Cigarette smoke and oxidative stress cause damage to epithelial cells, leading to apoptosis and emphysema and, on the other hand, promote the expression of hypoxia-inducible factor-1 α (HIF-1) and vascular endothelial growth factor (VEGF), accelerating the proliferation and invasion of tumors [48]. The gene discussed is VEGFA; the disease is pulmonary emphysema.