TGFB1 and idiopathic pulmonary fibrosis: Cyclin D1 gene expression was measured in the normal lung fibroblasts and the 3 IPF-derived lung fibroblast cell lines following growth factor treatment (Fig 2a), Cells were serum deprived for 48 hours to ensure quiescence and to synchronise cell proliferation; cells were then exposed to physiologically relevant concentrations of growth factors (CTGF and TGF-β1) known to be implicated in IPF pathogenesis [4,5].