Previous studies reported that MUC5B and MUC5AC were secreted at high levels in cigarette smoking, asthmatic inflammation, as well as chronic obstructive pulmonary disease, and suppression of the production of these proteins may be a therapeutic strategy for secretory chronic airway inflammatory diseases (Kesimer et al., 2017; Kim et al., 2019; Ramsey et al., 2020). Here, MUC5AC is linked to chronic obstructive pulmonary disease.