Rational drug design based on molecular targets is starting to revolutionize cancer care. To maximize its potential for patients, a concomitant leveraging of molecular knowledge for selection of patients to future and current therapeutic options is paramount. The terms “individualized”, “personalized”, or “precision therapy” are currently used to describe these efforts. Here, we summarize current knowledge for selection of systemic targeted and cytotoxic therapy for patients with non-small-cell lung cancer. Based on this knowledge, we present a potential decision algorithm to best select patients for currently available therapies, which include the treatment options single-agent erlotinib or gefitinib, the ALK inhibitor crizotinib, double agent gemcitabine and platinum, double agent platinum and pemetrexed, and as a default option a taxane combined with a non-platinum drug, for instance a vinca alkaloid. The addition of bevacizumab to double-agent chemotherapy is also discussed. Currently available data on predictive biomarkers are largely based on subgroup or companion biomarker analyses of patient cohorts or clinical trials. Current and emerging markers must be incorporated prospectively into the design of clinical trials that test novel and established agents to better understand their clinical utility and to refine selection parameters and marker interactions. Future development will lead to increasing complexity in clinical decision making with substantial anticipated benefits to patients including increased therapeutic efficacy, reduced toxicity, and better quality of life.
Lung cancer; ERCC1; RRM1; TS; EGFR; EML4-ALK; Crizotinib; Bevacizumab
Chronic obstructive pulmonary disease (COPD) and lung cancer represent two diseases that share a strong risk factor in smoking, and COPD increases risk of lung cancer even after adjusting for the effects of smoking. These diseases not only occur jointly within an individual but also there is evidence of shared occurrence within families. Understanding the genetic contributions to these diseases, both individually and jointly, is needed to identify the highest risk group for screening and targeted prevention, as well as aiding in the development of targeted treatments. The chromosomal regions that have been identified as being associated either jointly or independently with lung cancer, COPD, nicotine addiction, and lung function are presented. Studies jointly measuring genetic variation in lung cancer and COPD have been limited by the lack of detailed COPD diagnosis and severity data in lung cancer populations, the lack of lung cancer–specific phenotypes (histology and tumor markers) in COPD populations, and the lack of inclusion of minorities. African Americans, who smoke fewer cigarettes per day and have different linkage disequilibrium and disease patterns than whites, and Asians, also with different patterns of exposure to lung carcinogens and linkage patterns, will provide invaluable information to better understand shared and independent genetic contributions to lung cancer and COPD to more fully define the highest risk group of individuals who will most benefit from screening and to develop molecular signatures to aid in targeted treatment and prevention efforts.
lung cancer; COPD; smoking; genetics
Amplification of the fibroblast growth factor receptor 1 (FGFR1) gene has been described in tumors of non-small-cell lung cancer (NSCLC) patients. Prior reports showed conflicting rates of amplification frequency and clinical relevance.
Materials and Methods
We developed a reliable real-time quantitative PCR assay to assess the frequency of FGFR1 amplification and assessed the optimal cutoff level of amplification for clinical application.
In a training cohort of 203 NSCLCs, we established that a 3.5-fold amplification optimally divided patients into groups with different survival rates with a clear threshold level. Those with FGFR1 amplification levels above 3.5-fold had an inferior survival. These data were confirmed in a validation cohort of 142 NSCLC. After adjusting for age, sex, performance status, stage, and histology, patients with FGFR1 amplification levels above 3.5 fold had a hazard ratio of 2.91 (95% CI- 1.14, 7.41; pvalue-0.025) for death in the validation cohort. The rates of FGFR1 amplification using the cutoff level of 3.5 were 5.1% in squamous cell and 4.1% in adenocarcinomas. There was a non-significant trend towards higher amplifications rates in heavy smokers (> 15 pack-years of cigarette consumption) as compared to light smokers.
Our data suggest that a 3.5-fold amplification of FGFR1 is of clinical importance in NSCLC. Our cutpoint analysis showed a clear threshold effect for the impact of FGFR1 amplification on patients’ survival, which can be used as an initial guide for patient selection in trials assessing efficacy of novel FGFR inhibitors.
