Genome-wide association studies of European and East Asian populations have identified lung cancer susceptibility loci on chromosomes 5p15.33, 6p22.1-p21.31 and 15q25.1. We investigated whether these regions contain lung cancer susceptibly loci in African-Americans refined previous association signals by utilizing the reduced linkage disequilibrium observed in African-Americans.
1308 African-American cases and 1241 African-American controls from three centers were genotyped for 760 single nucleotide polymorphisms spanning three regions, and additional SNP imputation was performed. Associations between polymorphisms and lung cancer risk were estimated using logistic regression, stratified by tumor histology where appropriate.
The strongest associations were observed on 15q25.1 in/near CHRNA5, including a missense substitution (rs16969968: OR = 1.57, 95% CI = 1.25–1.97, P = 1.1 × 10−4) and variants in the 5′-UTR. Associations on 6p22.1-p21.31 were histology-specific and included a missense variant in BAT2 associated with squamous-cell carcinoma (rs2736158: OR = 0.64, 95% CI = 0.48–0.85, P = 1.82 × 10−3). Associations on 5p15.33 were detected near TERT, the strongest of which was rs2735940 (OR = 0.82, 95% CI = 0.73–0.93, P = 1.1 × 10−3). This association was stronger among cases with adenocarcinoma (OR = 0.75, 95% CI = 0.65–0.86, P = 8.1 × 10−5).
Polymorphisms in 5p15.33, 6p22.1-p21.31 and 15q25.1 are associated with lung cancer in African-Americans. Variants on 5p15.33 are stronger risk factors for adenocarcinoma and variants on 6p21.33 associated only with squamous-cell carcinoma.
Results implicate the BAT2, TERT and CHRNA5 genes in the pathogenesis of specific lung cancer histologies.
Lung cancer; adenocarcinoma; squamous-cell carcinoma; fine-mapping; African-American; genetic association
Studies in European and East Asian populations have identified lung cancer susceptibility loci in nicotinic acetylcholine receptor (nAChR) genes on chromosome 15q25.1 which also appear to influence smoking behaviors. We sought to determine if genetic variation in nAChR genes influences lung cancer susceptibly in African-Americans, and evaluated the association of these cancer susceptibility loci with smoking behavior. A total of 1308 African-Americans with lung cancer and 1241 African-American controls from three centers were genotyped for 378 single nucleotide polymorphisms (SNPs) spanning the sixteen human nAChR genes. Associations between SNPs and the risk of lung cancer were estimated using logistic regression, adjusted for relevant covariates. Seven SNPs in three nAChR genes were significantly associated with lung cancer at a strict Bonferroni-corrected level, including a novel association on chromosome 2 near the promoter of CHRNA1 (rs3755486: OR = 1.40, 95% CI = 1.18-1.67, P = 1.0 × 10−4). Association analysis of an additional 305 imputed SNPs on 2q31.1 supported this association. Publicly available expression data demonstrated that the rs3755486 risk allele correlates with increased CHRNA1 gene expression. Additional SNP associations were observed on 15q25.1 in genes previously associated with lung cancer, including a missense variant in CHRNA5 (rs16969968: OR = 1.60, 95% CI = 1.27-2.01, P = 5.9 × 10−5). Risk alleles on 15q25.1 also correlated with an increased number of cigarettes smoked per day among the controls. These findings identify a novel lung cancer risk locus on 2q31.1 which correlates with CHRNA1 expression and replicate previous associations on 15q25.1 in African-Americans.
Lung cancer; nicotine dependence; African-Americans; genetic association; smoking
Black/white disparities in lung cancer incidence and mortality mandate an evaluation of underlying biological differences. We have previously shown higher risks of lung cancer associated with prior emphysema in African American compared with white lung cancer patients.
We therefore evaluated a panel of 1440 inflammatory gene variants in a two phase analysis (discovery and replication), added top GWAS lung cancer hits from Caucasian populations, and 28 SNPs from a published gene panel. The discovery set (477 self-designated African Americans cases, 366 controls matched on age, ethnicity, and gender) were from Houston, Texas. The external replication set (330 cases, 342 controls) was from the EXHALE study at Wayne State University.
In discovery, 154 inflammation SNPs were significant (P<0.05) on univariate analysis, as was one of the gene panel SNPs (rs308738 in REV1, P=0.0013), and three GWAS hits, rs16969968 P=0.0014 and rs10519203 P=0.0003 in the 15q locus and rs2736100, the HTERT locus, P=0.0002. One inflammation SNP, rs950286, was successfully replicated with a concordant odds ratio of 1.46(1.14-1.87) in discovery, 1.37(1.05-1.77) in replication, and a combined OR of 1.40 (1.17-1.68). This SNP is intergenic between IRF4 and EXOC2 genes. We also constructed and validated epidemiologic and extended risk prediction models. The AUC for the epidemiologic discovery model was 0.77 and 0.80 for the extended model. For the combined datasets, the AUC values were 0.75 and 0.76, respectively.
