The majority of these DMRs are located outside gene promoters or other known regulatory elements, making it tricky to assign a biological meaning; however, some studies in IPF lungs reported different DNA methylation levels in the promoters and enhancers of genes known to be involved in the regulation of important cellular processes impaired in IPF, such as MUC5B, PTGER2 (Prostaglandin E receptor 2) and THY1 (Thy-1 antigen). Here, MUC5B is linked to idiopathic pulmonary fibrosis.