential to facilitate the analysis of the effects of both genes and environment. These types of studies integrate the population based approaches of classic epidemiology and the methods enabling the analysis of correlations between relatives sharing both genes and environment. The extent to which such studies are feasible will depend upon population- and disease-specific factors. To review this topic, a symposium was held to present and discuss the costs, requirements and advantages of population based family study designs. This article summarises the features of the meeting held at The University of Sheffield, August 2006.

The polyAT, intronic IVS11-6 and Lys939Gln XPC polymorphisms are not associated with transitional cell carcinoma of the bladder.

Chemical carcinogens from cigarette smoking and occupational exposure are risk factors for bladder transitional cell carcinoma (TCC). The Xeroderma Pigmentosum Group C (XPC) gene is essential for repair of bulky adducts from carcinogens. The Xeroderma Pigmentosum Group C gene polymorphisms may alter DNA repair capacity (DRC), thus giving rise to genetic predisposition to bladder cancer. Recent studies have demonstrated linkage disequilibrium between three polymorphisms in the XPC gene (polyAT, IVS11-6 and Lys939Gln) and these have been shown to influence the DRC, as well as to be associated with bladder cancer risk. We analysed all three XPC polymorphisms in 547 bladder TCC patients and 579 cancer-free controls to investigate the association between these polymorphisms and bladder cancer susceptibility, and we also attempted to assess gene-environmental interactions. We confirmed strong linkage disequilibrium among the polymorphisms (Lewontin's D' > 0.99). Using logistic regression adjusting for smoking, occupational and family history, neither the heterozygote nor the homozygote variants of these polymorphisms were associated with increased bladder cancer risk (adjusted odds ratio [95% confidence interval] for heterozygote 0.82 [0.63-1.07], 0.82 [0.63-1.08] and 0.83 [0.63-1.08] for PolyAT, IVS11-6 and Lys939Gln, respectively and homozygote variant, 0.98 [0.68-1.42], 0.99 [0.69-1.43] and 1.01 [0.70-1.46]). Moreover, we did not find any significant interaction between these XPC polymorphisms and environmental exposure to cigarette smoking and occupational carcinogens.

The relationship between the epidermal growth factor (EGF) 5'UTR variant A61G and melanoma/nevus susceptibility.

The inheritance of a G allele in position 61 in the 5'UTR of the epidermal growth factor (EGF) gene has been reported to increase melanoma susceptibility, a finding we have investigated in this study. The most potent phenotypic risk factor for melanoma is the atypical mole syndrome (AMS) phenotype. Our hypothesis is that the AMS is genetically determined and that nevus genes are also low penetrance melanoma susceptibility genes. We report that the G allele frequencies were the same in 697 healthy women and 380 melanoma cases (OR 0.97, 95% CI 0.8-1.2 p=0.76). We therefore found no evidence that this polymorphism is a melanoma susceptibility gene. Furthermore, we found no evidence that the polymorphism controls the nevus phenotype (nevus number, number atypical nevi or AMS phenotype). We did find some evidence that the G allele may be associated with decreased tumor Breslow thickness (OR 0.5, 95% CI 0.3-0.9) for the A/A genotype versus A/G and G/G combined in tumors of thickness >3.5 vs < or =3.5 mm and may therefore act as a predictor of survival, although this finding is not in accord with the original report. This is the second study to find no association between EGF +61 and melanoma susceptibility.

Modeling and dissection of longitudinal blood pressure and hypertension phenotypes in genetic epidemiological studies.

We discuss analyses of the Genetic Analysis Workshop 13 data from the Framingham Heart Study and simulations based on this study. We summarize analyses that investigated measures of systolic blood pressure or hypertension as the main phenotype, with the main focus being the modeling of this complex longitudinal phenotype. The approaches include familial aggregation methods and one-stage and two-stage linkage methods. For one-stage linkage methods, phenotype modeling is carried out jointly with the linkage analysis or incorporated in the analysis design. For two-stage linkage methods, phenotypes are first modeled in order to develop summary measures that are then analyzed in a subsequent linkage analysis. Results depend on phenotype selection and on how analyses account for longitudinality, treatment effects, and heterodasticity.

Linkage and association analysis of nevus density and the region containing the melanoma gene CDKN2A in UK twins.

Rare mutations in the CDKN2A gene are highly penetrant for melanoma. Density of nevi is under strong genetic control and high density is a potent risk factor for melanoma. We used linkage and association analysis in adolescent twins from the UK to examine the hypothesis that the region containing the CDKN2A gene also contains a quantitative trait locus influencing normal nevus development. Five markers in the CDKN2A region were genotyped in 115 dizygotic twin pairs, and one marker (D9S942) was genotyped in 103 monozygotic twin pairs, all of whom had been phenotyped for nevus density. Linkage analysis showed no evidence of a quantitative trait locus influencing nevus density in this chromosomal region. A model partitioning the variation in phenotype into within- and between-twin pair components showed weak evidence of association between higher nevus density and longer mean length of the two D9S942 alleles (P=0.01). This relation, which was also observed in an earlier Australian twin study, could be because of the linkage disequilibrium between D9S942 and a neighbouring functional locus. Further investigation of this region is warranted in large-scale linkage or association studies.

