CDKN2A and chronic obstructive pulmonary disease: Senescent cells can be identified by shortened telomeres, by immunohistochemical staining for senescence associated β-galactosidase, and by increased expression of p21WAF1 and p16INK4a and all of these markers have been reported in the lungs of COPD patients compared to smokers without COPD or nonsmoking controls [1]–[6].