To determine if DDX3 is associated with human lung fibrosis, we examined the distribution of DDX3 in lung tissue from chronic obstructive pulmonary disease (COPD) patients with relatively normal lungs (>80% forced vital capacity; FVC) and IPF patients with advanced disease (<50% FVC) (Supplemental Table 3). This evidence concerns the gene DDX3X and idiopathic pulmonary fibrosis.