Sulfamate proton solvent exchange in heparin oligosaccharides: evidence for a persistent hydrogen bond in the antithrombin-binding pentasaccharide Arixtra

Sulfamate groups (NHSO(3)(-)) are important structural elements in the glycosaminoglycans (GAGs) heparin and heparan sulfate (HS). In this work, proton nuclear magnetic resonance (NMR) line-shape analysis is used to explore the solvent exchange properties of the sulfamate NH groups within heparin-related mono-, di-, tetra- and pentasaccharides as a function of pH and temperature. The results of these experiments identified a persistent hydrogen bond within the Arixtra (fondaparinux sodium) pentasaccharide between the internal glucosamine sulfamate NH and the adjacent 3-O-sulfo group. This discovery provides new insights into the solution structure of the Arixtra pentasaccharide and suggests that 3-O-sulfation of the heparin N-sulfoglucosamine (GlcNS) residues pre-organize the secondary structure in a way that facilitates binding to antithrombin-III. NMR studies of the GlcNS NH groups can provide important information about heparin structure complementary to that available from NMR spectral analysis of the carbon-bound protons.

How the genetics of lung cancer may overlap with COPD

Over the last 30years, epidemiological studies have shown that COPD is the single most important risk factor for lung cancer after smoking exposure. Recent genetic studies using genome-wide approaches suggest that the genetic risk factors predisposing smokers to COPD and lung cancer may overlap. The genes identified by these studies suggest that this overlapping genetic susceptibility may be mediated through receptors expressed on the bronchial epithelium that implicate molecular pathways underlying both COPD and lung cancer. Furthermore, it appears that aberrant inflammatory and/or immune-modulatory pathways leading to excess matrix metalloproteinases, growth factors and airway remodelling in COPD may also be promoting malignant transformation of the bronchial epithelium. The process linking inflammation, remodelling and cancer formation is called epithelial-mesenchymal transition. There are several clinical implications arising from the COPD-lung cancer overlap. First, if COPD is a precursor disease to lung cancer then efforts to prevent COPD, might be even more important. Second, if drugs targeting the overlapping molecular pathways can be identified, chemoprevention that reduce the propensity to COPD and lung cancer is an attractive option. Finally, if low-dose computerized tomography can identify treatable lung cancer, gene-based tests of susceptibility might help identify those smokers who should undergo radiological screening.

GSTM1 null genotype in COPD and lung cancer: evidence of a modifier or confounding effect?

Background

Studies over the past two decades have reported associations between GSTM1 (glutathione S-transferase mu 1) null genotype and chronic obstructive pulmonary disease (COPD) or lung cancer. However, a modifier or confounding effect from COPD mediating the GSTM1 association with lung cancer has not been previously explored.

Aim and methods

This variant was examined in a case-control study of current or former smokers with COPD (n = 669), lung cancer (n = 454), or normal lung function (n = 488). Sex, age, and smoking history were comparable between groups.

Results

The GSTM1 null genotype was found to be more frequent in smokers with COPD alone (odds ratio [OR] 1.30, 95% confidence interval [CI] 1.02–1.66, P = 0.031) and lung cancer (OR 1.26, 95% CI 0.96–1.65, P = 0.083) than in matched smokers with normal lung function (62%, 61%, and 56%, respectively). However, when smokers with lung cancer were subgrouped according to the presence of COPD, then the association with all COPD subjects (OR 1.34, 95% CI 1.07–1.70, P = 0.010) and with COPD and lung cancer (OR 1.50, 95% CI 1.06–2.12, P = 0.018) continued to be significant while that with lung cancer only was reduced (OR 1.11, 95% CI 0.78–1.56, P = 0.55). These associations were independent of age, sex, height, lung function, and smoking history.

Conclusion

Findings suggest that COPD is an important subphenotype of lung cancer and may underlie previously reported associations with the GSTM1 null genotype.

Genetic evidence linking lung cancer and COPD: a new perspective

Epidemiological studies indicate that tobacco smoke exposure accounts for nearly 90% of cases of chronic obstructive pulmonary disease (COPD) and lung cancer. However, genetic factors may explain why 10%–30% of smokers develop these complications. This perspective reviews the evidence suggesting that COPD is closely linked to susceptibility to lung cancer and outlines the potential relevance of this observation. Epidemiological studies show that COPD is the single most important risk factor for lung cancer among smokers and predates lung cancer in up to 80% of cases. Genome-wide association studies of lung cancer, lung function, and COPD have identified a number of overlapping “susceptibility” loci. With stringent phenotyping, it has recently been shown that several of these overlapping loci are independently associated with both COPD and lung cancer. These loci implicate genes underlying pulmonary inflammation and apoptotic processes mediated by the bronchial epithelium, and link COPD with lung cancer at a molecular genetic level. It is currently possible to derive risk models for lung cancer that incorporate lung cancer-specific genetic variants, recently identified “COPD-related” genetic variants, and clinical variables. Early studies suggest that single nucleotide polymorphism-based risk stratification of smokers might help better target novel prevention and early diagnostic strategies in lung cancer.