As has been reported for other cancer sites and populations, incorporating top genetic hits into risk prediction models, provides little improvement in model performance and no clinical relevance.
Lung cancer in lifetime never smokers is distinct from that in smokers, but the role of separate or overlapping carcinogenic pathways has not been explored. We therefore evaluated a comprehensive panel of 11,737 SNPs in inflammatory-pathway genes in a discovery phase (451 lung cancer cases, 508 controls from Texas). SNPs that were significant were evaluated in a second external population (303 cases, 311 controls from the Mayo Clinic). An intronic SNP in the ACVR1B gene, rs12809597, was replicated with significance and restricted to those reporting adult exposure to environmental tobacco smoke Another promising candidate was a SNP in NR4A1, although the replication OR did not achieve statistical significance. ACVR1B belongs to the TGFR-β superfamily, contributing to resolution of inflammation and initiation of airway remodeling. An inflammatory microenvironment, (second hand smoking, asthma, or hay fever) is necessary for risk from these gene variants to be expressed. These findings require further replication, followed by targeted resequencing, and functional validation.
lung cancer; never smokers; inflammation genes; sidestream exposure
Tobacco-induced lung cancer is characterized by a deregulated inflammatory microenvironment. Variants in multiple genes in inflammation pathways may contribute to risk of lung cancer.
We therefore conducted a three-stage comprehensive pathway analysis (discovery, replication and meta-analysis) of inflammation gene variants in ever smoking lung cancer cases and controls. A discovery set (1096 cases; 727 controls) and an independent and non-overlapping internal replication set (1154 cases; 1137 controls) were derived from an ongoing case-control study. For discovery, we used an iSelect BeadChip to interrogate a comprehensive panel of 11737 inflammation pathway SNPs and selected nominally significant (p<0.05) SNPs for internal replication.
There were 6 SNPs that achieved statistical significance (p<0.05) in the internal replication dataset with concordant risk estimates for former smokers and 5 concordant and replicated SNPs in current smokers. Replicated hits were further tested in a subsequent meta-analysis using external data derived from two published GWAS and a case-control study. Two of these variants (a BCL2L14 SNP in former smokers and a SNP in IL2RB in current smokers) were further validated. In risk score analyses, there was a 26% increase in risk with each additional adverse allele when we combined the genotyped SNP and the most significant imputed SNP in IL2RB in current smokers and a 36% similar increase in risk for former smokers associated with genotyped and imputed BCL2L14 SNPs.
Before they can be applied for risk prediction efforts, these SNPs should be subject to further external replication and more extensive fine mapping studies.
Inflammation SNPS; lung cancer; smokers
We conducted imputation to the 1000 Genomes Project of four genome-wide association studies of lung cancer in populations of European ancestry (11,348 cases and 15,861 controls) and genotyped an additional 10,246 cases and 38,295 controls for follow-up. We identified large-effect genome-wide associations for squamous lung cancer with the rare variants of BRCA2-K3326X (rs11571833; odds ratio [OR]=2.47, P=4.74×10−20) and of CHEK2-I157T (rs17879961; OR=0.38 P=1.27×10−13). We also showed an association between common variation at 3q28 (TP63; rs13314271; OR=1.13, P=7.22×10−10) and lung adenocarcinoma previously only reported in Asians. These findings provide further evidence for inherited genetic susceptibility to lung cancer and its biological basis. Additionally, our analysis demonstrates that imputation can identify rare disease-causing variants having substantive effects on cancer risk from pre-existing GWAS data.
Risk prediction models are useful in clinical decision making. We have published an internally validated prediction tool for lung cancer based on easily obtainable epidemiologic and clinical data. Because the precision of the model was modest, we now estimate the improvement obtained by adding two markers of DNA repair capacity.
Assay data (host-cell reactivation and mutagen sensitivity) were available for 725 White lung cancer cases and 615 controls, all former or current smokers, a subset of cases and controls from the previous analysis. Multivariable models were constructed from the original variables with addition of the biomarkers separately and together. Pairwise comparisons of the area under the receiver operating characteristic curves (AUC) and 3-fold cross-validations were done.
For former smokers, the AUC and 95% confidence intervals were 0.67 (0.63–0.71) for the baseline model and 0.70 (0.66–0.74) for the expanded model. For current smokers, the comparable AUC values were 0.68 (0.64–0.72) and 0.73 (0.69–0.77). For both groups, the expanded models were statistically significantly better than the baseline models (P = 0.006 and P = 0.0048, respectively), although the increases in the concordance statistics were modest. We also recomputed 1-year absolute risks of lung cancer as described previously for two different risk profiles and showed that individuals who exhibited poor repair capacity or heightened mutagen sensitivity had increased absolute risks of lung cancer.
