Similar to the trend of qRT-PCR, Western blotting results indicated that the protein expression of cyclin D1 and TERT was significantly down-regulated in COPD group when compared with control group (p < 0.05), while the protein expression of p16 (INK4a) was significantly up-regulated (p < 0.0001). This evidence concerns the gene CDKN2A and chronic obstructive pulmonary disease.