Chromosome 4q31 locus in COPD is also associated with lung cancer

Chronic obstructive pulmonary disease (COPD) is the single greatest risk factor for lung cancer in smokers and is found in 50-90% of lung cancer cases. The link between COPD and lung cancer may stem in part from the matrix remodelling and repair processes underlying COPD, and the development of epithelial-mesenchymal transition (EMT) that underlies lung carcinogenesis. The Hedgehog-interacting protein (HHIP), which mediates the epithelial response (EMT) to smoking, has been implicated in COPD and lung cancer. Recent genome-wide and candidate gene studies of COPD implicate genetic variants on the chromosomal 4q31 (HHIP/glycophorin A (GYPA)) locus. In a case-control study of smokers with normal lung function, COPD and lung cancer (subphenotyped for COPD), we show the GG genotype of the rs 1489759 HHIP single-nucleotide polymorphism (SNP) and the CC genotype of the rs 2202507 GYPA SNP confers a "protective" effect on COPD (OR 0.59, p = 0.006 for HHIP and OR = 0.65, p = 0.006 for GYPA) and lung cancer (OR = 0.70 (p = 0.05) for HHIP and OR 0.70 (p = 0.02) for GYPA). This study suggests that, in smokers, genetic variants of the 4q31 locus conferring a protective effect for COPD are also protective in lung cancer. We conclude that genetic susceptibility to lung cancer includes COPD-related gene variants.

Pharmacological actions of statins: potential utility in COPD

Chronic obstructive pulmonary disease (COPD) is characterised by minimally reversible airflow limitation and features of systemic inflammation. Current therapies for COPD have been shown to reduce symptoms and infective exacerbations and to improve quality of life. However, these drugs have little effect on the natural history of the disease (progressive decline in lung function and exercise tolerance) and do not improve mortality. The anti-inflammatory effects of statins on both pulmonary and systemic inflammation through inhibition of guanosine triphosphatase and nuclear factor-κB mediated activation of inflammatory and matrix remodelling pathways could have substantial benefits in patients with COPD due to the following. 1) Inhibition of cytokine production (tumour necrosis factor-α, interleukin (IL)-6 and IL-8) and neutrophil infiltration into the lung; 2) inhibition of the fibrotic activity in the lung leading to small airways fibrosis and irreversible airflow limitation; 3) antioxidant and anti-inflammatory (IL-6 mediated) effects on skeletal muscle; 4) reduced inflammatory response to pulmonary infection; and 5) inhibition of the development (or reversal) of epithelial-mesenchymal transition, a precursor event to lung cancer. This review examines the pleiotropic pharmacological action of statins which inhibit key inflammatory and remodelling pathways in COPD and concludes that statins have considerable potential as adjunct therapy in COPD.

FAM13A locus in COPD is independently associated with lung cancer - evidence of a molecular genetic link between COPD and lung cancer

Recent genome-wide association studies have reported a FAM13A variant on chromosome 4q22.1 is associated with lung function and COPD. We examined this variant in a case-control study of current or former smokers with chronic obstructive pulmonary disease (COPD, n = 458), lung cancer (n = 454), or normal lung function (n = 488). Sex, age, and smoking history were comparable between groups. We confirmed the FAM13A variant (rs7671167) confers a protective effect on smoking-related COPD alone (C allele odds ratio [OR] = 0.79, P = 0.013, and CC genotype OR = 0.71, P = 0.024) and those with COPD, both with and without lung cancer (C allele OR = 0.80, P = 0.008, and CC genotype OR = 0.70, P = 0.007). The FAM13A variant also confers a protective effect on lung cancer overall (C allele OR = 0.75, P = 0.002, and CC genotype OR = 0.64, P = 0.003) even after excluding those with co-existing COPD (C allele OR = 0.67, P = 0.0007, and CC genotype OR = 0.58, P = 0.006). This was independent of age, sex, height, lung function, and smoking history. This protective effect was confined to those with nonsmall cell lung cancer (C allele OR = 0.72, P = 0.0009, and CC genotype OR = 0.61, P = 0.003). This study suggests that genetic predisposition to COPD is shared with lung cancer through shared pathogenetic factors such as the 4q22.1 locus implicating the Rho-kinase pathway.

