DNA microarray analysis followed by functional pathway analysis revealed unfolded protein response (UPR) pathways activated in normal human oral keratinocytes (NHOKs) by EC aerosols. (A) The canonical UPR pathway was generated with the Ingenuity Pathways Analysis (IPA) software. A number of genes of the UPR pathways such as XBP1 (X-box binding protein 1), IRE1α (inositol-requiring enzyme 1, a.k.a., endoplasmic reticulum to nucleus signaling 1), ATF4 (activating transcription factor 4), CHOP (a.k.a., DDIT3, DNA-damage-inducible transcript 3) and C/EBP were induced by EC aerosols. (B & C) TGF-β and HGF signals activated in EC aerosol-treated NHOKs.