Common and Rare Variants Genetic Association Analysis of Cigarettes per Day Among Ever-Smokers in Chronic Obstructive Pulmonary Disease Cases and Controls.
To assess if COPD-associated variants in 15q25.1 are methylation quantitative trait loci, epigenome-wide association analysis of four genetic variants, previously associated with COPD (P < 5 × 10<sup>-8</sup>) in the 15q25.1 locus (rs12914385:C>T-CHRNA3, rs8034191:T>C-HYKK, rs13180:C>T-IREB2 and rs8042238:C>T-IREB2), was performed in the Rotterdam study (n = 1489).
The FPRP test results were as follows: 1) when the prior probability was 0.001 and the OR was 1.5, ADAM33 rs612709, CHRNA3/5 rs1051730, CHRNA3/5 rs8034191, CHRNA3/5 rs16969968, and TGFB1 rs1800470 were truly associated with COPD risk (FPRP < 0.2); 2) when the prior probability was 0.000001 and the OR was 1.5, all the variants except TGFB1 rs1800470 remained noteworthy; and 3) when the probability was 0.000001 and the OR was 1.2, ADAM33 rs612709 and CHRNA3/5 rs1051730 remained true positives.
The C allele of a synonymous variant, rs8040868, predicting a p.(S45=) in the gene for cholinergic receptor nicotinic alpha 3 (CHRNA3) was associated with COPD (p = 8.8 x 10<sup>-3</sup>).
Single-nucleotide polymorphisms (SNPs) in the cholinergic nicotinic receptor subunit genes on chromosome 15q25.1, including CHRNA3, CHRNB4 and CHRNA5, are well-established biomarkers of chronic obstructive pulmonary disease (COPD) and lung cancer.
The rs13180 (IREB2), rs16969968 (CHRNA5) and rs1051730 (CHRNA3) were significantly associated with COPD in additive model [Padj =0.00001, odds ratio (OR)=0.64; Padj =0.0001, OR=1.41 and Padj =0.0001, OR=1.47].
Our data suggest that gene variance in the CHRNA5-CHRNA3-CHRNB4 cluster is associated with an increased risk of death, incidence of COPD and tobacco-related cancer in smokers.
Because the associations with lung disease remain after adjustment for self-reported smoking behaviors, it has been asserted that CHRNA5-CHRNA3-CHRNB4 variants increase COPD and lung cancer susceptibility independently of their effects on smoking.
Analysis of 6633 individuals with moderate to severe COPD and 5704 control individuals confirmed association at three known loci: CHRNA3 (p=6·38 × 10(-14)), FAM13A (p=1·12 × 10(-14)), and HHIP (p=1·57 × 10(-12)).
While the association of the AGPHD1/CHRNA3 locus with COPD is significantly mediated by smoking-related phenotypes, IREB2 appears to affect COPD independently of smoking.
This case-control analysis of 219 COPD patients and 305 control participants identified a significant association between an SNP of CHRNA3 (rs12910984) and COPD (p = 0.049).
Thus, in severe to very severe COPD, we demonstrate a replication of association between two SNPs previously associated with COPD (CHRNA3/5 and IREB2), as well as an association with COPD of one locus initially associated with lung function (ADCY2).
Besides, we confirmed that SNPs in these two gene loci were associated with pulmonary function and CHRNA3/5 polymorphism was associated with pack-year of smoking in COPD patients in the Chinese Han population.
Several genome-wide association and candidate gene studies have linked chromosome 15q24-q25.1 (a region including the CHRNA5-CHRNA3-CHRNB4 gene cluster) with alcohol dependence, nicotine dependence and smoking-related illnesses such as lung cancer and chronic obstructive pulmonary disease.