FcgammaRIIIA-158V and rheumatoid arthritis: a confirmation study.

OBJECTIVES: To develop a robust assay for genotyping the FcgammaRIIIA-158V/F polymorphism and to confirm the putative association between the FcgammaRIIIA-158V allele and rheumatoid arthritis (RA). METHODS: This allelic association study examined the FcgammaRIIIA-158V/F polymorphism for association with RA. A novel single-stranded conformational polymorphism assay was used to genotype 828 RA patients and 581 controls from the UK. RESULTS: The FcgammaRIIIA-158V allele was associated with both RA (P=0.02) and nodules (P=0.04). Individuals homozygous for this higher affinity allele had a significantly increased risk of RA (OR 1.53, 95% CI 1.08-2.18) and the development of nodules (OR 2.20, 95% CI 1.20-4.01). There was no evidence of an interaction with the shared epitope. CONCLUSIONS: We have developed a novel assay to genotype the FcgammaRIIIA-158F/V polymorphism and confirmed that homozygosity for the FcgammaRIIIA-158V allele is associated with UK Caucasian RA, particularly in those individuals with nodules, suggesting FcgammaRIIIA may play a role in determining disease severity or in the development of nodules per se.

Investigation of interaction between N-acetyltransferase 2 and heterocyclic amines as potential risk factors for colorectal cancer.

Fast N-acetyltransferase 2 (NAT2) acetylators may be at increased risk of colorectal cancer through the activation of carcinogenic heterocyclic amines (HA), which are produced by meat cooked at high temperatures and are found in cigarette smoke. A study of 500 incident colorectal cancer cases and population controls, matched for age, sex and general practitioner, was conducted in the UK to investigate this hypothesis. Usual meat intake and lifetime smoking habits were estimated using a detailed questionnaire administered by interview. Subjects also indicated how well cooked they ate their meat. Subjects were classified as fast or slow NAT2 acetylators on the basis of NAT2 genotype. Complete genotype data were available on 433 matched pairs. The risk of colorectal cancer showed a steady increase with meat intake, rising to an odds ratio of 1.51 [95% confidence interval (1.03, 2.23)] for the highest versus the lowest quartile, after adjustment for total energy intake, and this was even more pronounced for red meat [odds ratio 1.97 (1.30, 2.98)]. However, this effect was not influenced by the preference for well-done meat. Smoking was also associated with an increased risk [odds ratio 1.47 (1.10, 1.98) for ever- versus never-smokers]. In both cases and controls approximately 40% of subjects were classified as fast acetylators, and the risks associated with (red) meat intake and smoking did not vary with NAT2 status. This study provides no support for the hypothesis that fast NAT2 acetylators are at increased risk of colorectal cancer, even if exposed to high levels of HA from well-cooked meat or smoking.

Segregation analysis comparing liability and quantitative trait models for hypertension using the Genetic Analysis Workshop 13 simulated data.

Discrete (qualitative) data segregation analysis may be performed assuming the liability model, which involves an underlying normally distributed quantitative phenotype. The appropriateness of the liability model for complex traits is unclear. The Genetic Analysis Workshop 13 simulated data provides measures on systolic blood pressure, a highly complex trait, which may be dichotomized into a discrete trait (hypertension). We perform segregation analysis under the liability model of hypertensive status as a qualitative trait and compare this with results using systolic blood pressure as a quantitative trait (without prior knowledge at that stage of the true underlying simulation model) using 1050 pedigrees ascertained from four replicates on the basis of at least one affected member. Both analyses identify models with major genes and polygenic components to explain the family aggregation of systolic blood pressure. Neither of the methods estimates the true parameters well (as the true model is considerably more complicated than those considered for the analysis), but both identified the most complicated model evaluated as the preferred model. Segregation analysis of complex diseases using relatively simple models is unlikely to provide accurate parameter estimates but is able to indicate major gene and/or polygenic components in familial aggregation of complex diseases.

Juvenile idiopathic arthritis classified by the ILAR criteria: HLA associations in UK patients.

OBJECTIVE: To determine the HLA associations with juvenile idiopathic arthritis (JIA) and its subgroups as defined by the International League of Associations for Rheumatology (ILAR) classification criteria. METHODS: Five hundred and twenty-one UK Caucasian JIA patients and 537 UK Caucasian controls were typed for HLA class II alleles. Phenotype and haplotype frequencies were compared between all JIA cases and controls and between the seven ILAR-defined JIA subgroups. RESULTS: Three haplotypes (DRB1*08-DQA1*0401-DQB1*0402; DRB1*11-DQA1*05-DQB1*03; DRB1*1301-DQA1*01-DQB1*06) were associated with increased risk and one (DRB1*04-DQA1*03-DQB1*03) with decreased risk of JIA. However, in each case the frequencies also varied between JIA subgroups. CONCLUSION: This study categorically demonstrates that there are multiple HLA class II associations with JIA. It has also, for the first time, defined these associations in the seven different ILAR subgroups in UK JIA cases. Although there are a number of common associations, each ILAR subgroup exhibits different patterns of HLA associations, suggesting that the ILAR classification system does define genetically distinct groups of patients.