Increased p16 or p21 expression and increased percentages of SA-βgal-positive cells were also observed in fibroblasts [16], small airway epithelial cells (SAECs) [28], and endothelial progenitor cells [29] from patients with COPD compared to age-matched smokers [16] or non-smokers [28,29]. The gene discussed is CDKN2A; the disease is chronic obstructive pulmonary disease.