To clarify the role of previous lung diseases (chronic bronchitis, emphysema, pneumonia, and tuberculosis) in the development of lung cancer, the authors conducted a pooled analysis of studies in the International Lung Cancer Consortium. Seventeen studies including 24,607 cases and 81,829 controls (noncases), mainly conducted in Europe and North America, were included (1984–2011). Using self-reported data on previous diagnoses of lung diseases, the authors derived study-specific effect estimates by means of logistic regression models or Cox proportional hazards models adjusted for age, sex, and cumulative tobacco smoking. Estimates were pooled using random-effects models. Analyses stratified by smoking status and histology were also conducted. A history of emphysema conferred a 2.44-fold increased risk of lung cancer (95% confidence interval (CI): 1.64, 3.62 (16 studies)). A history of chronic bronchitis conferred a relative risk of 1.47 (95% CI: 1.29, 1.68 (13 studies)). Tuberculosis (relative risk = 1.48, 95% CI: 1.17, 1.87 (16 studies)) and pneumonia (relative risk = 1.57, 95% CI: 1.22, 2.01 (12 studies)) were also associated with lung cancer risk. Among never smokers, elevated risks were observed for emphysema, pneumonia, and tuberculosis. These results suggest that previous lung diseases influence lung cancer risk independently of tobacco use and that these diseases are important for assessing individual risk.
bronchitis; chronic; emphysema; lung diseases; lung neoplasms; meta-analysis; pneumonia; pulmonary disease; chronic obstructive; tuberculosis
Prior studies indicate that use of aspirin or other nonsteroidal anti-inflammatory drugs (NSAID) is associated with a decreased risk of non-small cell lung cancer (NSCLC); however, results have been contradictory in part because of variation in study design. Few studies have examined the use of aspirin or other NSAIDs on risk of NSCLC in women.
Through a case-control study of African American and Caucasian women with and without NSCLC, we examined the relationship between use of aspirin, NSAIDs, and acetaminophen and risk of NSCLC. Risk was estimated by calculating odds ratios and 95% confidence intervals for ever/never use, duration of use, and duration of use category (never, 1–5 years, >5 years) after adjusting for major risk factors for lung cancer. Risk estimates were stratified by race, age, smoking history, and body mass index.
Ever use of adult-strength aspirin was associated with a significant reduction in risk of NSCLC (odds ratio, 0.66; 95% confidence interval, 0.46–0.94). Additionally, there was a significant trend toward a reduced risk of NSCLC in adult-strength aspirin users with increasing duration of use (Ptrend = 0.02). In stratified analyses, aspirin use was associated with a significantly reduced risk of lung cancer among Caucasians and 55- to 64-year-olds. Baby aspirin and NSAID use was associated with a significant reduction in risk of NSCLC only among 65- to 74-year-olds.
Our results suggest that long-term use of adult-strength aspirin may reduce the risk of NSCLC in women.
Studies on the relationships between inflammatory pathway genes and lung cancer risk have not included African-Americans and have only included a handful of genes. In a population-based case-control study on 198 African-American and 744 Caucasian women, we examined the association between 70 cytokine and cytokine receptor single-nucleotide polymorphisms (SNPs) and risk of non–small cell lung cancer (NSCLC). Unconditional logistic regression was used to estimate odds ratios and 95% confidence intervals in a dominant model adjusting for major risk factors for lung cancer. Separate analyses were conducted by race and by smoking history and history of chronic obstructive pulmonary disease among Caucasians. Random forest analysis was conducted by race. On logistic regression analysis, IL6 (interleukin 6), IL7R, IL15, TNF (tumor necrosis factor), and IL10 SNP were associated with risk of non–small cell lung cancer among African-Americans; IL7R and IL10 SNPs were also associated with risk of lung cancer among Caucasians. Although random forest analysis showed IL7R and IL10 SNPs as being associated with risk for lung cancer among African-Americans, it also identified TNFRSF10A SNP as an important predictor. On random forest analysis, an IL1A SNP was identified as an important predictor of lung cancer among Caucasian women. Inflammatory SNPs differentially predicted risk for NSCLC according to race, as well as based on smoking history and history of chronic obstructive pulmonary disease among Caucasian women. Pathway analysis results are presented. Inflammatory pathway genotypes may serve to define a high risk group; further exploration of these genes in minority populations is warranted.
