Search

Cigarette smoke, containing both nicotine and carcinogens, causes lung cancer. However, not all smokers develop lung cancer, highlighting the importance of the interaction between host susceptibility and environmental exposure in tumorigenesis. Here, we aimed to delineate the interaction between metabolizing ability of tobacco carcinogens and smoking intensity in mediating genetic susceptibility to smoking-related lung tumorigenesis. Single-variant and gene-based associations of 43 tobacco carcinogen-metabolizing genes with lung cancer were analyzed using summary statistics and individual-level genetic data, followed by causal inference of Mendelian randomization, mediation analysis, and structural equation modeling. Cigarette smoke-exposed cell models were used to detect gene expression patterns in relation to specific alleles. Data from the International Lung Cancer Consortium (29,266 cases and 56,450 controls) and UK Biobank (2,155 cases and 376,329 controls) indicated that the genetic variant rs56113850 C>T located in intron 4 of CYP2A6 was significantly associated with decreased lung cancer risk among smokers (OR = 0.88, 95% confidence interval = 0.85-0.91, P = 2.18 × 10-16), which might interact (Pinteraction = 0.028) with and partially be mediated (ORindirect = 0.987) by smoking status. Smoking intensity accounted for 82.3% of the effect of CYP2A6 activity on lung cancer risk but entirely mediated the genetic effect of rs56113850. Mechanistically, the rs56113850 T allele rescued the downregulation of CYP2A6 caused by cigarette smoke exposure, potentially through preferential recruitment of transcription factor helicase-like transcription factor. Together, this study provides additional insights into the interplay between host susceptibility and carcinogen exposure in smoking-related lung tumorigenesis., Significance: The causal pathway connecting CYP2A6 genetic variability and activity, cigarette consumption, and lung cancer susceptibility in smokers highlights the need for behavior modification interventions based on host susceptibility for cancer prevention., (©2023 American Association for Cancer Research.)

Significance: Comprehensive single-cell proteomics analyses of lung adenocarcinoma progression reveal the role of tumor-associated macrophages in resistance to PD-1 blockade therapy. See related commentary by Lee et al., p. 2515., (©2022 American Association for Cancer Research.)

Clonal hematopoiesis (CH) is a phenomenon caused by expansion of white blood cells descended from a single hematopoietic stem cell. While CH can be associated with leukemia and some solid tumors, the relationship between CH and lung cancer remains largely unknown. To help clarify this relationship, we analyzed whole-exome sequencing (WES) data from 1,958 lung cancer cases and controls. Potential CH mutations were identified by a set of hierarchical filtering criteria in different exonic regions, and the associations between the number of CH mutations and clinical traits were investigated. Family history of lung cancer (FHLC) may exert diverse influences on the accumulation of CH mutations in different age groups. In younger subjects, FHLC was the strongest risk factor for CH mutations. Association analysis of genome-wide genetic variants identified dozens of genetic loci associated with CH mutations, including a candidate SNP rs2298110, which may promote CH by increasing expression of a potential leukemia promoter gene OTUD3 . Hundreds of potentially novel CH mutations were identified, and smoking was found to potentially shape the CH mutational signature. Genetic variants and lung cancer risk factors, especially FHLC, correlated with CH. These analyses improve our understanding of the relationship between lung cancer and CH, and future experimental studies will be necessary to corroborate the uncovered correlations. SIGNIFICANCE: Analysis of whole-exome sequencing data uncovers correlations between clonal hematopoiesis and lung cancer risk factors, identifies genetic variants correlated with clonal hematopoiesis, and highlights hundreds of potential novel clonal hematopoiesis mutations., (©2021 The Authors; Published by the American Association for Cancer Research.)

Although lung cancer is known to be caused by environmental factors, it has also been shown to have genetic components, and the genetic etiology of lung cancer remains understudied. We previously identified a lung cancer risk locus on 6q23-25 using microsatellite data in families with a history of lung cancer. To further elucidate that signal, we performed targeted sequencing on nine of our most strongly linked families. Two-point linkage analysis of the sequencing data revealed that the signal was heterogeneous and that different families likely had different risk variants. Three specific haplotypes were shared by some of the families: 6q25.3-26 in families 42 and 44, 6q25.2-25.3 in families 47 and 59, and 6q24.2-25.1 in families 30, 33, and 35. Region-based logarithm of the odds scores and expression data identified the likely candidate genes for each haplotype overlap: ARID1B at 6q25.3, MAP3K4 at 6q26, and UTRN (6q24.1) and PHACTR2 (6q24.2). Further annotation was used to zero in on potential risk variants in those genes. All four genes are good candidate genes for lung cancer risk, having been linked to either lung cancer specifically or other cancers. However, this is the first time any of these genes has been implicated in germline risk. Functional analysis of these four genes is planned for future work. SIGNIFICANCE: This study identifies four genes associated with lung cancer risk, which could help guide future lung cancer prevention and treatment approaches., (©2021 American Association for Cancer Research.)

Lung cancer is the leading cause of cancer-related death globally. An improved risk stratification strategy can increase efficiency of low-dose CT (LDCT) screening. Here we assessed whether individual's genetic background has clinical utility for risk stratification in the context of LDCT screening. On the basis of 13,119 patients with lung cancer and 10,008 controls with European ancestry in the International Lung Cancer Consortium, we constructed a polygenic risk score (PRS) via 10-fold cross-validation with regularized penalized regression. The performance of risk model integrating PRS, including calibration and ability to discriminate, was assessed using UK Biobank data ( N = 335,931). Absolute risk was estimated on the basis of age-specific lung cancer incidence and all-cause mortality as competing risk. To evaluate its potential clinical utility, the PRS distribution was simulated in the National Lung Screening Trial ( N = 50,772 participants). The lung cancer ORs for individuals at the top decile of the PRS distribution versus those at bottom 10% was 2.39 [95% confidence interval (CI) = 1.92-3.00; P = 1.80 × 10 -14 ] in the validation set ( P trend ). The OR per SD of PRS increase was 1.26 (95% CI = 1.20-1.32; -20 ). The OR per SD of PRS increase was 1.26 (95% CI = 1.20-1.32; P = 9.69 × 10 -23 ) for overall lung cancer risk in the validation set. When considering absolute risks, individuals at different PRS deciles showed differential trajectories of 5-year and cumulative absolute risk. The age reaching the LDCT screening recommendation threshold can vary by 4 to 8 years, depending on the individual's genetic background, smoking status, and family history. Collectively, these results suggest that individual's genetic background may inform the optimal lung cancer LDCT screening strategy. SIGNIFICANCE: Three large-scale datasets reveal that, after accounting for risk factors, an individual's genetics can affect their lung cancer risk trajectory, thus may inform the optimal timing for LDCT screening., (©2021 American Association for Cancer Research.)

