VEGFA and chronic obstructive pulmonary disease: Some cell studies in which tissues were collected from the lung have reported that the overexpression of related proteins such as hypoxia-inducible factor (HIF) 1α, vascular endothelial growth factor (VEGF), and VEGF receptor 2 in patients with COPD [10,11], and HIF-1α may stimulate cell growth in a hypoxic environment [12].