Three genome-wide association studies identified a region on chromosome 15q25.1 associated with lung cancer and measures of nicotine addiction. This region includes nicotinic acetylcholine receptor subunit genes CHRNA3 and CHRNA5. These studies were conducted in European or European American populations and do not provide risk estimates for African Americans. The goal of this study was to determine whether recently identified genetic variation in 3 SNPs (rs1051730, rs931794, rs8034191) on chromosome 15q25.1 contributes to risk of lung cancer in African Americans.
Data were derived from three case-control studies. Participants included 1058 population-based non-small cell lung cancer cases selected from the Detroit area SEER registry and 1314 controls matched within study by age, race, and sex. Thirty-nine percent of participants were African American.
Risk associated with rs1051730 (odds ratio 1.59; 95% confidence interval 1.16–2.19) and rs931794 (odds ratio 1.39; 95% confidence interval 1.09–1.78) increased in ever smoking African Americans adjusting for cigarettes smoked per day. Among white cases, the number of cigarettes smoked varied by genotype at all three SNPs, and when smoking quantity was included in the models, risk was not significantly associated with any of the three SNPs.
These findings suggest that SNPs in the CHRNA3 and CHRNA5 region contribute to lung cancer risk, and while variant alleles are less frequent in African Americans, risk in this group may be greater than in whites and less likely to reflect an indirect effect on lung cancer risk through nicotine dependence.
Non-small cell lung cancer; Smoking; SNPs
Background and Methods
Familial aggregation of lung cancer exists after accounting for cigarette smoking. However, the extent to which family history affects risk by smoking status, histology, relative type and ethnicity is not well described. This pooled analysis included 24 case-control studies in the International Lung Cancer Consortium. Each study collected age of onset/interview, gender, race/ethnicity, cigarette smoking, histology and first-degree family history of lung cancer. Data from 24,380 lung cancer cases and 23,305 healthy controls were analyzed. Unconditional logistic regression models and generalized estimating equations were used to estimate odds ratios and 95% confidence intervals.
Individuals with a first-degree relative with lung cancer had a 1.51-fold increase in risk of lung cancer, after adjustment for smoking and other potential confounders(95% CI: 1.39, 1.63). The association was strongest for those with a family history in a sibling, after adjustment (OR=1.82, 95% CI: 1.62, 2.05). No modifying effect by histologic type was found. Never smokers showed a lower association with positive familial history of lung cancer (OR=1.25, 95% CI: 1.03, 1.52), slightly stronger for those with an affected sibling (OR=1.44, 95% CI: 1.07, 1.93), after adjustment.
The increased risk among never smokers and similar magnitudes of the effect of family history on lung cancer risk across histological types suggests familial aggregation of lung cancer is independent of those associated with cigarette smoking. While the role of genetic variation in the etiology of lung cancer remains to be fully characterized, family history assessment is immediately available and those with a positive history represent a higher risk group.
We aimed at extending the natural and orthogonal interaction (NOIA) framework, developed for modeling gene-gene interactions in the analysis of quantitative traits, to allow for reduced genetic models, dichotomous traits, and gene-environment interactions. We evaluate the performance of the NOIA statistical models using simulated data and lung cancer data.
The NOIA statistical models are developed for the additive, dominant, recessive genetic models, and a binary environmental exposure. Using the Kronecker product rule, a NOIA statistical model is built to model gene-environment interactions. By treating the genotypic values as the logarithm of odds, the NOIA statistical models are extended to the analysis of case-control data.
Our simulations showed that power for testing associations while allowing for interaction using the statistical model is much higher than using functional models for most of the scenarios we simulated. When applied to the lung cancer data, much smaller P-values were obtained using the NOIA statistical model for either the main effects or the SNP-smoking interactions for some of the SNPs tested.
The NOIA statistical models are usually more powerful than the functional models in detecting main effects and interaction effects for both quantitative traits and binary traits.
Statistical power; Genetic association studies; Case-control association analysis; Gene-environment interaction; Environmental risk factor; Association mapping; Orthogonal modeling
Genome-wide sequencing identified heterozygous, constitutional, Ataxia telangiectaisa mutated (ATM) gene mutations in two kindreds with familial pancreatic cancer. Mutations segregated with disease in both kindreds and tumor analysis demonstrated LOH of the wildtype allele. Sequence analysis of an additional 166 familial pancreatic cancer probands indentified four additional patients with deleterious mutations in the ATM gene, while no deleterious mutations were identified in 190 spouse controls (p=0.046). These results indicate that ATM mutations play an important role in familial pancreatic cancer predisposition.