Observational studies have suggested that physical activity might lower the risk of lung cancer in former and current smokers, but not in never-smokers. Using genetic instruments for self-reported and accelerometer-measured physical activity traits implemented through two-sample Mendelian randomization (MR), we sought to strengthen the evidence for causality. We used 18 genome-wide significant ( P < 5 × 10 -8 ) single-nucleotide polymorphisms (SNP) for self-reported moderate-to-vigorous physical activity and seven SNP for accelerometer-measured ("average acceleration") physical activity from up to 377,234 UK Biobank participants and evaluated these in relation to risk using 29,266 lung cancer cases (including 11,273 adenocarcinomas, 7,426 squamous cell carcinoma, and 2,664 small-cell carcinoma cases) and 56,450 controls. MR analysis suggested no effect of self-reported physical activity [OR (95% confidence interval (CI)) = 0.67 (0.42-1.05); P = 0.081; Q-value = 0.243] and accelerometer-measured activity [OR (95% CI) = 0.98 (0.93-1.03); P = 0.372; Q-value = 0.562] on lung cancer. There was no evidence for associations of physical activity with histologic types and lung cancer in ever and never smokers. Replication analysis using genetic instruments from a different genome-wide study and sensitivity analysis to address potential pleiotropic effects led to no substantive change in estimates. Collectively, these findings do not support a protective relationship between physical activity and the risk of lung cancer. SIGNIFICANCE: A new genetic study provides little evidence that recommending physical activity would help prevent lung cancer., (©2020 American Association for Cancer Research.)

To identify genetic variants for risk of squamous cell carcinoma of the head and neck (SCCHN), we conducted a two-phase genome-wide association study consisting of 7,858,089 SNPs in 2,171 cases and 4,493 controls of non-Hispanic white, of which, 434,839 typed and 7,423,250 imputed SNPs were used as the discovery. SNPs with P < 1 × 10 -3 were further validated in the OncoArray study of oral and pharynx cancer (5,205 cases and 3,232 controls of European ancestry) from databases of Genotypes and Phenotypes. Meta-analysis of the discovery and replication studies identified one novel locus 6p22.1 ( P = 2.96 × 10 -9 for the leading rs259919) and two cancer susceptibility loci 6p21.32 (rs3135001, HLA-DQB1 ) and 6p21.33 (rs1265081, CCHCR1 ) associated with SCCHN risk. Further stratification by tumor site revealed four known cancer loci (5p15.33, 6p21.32, 6p21.33, and 2p23.1) associated with oral cavity cancer risk and oropharyngeal cancer risk, respectively. In addition, one novel locus 18q22.2 ( P = 2.54 × 10 -9 for the leading SNP rs142021700) was identified for hypopharynx and larynx cancer risk. For SNPs in those reported or novel loci, we also performed functional annotations by bioinformatics prediction and expression quantitative trait loci analysis. Collectively, our identification of four reported loci (2p23.1, 5p15.33, 6p21.32, and 6p21.33) and two novel loci (6p22.1 and 18q22.2) for SCCHN risk highlight the importance of human leukocyte antigen loci for oropharyngeal cancer risk, suggesting that immunologic mechanisms are implicated in the etiology of this subset of SCCHN. SIGNIFICANCE: Two novel risk loci for SCCHN in non-Hispanic white individuals highlight the importance of immunologic mechanism in the disease etiology., (©2020 American Association for Cancer Research.)

Li-Fraumeni syndrome (LFS) is a rare autosomal dominant disorder associated with TP53 germline mutations and an increased lifetime risk of multiple primary cancers (MPC). Penetrance estimation of time to first and second primary cancer within LFS remains challenging because of limited data and the difficulty of characterizing the effects of a primary cancer on the penetrance of a second primary cancer. Using a recurrent events survival modeling approach that incorporates a family-wise likelihood to efficiently integrate the pedigree structure, we estimated the penetrance for both first and second primary cancer diagnosis from a pediatric sarcoma cohort at MD Anderson Cancer Center [MDACC, Houston, TX; number of families = 189; single primary cancer (SPC) = 771; and MPC = 87]. Validation of the risk prediction performance was performed using an independent MDACC clinical cohort of TP53 tested individuals (SPC = 102 and MPC = 58). These findings showed that an individual diagnosed at a later age was more likely to be diagnosed with a second primary cancer. In addition, TP53 mutation carriers had a HR of 1.65 (95% confidence interval, 1.1-2.5) for developing a second primary cancer versus SPC. The area under the ROC (AUC) curve for predicting individual outcomes of MPC versus SPC was 0.77. In summary, we provide the first set of penetrance estimates for first and second primary cancer for TP53 germline mutation carriers and demonstrate its accuracy for cancer risk assessment. SIGNIFICANCE: These findings present an open-source R package LFSPRO that could be used for genetic counseling and health management of individuals with LFS as it estimates the risk of both first and second primary cancer diagnosis. See related article by Shin et al., p. 354 ., (©2019 American Association for Cancer Research.)

Li-Fraumeni syndrome (LFS) is a rare hereditary cancer syndrome associated with an autosomal-dominant mutation inheritance in the TP53 tumor suppressor gene and a wide spectrum of cancer diagnoses. The previously developed R package, LFSPRO, is capable of estimating the risk of an individual being a TP53 mutation carrier. However, an accurate estimation of the penetrance of different cancer types in LFS is crucial to improve the clinical characterization and management of high-risk individuals. Here, we developed a competing risk-based statistical model that incorporates the pedigree structure efficiently into the penetrance estimation and corrects for ascertainment bias while also increasing the effective sample size of this rare population. This enabled successful estimation of TP53 penetrance for three LFS cancer types: breast (BR), sarcoma (SA), and others (OT), from 186 pediatric sarcoma families collected at MD Anderson Cancer Center (Houston, TX). Penetrance validation was performed on a combined dataset of two clinically ascertained family cohorts with cancer to overcome internal bias in each (total number of families = 668). The age-dependent onset probability distributions of specific cancer types were different. For breast cancer, the TP53 penetrance went up at an earlier age than the reported BRCA1/2 penetrance. The prediction performance of the penetrance estimates was validated by the combined independent cohorts (BR = 85, SA = 540, and OT = 158). Area under the ROC curves (AUC) were 0.92 (BR), 0.75 (SA), and 0.81 (OT). The new penetrance estimates have been incorporated into the current LFSPRO R package to provide risk estimates for the diagnosis of breast cancer, sarcoma, or other cancers. SIGNIFICANCE: These findings provide specific penetrance estimates for LFS-associated cancers, which will likely impact the management of families at high risk of LFS. See related article by Shin et al., p. 347 ., (©2019 American Association for Cancer Research.)

