CDKN2A and idiopathic pulmonary fibrosis: Evidence suggests that much of the phenotypic variation linked to 9p21 may be explained by genotypic variation in ANRIL [17], a long non-coding RNA (lncRNA) gene that might promote cis-acting epigenetic silencing of the 9p21 region by promoting recruitment of polycomb repressive complexes [18], leading to decreased expression of CDKN2A and CDKN2B. A recent study found that CDKN2B is highly methylated in IPF fibroblasts, possibly contributing to increased cyclin-dependent kinase activity and fibroblast proliferation in IPF [19].