Addition of biomarker assays improved the sensitivity of the expanded models.
Symptom clusters, the multiple, co-occurring symptoms experienced by cancer patients, are debilitating and affects quality of life. We assessed if a panel of immune-response genes may underlie the co-occurrence of severe pain, depressed mood and fatigue and help identify patients with severe versus non-severe symptom clusters.
Symptoms were assessed at presentation, prior to cancer treatment in 599 newly diagnosed lung cancer patients. We applied cluster analyses to determine the patients with severe versus non-severe symptom clusters of pain, depressed mood, and fatigue.
Two homogenous clusters were identified. One hundred sixteen patients (19%) comprised the severe symptom cluster, reporting high intensity of pain, depressed mood and fatigue and 183 (30%) patients reported low intensity of these symptoms. Using Bayesian model averaging methodology, we found that of the 55 SNPs assessed, an additive effect of mutant alleles in ENOS (-1474 T/A) (Posterior Probability of Inclusion (PPI) = 0.78, OR = 0.54, 95% CI = (0.31, 0.93); IL1B T-31C (PPI = 0.72, OR = 0.55, 95% CI = (0.31, 0.97)); TNFR2 Met196Arg (PPI = 0.70; OR=1.85;95%CI=(1.03,3.36)); PTGS2 exon 10+837T>C (PPI = 0.69, OR = 0.54, 95%CI = (0.28, 0.99)); and IL10RB Lys47Glu (PPI = 0.68; OR=1.74; 95%CI=(1.04,2.92)) were predictive for symptom clusters.
Genetic polymorphisms may facilitate identification of high risk patients and development of individualized symptom therapies.
pain; depression; fatigue; cytokines; symptoms; genes; epidemiology; lung cancer; SNPs
Common variants in the nicotinic acetylcholine receptor gene cluster on chromosome 15q24-25.1 were associated with lung cancer risk in three recently published independently conducted genome-wide association studies, with no consensus as to the relative impact of the variants on the propensity to smoke vs a direct carcinogenic effect. To further explore our hypothesis that these variants are indeed associated with both cancer causation and nicotine dependence, we performed a more detailed analysis of the association of these putative risk genotypes with smoking phenotype, as well as in lifetime never smokers, and in other smoking-related cancers. We demonstrate a statistically significant association of the variants with both nicotine dependence, as well as lung cancer phenotypes, including earlier age at lung cancer onset. The variants were associated with higher risks of lung cancer in lower smoking-exposed strata, and in individuals with a strong family history of lung or smoking-related cancers. In contrast, we found no evidence that the variants were associated with elevated risks in 547 lifetime never-smoking lung cancer case subjects, nor in other smoking-related cancers (bladder and renal). Thus, we conclude that the variants are implicated both in smoking behavior and more directly in lung cancer risk.
Head and neck squamous cell carcinoma (HNSCC) patients are at an increased risk of developing a second primary tumor (SPT) or recurrence following curative treatment. 13-cis-retinoic acid (13-cRA) has been tested in chemoprevention clinical trials but the results have been inconclusive. We genotyped 9,465 SNPs in 450 patients from the Retinoid Head and Neck Second Primary Trial. SNPs were analyzed for associations with SPT/recurrence in patients receiving placebo to identify prognosis markers and further analyzed for effects of 13-cRA in patients with these prognostic loci. Thirteen loci identified a majority subgroup of patients at a high risk of SPT/recurrence and in whom 13-cRA was protective. Patients carrying the common genotype of rs3118570 in the retinoid X receptor (RXRA) were at a 3.33-fold increased risk (95% confidence interval [CI], 1.67–6.67) and represented over 70% of the study population. This locus also identified individuals who received benefit from chemoprevention with a 38% reduced risk (95% CI, 0.43–0.90). Analyses of cumulative effect and potential gene-gene interactions also implicated CDC25C:rs6596428 and JAK2:rs1887427 as two other genetic loci with major roles in prognosis and 13-cRA response. Patients with all three common genotypes had a 76% reduction in SPT/recurrence (95% CI, 0.093–0.64) following 13-cRA chemoprevention. Carriers of these common genotypes constituted a substantial percentage of the study population, indicating that a pharmacogenetics approach could help select patients for 13-cRA chemoprevention. The lack of any alternatives for reducing risk in these patients highlights the need for future clinical trials to prospectively validate our findings.