Approximately 20% of colorectal cancer patients with colorectal adenocarcinomas present with metastases at the time of diagnosis, and therapies that specially target these metastases are lacking. We present a novel approach for investigating transcriptomic differences between primary colorectal adenocarcinoma and distant metastases, which may help to identify primary tumors with high risk for future dissemination and to inform the development of metastasis-targeted therapies. To effectively compare the transcriptomes of primary colorectal adenocarcinoma and metastatic lesions at both the gene and pathway levels, we eliminated tissue specificity of the "host" organs where tumors are located and adjusted for confounders such as exposure to chemotherapy and radiation, and identified that metastases were characterized by reduced epithelial-mesenchymal transition (EMT) but increased MYC target and DNA-repair pathway activities. FBN2 and MMP3 were the most differentially expressed genes between primary tumors and metastases. The two subtypes of colorectal adenocarcinoma metastases that were identified, EMT inflammatory and proliferative, were distinct from the consensus molecular subtype (CMS) 3, suggesting subtype exclusivity. In summary, this study highlights transcriptomic differences between primary tumors and colorectal adenocarcinoma metastases and delineates pathways that are activated in metastases that could be targeted in colorectal adenocarcinoma patients with metastatic disease. SIGNIFICANCE: These findings identify a colorectal adenocarcinoma metastasis-specific gene-expression signature that is free from potentially confounding background signals coming from treatment exposure and the normal host tissue that the metastasis is now situated within., (©2019 American Association for Cancer Research.)

Identifying genetic variants with pleiotropic associations can uncover common pathways influencing multiple cancers. We took a two-stage approach to conduct genome-wide association studies for lung, ovary, breast, prostate, and colorectal cancer from the GAME-ON/GECCO Network (61,851 cases, 61,820 controls) to identify pleiotropic loci. Findings were replicated in independent association studies (55,789 cases, 330,490 controls). We identified a novel pleiotropic association at 1q22 involving breast and lung squamous cell carcinoma, with eQTL analysis showing an association with ADAM15/THBS3 gene expression in lung. We also identified a known breast cancer locus CASP8/ALS2CR12 associated with prostate cancer, a known cancer locus at CDKN2B-AS1 with different variants associated with lung adenocarcinoma and prostate cancer, and confirmed the associations of a breast BRCA2 locus with lung and serous ovarian cancer. This is the largest study to date examining pleiotropy across multiple cancer-associated loci, identifying common mechanisms of cancer development and progression. Cancer Res; 76(17); 5103-14. ©2016 AACR., Competing Interests: of Potential Conflicts of Interest: Dr. David Nickle is a full time employee at Merck & Co. No potential conflicts of interest were disclosed by other authors., (©2016 American Association for Cancer Research.)

Suboptimal cellular DNA repair capacity (DRC) has been shown to be associated with enhanced cancer risk, but genetic variants affecting the DRC phenotype have not been comprehensively investigated. In this study, with the available DRC phenotype data, we analyzed correlations between the DRC phenotype and genotypes detected by the Illumina 317K platform in 1,774 individuals of European ancestry from a Texas lung cancer genome-wide association study. The discovery phase was followed by a replication in an independent set of 1,374 cases and controls of European ancestry. We applied a generalized linear model with single nucleotide polymorphisms as predictors and DRC (a continuous variable) as the outcome. Covariates of age, sex, pack-years of smoking, DRC assay-related variables, and case-control status of the study participants were adjusted in the model. We validated that reduced DRC was associated with an increased risk of lung cancer in both independent datasets. Several suggestive loci that contributed to the DRC phenotype were defined in ERCC2/XPD, PHACTR2, and DUSP1. In summary, we determined that DRC is an independent risk factor for lung cancer, and we defined several genetic loci contributing to DRC phenotype.

The detection of tumor suppressor gene promoter methylation in sputum-derived exfoliated cells predicts early lung cancer. Here, we identified genetic determinants for this epigenetic process and examined their biologic effects on gene regulation. A two-stage approach involving discovery and replication was used to assess the association between promoter hypermethylation of a 12-gene panel and common variation in 40 genes involved in carcinogen metabolism, regulation of methylation, and DNA damage response in members of the Lovelace Smokers Cohort (N = 1,434). Molecular validation of three identified variants was conducted using primary bronchial epithelial cells. Association of study-wide significance (P < 8.2 × 10(-5)) was identified for rs1641511, rs3730859, and rs1883264 in TP53, LIG1, and BIK, respectively. These single-nucleotide polymorphisms (SNP) were significantly associated with altered expression of the corresponding genes in primary bronchial epithelial cells. In addition, rs3730859 in LIG1 was also moderately associated with increased risk for lung cancer among Caucasian smokers. Together, our findings suggest that genetic variation in DNA replication and apoptosis pathways impacts the propensity for gene promoter hypermethylation in the aerodigestive tract of smokers. The incorporation of genetic biomarkers for gene promoter hypermethylation with clinical and somatic markers may improve risk assessment models for lung cancer., (©2011 AACR.)

