The protein expression of KRT17 (COPD-NE, n = 13, COPD-E, n = 24; p < 0.01) and DHRS9 (COPD-NE, n = 13, COPD-E, n = 24; p < 0.01) in the COPD-E group was higher than that in the COPD-NE group. Here, DHRS9 is linked to chronic obstructive pulmonary disease.