ATM; predisposition; familial; pancreas; cancer
Airflow obstruction and/or emphysema have been associated with lung cancer risk, however this relationship and the joint occurrence of these conditions are not well studied in the African American population.
Describe the prevalence of airflow obstruction and/or emphysema in African Americans with lung cancer and evaluate their impact on the management and outcome of lung cancer.
Medical records were reviewed for 114 African Americans who had participated in population-based case-control studies of lung cancer and who sought medical care at the Karmanos Cancer Center in Detroit, Michigan. The medical records of these patients were reviewed for demographics, type and stage of lung cancer, spirometry, treatment and outcome. The chest CT scans around the time of the diagnosis of lung cancer were reviewed by a radiologist for evidence of emphysema. COPD was diagnosed when there were changes consistent with emphysema on CT scan and/or airflow obstruction by spirometry.
There were no differences by sex for age at lung cancer diagnosis (p=0.78) and tumor histology (p=0.43). Men were more likely to present at a later stage of lung cancer diagnosis compared to women (p=0.04) and women were more likely to have surgery than men (p=0.03). Overall, 94% of men and 78% of women in this population had spirometry and/or CT evidence of COPD. Men were somewhat more likely to have COPD diagnosed by either CT or spirometry than women (p=0.06), but the GOLD Classification scores did not differ by gender among those with spirometry-diagnosed COPD (p=0.34). Seventy eight percent of individuals who did not report a previous diagnosis of COPD had clinical evidence of COPD, whereas 94% of individuals who reported a previous diagnosis of COPD also had clinical evidence of COPD (p=0.03). Among individuals who had both spirometry and CT data available, 29% had CT evidence of emphysema but normal spirometry. No differences in COPD diagnosis (p=0.82) or emphysema diagnosis (p=0.51) were noted by tumor histology. Stage at diagnosis also did not differ by COPD or emphysema diagnosis (p=0.30 and p=0.06, respectively), nor did treatment modality (p=0.54 and p=0.10, respectively). Lung cancer patients with COPD diagnosed either via spirometry or CT did not show an increased risk of death compared to lung cancer patients without COPD after adjusting for age at diagnosis, gender and stage (HR=1.31 95% CI: 0.68-2.53).
There is a high incidence of COPD, emphysema in particular, in a selected group of African American patients with lung cancer. A significant number of these patients were not aware that they had COPD. There was no significant difference in the outcome of lung cancer in relation to the presence or absence of COPD.
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
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.
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.
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_T, A_C, and G_C) and provided stronger evidence for association of 15q24–25.1 with lung cancer (P = 9.72 × 10−9). These two variants represent three levels of risk associated with lung cancer. The most common haplotype G_T is neutral; the haplotype A_C is associated with increased risk for lung cancer with 5.0% higher frequency in cases than in controls [P = 1.68 × 10−7; odds ratio (OR), 1.24; 95% confidence interval (95% CI), 1.14–1.35]; whereas the haplotype G_C is associated with reduced risk for lung cancer with 4.4% lower frequency in cases than in controls (P = 7.39 × 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 × 10−11; OR, 1.60; 95% CI, 1.46–1.74; rs481134: P = 7.01 × 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.
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
Lung cancer continues to be the leading cause of cancer death, and although most lung cancer is attributable to cigarette smoking, underlying genetic susceptibility is suggested by studies demonstrating familial aggregation. The first family linkage study of lung cancer has identified linkage of lung, laryngeal, and pharyngeal cancer in families to a region on chromosome 6q23–25. Because lung cancer and chronic obstructive pulmonary disease (COPD) are known to aggregate in families beyond shared risk associated with smoking, the linkage results are compared and contrasted with results from genomewide linkage and association studies and candidate gene studies searching for genes for lung cancer, lung function, and COPD. Linkage on chromosome 6q to both lung cancer and lung function, and on 12 to lung cancer, COPD, and lung function, together with overlap in candidate genes for these outcomes, suggests that future research into underlying genetic mechanisms of lung disease would benefit from broadening the collection of family history data and better defining the “high risk” population. As familial risk of lung disease is better defined, referral into screening programs and prevention trials can be better targeted to reach families with both a history of lung cancer and COPD.
chronic obstructive pulmonary disease; genetics; linkage; lung cancer
The detection of mutations in the epidermal growth factor receptor (EGFR) gene, which predict sensitivity to treatment with EGFR tyrosine kinase inhibitors (TKIs), represents a major advance in the treatment of lung adenocarcinoma. KRAS mutations confer resistance to EGFR -TKIs. The prevalence of these mutations in African-American patients has not been thoroughly investigated.