A common variant on chromosomal region 15q24-25.1, marked by rs1051730, was found to be associated with lung cancer risk. Here, we attempted to confirm the second variant on 15q24-25.1 in several large sporadic lung cancer populations and determined what percentage of additional risk for lung cancer is due to the genetic effect of the second variant. SNPs rs1051730 and rs481134 were genotyped in 2,818 lung cancer cases and 2,766 controls from four populations. Joint analysis of these two variants (rs1051730 and rs481134) on 15q24-25.1 identified three major haplotypes (G&#95;T, A&#95;C, and G&#95;C) and provided stronger evidence for association of 15q24-25.1 with lung cancer (P = 9.72 x 10(-9)). These two variants represent three levels of risk associated with lung cancer. The most common haplotype G&#95;T is neutral; the haplotype A&#95;C is associated with increased risk for lung cancer with 5.0% higher frequency in cases than in controls [P = 1.68 x 10(-7); odds ratio (OR), 1.24; 95% confidence interval (95% CI), 1.14-1.35]; whereas the haplotype G&#95;C is associated with reduced risk for lung cancer with 4.4% lower frequency in cases than in controls (P = 7.39 x 10(-7); OR, 0.80; 95% CI, 0.73-0.87). We further showed that these two genetic variants on 15q24-25.1 independently influence lung cancer risk (rs1051730: P = 4.42 x 10(-11); OR, 1.60; 95% CI, 1.46-1.74; rs481134: P = 7.01 x 10(-4); OR, 0.81; 95% CI, 0.72-0.92). The second variant on 15q24-25.1, marked by rs481134, explains an additional 13.2% of population attributable risk for lung cancer., ((c) 2010 AACR.)

Cigarette smoking is the major cause for lung cancer, but genetic factors also affect susceptibility. We studied families that included multiple relatives affected by lung cancer. Results from linkage analysis showed strong evidence that a region of chromosome 6q affects lung cancer risk. To characterize the effects that this region of chromosome 6q region has on lung cancer risk, we identified a haplotype that segregated with lung cancer. We then performed Cox regression analysis to estimate the differential effects that smoking behaviors have on lung cancer risk according to whether each individual carried a risk-associated haplotype or could not be classified and was assigned unknown haplotypic status. We divided smoking exposures into never smokers, light smokers (<20 pack-years), moderate smokers (20 to <40 pack-years), and heavy smokers (>or=40 pack-years). Comparing results according to smoking behavior stratified by carrier status, compared with never smokers, there was weakly increasing risk for increasing smoking behaviors, with the hazards ratios being 3.44, 4.91, and 5.18, respectively, for light, moderate, or heavy smokers, whereas among the individuals from families without the risk haplotype, the risks associated with smoking increased strongly with exposure, the hazards ratios being, respectively, 4.25, 9.17, and 11.89 for light, moderate, and heavy smokers. The never smoking carriers had a 4.71-fold higher risk than the never smoking individuals without known risk haplotypes. These results identify a region of chromosome 6q that increases risk for lung cancer and that confers particularly higher risks to never and light smokers.

Recent genome-wide association studies have linked the chromosome 15q24-25.1 locus to nicotine addiction and lung cancer susceptibility. To refine the 15q24-25.1 locus, we performed a haplotype-based association analysis of 194 familial lung cases and 219 cancer-free controls from the Genetic Epidemiology of Lung Cancer Consortium (GELCC) collection, and used proliferation and apoptosis analyses to determine which gene(s) in the 15q24-25.1 locus mediates effects on lung cancer cell growth in vitro. We identified two distinct subregions, hapL (P = 3.20 x 10(-6)) and hapN (P = 1.51 x 10(-6)), which were significantly associated with familial lung cancer. hapL encompasses IREB2, LOC123688, and PSMA4, and hapN encompasses the three nicotinic acetylcholine receptor subunit genes CHRNA5, CHRNA3, and CHRNB4. Examination of the genes around hapL revealed that PSMA4 plays a role in promoting cancer cell proliferation. PSMA4 mRNA levels were increased in lung tumors compared with normal lung tissues. Down-regulation of PSMA4 expression decreased proteasome activity and induced apoptosis. Proteasome dysfunction leads to many diseases including cancer, and drugs that inhibit proteasome activity show promise as a form of cancer treatment. Genes around hapN were also investigated, but did not show any direct effect on lung cancer cell proliferation. We concluded that PSMA4 is a strong candidate mediator of lung cancer cell growth, and may directly affect lung cancer susceptibility through its modulation of cell proliferation and apoptosis.

To explore the impact of common variation on the risk of developing lung cancer, we conducted a two-phase genome-wide association (GWA) study. In phase 1, we compared the genotypes of 511,919 tagging single nucleotide polymorphisms (SNP) in 1,952 cases and 1,438 controls; in phase 2, 30,568 SNPs were genotyped in 2,465 cases and 3,005 controls. SNP selection was based on best supported P values from phase 1 and two other GWA studies of lung cancer. In the combined analysis of phases 1 and 2, the strongest associations identified were defined by SNPs mapping to 15q25.1 (rs12914385; P = 3.19 x 10(-16)), 5p15.33 (rs4975616; P = 6.66 x 10(-7)), and 6p21.33 (rs3117582; P = 9.13 x 10(-7)). Variation at 15q25.1, but not 5p15.33 or 6p21.33, was strongly associated with smoking behavior with risk alleles correlated to higher consumption. Variation at 5p15.33 was shown to significantly influence induction of lung cancer histology. Pooling data from the four series provided 21,620 genotypes for 7,560 cases and 8,205 controls. A meta-analysis provided increased support that variation at 15q25.1 (rs8034191; P = 3.24 x 10(-26)), 5p15.33 (rs4975616; P = 2.99 x 10(-9)), and 6p21.33 (rs3117582; P = 4.46 x 10(-10)) influences lung cancer risk. The next best-supported associations were attained at 15q15.2 (rs748404: P = 1.08 x 10(-6)) and 10q23.31 (rs1926203; P = 1.28 x 10(-6)). These data indicate few common variants account for 1% of the excess familial risk underscoring the necessity of having additional large sample series for gene discovery.

