TGFB1 and idiopathic pulmonary fibrosis: In fact, overexpression of class I isoform p110γ in lung homogenates occurs in IPF patients [173], and has been shown to activate the downstream signalling of several key profibrotic growth factors implicated in IPF, including PDGF and TGFβ1 [174,175], as well as abnormal proliferation of epithelial basal cells [173] and TGF-β-induced fibroblast proliferation and differentiation [176].