We collected formalin-fixed, paraffin-embedded material from resected lung adenocarcinomas from African-American patients at three institutions for DNA extraction. The frequencies of EGFR exon 19 deletions, exon 21 L858R substitutions and KRAS mutations in tumor specimens from African-American patients were compared to data in Caucasian patients (n=476).
EGFR mutations were detected in 23 of the 121 specimens from African-American patients (19%, 95% CI 13–27%), while KRAS mutations were found in 21 (17%, 95% CI 12−25%). There was no significant difference between frequencies of EGFR mutations comparing African-American and Caucasian patients, 19% vs. 13% (61/476, 95% CI 10–16%) (p=0.11). KRAS mutations were more likely among Caucasians, 26% (125/476, 95% CI 23−30%) (p=0.04).
This is the largest study to date examining the frequency of mutations in lung adenocarcinomas in African-Americans. Although KRAS mutations were somewhat less likely, there was no difference between the frequencies of EGFR mutations in African-American patients as compared to Caucasians. These results suggest that all patients with advanced lung adenocarcinomas should undergo mutational analysis prior to initiation of therapy.
EGFR mutation; KRAS; African-Americans; racial differences
Lung cancer continues to be the leading cause of cancer death in the USA and the best example of a cancer with undisputed evidence of environmental risk. However, a genetic contribution to lung cancer has also been demonstrated by studies of familial aggregation, family-based linkage, candidate gene studies and most recently genome-wide association studies (GWAS). The African-American population has been underrepresented in these genetic studies and has patterns of cigarette use and linkage disequilibrium that differ from patterns in other populations. Therefore, studies in African-Americans can provide complementary data to localize lung cancer susceptibility genes and explore smoking dependence-related genes. We used admixture mapping to further characterize genetic risk of lung cancer in a series of 837 African-American lung cancer cases and 975 African-American controls genotyped at 1344 ancestry informative single-nucleotide polymorphisms. Both case-only and case–control analyses were conducted using ADMIXMAP adjusted for age, sex, pack-years of smoking, family history of lung cancer, history of emphysema and study site. In case-only analyses, excess European ancestry was observed over a wide region on chromosome 1 with the largest excess seen at rs6587361 for non-small-cell lung cancer (NSCLC) (Z-score = −4.33; P = 1.5 × 10−5) and for women with NSCLC (Z-score = −4.82; P = 1.4 × 10−6). Excess African ancestry was also observed on chromosome 3q with a peak Z-score of 3.33 (P = 0.0009) at rs181696 among ever smokers with NSCLC. These results add to the findings from the GWAS in Caucasian populations and suggest novel regions of interest.
Epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer predict response to tyrosine kinase inhibitors (TKIs). Mutations occur more commonly in never-smokers and East Asians but there are conflicting reports on the frequency of EGFR mutations in tumors from African Americans.
Tumors from 67 African American and 77 Caucasian participants in previous case-control studies of lung cancer were selected to determine EGFR mutational status. Mutation analysis was performed using the Sequenom mass array analyzer (Sequenom, San Diego, CA).
Overall, 13.9% of the study population carried an EGFR mutation. EGFR mutations occurred in 11.9% of tumors from African Americans compared with 15.6% in Caucasians (p=0.53). All mutations found in African Americans were deletions in exon 19. The majority of mutations were found in non-smokers among both African Americans (7/8) and Caucasians (8/12).
These results indicate that African Americans with non-small cell lung cancer (NSCLC) harbor somatic EGFR mutations at a frequency similar to Caucasians with NSCLC. Thus, clinicians should not use race as a clinical decision parameter for the use of EGFR-TKIs.
EGFR mutation; race; African American; lung cancer
Genetic susceptibility for cancer can differ substantially among families. We use trait-related covariates to identify a genetically homogeneous subset of families with the best evidence for linkage in the presence of heterogeneity.