DNA pooling in combination with high-throughput sequencing was done as a part of the Sequenom-Genefinder project. In the pilot study, we tested 83,715 single nucleotide polymorphisms (SNP), located primarily in gene-based regions, to identify polymorphic susceptibility variants for lung cancer. For this pilot study, 369 male cases and 287 controls of both sexes (white Europeans of Southern German origin) were analyzed. The study identified a candidate region in 22q12.2 that contained numerous SNPs showing significant case-control differences and that coincides with a region that was shown previously to be frequently deleted in lung cancer cell lines. The candidate region overlies the seizure 6-like (SEZ6L) gene. The pilot study identified a polymorphic Met430Ile substitution in the SEZ6L gene (SNP rs663048) as the top candidate for a variant modulating risk of lung cancer. Two replication studies were conducted to assess the association of SNP rs663048 with lung cancer risk. The M. D. Anderson Cancer Center study included 289 cases and 291 controls matched for gender, age, and smoking status. The Liverpool Lung Project (a United Kingdom study) included 248 cases and 233 controls. Both replication studies showed an association of the rs663048 with lung cancer risk. The homozygotes for the variant allele had more than a 3-fold risk compared with the wild-type homozygotes [combined odds ratio (OR), 3.32; 95% confidence interval (95% CI), 1.81-7.21]. Heterozygotes also had a significantly elevated risk of lung cancer from the combined replication studies with an OR of 1.15 (95% CI, 1.04-1.59). The effect remained significant after adjusting for age, gender, and pack-years of tobacco smoke. We also compared expression of SEZ6L in normal human bronchial epithelial cells (n = 7), non-small cell lung cancer (NSCLC; n = 52), and small cell lung cancer (SCLC; n = 22) cell lines by using Affymetrix HG-U133A and HG-U133B GeneChips. We found that the average expression level of SEZ6L in NSCLC cell lines was almost two times higher and in SCLC cell lines more than six times higher when compared with normal lung epithelial cell lines. Using the National Center for Biotechnology Information Gene Expression Omnibus database, we found a approximately 2-fold elevated and statistically significant (P = 0.004) level of SEZ6L expression in tumor samples compared with normal lung tissues. In conclusion, the results of these studies representing 906 cases compared with 811 controls indicate a role of the SEZ6L Met430Ile polymorphic variant in increasing lung cancer risk.

The use of tyrosine kinase inhibitors (TKI) has yielded great success in treatment of lung adenocarcinomas. However, patients who develop resistance to TKI treatment often acquire a somatic resistance mutation (T790M) located in the catalytic cleft of the epidermal growth factor receptor (EGFR) enzyme. Recently, a report describing EGFR-T790M as a germ-line mutation suggested that this mutation may be associated with inherited susceptibility to lung cancer. Contrary to previous reports, our analysis indicates that the T790M mutation confers increased Y992 and Y1068 phosphorylation levels. In a human bronchial epithelial cell line, overexpression of EGFR-T790M displayed a growth advantage over wild-type (WT) EGFR. We also screened 237 lung cancer family probands, in addition to 45 bronchoalveolar tumors, and found that none of them contained the EGFR-T790M mutation. Our observations show that EGFR-T790M provides a proliferative advantage with respect to WT EGFR and suggest that the enhanced kinase activity of this mutant is the basis for rare cases of inherited susceptibility to lung cancer.

In this study, we observed loss of heterozygosity (LOH) in human chromosomal fragment 6q25.1 in sporadic lung cancer patients. LOH was observed in 65% of the 26 lung tumors examined and was narrowed down to a 2.2-Mb region. Single-nucleotide polymorphism (SNP) analysis of genes located within this region identified a candidate gene, termed p34. This gene, also designated as ZC3H12D, C6orf95, FLJ46041, or dJ281H8.1, carries an A/G nonsynonymous SNP at codon 106, which alters the amino acid from lysine to arginine. Nearly 73% of heterozygous lung cancer tissues with LOH and the A/G SNP also exhibited loss of the A allele. In vitro clonogenic and in vivo nude mouse studies showed that overexpression of the A allele exerts tumor suppressor function compared with the G allele. p34 is located within a recently mapped human lung cancer susceptibility locus, and association of the p34 A/G SNP was tested among these families. No significant association between the less frequent G allele and lung cancer susceptibility was found. Our results suggest that p34 may be a novel tumor suppressor gene involved in sporadic lung cancer but it seems not to be the candidate familial lung cancer susceptibility gene linked to chromosomal region 6q23-25.

Germ-line p53 mutations have been identified in most families with Li-Fraumeni syndrome (LFS). For germ-line p53 mutation carriers, there is considerable variability with respect to age of cancer onset and tumor type, suggesting that additional genetic effects influence the clinical severity and tumor spectrum. To identify factors that might contribute to the observed heterogeneity in time to onset, we used segregation analysis to analyze the joint effects of germ-line p53 mutations and risk modifier(s) on cancer incidence. We studied 159 kindreds, ascertained through probands who had been diagnosed with childhood soft-tissue sarcoma before 16 years of age, survived >3 years after diagnosis, and treated at The University of Texas M.D. Anderson Cancer Center (Houston, TX) from 1944 to 1975. This unique cohort has been followed systematically for >20 years and has had germ-line p53 mutation testing in probands and extended family members. The analyses revealed that germ-line p53 mutations and sex had significant effects on cancer risk: men with p53 mutations had 151-fold higher odds of developing cancer than did those without mutations [95% confidence interval (95% CI), 60-380], and women with p53 mutations had 1,075-fold higher odds than did those without mutations (95% CI, 358-3,229) and 7.1-fold higher odds of having cancer than did men with mutations (95% CI, 2.5-20.3). These findings provide quantitative cancer risk assessments for LFS families.

Despite numerous studies showing that mutagen sensitivity is a cancer predisposition factor, the heritability of mutagen sensitivity has not been clearly established. In this report, we used a classic twin study design to examine the role of genetic and environmental factors on the mutagen sensitivity phenotype. Mutagen sensitivity was measured in peripheral blood lymphocytes from 460 individuals [148 pairs of monozygotic (MZ) twins, 57 pairs of dizygotic (DZ) twins, and 50 siblings]. The intraclass correlation coefficients were all significantly higher in MZ twins than in dizygotes (DZ pairs and MZ-sibling pairs combined) for sensitivity to four different mutagen challenges. Applying biometric genetic modeling, we calculated a genetic heritability of 40.7%, 48.0%, 62.5%, and 58.8% for bleomycin, benzo[a]pyrene diol epoxide, gamma-radiation, and 4-nitroquinoline-1-oxide sensitivity, respectively. This study provides the strongest and most direct evidence that mutagen sensitivity is highly heritable, thereby validating the use of mutagen sensitivity as a cancer susceptibility factor.

Peutz-Jeghers syndrome (PJS) is a dominantly inherited disorder characterized by gastrointestinal hamartomatous polyps and mucocutaneous melanin pigmentation. Germ line mutations in LKB1 cause PJS. We have generated mice carrying an Lkb1 exon 2 to 8 deletion by gene targeting in embryonic stem cells. Heterozygotes develop gastric hamartomas that are histologically similar to those found in humans with PJS. LKB1 is also reportedly a mediator of p53-dependent apoptosis. To explore the potential combined effects of p53 and Lkb1 alterations on tumorigenesis, we carried out a series of matings with Lkb1(+/-) and p53 null mice to generate Lkb1(+/-)/p53(+/-) and Lkb1(+/-)/p53(-/-) mice. Similar to the Lkb1(+/-) mice, gastrointestinal hamartomas have also been detected in the mice with these two genotypes. The Lkb1(+/-)/p53(+/-) mice displayed a dramatically reduced life span and increased tumor incidence compared to the mice with either Lkb1 or p53 single gene knockout. The time to onset of polyposis in Lkb1(+/-)/p53(-/-) mice is approximately 2 months earlier than Lkb1(+/-)/p53(+/-) and Lkb1(+/-) mice, whereas the latter two show a similar time to onset which is at approximately 6 months of age. These results strongly suggested that mutations of p53 and Lkb1 gene cooperate in the acceleration of tumorigenesis.

