gdc-0449 and Fibrosis

Hedgehog signalling plays a critical role during the pathogenesis of fibrosis in systemic sclerosis (SSc). Besides canonical hedgehog signalling with smoothened (SMO)-dependent activation of GLI transcription factors, GLI can be activated independently of classical hedgehog ligands and receptors (so-called non-canonical pathways). Here, we aimed to evaluate the role of non-canonical hedgehog signalling in SSc and to test the efficacy of direct GLI inhibitors that target simultaneously canonical and non-canonical hedgehog pathways.. The GLI inhibitor GANT-61 was used to inhibit canonical as well as non-canonical hedgehog signalling, while the SMO inhibitor vismodegib was used to selectively target canonical hedgehog signalling. Furthermore, GLI2 was selectively depleted in fibroblasts using the Cre-LoxP system. The effects of pharmacological or genetic of GLI2 on transforming growth factor-β (TGF-β) signalling were analysed in cultured fibroblasts, in bleomycin-induced pulmonary fibrosis and in mice with overexpression of a constitutively active TGF-β receptor I.. TGF-β upregulated GLI2 in a Smad3-dependent manner and induced nuclear accumulation and DNA binding of GLI2. Fibroblast-specific knockout of GLI2 protected mice from TBR. Our data demonstrate that hedgehog pathways and TGF-β signalling both converge to GLI2 and that GLI2 integrates those signalling to promote tissue fibrosis. These findings may have translational implications as non-selective inhibitors of GLI2 are in clinical use and selective molecules are currently in development.

Topics: Adult; Aged; Anilides; Animals; Cells, Cultured; Collagen Type I; Connective Tissue Growth Factor; Female; Fibroblasts; Fibrosis; Gene Knockout Techniques; Hedgehog Proteins; Humans; Kruppel-Like Transcription Factors; Male; Mice; Mice, Knockout; Mice, Transgenic; Middle Aged; Plasminogen Activator Inhibitor 1; Protein Serine-Threonine Kinases; Pteridines; Pulmonary Fibrosis; Pyridines; Pyrimidines; Receptor, Transforming Growth Factor-beta Type I; Receptors, Transforming Growth Factor beta; Recombinant Proteins; RNA, Messenger; Scleroderma, Systemic; Signal Transduction; Skin; Smad3 Protein; Smoothened Receptor; Transforming Growth Factor beta; Young Adult; Zinc Finger Protein Gli2