We performed a genome-wide linkage screen in 93 families. Samples and data were collected by the familial lung cancer recruitment sites of the Genetic Epidemiology of Lung Cancer Consortium. We estimated linkage scores for each family by the Markov chain Monte Carlo procedure using SimWalk2 software. We used ordered subset analysis (OSA) to identify genetically homogenous families by ordering families based on a disease-associated covariate. We performed permutation tests to determine the relationship between the trait-related covariate and the evidence for linkage.
A genome-wide screen for lung cancer loci identified strong evidence for linkage to 6q23-25 and suggestive evidence for linkage to 12q24 using OSA, with peak logarithm of odds (LOD) scores of 4.19 and 2.79, respectively. We found other chromosomes also suggestive for linkages, including 5q31-q33, 14q11, and 16q24.
Our OSA results support 6q as a lung cancer susceptibility locus and provide evidence for disease linkage on 12q24. This study further increased our understanding of the inheritability for lung cancer. Validation studies using larger sample size are needed to verify the presence of several other chromosomal regions suggestive of an increased risk for lung cancer and/or other cancers.
OSA can reduce genetic heterogeneity in linkage study and may assist in revealing novel susceptibility loci.
Ordered subset analysis; lung cancer; cancer susceptibility genes; linkage analysis; standardized incidence ratio
In developed countries, the lifetime risk of developing colorectal cancer (CRC) is 5%, and it is the second leading cause of death from cancer. The presence of family history is a well established risk factor with 25-35% of CRCs attributable to inherited and/or familial factors. The highly penetrant inherited colon cancer syndromes account for approximately 5%, leaving greater than 20% without clear genetic definition. Familial colorectal cancer has been linked to chromosome 7q31 by multiple affected relative pair studies. The MET proto-oncogene which resides in this chromosomal region is considered a candidate for genetic susceptibility.
MET exons were amplified by PCR from germline DNA of 148 affected sibling pairs with colorectal cancer. Amplicons with altered sequence were detected with high-resolution melt-curve analysis using a LightScanner (Idaho Technologies). Samples demonstrating alternative melt curves were sequenced. A TaqMan assay for the specific c.2975C >T change was used to confirm this mutation in a cohort of 299 colorectal cancer cases and to look for allelic amplification in tumors.
Here we report a germline non-synonymous change in the MET proto-oncogene at amino acid position T992I (also reported as MET p.T1010I) in 5.2% of a cohort of sibling pairs affected with CRC. This genetic variant was then confirmed in a second cohort of individuals diagnosed with CRC and having a first degree relative with CRC at prevalence of 4.1%. This mutation has been reported in cancer cells of multiple origins, including 2.5% of colon cancers, and in <1% in the general population. The threonine at amino acid position 992 lies in the tyrosine kinase domain of MET and a change to isoleucine at this position has been shown to promote metastatic behavior in cell-based models. The average age of CRC diagnosis in patients in this study is 63 years in mutation carriers, which is 8 years earlier than the general population average for CRC.
Although the MET p.T992I genetic mutation is commonly found in somatic colorectal cancer tissues, this is the first report also implicating this MET genetic mutation as a germline inherited risk factor for familial colorectal cancer. Future studies on the cancer risks associated with this mutation and the prevalence in different at-risk populations will be an important extension of this work to define the clinical significance.
In the Women's Health Initiative (WHI) randomized controlled trial, use of estrogen plus progestin increased lung cancer mortality. We conducted post hoc analyses in the WHI trial evaluating estrogen alone to determine whether use of conjugated equine estrogen without progestin had a similar adverse influence on lung cancer.
The WHI study is a randomized, double-blind, placebo-controlled trial conducted in 40 centers in the United States. A total of 10 739 postmenopausal women aged 50–79 years who had a previous hysterectomy were randomly assigned to receive a once-daily 0.625-mg tablet of conjugated equine estrogen (n = 5310) or matching placebo (n = 5429). Incidence and mortality rates for all lung cancers, small cell lung cancers, and non–small cell lung cancers in the two randomization groups were compared by use of hazard ratios (HRs) and 95% confidence intervals (CIs) that were estimated from Cox proportional hazards regression analyses. Analyses were by intention to treat, and all statistical tests were two-sided.
