NCOA4 and chronic obstructive pulmonary disease: Intriguingly, correlation analysis in human lung homogenates from never smokers (n = 10), non-COPD smokers (n = 6), and COPD patients (n = 15) revealed that NCOA4 protein level was negatively associated with percentage of forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) (Fig. 5c).