Inhibition of Transforming Growth Factor ␤ Signaling Reduces Pancreatic Adenocarcinoma Growth and Invasiveness □ S

ABSTRACT Transforming growth factor ␤ (TGF␤) is a pleiotropic factor that regulates cell proliferation, angiogenesis, metastasis, and immune suppression. Dysregulation of the TGF␤ pathway in tumor cells often leads to resistance to the antiproliferative effects of TGF␤ while supporting other cellular processes that promote tumor invasiveness and growth. In the present study, SD-208, a 2,4-disubstituted pteridine, ATP-competitive inhibitor of the TGF␤ receptor I kinase (TGF␤RI), was used to inhibit cellular activities and tumor progression of PANC-1, a human pancreatic tumor line. SD-208 blocked TGF␤-dependent Smad2 phosphorylation and expression of TGF␤-inducible proteins in cell culture. cDNA microarray analysis and functional gene clustering identified groups of TGF␤-regulated genes involved in metastasis, angiogenesis, cell proliferation, survival, and apoptosis. These gene responses were inhibited by SD-208. Using a Boyden chamber motility assay, we demonstrated that SD-208 inhibited TGF␤-stimulated invasion in vitro. An orthotopic xenograft mouse model revealed that SD-208 reduced primary tumor growth and decreased the incidence of metastasis in vivo. Our findings suggest mechanisms through which TGF␤ signaling may promote tumor progression in pancreatic adenocarcinoma. Moreover, they suggest that inhibition of TGF␤RI with a small-molecule inhibitor may be effective as a therapeutic approach to treat human pancreatic cancer

Transforming Growth Factor-β Receptor Type 1 (TGFβRI) Kinase Activity but Not p38 Activation Is Required for TGFβRI-Induced Myofibroblast Differentiation and Profibrotic Gene Expression

Transforming growth factor-β (TGFβ) is a major mediator of normal wound healing and of pathological conditions involving fibrosis, such as idiopathic pulmonary fibrosis. TGFβ also stimulates the differentiation of myofibroblasts, a hallmark of fibrotic diseases. In this study, we examined the underlying processes of TGFβRI kinase activity in myofibroblast conversion of human lung fibroblasts using specific inhibitors of TGFβRI (SD-208) and p38 mitogen-activated kinase (SD-282). We demonstrated that SD-208, but not SD-282, inhibited TGFβ-induced SMAD signaling, myofibroblast transformation, and collagen gel contraction. Furthermore, we extended our findings to a rat bleomycin-induced lung fibrosis model, demonstrating a significant decrease in the number of myofibroblasts at fibroblastic foci in animals treated with SD-208 but not those treated with SD-282. SD-208 also reduced collagen deposition in this in vivo model. Microarray analysis of human lung fibroblasts identified molecular fingerprints of these processes and showed that SD-208 had global effects on reversing TGFβ-induced genes involved in fibrosis, inflammation, cell proliferation, cytoskeletal organization, and apoptosis. These studies also revealed that although the p38 pathway may not be needed for appearance or disappearance of the myofibroblast, it can mediate a subset of inflammatory and fibrogenic events of the myofibroblast during the process of tissue repair and fibrosis. Our findings suggest that inhibitors such as SD-208 may be therapeutically useful in human interstitial lung diseases and pulmonary fibrosis