Abstract B31: Gene-based lung cancer risk test (Respiragene), identifies high-risk smokers for early detection of lung cancer

Lung cancer results from the combined effects of smoking and genetic susceptibility. Recent studies show that between 50-90% of lung cancer cases have preexisting COPD and reduced FEV1 has been shown to be the single most important risk factor for lung cancer among smokers. Given the heritability for COPD and lung cancer is 40-75% and 15-25% respectively, it is clear genes conferring risk of COPD also underlies lung cancer susceptibility. In a study of 930 subjects, we have developed a gene-based lung cancer susceptibility model that combines genetic markers (SNPs) associated with COPD and lung cancer, with non-genetic variables (age and family history), to derive a score that helps to distinguish those smokers (and ex-smokers) at greatest risk of lung cancer. The panel includes SNPs validated in candidate and GWAS studies. In a prospective study of 1212 smokers we identified 52 new lung cancers and show their lung cancer scores are very similar to that of the original lung cancer cases (n=446). In a 2nd cross-sectional study of 606 lung cancer cases from the United Kingdom, the lung cancer score was also similarly distributed and showed similar performance in an ROC analysis. In a CT study of 25 lung cancer detected through CT screening in Spain, a similar high score was shown. Current CT screening programs for lung cancer generally target smokers over 50 years with a minimum 20 pack year history and achieve pick up rates of 1%. Using our gene-based model, where age, family history, COPD and genetic variants are combined, lung cancer detection rates maybe even higher.

Citation Information: Cancer Prev Res 2010;3(12 Suppl):B31.

Abstract A65: Gene-based test for lung cancer risk motivates smoking cessation in randomly selected smokers

Personalized risk assessment has been successfully used in coronary heart disease prevention to motivate lifestyle change and target drug therapy. In the Tension, Trigger and Treatment (3Ts) paradigm of smoking cessation, smokers quit smoking when the perceived harms outweigh benefits (or when motivational tension outweighs optimistic bias). Using a gene-based test for lung cancer risk, recently validated in a prospective study, we examined the effect of risk assessment on smoker's attitudes and actions to quitting. In this pilot study, 28 smokers were randomly recruited from a hospital database (eligibility: ≥40 years old, current smoker, and 20+ pack year smoking history). Through a telephone questionnaire, baseline smoking history and recent quit attempts were documented. Smokers were also offered a gene-based risk test for lung cancer risk. 25 (90%) accepted and were followed. On visit 1, smokers were counseled, consented and a cheek swab was taken for genotyping. On visit 2, the lung cancer risk test result was given along with materials on smoking cessation services and medications.

Based on a telephone questionnaire at 6 months after genetic testing (n=25) we found the following; 32% had quit smoking while 48% had reduced their smoking consumption (overall 80% had taken positive steps toward reducing smoking), 48% had used a smoking cessation service or product and only 4% of smokers appeared less committed to quitting. Quit rates were comparable in moderate- and high-risk groups.

We conclude from this pilot study that personalized risk assessment using a gene-based test of lung cancer susceptibility appears to confer a positive effect on quitting smoking. The quit rates achieved in this study occurred in randomly selected smokers and compares favorably with other approaches. We suggest that the risk test provides a teachable moment and enhances motivational tension towards quitting.

Citation Information: Cancer Prev Res 2010;3(12 Suppl):A65.

Abstract B30: Susceptibility loci for lung cancer: Are COPD genes the missing link?

Epidemiological studies show COPD, characterized by reduced FEV1, is the most important independent risk factor for susceptibility to lung cancer. When spirometry is routinely measured, co-existing COPD is found in 50-80% of lung cancer cases compared to only 15-20% of randomly selected matched smokers. Recent GWA studies have identified a number of susceptibility loci for COPD, lung function and lung cancer. Several of these loci overlap suggesting that the gene conferring susceptibility to lung cancer might include COPD-related genes.

In this case control study of Caucasian smokers matched for smoking exposure with COPD (n=458), lung cancer (N=454) and healthy smoker status (n=488) we compared the genotype frequencies of 12 loci on chromosomes 1q23, 4q22-24, 4q31, 5p15, 5q33, 6p21, 6q24 and 15q25. All subjects underwent spirometry, completed a modified ATS respiratory questionnaire and gave blood for DNA. Genotyping was done using Taqman real-time PCR (ABI 7900).

We found (1) the AA genotype of CHRNA3/5 (previously associated with lung cancer) conferred susceptibility to lung cancer (OR=1.76, P=0.005) and COPD (OR-1.47, P=0.06), (2) the GG genotype of HHIP (previously associated with reduced risk of COPD) conferred protection from COPD (OR=0.59, P=0.006) and lung cancer (OR=0.70, P=0.05) and the CC genotype of FAM13A (previously associated with reduced risk of COPD) conferred protection from COPD (OR=0.71, P=0.02) and lung cancer (OR=0.64, P=0.003). These overlapping effects in lung cancer were independent of co-existing COPD.