Li-Fraumeni syndrome (LFS) is a clinically and genetically heterogeneous inherited cancer syndrome. Most cases ( approximately 70%) identified and characterized to date are associated with dominantly inherited germ line mutations in the tumor suppressor gene TP53 (p53) in chromosome 17p13.1. In a subset of non-p53 patients with LFS, CHEK2 in chromosome 22q11 has been identified as another predisposing locus. Studying a series of non-p53 LFS kindred, we have shown that there is additional genetic heterogeneity in LFS kindred with inherited predisposition at loci other than p53 or CHEK2. Using a genome-wide scan for linkage with complementing parametric and nonparametric analysis methods, we identified linkage to a region of approximately 4 cM in chromosome 1q23, a genomic region not previously implicated in this disease. Identification ofa third predisposing gene and its underlying mutation(s) should provide insight into other genetic events that predispose to the genesis of the diverse tumor types associated with LFS and its variants.

Genetic variants in genes controlling cellular processes such as cell cycle, DNA repair, and apoptosis may modulate lung cancer risk. p73 has some p53-like activity and plays an important role in modulating these processes. The noncoding region of exon 2 of the p73 gene has two polymorphisms that are in complete linkage disequilibrium with one another, which may alter translation efficiency of the p73 protein. To test the hypothesis that this p73 polymorphism plays a role in the etiology of lung cancer, we conducted a hospital-based case-control study of 1054 patients newly diagnosed with lung cancer and 1139 cancer-free controls and evaluated the association between the p73 variant AT allele and risk of lung cancer. Cancer-free controls were frequency matched to the cases by age (+/-5 years), sex, and smoking status, and all subjects were non-Hispanic whites. The variant AT allele and genotypes were more common among the cases than among the controls (P = 0.0007 and P < 0.001, respectively). Compared with the GC/GC genotype, the variant GC/AT and AT/AT genotypes were associated with a statistically significantly increased risk for lung cancer [adjusted odds ratio (OR) = 1.32, 95% confidence interval (CI), 1.10-1.59 and OR = 1.54, 95% CI, 1.05-2.26, respectively] in an allele dose-effect relationship (trend test: P < 0.001). The risk associated with the AT allele (GC/AT+AT/AT) was more pronounced in younger (

Given that there are millions of single-nucleotide polymorphisms (SNPs) in the entire human genome, a major difficulty faced by scientists in planning costly population-based genotyping is to choose target SNPs that are most likely to affect phenotypic functions and ultimately contribute to disease development. Although it is widely accepted that sequences with important functionality tend to be less variable across species because of selective pressure, to what extent evolutionary conservation is mirrored by epidemiological outcome has never been demonstrated. In this study, we surveyed odds ratios detected for 46 SNPs in 39 different cancer-related genes from 166 molecular epidemiological studies. The conservation levels of amino acid that these SNPs affected were calculated as a tolerance index by comparing sequences from different species. Our results provide evidence of a significant relationship between the detected odds ratios associated with cancer risk and the conservation levels of the SNP-affected amino acids (P = 0.002; R(2) = 0.06). Tolerance indices were further calculated for 355 nonsynonymous SNPs identified in 90 human DNA repair genes, of which 103 caused amino acid changes in very conserved positions. Our findings support the concept that SNPs altering the conserved amino acids are more likely to be associated with cancer susceptibility. Using such a molecular evolutionary approach may hold great promise for prioritizing SNPs to be genotyped in future molecular epidemiological studies.

Studies of familial aggregation of cancer provide indirect evidence for the role of genetic predisposition to cancer. In an ongoing case-control study, we evaluated whether first-degree relatives of lung cancer cases are at increased risk of lung and other cancers. Smoking-related cancers were defined as cancers of the lung, bladder, head and neck, kidney, and pancreas. The 806 probands included in this analysis were patients referred to The University of Texas M. D. Anderson Cancer Center (Houston, TX). We identified 663 controls, matched to the cases on age (+/-5 years), sex, ethnicity, and smoking history, who were recruited from a local multispecialty physician practice in the Houston metropolitan area. Self-reported cancer family history data were available for 6430 first-degree relatives of the cases and 4936 first-degree relatives of the controls. An excess of cancer in relatives was evaluated by comparing the observed cancer cases among relatives of the cases with relatives of the controls. We conducted further analysis after stratifying on age of lung cancer onset (age at study registration for controls) and smoking status (never, former, or current) of the probands. We also conducted Cox regression analysis and compared time to cancer diagnosis among the relatives of the cases and controls adjusted for age and smoking status of proband and family members. Siblings [relative risk (RR) = 1.85; P = 0.003] of cases had a significant excess of lung cancer and an excess of smoking-related cancers (RR = 1.29; P = 0.01). We observed evidence of familial aggregation (RR = 1.71; P < 0.001) of lung cancer among relatives of late-onset lung cancer cases. From the Cox regression, we observed a moderate risk for development of lung (RR = 1.25; P = 0.09) and other smoking-related cancers (RR = 1.23; P = 0.05). After adjustment for smoking behavior of probands and their relatives, the risks of lung cancer (RR = 1.33; P = 0.03) and smoking-related cancers (RR = 1.28; P = 0.02) were statistically significant. We further stratified on age at onset and observed no evidence (P = 0.81) of familial aggregation of lung cancer among young onset (

Methylation of promoter CpG islands in colorectal cancer (CRC) falls into two categories: age related and cancer specific. Most cancer-specific methylation at CpG islands occurs in a subset of cases that display the CpG island methylator phenotype (CIMP). The underlying cause of CIMP is not known. Using methylation-specific PCR, we studied 47 CRC patients for methylation at five loci to determine whether the methylation status of CpG islands is associated with family history of cancer. Four of the loci were differentially methylated between the CRC cases with a family history and those with no family history. Patients with methylation at all four loci were 14 times more likely to have a family history of cancer than patients with methylation at none of the four loci. These findings suggest that there may be a genetic component to CIMP in CRC.

