New Paradigms for Targeting Truncal Driver Mutations

总结： 实体瘤在其进化和扩展过程中产生遗传上不同的亚克隆。深度测序 随后定量给定肿瘤内的突变等位基因频率， 由共享的早期驱动（“主干”）突变和发散的晚期驱动（“分支”）突变组成的树。这 知识表明，应该治疗性地靶向截断突变，因为它们理论上是由以下基因共享的： 肿瘤内的所有细胞，而不是晚期突变。此外，很可能发生的一些突变 在肿瘤演变的晚期，由于突变， 在他们之前，在这种情况下，靶向截断突变可以通过暴露 由晚期突变引起的对肿瘤细胞的有害作用。事实上，几乎所有成功的目标 癌症药物攻击已知或怀疑是躯干的遗传事件。联合使用两种药物 同样的躯干病变以不同的方式，如当联合维甲酸与三氧化二砷抑制 PML-RAR融合蛋白在急性早幼粒细胞白血病中，应增强疗效并减少治疗性 阻力Kaelin实验室长期以来一直对pRB和pVHL肿瘤抑制蛋白感兴趣， 最近，在IDH癌蛋白中。影响这些蛋白质的突变发生在特定的早期躯干事件中， 癌症如小细胞肺癌（pRB）、透明细胞肾癌（pVHL）和急性骨髓性白血病（AML）。 白血病（IDH 1和IDH 2）。凯林实验室在证明pRB丢失的作用方面发挥了重要作用， pVHL损失和突变体IDH在肿瘤维持和鉴定其致病性下游靶标中的作用。这 一项提案旨在为靶向躯干突变创造新的范例，包括那些目前认为 不可用药的（例如，功能丧失突变或编码蛋白质而不具有可用药性的突变） 口袋）。功能丧失突变将通过利用上位关系和合成致死突变来解决。 关系，使用假设驱动和基于CRISPR的筛选方法。Kaelin实验室 最近显示，沙利度胺样药物重定向cereblon泛素连接酶降解IKF 1和IKF 3， 在骨髓瘤中起重要作用的转录因子。在这项工作的过程中，他们开发了一种 这项技术使他们能够筛选出在特定条件下不稳定（或稳定）的蛋白质。 化学或遗传干扰物，以及筛选可使细胞不稳定的化学和遗传干扰物。 (or稳定）目的蛋白质。前者将用于识别基于蛋白质的生物标志物以进行监测 目标分子途径，后者将用于寻找能够 目的去稳定化癌蛋白。他们还确定了一个带有IKZF 1/3的模块化降解决定子，可用于 靶向异源蛋白进行破坏，这将纳入临床前靶向验证研究。 最后，基于CRISPR的基因编辑将用于快速制作由特定基因驱动的癌症小鼠模型。 树干突变并用于测试这些研究中出现的治疗和监测策略。

Summary: Solid tumors generate genetically distinct subclones during their evolution and expansion. Deep sequencing followed by quantification of mutant allele frequencies within a given tumor allows one to infer evolutionary trees consisting of shared early driver (“truncal”) mutations and divergent late driver (“branch”) mutations. This knowledge suggests one should therapeutically target truncal mutations, since they are theoretically shared by all of the cells within a tumor, rather than late mutations. Moreover, it is likely that some mutations that occur late during tumor evolution are only advantageous to (or tolerated by) tumor cells because of the mutations that preceded them. In such cases targeting truncal mutations could have therapeutic effects by unmasking deleterious effects to the tumor cell caused by the late mutations. In fact, virtually every successful targeted cancer drug attacks a genetic event that is known or suspected to be truncal. Combining two drugs that inhibit the same truncal lesion in different ways, such as when combining retinoic acid with arsenic trioxide to inhibit the PML-RAR fusion protein in acute promyelocytic leukemia, should enhance efficacy and reduce therapeutic resistance. The Kaelin Lab has had a longstanding interest in pRB and pVHL tumor suppressor proteins and most recently, in IDH oncoproteins. Mutations affecting these proteins occur as early truncal events in specific cancers such as small cell lung cancer (pRB), clear cell renal cancer (pVHL), and acute myelogenous leukemia (IDH1 and IDH2). The Kaelin Lab has played an important role in demonstrating the roles of pRB loss, pVHL loss, and mutant IDH in tumor maintenance and in identifying their pathogenic downstream targets. This proposal seeks to create new paradigms for targeting truncal mutations, including those currently deemed undruggable (for example, loss of function mutations or mutations encoding proteins without druggable pockets). Loss of function mutations will be addressed by exploiting epistatic relationships and synthetic lethal relationships, using both hypothesis-driven and CRISPR-based screening approaches. The Kaelin Lab recently showed that thalidomide-like drugs redirect the cereblon ubiquitin ligase to degrade the IKF1 and IKF3 transcription factors, which play important roles in myeloma. In the course of this work they developed a technology that allows them to screen for proteins that are destabilized (or stabilized) in response to specific chemical or genetic perturbants, as well as to screen for chemical and genetic perturbants that can destabilize (or stabilize) proteins of interest. The former will be used to identify protein-based biomarkers for monitoring molecular pathways of interest and the latter will be used to look for small molecules/targets capable of destabilizing oncoproteins of interest. They also identified a modular degron with IKZF1/3 that can be used to target heterologous proteins for destruction, which will be incorporated into preclinical target validation studies. Finally, CRISPR-based gene editing will be used to rapidly make mouse models of cancer driven by specific truncal mutations and for testing therapeutic and monitoring strategies emerging from these studies.