α₁-antitrypsin and neutrophil elastase imbalance and lung cancer risk

Objective: Imbalance between α₁-antitrypsin and neutrophil elastase is an underlying cause of lung tissue damage that may create a favorable host environment for carcinogenesis. We conducted a case-control study to investigate whether genetic variations indicative of α₁- antitrypsin deficiency (A1ATD) or an excess of neutrophil elastase modify lung cancer risk Design: The case patients were 305 consecutively identified primary lung cancer patients, and the control subjects were 338 community residents. Protease inhibitor-1 (PI1), encoding α₁-antitrypsin, was typed by an isoelectric focusing assay. Neutrophil elastase-2 (ELA2), encoding neutrophil elastase, was typed by two single-nucleotide polymorphism sites. Multivariable logistic regression models tested the independent and interactive effects of PI1, ELA2, tobacco smoke exposure, COPD, and family history of lung cancer Results: Sex and ethnicity were comparable between case patients and control subjects, but case patients were more likely to be smokers, and to have a history of COPD, environmental tobacco smoke exposure, and a positive family history of lung cancer. Haplotype analysis indicated an overall strong association between the two ELA2 markers and lung cancer risk. Our best-fitting model showed significant and independent effects of the PI1-deficient allele (odds ratio [OR], 2.0; 95% confidence interval [CI], 1.4 to 3.0) and the ELA2 T-G haplotype (OR, 4.1; 95% CI, 1.9 to 8.9) on lung cancer risk, and an increased risk (OR, 2.6; 95% CI, 2.4 to 2.8) for individuals carrying both a PI1-deficient allele and a G-G haplotype Conclusions: Genotypes indicative of A1ATD and/or an excess of neutrophil elastase are significantly associated with lung cancer risk. Our findings may provide opportunities to better understand the mechanisms of lung cancer development and risk reduction.