Susceptibility to radiation-induced pulmonary fibrosis is a heritable trait in mice. In a prior study of C57BL/6J (susceptible), C3Hf/Kam (resistant), and F1 and F2 mice derived from these strains, we estimated that approximately 38% of the measured phenotypic variation could be attributed to effects from a few genetic factors. In addition, we identified one genetic factor on chromosome 17 in the MHC region. To identify any additional genetic loci that might influence interstrain variability, we conducted a genome-wide linkage scan using 214 markers and the phenotypically extreme 94 (of 268) F2 mice. In regions exceeding suggestive linkage (LOD = 2.8), we followed up with additional markers. This scan revealed evidence for quantitative trait locus (QTL) on chromosomes 17 (LOD = 4.2), 1 (LOD = 4.5), and 18 (LOD = 3.9), which influence susceptibility to radiation-induced pulmonary fibrosis. An additional region containing a QTL on chromosome 6, LOD = 4.6, showed linkage in female mice only. The evidence for linkage to chromosome 18 weakened when it was analyzed jointly with other markers. These four loci are estimated to account for 70% of the genetic contribution to this trait with chromosome 17 and 1 accounting for 28 and 24%, respectively. To confirm and better define the influence of the chromosome 17-linked QTL on radiation sensitivity, we conducted studies on congenic mice in which the linked region on chromosome 17 had been transferred onto a B6.AKR or a C3.SW background. The chromosome 17-linked QTL was confirmed to influence the phenotype as the fibrotic radiation response of B6.AKR-H2(k) mice was significantly less than that of B6 mice (P = 0.0001). The QTL on chromosome 17 for radiation-induced lung fibrosis is within the same region as QTLs identified for lung damage after other insults, including bleomycin, ozone, and particle exposure, as well as for asthma, suggesting that this region of chromosome 17 may harbor a "universal" lung injury gene.

Sequence variations have been identified in a number of DNA repair genes, including XPD, but the effect of these polymorphisms on DNA repair capacity (DRC) is uncertain. We therefore examined XPD polymorphisms at Lys751Gln and Asp312Asn in 341 white lung cancer cases and 360 age-, sex-, ethnicity-, and smoking-matched controls accrued in a hospital-based molecular epidemiological study of susceptibility markers for lung cancer. As previously reported, DRC was statistically significantly lower in the cases than in the controls (7.8% versus 9.5%; P < 0.001), which represents an average 18% reduction among the cases. The variant Lys751Gln and Asp312Asn allele frequencies were 0.36 and 0.29, respectively, for the cases and 0.33 and 0.27, respectively, for the controls. For subjects homozygous for the variant genotype at either locus, the adjusted odds ratio [95% confidence interval (CI)] was 1.84 (1.11-3.04; P = 0.018, for trend). Both cases and controls with the wild-type genotypes exhibited the most proficient DRC. The risk (95% CI) for suboptimal DRC (defined as less than the median DRC value among the controls) was 1.57 (0.74-3.35) for those with the Gln/Gln751 genotype. For cases with the Asn/Asn312 genotype, the risk (95% CI) was 3.50 (1.06-11.59). For cases who were homozygous at either locus, the risk was 2.29 (1.03-5.12; P = 0.048, for trend). The pattern was less evident among the controls, although there was a nonsignificant 41% increase in the risk of suboptimal DRC for controls who were homozygous at either locus. These results suggest that the two XPD polymorphisms have a modulating effect on DRC, especially in the cases.

Mutations in N-acetyltransferase 2 (NAT2), a highly polymorphic enzyme involved in the metabolism of xenobiotics and carcinogens, may affect risk for colorectal cancer (CRC), especially among individuals with germ-line mutations in DNA mismatch repair genes. We determined the NAT2 genotypes and allele frequencies for 86 individuals with CRC who had mutations in hMLH1, hMSH2, or hPMS1. No significant difference in time to onset was observed between rapid (NAT2*4) and slow (NAT2*5, NAT2*6, and NAT2*7) acetylators. However, when individuals were stratified separately by NAT2 polymorphism (NAT2*5, NAT2*6, and NAT2*7), those who were heterozygous at the mutant locus NAT2*7 after adjustment for the NAT2 mutant loci NAT2*5 and NAT2*6 had a significantly higher risk of CRC (hazard ratio, 2.96; P = 0.012) and all of the cancers (hazard ratio, 3.37; P = 0.00004) than individuals homozygous for wild type at the NAT2*7 allele. These findings suggest that NAT2 genotype may be an important factor in tumorigenesis of CRC and cancers related to hereditary nonpolyposis CRC among individuals with mismatch repair defects.

The etiology of Wilms tumor, an embryonic kidney tumor, is genetically heterogeneous. One Wilms tumor gene, WT1, which encodes a zinc finger transcription factor, is mutated in 10-20% of Wilms tumors, but it is still not clear what critical cellular pathway(s) is affected by these mutations. Recently beta-catenin mutations have been reported in 6 of 40 (15%) of Wilms tumors. Beta-catenin is the central effector in the Wnt signal transduction pathway, and deregulation of beta-catenin signaling is critical in the development of a number of malignancies. The observation of beta-catenin mutations in Wilms tumors suggests that abrogation of the Wnt signaling pathway also plays a role in some Wilms tumors. To assess the relationship of WT1 mutations vis-à-vis beta-catenin mutations in Wilms tumor, we analyzed 153 primary tumors, and 21 of 153 (14%) carried beta-catenin mutations. Surprisingly, we observed a highly significant (P = 3.6 x 10(-13)) association between WT1 and beta-catenin mutations; 19 of 20 beta-catenin-mutant tumors had also sustained WT1 mutations. By analogy to the patterns of concordant and discordant gene mutations observed in other tumors, our data suggest that mutation of WT1 and beta-catenin affects two different cellular pathways, both of which are critically altered in at least a subset of Wilms tumors.

