Imatinib mesylate inhibits the profibrogenic activity of TGF-β and prevents bleomycin-mediated lung fibrosis
J. Clin. Invest. Craig E. Daniels, et al. 114:1308 doi:10.1172/JCI19603 [Go to this article.]

Figure 5
TGF-β stimulates c-Abl–dependent signaling. (A) IMR90 cells were treated with DMEM alone (–) or containing 10 ng/ml TGF-β2 (+). Following 30-minute stimulation, c-Abl kinase activity or Smad2 (p-Smad2) and Smad3 (p-Smad3) phosphorylation was determined. Total c-Abl, Smad2, and Smad3 protein is shown below the corresponding activity. (B) Top blots: IMR90 cells, Abl^–/–Arg^–/– MEFs, Abl^–/–Arg^–/– fibroblasts stably expressing (+) WT-c-Abl or dominant negative c-Abl, or PDGF-α and -β receptor–null F cells (PDGFR^–/–) were left untreated (–) or treated (+) for 24 hours with TGF-β2 (10 ng/ml) and/or imatinib (10 μg/ml). Imatinib was added 20 minutes before TGF-β2, and fibronectin mRNA accumulation was determined. Bottom blots: Ethidium bromide staining for 28S and 18S ribosomal RNA subunits prior to Northern analysis. Top left graph: The fold fibronectin mRNA stimulation by TGF-β2 is indicated for the various cell types. Results represent the mean ± SE of 2 separate experiments. Bottom left graph: Cell lines as described above were transfected with a fibronectin luciferase construct. The fold induction of 10 ng/ml TGF-β2 with or without 5 μg/ml imatinib was determined as described in Methods and by Penheiter et al. (51). Right graphs: Collagen I (top) and collagen III (bottom) luciferase activity was determined as described for the bottom left graph. Results for all luciferase assays represent the mean ± SE of 2 separate experiments, each done in triplicate.