HNSCC; SPT; single nucleotide polymorphisms; retinoids
Many studies examining genetic influences on physical activity (PA) have evaluated the impact of single nucleotide polymorphisms (SNPs) related to the development of lifestyle-related chronic diseases, under the hypothesis that they would be associated with PA. However, PA is a multi-determined behavior and associated with a multitude of health consequences. Thus, examining a broader range of candidate genes associated with a boarder range of PA correlates may provide new insights into the genetic underpinnings of PA. In this study we focus on one such correlate – sensation seeking behavior. Participants (N=1,130 Mexican origin youth) provided a saliva sample and data on PA and sensation seeking tendencies in 2008–09. Participants were genotyped for 630 functional and tagging variants in the dopamine, serotonin, and cannabinoid pathways. Overall 30% of participants (males – 37.6%; females – 22.0%) reported ≥60 minutes of PA on five out of seven days. After adjusting for gender, age and population stratification, and applying the Bayesian False Discovery Probability approach for assessing noteworthiness, four gene variants were significantly associated with PA. In a multivariable model, being male, having higher sensation seeking tendencies and at least one copy of the minor allele for SNPs in ACE (rs8066276 OR=1.44; p=0.012) and TPH2 (rs11615016 OR=1.73; p=0.021) were associated with increased likelihood of meeting PA recommendations. Participants with at least one copy of the minor allele for SNPs in SNAP25 (rs363035 OR=0.53; p=0.005) and CNR1 (rs6454672 OR=0.62; p=0.022) have decreased likelihood of meeting PA recommendations. Our findings extend current knowledge of the complex relationship between PA and possible genetic underpinnings.
Physical Activity; Genes; Sensation Seeking; Mexican origin youth
Genome-wide association studies (GWAS) have identified 36 loci associated with body mass index (BMI), predominantly in populations of European ancestry. We conducted a meta-analysis to examine the association of >3.2 million SNPs with BMI in 39,144 men and women of African ancestry, and followed up the most significant associations in an additional 32,268 individuals of African ancestry. We identified one novel locus at 5q33 (GALNT10, rs7708584, p=3.4×10−11) and another at 7p15 when combined with data from the Giant consortium (MIR148A/NFE2L3, rs10261878, p=1.2×10−10). We also found suggestive evidence of an association at a third locus at 6q16 in the African ancestry sample (KLHL32, rs974417, p=6.9×10−8). Thirty-two of the 36 previously established BMI variants displayed directionally consistent effect estimates in our GWAS (binomial p=9.7×10−7), of which five reached genome-wide significance. These findings provide strong support for shared BMI loci across populations as well as for the utility of studying ancestrally diverse populations.
The development of second primary tumors (SPT) or recurrence alters prognosis for curatively-treated head and neck squamous cell carcinoma (HNSCC) patients. 13-cis-retnoic acid (13-cRA) has been tested as a chemoprevention agent in clinical trials with mixed results. Therefore, we investigated if genetic variants in the PI3K/PTEN/AKT/MTOR pathway could serve as biomarkers to identify which patients are at high risk of an SPT/recurrence while also predicting response to 13-cRA chemoprevention.
A total of 137 pathway SNPs were genotyped in 440 patients from the Retinoid Head and Neck Second Primary Trial and assessed for SPT/recurrence risk and response to 13-cRA. Risk models were created based on epidemiology, clinical, and genetic data.
Twenty-two genetic loci were associated with increased SPT/recurrence risk with six also being associated with a significant benefit following chemoprevention. Combined analysis of these high-risk/high-benefit loci identified a significant (P = 1.54×10−4) dose-response relationship for SPT/recurrence risk, with patients carrying 4–5 high-risk genotypes having a 3.76-fold (95%CI:1.87–7.57) increase in risk in the placebo group (n=215). Patients carrying 4–5 high-risk loci showed the most benefit from 13-cRA chemoprevention with a 73% reduction in SPT/recurrence (95%CI:0.13–0.58) compared to those with the same number of high-risk genotypes who were randomized to receive placebo. Incorporation of these loci into a risk model significantly improved the discriminatory ability over models with epidemiology, clinical, and previously identified genetic variables.
These results demonstrate that loci within this important pathway could identify individuals with a high-risk/high-benefit profile and are a step towards personalized chemoprevention for HNSCC patients.
Genome-wide association studies have identified variants on chromosome 15q25.1 that increase the risks of both lung cancer and nicotine dependence and associated smoking behavior. However, there remains debate as to whether the association with lung cancer is direct or is mediated by pathways related to smoking behavior. Here, the authors apply a novel method for mediation analysis, allowing for gene-environment interaction, to a lung cancer case-control study (1992–2004) conducted at Massachusetts General Hospital using 2 single nucleotide polymorphisms, rs8034191 and rs1051730, on 15q25.1. The results are validated using data from 3 other lung cancer studies. Tests for additive interaction (P = 2 × 10−10 and P = 1 × 10−9) and multiplicative interaction (P = 0.01 and P = 0.01) were significant. Pooled analyses yielded a direct-effect odds ratio of 1.26 (95% confidence interval (CI): 1.19, 1.33; P = 2 × 10−15) for rs8034191 and an indirect-effect odds ratio of 1.01 (95% CI: 1.00, 1.01; P = 0.09); the proportion of increased risk mediated by smoking was 3.2%. For rs1051730, direct- and indirect-effect odds ratios were 1.26 (95% CI: 1.19, 1.33; P = 1 × 10−15) and 1.00 (95% CI: 0.99, 1.01; P = 0.22), respectively, with a proportion mediated of 2.3%. Adjustment for measurement error in smoking behavior allowing up to 75% measurement error increased the proportions mediated to 12.5% and 9.2%, respectively. These analyses indicate that the association of the variants with lung cancer operates primarily through other pathways.
