Pharmacogenetics of chronic obstructive pulmonary disease

Predicting treatable traits for long-acting bronchodilators in patients with stable COPD

Purpose

There is currently no measure to predict a treatability of long-acting β-2 agonist (LABA) or long-acting muscarinic antagonist (LAMA) in patients with chronic obstructive pulmonary disease (COPD). We aimed to build prediction models for the treatment response to these bronchodilators, in order to determine the most responsive medication for patients with COPD.

Methods

We performed a prospective open-label crossover study, in which each long-acting bronchodilator was given in a random order to 65 patients with stable COPD for 4 weeks, with a 4-week washout period in between. We analyzed 14 baseline clinical traits, expression profiles of 31,426 gene transcripts, and damaged-gene scores of 6,464 genes acquired from leukocytes. The gene expression profiles were measured by RNA microarray and the damaged-gene scores were obtained after DNA exome sequencing. Linear regression analyses were performed to build prediction models after using factor and correlation analyses.

Results

Using a prediction model for a LABA, traits found associated with the treatment response were post-bronchodilator forced expiratory volume in 1 second, bronchodilator reversibility (BDR) to salbutamol, expression of three genes (CLN8, PCSK5, and SKP2), and damage scores of four genes (EPG5, FNBP4, SCN10A, and SPTBN5) (R²=0.512, p<0.001). Traits associated with the treatment response to a LAMA were COPD assessment test score, BDR, expression of four genes (C1orf115, KIAA1618, PRKX, and RHOQ) and damage scores of three genes (FBN3, FDFT1, and ZBED6) (R²=0.575, p<0.001). The prediction models consisting only of clinical traits appeared too weak to predict the treatment response, with R²=0.231 for the LABA model and R²=0.121 for the LAMA model.

Conclusion

Adding the expressions of genes and damaged-gene scores to the clinical traits may improve the predictability of treatment response to long-acting bronchodilators.

Association Between ADRB2 Genetic Polymorphisms and the Risk of Chronic Obstructive Pulmonary Disease: A Case-Control Study in a Chinese Population

OBJECTIVE

This study was designed to investigate the association between single nucleotide polymorphisms (SNPs) of the β2-adrenergic receptor (ADRB2) gene and the risk of chronic obstructive pulmonary disease (COPD) in a Chinese population.

METHODS

From January 2010 to October 2014, 261 COPD patients were selected as the case group and 239 healthy subjects were selected as the control group. Pulmonary function tests were performed to detect forced vital capacity (FVC), 1-s forced expiratory volume (FEV₁), and FEV₁/FVC (%). rs1042711, rs1042714, and rs1042718 were selected as tagSNPs of the ADRB2 gene from the HapMap database in accordance with previous studies. The ADRB2 genotypes were established by real-time polymerase chain reaction assays using TaqMan-labeled probes. The relationships between the ADRB2 polymorphisms and COPD risk were estimated using logistic regression analyses.

RESULTS

The frequency of the genotypes and alleles of rs1042711 in ADRB2 showed a significant difference between the COPD and control groups (p < 0.05); compared with the CC genotype, the non-CC genotypes showed an increased COPD risk (p = 0.002). Compared with the CC haplotype, the TG haplotype increased COPD risk, while the CG haplotype reduced COPD risk for normal individuals. Compared with the CC genotype, the TT genotype showed significantly lower FEV₁ and FEV₁/FVC (p = 0.022, p = 0.0191, respectively). Both the TC and TG haplotypes showed lower FEV₁ and FEV₁/FVC in comparison with the CC haplotype (both p < 0.05). The results of logistic regression analysis showed that rs1042711 of ADRB2 and smoking history were associated with COPD risk (both p < 0.05).

CONCLUSION

It is indicated that the TT genotype of rs1042711 and smoking pack years are both risk factors for COPD.

GLCCI1 rs37973: a potential genetic predictor of therapeutic response to inhaled corticosteroids in Chinese chronic obstructive pulmonary disease patients

Inhaled corticosteroids (ICSs) are widely prescribed in chronic obstructive pulmonary disease (COPD). However, little is known about predictors of ICSs therapeutic response. To investigate whether the variation in glucocorticoid-induced transcript 1 (GLCCI1) rs37973 is associated with ICS efficacy. A total of 204 clinically stable COPD patients were recruited and administered to inhaled fluticasone propionate/salmeterol combination (500/50 ug, twice daily) for 24 weeks. We genotyped the functional rs37973 and mainly assessed its effects on changes in lung function. In vitro, neutrophils isolated from parts of patients were incubated with various concentrations of dexamethasone (0, 10⁻⁶ M and 10⁻⁴ M) in the presence or absence of cigarette smoke extract, apoptosis was then assessed by flow cytometry. Patients with the homozygous GG genotype (increases of 15.3 ± 33.2 mL) had significantly poorer improvement in FEV₁ than those with the AA (92.7 ± 29.6 mL; p < 0.001) or AG (59.4 ± 26.9 mL; p < 0.001) genotypes after 24-week treatment. In vitro, dexamethasone had less inhibitory effect of neutrophil apoptosis on GG genotype, which further validated the presence of mutant allele ‘G’ might negatively affect glucocorticoid responsiveness irrespective of smoking status. The GG genotype of rs37973 may associated with decreased ICSs efficacy in Chinese COPD patients.

LAMA/LABA vs ICS/LABA in the treatment of COPD in Japan based on the disease phenotypes

In the combined use of bronchodilators of different classes, ie, long-acting β2-agonists (LABAs) and long-acting muscarinic antagonists (LAMAs), bronchodilation is obtained both directly, through LABA-mediated stimulation of β2-adrenergic receptors, and indirectly, through LAMA-mediated inhibition of acetylcholine action at muscarinic receptors. The clinical trial data for LABAs/LAMAs in the treatment of chronic obstructive pulmonary disease (COPD) continue to be promising, and these combinations will provide the convenience of delivering the two major bronchodilator classes, recommended as first-line maintenance options in COPD treatment guidelines. COPD is a complex condition that has pulmonary and extrapulmonary manifestations. These clinical manifestations are highly variable, and several are associated with different responses to currently available therapies. The concept of a COPD phenotype is rapidly evolving from one focusing on the clinical characteristics to one linking the underlying biology to the phenotype of the disease. Identification of the peculiarities of the different COPD phenotypes will permit us to implement a more personalized treatment in which the patient's characteristics, together with his or her genotype, will be key to choosing the best treatment option. At present in Japan, fixed combinations of inhaled corticosteroids (ICSs) and LABAs are frequently prescribed in the earlier stages of COPD. However, ICSs increase the risk of pneumonia. Notably, 10%-30% of patients with COPD with or without a history of asthma have persistent circulating and airway eosinophilia associated with an increased risk of exacerbations and sensitivity to steroids. Thus, sputum or blood eosinophil counts might identify a subpopulation in which ICSs could have potentially deleterious effects as well as a subpopulation that benefits from ICSs. In this review, I propose one plausible approach to position ICSs and LABAs/LAMAs in clinical practice, based on both the extent of airflow obstruction and the presence of an asthma component or airway eosinophilic inflammation. This approach is a tentative move toward personalized treatment for COPD patients, and with progress in knowledge and developments in physiology, lung imaging, medical biology, and genetics, identification of COPD phenotypes that provide prognostic and therapeutic information that can affect clinically meaningful outcomes is an urgent medical need.