A common polymorphism in the cyclin D1 gene enhances the gene's alternate splicing. The alternatively spliced product encodes an altered protein that does not contain sequences involved in the turnover of the protein. We found that hereditary nonpolyposis colorectal carcinoma patients who were homozygous or heterozygous for the mutant allele developed colorectal cancer an average of 11 years earlier than patients who were homozygous for the normal alleles. This is the first report indicating that the cyclin D1 polymorphism influences age of onset of cancer. Because cyclin D1 plays an important role in the G1 to S phase transition of the cell cycle, our findings suggest that cells with the mutant allele accumulate mutations as a result of defective mismatch repair and may also bypass the G1-S checkpoint of the cell cycle more easily than in cells not carrying the polymorphism. The polymorphism has a dominant phenotype.

Peutz-Jeghers syndrome (PJS) was recently mapped in a single report to the telomeric region of chromosome 19p (A. Hemminki et al., Nat. Genet., 15: 87-90, 1997). Our studies confirm this location and provide further localization of the PJS locus. In the five families examined, there were no recombinants with the marker D19S886. The multipoint log odds score at D19S886 is 7.52, and we found no evidence for genetic heterogeneity. We also found that all carriers expressed the PJS phenotype and no noncarriers displayed PJS sequellae, indicating complete penetrance with no sporadic cases.

Wilms' tumor (WT), a childhood kidney cancer, occurs both sporadically and, less frequently, in a familial context. Genetic linkage studies of several large WT families have excluded the one cloned WT gene, WT1, as the locus responsible for familial predisposition. These data demonstrate the existence of a familial predisposition gene distinct from WT1 and, more broadly, imply that the genetic etiology of WT is heterogenous. However, it has been unknown whether the predisposition observed in large WT families is also heterogenous or perhaps is due to mutations at a single locus. Recently, examination of a large French-Canadian WT family has demonstrated genetic linkage to 17q12-q21. We report here the results from a genetic linkage study of six WT pedigrees. Analyses of genotype data from eight loci within the 17q12-q21 region in these families resulted in cumulative lod scores of <-4.0 through the region, thereby excluding linkage. The ability to rule out the 17q region as the site of a predisposition gene in several of these pedigrees individually demonstrates the existence of more than one gene that predisposes to WT in large pedigrees and again emphasizes that the etiology of WT is genetically heterogenous.

Based on the range of patient responses to treatment, and on animal studies, it is hypothesized that individual variation in sensitivity to bleomycin-induced pulmonary fibrosis is controlled genetically. A genetic model has been developed by (a) establishing a distinct difference in bleomycin-induced lung damage in two inbred strains of mice [parental generation: C57BL/6J (fibrosis-prone phenotype) and C3Hf/Kam (fibrosis-resistant phenotype)] and (b) characterizing inheritance of the fibrosing phenotype in the F1 (first filial) and F2 (F1 intercross; second filial) generations derived from the parental strains. Male mice received 100 mg/kg and female mice 125 mg/kg of bleomycin via s.c. osmotic minipump. The animals were sacrificed 8 weeks after treatment or when their breathing rate indicated respiratory distress. The percentage of lung with fibrosis for each mouse was quantified with image analysis of a histological section of the left lung. The mean percentage of fibrosis for the C57BL/6J males was 8.4 +/- 0.8% (SE) and 4.4 +/- 0.8% for females, and the C3Hf/Kam mice of either sex did not present the fibrosing lesion (mean score, 0%). Significant difference (P = 6 x 10(-6)) was measured in percentage of fibrosis between the two strains of F1 males, but not F1 females (P = 0.38), suggesting the presence of an X-linked factor associated with the fibrosing phenotype. From an ANOVA the X-linked factor is estimated to contribute 19% of the fibrosis phenotype. A genetic model of two or three loci controlling the fibrosing phenotype is proposed from the data of the parental, F1, and F2 generations. The mouse model demonstrates that susceptibility to bleomycin-induced pulmonary fibrosis is a heritable trait controlled by a few genetic loci.

We used a case-control study design to determine the association between bleomycin-induced chromatid breaks and the risk of lung cancer in general and by specific histopathological types. Lymphocytes from primary blood cultures of 78 controls and 75 cases with 4 histopathological types of lung cancer were treated with 0.03 unit/ml bleomycin for 5 h, and the frequency of induced chromatid breakage and the locations of the breaks were determined in Q-banded preparations. After adjustment for their length, the larger chromosomes had more breaks than the smaller chromosomes in both cases and controls. The cases had significantly more breaks on chromosomes 4 and 5 than the controls did, with odds ratios (ORs) of 4.9 [95% confidence limits (CL), 2.0, 11.7] and 3.9 (95% CL, 1.6, 9.3), respectively. When the lung cancers were classified by histopathological type, adenocarcinomas had significantly more breaks on chromosomes 4 and 5, with ORs of 3.0 (95% CL, 1.0, 8.7) and 3.5 (95% CL, 1.2, 10.7), respectively. For squamous cell carcinoma, the ORs were significantly elevated for breaks on chromosomes 2, 4, and 5 with ORs of 3.5 (95% CL, 1.0, 11.7), 10.2 (95% CL, 2.5, 41.9), and 7.9 (95% CL, 1.9, 32.8). For small cell carcinoma, breaks on chromosomes 2 and 4 showed significantly increased ORs of 33.2 (95% CL, 2.2, 513.3) and 20.4 (95% CL, 1.7, 250.1), respectively. However, no specific chromatid breaks were detected in cases with large cell carcinoma. When the frequency of chromatid breaks at specific regions was calculated, breaks at 4p14, 4q27, 4q31, 5q21-q22, 5q31, and 5q33 were significantly more common in lung cancer cases than in controls. Lung cancer risk had a dose-response relationship with breaks on chromosomes 4 and 5. Cigarette smoking had a strong interaction with breaks on chromosomes 2, 4, and 5. The findings suggest that the susceptibility of particular chromosome loci to mutagenic damage may be a risk factor for specific types of lung cancer.

Familial patterns of the occurrence of breast cancer were studied in a population-based case-control series of black women from the Cancer and Steroid Hormone study. The risks of breast cancer among relatives of breast cancer cases were compared to those of controls who were matched for age and locale. Using the term "proband" to indicate either case or control status, significant predictors of risk to the relatives of probands included case/control status of the proband and the number of years of education completed by the proband. Genetic segregation analysis of the case families using external risks generated from SEER data indicated that the familial aggregation was consistent with Mendelian recessive transmission of a single major gene. The use of internally estimated risks, which are much less stable than the SEER risks, no longer permitted discrimination among the major locus models examined. To avoid possible reporting bias, we also performed segregation analysis on families of probands who had completed at least 12 years of education. The results from this analysis reflected the results from the entire data.