After a mean of 7.9 years (standard deviation = 1.8 years) of follow-up, 61 women in the hormone therapy group were diagnosed with lung cancer compared with 54 in the placebo group (incidence of lung cancer per year = 0.15% vs 0.13%, respectively; HR of incidence = 1.17, 95% CI = 0.81 to 1.69, P = .39). Non–small cell lung cancers were of comparable number, stage, and grade in both groups. Deaths from lung cancer did not differ between the two groups (34 vs 33 deaths in estrogen and placebo groups, respectively; HR of death = 1.07, 95% CI = 0.66 to 1.72, P = .79).
Unlike use of estrogen plus progestin, which increased deaths from lung cancer, use of conjugated equine estrogen alone did not increase incidence or death from lung cancer.
Approximately 10% of pancreatic ductal adenocarcinomas have a familial basis. While a small portion of this familial clustering can be explained by inherited mutations in known genes (BRCA2, p16/CDKN2A, PRSS1, and STK11), the genetic basis for the majority of this familial clustering remains unknown. In addition, a pancreatic cancer susceptibility locus has been reported to be linked to chromosome 4q32-34 in a single family having a high penetrance of early-onset pancreatic ductal adenocarcinoma and pancreatic insufficiency. The goal of this study is to determine if linkage to chromosome 4q exists in our series of well-characterized families with idiopathic familial pancreatic cancer enrolled in the Pancreatic Cancer Genetic Epidemiology Consortium (PACGENE).
Parametric and nonparametric linkage analyses were performed using 21 microsatellite markers on chromosome 4 on affected individuals with pancreatic cancer from 42 familial pancreatic cancer kindreds.
Markov Chain Monte Carlo parametric and nonparametric linkage analyses using SIMWALK2 as well as nonparametric linkage analysis using MERLIN did not provide strong evidence of linkage in this region (LOD < 1.0). Only one family provided a multipoint LOD score of >0.5 adjacent to the reported region.
Our results do not support linkage to the 4q32-34 region in the majority of our familial pancreatic cancer kindreds. However, because multiple pancreatic cancer susceptibility genes are likely to exist, it is possible that a subset of the families in this study may be linked to this region.
pancreatic cancer; genetics; linkage analysis; adenocarcinoma; familial pancreatic cancer; hereditary; gastrointestinal cancer
Genome-wide association studies have identified three chromosomal regions at 15q25, 5p15, and 6p21 as being associated with the risk of lung cancer. To confirm these associations in independent studies and investigate heterogeneity of these associations within specific subgroups, we conducted a coordinated genotyping study within the International Lung Cancer Consortium based on independent studies that were not included in previous genome-wide association studies.
Genotype data for single-nucleotide polymorphisms at chromosomes 15q25 (rs16969968, rs8034191), 5p15 (rs2736100, rs402710), and 6p21 (rs2256543, rs4324798) from 21 case–control studies for 11 645 lung cancer case patients and 14 954 control subjects, of whom 85% were white and 15% were Asian, were pooled. Associations between the variants and the risk of lung cancer were estimated by logistic regression models. All statistical tests were two-sided.
Associations between 15q25 and the risk of lung cancer were replicated in white ever-smokers (rs16969968: odds ratio [OR] = 1.26, 95% confidence interval [CI] = 1.21 to 1.32, Ptrend = 2 × 10−26), and this association was stronger for those diagnosed at younger ages. There was no association in never-smokers or in Asians between either of the 15q25 variants and the risk of lung cancer. For the chromosome 5p15 region, we confirmed statistically significant associations in whites for both rs2736100 (OR = 1.15, 95% CI = 1.10 to 1.20, Ptrend = 1 × 10−10) and rs402710 (OR = 1.14, 95% CI = 1.09 to 1.19, Ptrend = 5 × 10−8) and identified similar associations in Asians (rs2736100: OR = 1.23, 95% CI = 1.12 to 1.35, Ptrend = 2 × 10−5; rs402710: OR = 1.15, 95% CI = 1.04 to 1.27, Ptrend = .007). The associations between the 5p15 variants and lung cancer differed by histology; odds ratios for rs2736100 were highest in adenocarcinoma and for rs402710 were highest in adenocarcinoma and squamous cell carcinomas. This pattern was observed in both ethnic groups. Neither of the two variants on chromosome 6p21 was associated with the risk of lung cancer.
In this international genetic association study of lung cancer, previous associations found in white populations were replicated and new associations were identified in Asian populations. Future genetic studies of lung cancer should include detailed stratification by histology.