Inhibitors of B-raf through the Dimerization Interface

通过二聚化界面的 B-raf 抑制剂

• 批准号: 9212791
• 负责人: Campbell McInnes
• 金额: $ 18.28万
• 依托单位: UNIVERSITY OF SOUTH CAROLINA AT COLUMBIA
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-02-01 至 2019-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9212791
• 关键词: Adverse effects; Affinity; Amino Acids; Binding; Biological Assay; Biology; Biophysics; Cells; Chemicals; Chimeric Proteins; Clinical; Collaborations; Complement; Crystallization; Cyclization; Data; Development; Dimerization; Dose; Drug resistance; Evaluation; Event; Heterodimerization; Homo; In Vitro; Investigation; Laboratories; Malignant Neoplasms; Mediating; Modeling; Molecular Conformation; Mutation; Oncogenic; Pathway interactions; Patients; Peptide Library; Peptides; Pharmaceutical Preparations; Phosphorylation; Phosphotransferases; Play; Proto-Oncogene Proteins B-raf; RNA Splicing; Ras/Raf; Regulation; Resistance; Role; Signal Transduction; Skin Neoplasms; Structure; Synthetic Peptide Libraries; Therapeutic; Time; Transactivation; Variant; base; design; dimer; driving force; experimental study; improved; inhibitor/antagonist; insight; melanoma; mutant; prevent; protein aminoacid sequence; public health relevance; resistance mechanism; success; therapeutic target; tool; tumor

 DESCRIPTION (provided by applicant): Despite the clinical success of B-Raf inhibitors like vemurafenib, resistance has emerged in treated patients thereby dampening the initial enthusiasm for this approach. Further investigation into resistance mechanisms has provided considerable insights and determined that a major cause results from "paradoxical MEK/ERK signaling". Studies have demonstrated that while vemurafenib inhibits B-Raf V600E potently, in the context of WT B-Raf homodimers and heterodimers and activating Ras mutations, it leads to kinase activation of the other partner in the dimer thereby stimulating the downstream pathway rather than inhibiting it. Further efforts are therefore required to complement inhibition of the mutant V600E kinase with other ways of preventing downstream signalling. The Brummer group recently investigated the importance of dimerization for wildtype, oncogenic and drug inhibited B-Raf and showed that conserved residues in the dimer interface (DIF) play an important role for the signaling potential of wildtype B-Raf in cells expressing oncogenic Ras. Furthermore, the formation of B-Raf homo- and heterodimers is based on distinct structural requirements and is essential for Ras/Raf-1 mediated paradoxical MEK/ERK activation by drug-bound B-Raf. These findings identify not only the DIF as potential therapeutic target (in Ras-driven tumors) or to avoid paradoxical MEK/ERK activation, but also lend strong support to an allosteric model of Raf activation by DIF mediated transactivation. The McInnes laboratory has designed peptidic inhibitors of Raf dimerization and has recently initiated a collaboration with the Brummer group in order to demonstrate their potential as chemical biology probes of oncogenic Ras signaling events. After achieving proof of concept of blocking paradoxical activation of MEK/ERK signalling, such inhibitors could then be considered as leads for the development of more drug-like compounds as cancer therapeutics. We propose to synthesize a library of peptidic inhibitors to explore the effects of truncation, substitution and conformational stabilization approaches on the inhibition of dimerization events by the B-Raf DIF peptide sequence. The development of peptidic tools compounds and subsequent cellular experiments will enable to us to achieve the objectives of further understanding how Raf dimerization events contribute to propagation of signals in the Ras/Raf/MEK/ERK pathway while providing the basis for exploiting these in the context of tumors resistant to vemurafenib through paradoxical activation of MEK/ERK.

 描述（由申请人提供）：尽管维莫非尼等 B-Raf 抑制剂在临床上取得了成功，但治疗患者中已经出现了耐药性，从而削弱了对该方法的最初热情。对耐药机制的进一步研究提供了相当多的见解，并确定主要原因是“矛盾的 MEK/ERK 信号传导”。研究表明，虽然 vemurafenib 有效抑制 B-Raf V600E，但在 WT B-Raf 同二聚体和异二聚体以及激活 Ras 突变的情况下，它会导致二聚体中其他伙伴的激酶激活，从而刺激下游途径而不是抑制它。因此，需要进一步努力，用其他阻止下游信号传导的方法来补充对突变 V600E 激酶的抑制。 Brummer 小组最近研究了二聚化对于野生型、致癌性和药物抑制 B-Raf 的重要性，并表明二聚体界面 (DIF) 中的保守残基对于野生型 B-Raf 在表达致癌 Ras 的细胞中的信号传导潜力发挥着重要作用。此外，B-Raf 同二聚体和异二聚体的形成基于不同的结构要求，对于药物结合的 B-Raf 介导的 Ras/Raf-1 介导的矛盾 MEK/ERK 激活至关重要。这些发现不仅确定了 DIF 作为潜在的治疗靶点（在 Ras 驱动的肿瘤中）或避免矛盾的 MEK/ERK 激活，而且还为 DIF 介导的反式激活激活 Raf 的变构模型提供了强有力的支持。 McInnes 实验室设计了 Raf 二聚化的肽抑制剂，并最近启动了与 Brummer 小组的合作，以证明它们作为致癌 Ras 信号事件的化学生物学探针的潜力。在实现阻断 MEK/ERK 信号传导的矛盾激活的概念证明后，此类抑制剂可以被视为开发更多类药物化合物作为癌症治疗药物的先导。我们建议合成一个肽抑制剂库，以探索截短、取代和构象稳定方法对 B-Raf DIF 肽序列二聚化事件抑制的影响。肽工具化合物的开发和随后的细胞实验将使我们能够实现进一步了解 Raf 二聚化事件如何促进 Ras/Raf/MEK/ERK 通路中信号传播的目标，同时为通过 MEK/ERK 的矛盾激活在对维莫非尼耐药的肿瘤中利用这些信号提供基础。