SESN2 and pulmonary emphysema: Because earlier experiments involving Affymetrix Chip arrays suggested an upregulation of platelet derived growth factor receptor beta (PDGFRβ) in lung fibroblasts of Sesn2 KO mice, and because PDGFR signalling is essential for lung morphogenesis and regeneration (Boström et al., 1996; Levéen et al., 1994), we hypothesised that PDGFRβ might participate in lung protection against emphysema caused by cigarette smoke.