MUC5AC and nasal cavity polyp: Besides, the expression of MUC5AC was up-regulated by IL-17A in nasal polyps via the Act1-mediated pathway [20], and neutrophil elastase in respiratory epithelial cells [21], and negatively regulated by Src homology 2-containing protein tyrosine phosphatase-2 via the down-regulation of the ERK1/2 MAPK pathway in the airway [22].