Likewise, no correlations were found between claudin-3 expression and smoking status (p = 0.5422), COPD severity (rs = −0.1605, p = 0.4336), and cumulative cigarette exposure (i.e., pack-years) (rs = −0.1624, p = 0.4379) (Figure S2). The gene discussed is CLDN3; the disease is chronic obstructive pulmonary disease.