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DECOUVERTE ET CARACTERISATION PHARMACOLOGIQUE DE NOUVEAUX ANTAGONISTES DU RECEPTEUR SMOOTHENED : LES COMPOSES MRT

Abstract : The Sonic Hedgehog (Shh) signaling pathway is implicated in multiple physiological responses including the control of brain functions. In mammals, the Shh pathway is expressed at the primary cilium and its activation requires the binding of a Shh peptide to the Patched (Ptc) receptor which represses the constitutive activity of Smoothened (Smo), a proposed member of the G-protein-coupled receptor (GPCR) family. Recently, clinical trials for treating medulloblastoma and various solid tumors in human have been conducted with Smo antagonists such as GDC-0449 or LDE-225. Such molecules may have some limitations leading to treatment resistance. In the present work, the development of a pharmacophoric model of Smo antagonists allowed a virtual screening strategy to identify novel Smo inhibitors. The acylthiourea MRT- 10 and the acylurea MRT-14 were the two first leads identified. Structure-activity relationship experiments led to the discovery of new series of Smo inhibitors with high potency and to which the acylguanidine MRT-83 belongs. This inhibitor perfectly fits with the proposed pharmacophoric model for Smo antagonists. The discrete structural differences between MRT-83 and the original leads may account for the increased potency of MRT-83 observed in various in vitro Shh-based assays. MRT-83 inhibits BODIPY-cyclopamine binding to human Smo and Shh-mediated proliferation of rat granule cell proliferation with nanomolar potency similar to GDC-0449 or LDE-225. Despite significant homology of Smo with the Frizzled family of receptors which are involved in the Wnt signaling pathway, MRT-83 displays no significant effect on this pathway. MRT-83 blocks Smo translocation induced by Shh pathway activation to the primary cilia of NT2 cells that derive from a pluripotent testicular carcinoma whereas cyclopamine, a reference Smo antagonist, induces Smo accumulation of Smo signals at the primary cilium. Therefore, it might be anticipated that MRT-83, like GDC-0449 and LDE- 225, interacts with Smo in a manner different from that of cyclopamine, suggesting that while their binding sites are overlapping, they are not identical. Stereotaxic injection of MRT-83 into the lateral ventricle of adult mice but not of a structurally-related compound inactive at Smo, abolished upregulation of Ptc transcription induced by Shh in the neighboring subventricular zone, one of the two main neurogenic areas of the adult brain. These data demonstrate that MRT derivatives efficiently antagonize Shh signaling in vivo. Thus, MRT-10, MRT-14, MRT-83 and structurally-related molecules are potent Smo antagonists. These compounds should be useful for clarifying the molecular and biochemical mechanisms underlying the resistance of Smo inhibitors in brain cancer cells and may help develop new therapies against Shh pathway-related brain diseases.
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https://tel.archives-ouvertes.fr/tel-00638720
Contributor : Hermine Roudaut <>
Submitted on : Monday, November 7, 2011 - 11:06:58 AM
Last modification on : Friday, October 23, 2020 - 4:45:57 PM
Long-term archiving on: : Wednesday, February 8, 2012 - 2:26:58 AM

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  • HAL Id : tel-00638720, version 1

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Hermine Roudaut. DECOUVERTE ET CARACTERISATION PHARMACOLOGIQUE DE NOUVEAUX ANTAGONISTES DU RECEPTEUR SMOOTHENED : LES COMPOSES MRT. Neurosciences [q-bio.NC]. Université Paris Sud - Paris XI, 2011. Français. ⟨tel-00638720⟩

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