NKX2-1 and chronic obstructive pulmonary disease: Decreased NKX2-1 expression has also been observed in human lung tissues derived from COPD patients and is associated with cigarette smoking, WNT-5A overexpression, and distal-to-proximal airway re-patterning (Baarsma et al., 2017; Yang et al., 2017; Huang et al., 2019).