gene-environment interaction; lung neoplasms; mediation; pathway analysis; smoking
Folate metabolism, with its importance to DNA repair, provides a promising region for genetic investigation of lung cancer risk. This project investigates genes (MTHFR, MTR, MTRR, CBS, SHMT1, TYMS), folate metabolism related nutrients (B vitamins, methionine, choline, and betaine) and their gene-nutrient interactions.
We analyzed 115 tag single nucleotide polymorphisms (SNPs) and 15 nutrients from 1239 and 1692 non-Hispanic white, histologically-confirmed lung cancer cases and controls, respectively, using stochastic search variable selection (a Bayesian model averaging approach). Analyses were stratified by current, former, and never smoking status.
Rs6893114 in MTRR (odds ratio [OR] = 2.10; 95% credible interval [CI]: 1.20–3.48) and alcohol (drinkers vs. non-drinkers, OR = 0.48; 95% CI: 0.26–0.84) were associated with lung cancer risk in current smokers. Rs13170530 in MTRR (OR = 1.70; 95% CI: 1.10–2.87) and two SNP*nutrient interactions [betaine*rs2658161 (OR = 0.42; 95% CI: 0.19–0.88) and betaine*rs16948305 (OR = 0.54; 95% CI: 0.30–0.91)] were associated with lung cancer risk in former smokers. SNPs in MTRR (rs13162612; OR = 0.25; 95% CI: 0.11–0.58; rs10512948; OR = 0.61; 95% CI: 0.41–0.90; rs2924471; OR = 3.31; 95% CI: 1.66–6.59), and MTHFR (rs9651118; OR = 0.63; 95% CI: 0.43–0.95) and three SNP*nutrient interactions (choline*rs10475407; OR = 1.62; 95% CI: 1.11–2.42; choline*rs11134290; OR = 0.51; 95% CI: 0.27–0.92; and riboflavin*rs8767412; OR = 0.40; 95% CI: 0.15–0.95) were associated with lung cancer risk in never smokers.
This study identified possible nutrient and genetic factors related to folate metabolism associated with lung cancer risk, which could potentially lead to nutritional interventions tailored by smoking status to reduce lung cancer risk.
Established psychosocial risk factors increase the risk for experimentation among Mexican-origin youth. Now we comprehensively investigate the added contribution of select polymorphisms in candidate genetic pathways associated with sensation seeking, risk taking, and smoking phenotypes to predict experimentation.
Participants, (N=1,118 Mexican origin youth) recruited from a large population-based cohort study in Houston, Texas, provided prospective data on cigarette experimentation over three years. Psychosocial data were elicited twice—baseline and final follow-up. Participants were genotyped for 672 functional and tagging variants in the dopamine, serotonin and opioid pathways.
After adjusting for gender and age, with a Bayesian False Discovery Probability set at 0.8 and prior probability of 0.05, six gene variants were significantly associated with risk of experimentation. After controlling for established risk factors, multivariable analyses revealed that participants with six or more risk alleles were 2.25 (95%CI: 1.62–3.13) times more likely to have experimented since baseline compared to participants with five or fewer. Among committed never smokers (N=872), three genes (OPRM1, SNAP25, HTR1B) were associated with experimentation as were all psychosocial factors. Among susceptible youth (N=246) older age at baseline, living with a smoker, and three different genes (HTR2A, DRD2, SLC6A3) predicted experimentation.
Our findings, which have implications for development of culturally-specific interventions, need to be validated in other ethnic groups.
These results suggest that variations in select genes interact with a cognitive predisposition toward smoking. In susceptible adolescents, the impact of the genetic variants appears to be larger compared to committed never smokers.
