apoptosis (1,113/13.1%), ROS (953/11.3%), COPD (753/8.9%), cancer (720/8.5%), asthma (662/7.8%), biomarker (655/7.7%), lung injury (652/7.7%), SOD (652/7.7%), age (611/7.2%), MDA (509/6.0%), lung cancer (495/5.8%), TNF-alpha (491/5.8%), mortality (486/5.7%), glutathione (481/5.7%), acute lung injury (417/4.9%), NRF2 (417/4.9%), caspase (405/4.8%), cigarette smoke (404/4.8%), serum (370/4.4%), nitric oxide (357/4.2%), NF-κB (352/4.2%), catalase (344/4.1%), bronchoalveolar lavage fluid (319/3.8%), cardiovascular disease (309, 3.6%) LPS (248, 2.9%). The gene discussed is CAT; the disease is chronic obstructive pulmonary disease.