We conclude the genes conferring susceptibility to lung cancer overlap with those of COPD. Such an observation requires healthy smokers with normal lung function to be used as controls to best identify these COPD-related genes affecting the susceptibility of smokers to lung cancer.

Citation Information: Cancer Prev Res 2010;3(12 Suppl):B30.

Within a smoking-cessation program, what impact does genetic information on lung cancer need to have to demonstrate cost-effectiveness?

Background

Many smoking-cessation programs and pharmaceutical aids demonstrate substantial health gains for a relatively low allocation of resources. Genetic information represents a type of individualized or personal feedback regarding the risk of developing lung cancer, and hence the potential benefits from stopping smoking, may motivate the person to remain smoke-free. The purpose of this study was to explore what the impact of a genetic test needs to have within a typical smoking-cessation program aimed at heavy smokers in order to be cost-effective.

Methods

Two strategies were modelled for a hypothetical cohort of heavy smokers aged 50 years; individuals either received or did not receive a genetic test within the course of a usual smoking-cessation intervention comprising nicotine replacement therapy (NRT) and counselling. A Markov model was constructed using evidence from published randomized controlled trials and meta-analyses for estimates on 12-month quit rates and long-term relapse rates. Epidemiological data were used for estimates on lung cancer risk stratified by time since quitting and smoking patterns. Extensive sensitivity analyses were used to explore parameter uncertainty.

Results

The discounted incremental cost per QALY was AU$34,687 (95% CI $12,483, $87,734) over 35 years. At a willingness-to-pay of AU$20,000 per QALY gained, the genetic testing strategy needs to produce a 12-month quit rate of at least 12.4% or a relapse rate 12% lower than NRT and counselling alone for it to be equally cost-effective. The likelihood that adding a genetic test to the usual smoking-cessation intervention is cost-effective was 20.6% however cost-effectiveness ratios were favourable in certain situations (e.g., applied to men only, a 60 year old cohort).

Conclusions

The findings were sensitive to small changes in critical variables such as the 12-month quit rates and relapse rates. As such, the cost-effectiveness of the genetic testing smoking cessation program is uncertain. Further clinical research on smoking-cessation quit and relapse rates following genetic testing is needed to inform its cost-effectiveness.

The cyclooxygenase-2-765C promoter polymorphism protects against the development of chronic obstructive pulmonary disease

BACKGROUND

Susceptibility to Chronic Obstructive Pulmonary Disease (COPD) has a genetic component. We undertook a study to determine if a genetic variant of the gene encoding the cyclooxygenase-2 gene influences the likelihood of developing COPD.

METHODS

In a case control study the frequency of a single nucleotide polymorphism in the promoter region of the cyclooxygenase-2 gene (-765 G → C) was determined in 205 subjects with COPD, 171 chronic smokers with normal lung function (resistant smokers) and 95 healthy blood donors using the polymerase chain reaction and restriction enzyme fragment length polymorphism.

RESULTS

The frequency of the C allele of the -765 cyclooxygenase-2 polymorphism was higher in resistant smokers (24.6%) compared with subjects with COPD (14.4%, OR = 1.98, 95% CI = 1.28-3.06, p = 0.003) and blood donors (14.7%, OR = 1.97, 95% CI = 1.14-3.41, p = 0.03).

CONCLUSIONS

The -765C allele, which has been shown to be associated with decreased promoter activity of the cyclooxygenase-2 gene, is more common in resistant smokers. This raises the possibility that decreased activity of cyclooxygenase-2 may protect smokers against the development of COPD.

Smoking cessation: the potential role of risk assessment tools as motivational triggers

Smoking is the most important and preventable cause of morbidity and premature mortality in developed and developing countries. To date, efforts to reduce the burden of smoking have focused on non-personalised strategies. Anxiety about ill health, especially lung cancer and emphysema, is the foremost concern for smokers and a major reason for quitting. Recent efforts in cessation management focus on behaviour change and pharmacotherapy. The '3 Ts' (tension, trigger, treatment) model of behaviour change proposes that at any one time a smoker experiences varying degrees of motivational tension, which in the presence of a trigger may initiate or enhance quitting. Smokers' optimistic bias (ie, denial of one's own vulnerability) sustains continued smoking, while increasing motivational tension (eg, illness) favours quitting. The 1 year quit rates achieved when smokers encounter a life threatening event, such as a heart attack or lung cancer, are as much as 50-60%. Utilising tests of lung function and/or genetic susceptibility personalises the risk and have been reported to achieve 1 year quit rates of 25%. This is comparable to quit rates achieved among healthy motivated smokers using smoking cessation drug therapy. In this paper we review existing evidence and propose that identifying those smokers at increased risk of an adverse smoking related disease may be a useful motivational tool, and enhance existing public health strategies directed at smoking cessation.