Cell cycle progression contributes to the cellular response to DNA-damaging factors, such as chemotherapy and radiation. We hypothesized that the genetic variations in cell cycle pathway genes may modulate treatment responses and affect survival in patients with advanced non-small-cell lung cancer (NSCLC). We genotyped 374 single-nucleotide polymorphisms (SNPs) from 49 cell cycle-related genes in 598 patients with stages III–IV NSCLC treated with first-line platinum-based chemotherapy with/without radiation. We analyzed the individual and combined associations of these SNPs with survival and evaluated their gene–gene interactions using survival tree analysis. In the analysis of survival in all the patients, 39 SNPs reached nominal significance (P < 0.05) and 4 SNPs were significant at P <0.01. However, none of these SNPs remained significant after correction for multiple comparisons at a false discovery rate of 10%. In stratified analysis by treatment modality, after adjusting for multiple comparisons, nine SNPs in chemotherapy alone and one SNP in chemoradiation remained significant. The most significant SNP in chemotherapy group was CCNB2:rs1486878 [hazard ratio (HR) = 1.69, 95% confidence interval (CI), 1.25–2.30, P = 0.001]. TP73: rs3765701 was the only significant SNP in chemoradiation group (HR = 1.87; 95% CI = 1.35–2.59, P = 1.8 × 10−4). In cumulative analysis, we found a significant gene-dosage effect in patients receiving chemotherapy alone. Survival tree analysis demonstrated potential higher order gene–gene and gene–treatment interactions, which could be used to predict survival status based on distinct genetic signatures. These results suggest that genetic variations in cell cycle pathway genes may affect the survival of patients with stages III–IV NSCLC individually and jointly.
Genetic variants located at 15q25, including those in the cholinergic receptor nicotinic cluster (CHRNA5) have been implicated in both lung cancer risk and nicotine dependence in recent genome-wide association studies. Among these variants, a 22 base pair insertion/deletion, rs3841324 showed the strongest association with CHRNA5 mRNA expression levels. However the influence of rs3841324 on lung cancer risk has not been studied in depth.
We have therefore evaluated the association of rs3841324 genotypes with lung cancer risk in a case-control study of 624 Caucasian subjects with lung cancer and 766 age- and sex-matched cancer-free Caucasian controls. We also evaluated the joint effects of rs3841324 with single-nucleotide polymorphisms (SNPs) rs16969968 and rs8034191 in the 15q25 region that have been consistently implicated in lung cancer risk.
We found that the homozygous genotype with both short alleles (SS) of rs3841324 was associated with a decreased lung cancer risk in female ever smokers relative to the homozygous wild-type (LL) and heterozygous (LS) genotypes combined in a recessive model (OR adjusted = 0.55, 95% CI = 0.31–0.89, P = 0.0168). There was no evidence for a sex difference in the association between this variant and cigarettes smoked per day (CPD). Diplotype analysis of rs3841324 with either rs16969968 or rs8034191 showed that these polymorphisms influenced the lung cancer risk independently.
Conclusions and impact
This study has shown a sex difference in the association between the 15q25 variant rs3841324 and lung cancers. Further research is warranted to elucidate the mechanisms underlying these observations.
lung cancer; CHRNA5; Chromosome 15q25; rs3841324; sex-specific association
In an analysis of 31,717 cancer cases and 26,136 cancer-free controls drawn from 13 genome-wide association studies (GWAS), we observed large chromosomal abnormalities in a subset of clones from DNA obtained from blood or buccal samples. Mosaic chromosomal abnormalities, either aneuploidy or copy-neutral loss of heterozygosity, of size >2 Mb were observed in autosomes of 517 individuals (0.89%) with abnormal cell proportions between 7% and 95%. In cancer-free individuals, the frequency increased with age; 0.23% under 50 and 1.91% between 75 and 79 (p=4.8×10−8). Mosaic abnormalities were more frequent in individuals with solid-tumors (0.97% versus 0.74% in cancer-free individuals, OR=1.25, p=0.016), with a stronger association for cases who had DNA collected prior to diagnosis or treatment (OR=1.45, p=0.0005). Detectable clonal mosaicism was common in individuals for whom DNA was collected at least one year prior to diagnosis of leukemia compared to cancer-free individuals (OR=35.4, p=3.8×10−11). These findings underscore the importance of the role and time-dependent nature of somatic events in the etiology of cancer and other late-onset diseases.
