EPAS1 and chronic obstructive pulmonary disease: The difference was similar for endothelial cells (EPAS1 high in 4 of 4 non-COPD samples and low in 3 of 5 COPD samples) and alveolar (EPAS1 high in 4 of 4 non-COPD samples and low in 3 of 5 COPD samples) cells.