Global DNA methylation and DNMT activity were increased in CRSwNP and CRSsNP vs. controls.TGF beta-1 dose-dependently induced DNMT expression and global DNA methylation. 5-azacytidine inhibited TGF beta-1-induced DNMT in primary HNECs and air–liquid interface cultures.Inhibition of DNMT suppressed the EMT process and therefore may be potentially a CRS therapeutic strategy. Here, DNMT1 is linked to chronic rhinosinusitis without nasal polyps.