ATM gene mutations have been implicated in many human cancers. However, the role of ATM polymorphisms in lung carcinogenesis is largely unexplored. We conducted a case-control analysis of 556 Caucasian non-small-cell lung cancer (NSCLC) patients and 556 controls frequency-matched on age, gender and smoking status. We genotyped 11 single nucleotide polymorphisms of the ATM gene and found that compared with the wild-type allele-containing genotypes, the homozygous variant genotypes of ATM08 (rs227060) and ATM10 (rs170548) were associated with elevated NSCLC risk with ORs of 1.55 (95% CI: 1.02–2.35) and 1.51 (0.99–2.31), respectively. ATM haplotypes and diplotypes were inferred using the Expectation-Maximization algorithm. Haplotype H5 was significantly associated with reduced NSCLC risk in former smokers with an OR of 0.47 (0.25–0.96) compared with the common H1 haplotype. Compared with the H1–H2 diplotype, H2–H2 and H3–H4 diplotypes were associated with increased NSCLC risk with ORs of 1.58 (0.99–2.54) and 2.29 (1.05–5.00), respectively. We then evaluated genotype–phenotype correlation in the control group using the comet assay to determine DNA damage and DNA repair capacity. Compared with individuals with at least 1 wild-type allele, the homozygous variant carriers of either ATM08 or ATM10 exhibited significantly increased DNA damage as evidenced by a higher mean value of the radiation-induced olive tail moment (ATM08: 4.86 ± 2.43 vs. 3.79 ± 1.51, p = 0.04; ATM10: 5.14 ± 2.37 vs. 3.79 ± 1.54, p = 0.01). Our study presents the first epidemiologic evidence that ATM genetic variants may affect NSCLC predisposition, and that the risk-conferring variants might act through down-regulating the functions of ATM in DNA repair activity upon genetic insults such as ionizing radiation.
ATM; polymorphism; haplotype; diplotype; NSCLC
A mediation model explores the direct and indirect effects between an independent variable and a dependent variable by including other variables (or mediators). Mediation analysis has recently been used to dissect the direct and indirect effects of genetic variants on complex diseases using case-control studies. However, bias could arise in the estimations of the genetic variant-mediator association because the presence or absence of the mediator in the study samples is not sampled following the principles of case-control study design. In this case, the mediation analysis using data from case-control studies might lead to biased estimates of coefficients and indirect effects. In this article, we investigated a multiple-mediation model involving a three-path mediating effect through two mediators using case-control study data. We propose an approach to correct bias in coefficients and provide accurate estimates of the specific indirect effects. Our approach can also be used when the original case-control study is frequency matched on one of the mediators. We employed bootstrapping to assess the significance of indirect effects. We conducted simulation studies to investigate the performance of the proposed approach, and showed that it provides more accurate estimates of the indirect effects as well as the percent mediated than standard regressions. We then applied this approach to study the mediating effects of both smoking and chronic obstructive pulmonary disease (COPD) on the association between the CHRNA5-A3 gene locus and lung cancer risk using data from a lung cancer case-control study. The results showed that the genetic variant influences lung cancer risk indirectly through all three different pathways. The percent of genetic association mediated was 18.3% through smoking alone, 30.2% through COPD alone, and 20.6% through the path including both smoking and COPD, and the total genetic variant-lung cancer association explained by the two mediators was 69.1%.
Chromosome 5p15.33 has been identified by genome-wide association studies as one of the regions that associate with lung cancer risk. A few single-nucleotide polymorphisms (SNPs) in the telomerase reverse transcriptase (TERT) and cleft lip and palate transmembrane 1-like (CLPTM1L) genes located in this region have shown consistent associations. We performed dense genotyping of SNPs in this region to refine the previously reported association signals for lung cancer risk. Two hundred and fifteen SNPs were genotyped on an Illumina iSelect panel, in a hospital-based case–control study of 1681 lung cancer cases and 1235 unaffected controls. Association was tested using unconditional logistic regression, while adjusting for age, sex and pack-years smoked. Furthermore, since many of the SNPs were in linkage disequilibrium (LD), haplotype blocks were constructed, from which tagging SNPs at an r2 threshold of ≥0.95 were included in a stepwise forward selection logistic regression model. Of the 215 SNPs, 69 were significant at P < 0.05 in univariate analysis; of these, 35 SNPs meeting the r2 threshold were included in the multiple logistic regression model. Two SNPs, rs370348 (odds ratio = 0.76, P = 1.6 × 10−6) and rs4975538 (odds ratio = 1.18, P = 0.005), significantly associated with risk in the overall sample. Among ever smokers, rs4975615 (odds ratio = 0.75, P = 1.2 × 10−4) and rs4975538 (odds ratio = 1.26, P = 0.002) were significant, whereas among never-smokers, rs451360 (odds ratio = 0.62, P = 7.6 × 10−5) was significant. We refined the consistent association signal in this region, allowing for the considerable LD between SNPs and identified four novel SNPs that were independently and significantly associated with lung cancer risk. Results of these analyses strongly suggest effects on risk from several loci in the TERT/CLPTM1L region.
We previously showed that select cytokine gene polymorphisms are a significant predictor for pain reported at initial presentation in 446 white patients newly diagnosed with non–small cell lung cancer. This follow-up study explores the extent to which polymorphisms in tumor necrosis factor-α (TNF- α-308 G/A), interleukin (IL)-6 −174G/C, and IL-8 −251T/A could explain variability in pain and analgesic response among those patients (n = 140) subsequently referred for pain treatment.
