Gli1-selective inhibitors of the Hedgehog signaling pathway

 描述（由申请人提供）：Gli转录因子活性不受控制可导致多种人类癌症，包括基底细胞癌、髓母细胞瘤、脑膜瘤和横纹肌肉瘤。致癌Gli功能通常源于Hedgehog（Hh）通路失调，该发育信号通路的化学抑制剂目前已在临床上使用。尽管我们在理解和治疗Gli依赖性癌症方面取得了这些显著进展，但目前的Hh通路靶向疗法具有若干局限性。首先，几乎所有的Hh通路靶向药物抑制Smoothened（Smo），这是一种Hh信号转导所需的G蛋白偶联受体样蛋白。因此，它们主要是有效的 针对Patched 1（Ptch 1）缺失引起的癌症，Patch 1是Smo的跨膜阻遏物，或Smo中的某些激活突变。由下游或平行信号传导机制引发的Gli依赖性肿瘤对这些化合物不敏感。其次，Smo拮抗剂诱导的肿瘤消退通常是短暂的，因为耐药癌细胞可以迅速出现。第三，Smo靶向药物可以破坏正常的Hh通路依赖性生理学，临床前研究进一步表明Smo阻断可能导致儿童发育缺陷。 Hh通路抑制剂作用于Smo下游并更直接地抑制Gli功能可以克服这些限制。特别是，选择性抑制Gli 1的化合物可能是更通用和有效的抗癌剂，因为这种Gli同种型是一种有效的致癌基因，但对哺乳动物的发育和生理学不利。为了实现这一目标，我们的实验室最近调查了325，120种化合物在缺乏融合抑制因子（Sufu）（一种直接Gli拮抗剂）的细胞中抑制组成型Gli活性的能力。通过这种大规模的化学筛选，我们已经确定了一种咪唑衍生物（“glimidazole”），它可以抑制Gli 1的功能，但对Gli 2或Gli 3没有明显的影响。我们还开发了几种在基于细胞的测定中具有纳摩尔效力的格列咪唑类似物，使用光亲和标记来发现可能连接线粒体信号传导和Gli 1调节的特异性格列咪唑结合蛋白，并证明了这些Gli 1选择性抑制剂在体外和体内阻断肿瘤生长的能力。 我们现在正在进行下一步的工作，以建立一种新的Hh通路靶向化疗药物，以格列咪唑为基础的化合物。我们的目标是：（1）表征在我们的光亲和标记实验中发现的格列咪唑靶点，并确定其在Gli 1调节中的作用;（2）开发具有优化效力、靶点选择性和药代动力学特性的格列咪唑类似物;（3）在髓母细胞瘤小鼠模型中比较选定的格列咪唑类分子与Smo拮抗剂的疗效。总之，我们的研究将为Gli 1调控机制提供新的见解，发现抗癌疗法的新靶点，并为未来的药物开发工作提供化学线索。

 DESCRIPTION (provided by applicant): Uncontrolled Gli transcription factor activity causes several human cancers, including basal cell carcinoma, medulloblastoma, meningioma, and rhabdomyosarcoma. Oncogenic Gli function frequently stems from Hedgehog (Hh) pathway dysregulation, and chemical inhibitors of this developmental signaling pathway are now in clinical use. Despite these significant advances in our understanding and treatment of Gli- dependent cancers, current Hh pathway-targeting therapies have several limitations. First, nearly all Hh pathway-targeting drugs inhibit Smoothened (Smo), a G protein-coupled receptor-like protein that is required for Hh signal transduction. As a result, they are primarily effective against cancers caused by loss of Patched1 (Ptch1), a transmembrane repressor of Smo, or by certain activating mutations in Smo. Gli-dependent tumors initiated by downstream or parallel signaling mechanisms are insensitive to these compounds. Second, tumor regressions induced by Smo antagonists are often transient, as drug-resistant cancer cells can rapidly emerge. Third, Smo-targeting drugs can disrupt normal Hh pathway-dependent physiology, and preclinical studies further suggest that Smo blockade could cause developmental defects in children. Hh pathway inhibitors that act downstream of Smo and more directly suppress Gli function could overcome these constraints. In particular, compounds that selectivity inhibit Gli1 could be more general and effective anti-cancer agents, since this Gli isoform is a potent oncogene but dispensable for mammalian development and physiology. Toward this goal, our laboratory recently surveyed 325,120 compounds for their ability to inhibit the constitutive Gli activity in cells lacking Suppressor of Fused (Sufu), a direct Gli antagonist. Through this large-scale chemical screen, we have identified an imidazole derivative ("glimidazole") that can inhibit Gli1 function but has no apparent effect on Gli2 or Gli3. We have also developed several glimidazole analogs with nanomolar potencies in cell-based assays, used photoaffinity labeling to discover a specific glimidazole-binding protein that may link mitochondrial signaling and Gli1 regulation, and demonstrated the ability of these Gli1-selective inhibitors to block tumor growth in vitro and in vivo. We are now pursuing the next steps required to establish glimidazole-based compounds as a new class of Hh pathway-targeting chemotherapies. Our aims are: (1) to characterize the glimidazole target discovered in our photoaffinity labeling experiments and determine its roles in Gli1 regulation; (2) to develop glimidazole analogs with optimized potency, target selectivity, and pharmacokinetic properties; and (3) to compare the efficacy of selected glimidazole-class molecules to Smo antagonists in murine models of medulloblastoma. Taken together, our studies will provide new insights into the mechanisms of Gli1 regulation, uncover novel targets for anti-cancer therapies, and yield chemical leads for future drug development efforts.