Third, cigarette smoking exposure could cause excessive endothelial apoptosis and emphysema through other signaling pathways involving downregulation of vascular endothelial growth factor (VEGF), focal adhesion kinase (FAK), α-1-antitrypsin (AAT), and upregulation of ceramide, p38, and p53 [50]. Here, TP53 is linked to pulmonary emphysema.