Pain severity (0, no pain; 10, worst pain) was assessed at initial consultation and at follow-up visit. The total dose of opioids at the time of first-follow up visit (30 days postconsult) was converted to an equivalent dose of parenteral morphine.
Forty-one percent (57 of 140) of the patients reported severe pain (score >7/10) at initial consultation (mean, 5.5), which significantly decreased to 25% (mean, 4) at first follow-up visit (McNemar = P < 0.001). Polymorphisms in TNF and IL-6 were significantly associated with pain severity (for TNF GG, 4.12; GA, 5.38; AA, 5.50; P = 0.04) and with morphine equivalent daily dose (IL-6 GG, 69.61; GC, 73.17; CC, 181.67; P = 0.004), respectively. Adjusting for demographic and clinical variables, variant alleles in TNFα −308 G/A remained significantly associated with pain severity (b = 0.226; P = 0.036) and carriers of the IL-6 −174C/C genotypes required 4.7 times higher dose of opioids for pain relief (odds ratio, 4.7; 95% confidence interval, 1.2;15.0) relative to GG and GC genotypes.
We provide preliminary evidence of the influence of cytokine genes on pain and response to analgesia in lung cancer patients. Additional studies are needed to validate our findings. The long-term application is to tailored pain therapies.
The magnitude of benefit is variable for advanced non-small cell lung cancer (NSCLC) patients receiving platinum-based chemotherapy. The purpose of this study is to determine whether genetic variations in the transforming growth factor-beta (TGF-β) pathway are associated with clinical outcomes in NSCLC patients receiving first-line platinum-based chemotherapy. Five hundred and ninety-eight advanced-stage NSCLC patients who received first-line platinum-based chemotherapy with or without radiotherapy were recruited at the MD Anderson Cancer Center between 1995 and 2007. DNA from blood was genotyped for 227 single nucleotide polymorphisms (SNPs) in 23 TGF-β pathway-related genes to evaluate their associations with overall survival. In individual SNP analysis, 22 variants were significantly associated with overall survival, of which the strongest associations were found for BMP2:rs235756 [hazard ratio (HR) = 1.45; 95% confidence interval (CI), 1.11–1.90] and SMAD3:rs4776342 (HR = 1.25; 95% CI, 1.06–1.47). Fifteen and 18 genetic loci displayed treatment-specific associations for chemotherapy and chemoradiation, respectively, identifying a majority of the cases who would be predicted to respond favorably to a specific treatment regimen. BMP2:rs235753 and a haplotype in SMAD3 were associated with overall survival for both treatment modalities. Cumulative effect analysis showed that multiple risk genotypes had a significant dose-dependent effect on overall survival (Ptrend = 2.44 x 10−15). Survival tree analysis identified subgroups of patients with dramatically different median survival times of 45.39 versus 13.55 months and 18.02 versus 5.89 months for high- and low- risk populations when treated with chemoradiation and chemotherapy, respectively. These results suggest that genetic variations in the TGF-β pathway are potential predictors of overall survival in NSCLC patients treated with platinum-based chemotherapy with or without radiation.
The double-strand break (DSB) repair capacity has been implicated in the survival of patients in several cancer types. However, little is known about the prognostic importance of the key DSB repair genes—ataxia-telangiectasia mutated (ATM), DNA-dependent protein kinase catalytic subunit (DNA-PKcs), and the Ku heterodimeric regulatory complex 86-kD subunit (Ku80)—in nonsmall cell lung cancer (NSCLC). To address this issue, the authors determined the messenger RNA (mRNA) expression of these genes in patients NSCLC and assessed their prognostic relevance.
mRNA expression levels of ATM, DNA-PKcs, and Ku80 were measured in tumor and adjacent normal tissues from 140 patients with NSCLC by using quantitative real-time polymerase chain reaction analysis. Then, a Cox proportional hazards regression model and Kaplan-Meier plots were used to evaluate the association between the tumor:normal (T/N) expression ratios of the 3 genes and the overall survival rate and duration in patients with NSCLC.
mRNA expression of ATM and DNA-PKcs, but not of Ku80, was significantly higher in tumor tissues than in adjacent normal tissues (P = .003 and P < .001, respectively). The high T/N expression ratios of ATM and DNA-PKcs were associated significantly with a 1.82-fold increased risk of death (95% confidence interval, 1.05–2.70) and a 2.13-fold increased risk of death (95% confidence interval, 1.21–3.76), respectively. However, no significant association with risk was observed for Ku80. Kaplan-Meier analyses revealed that patients with high T/N expression ratios of ATM or DNA-PKcs had notably shorter median survival than patients with low ratios.
The current findings suggested that the T/N expression ratios of ATM and DNA-PKcs may be useful for identifying NSCLC patients with a poor prognosis who may benefit from more aggressive therapy.
DNA repair; DNA double-strand break; nonsmall cell lung cancer; prognosis