CASP6 and chronic obstructive pulmonary disease: Based on the FDR < 0.05, we found that 9 pyroptosis-related genes were related to the occurrence of COPD significantly, with 8 up-regulated (CASP4, CASP5, CHMP7, GZMB, IL1B, AIM2, CASP6, GSDMC) and 1 down-regulated genes (PLCG1) in COPD patients in both train set and test set (Supplemental Table 3).