Improving Therapeutic Approaches for RAS-driven Embryonal Rhabdomyosarcoma

摘要 尽管使用了积极的化疗和放射治疗，患有高危横纹肌肉瘤(RMS)的儿童 包括带有RAS突变的晚期或转移性胚胎性RMS(ERMS)，预后非常差(20- 确诊后5年存活率为30%)，在过去30年中没有明显改善。更进一步，当前 多模式治疗与危及生命的后遗症有关。这个项目的重点是 为RAS突变型ERMS开发基因毒性较低的靶向治疗。初步数据支持快速翻译 垂直靶向MAPK通路作为ERMS的一种治疗方法。提议的目标是基于 根据以下观察：(I)在RAS驱动的ERMS中，对MEK抑制剂的耐药性是以下结果 CRAF途径的再激活；(Ii)新一代2型RAF抑制剂与MEK抑制剂的联合 导致大多数RAS突变型ERMS PDX模型的戏剧性回归，但不是治愈的。因此，两者 固有和获得性耐药性将是长期疗效的障碍；(3)创新的单一小鼠 测试(SMT)实验设计表明，与他们的高危分类一致，RAS突变体ERM PDX/CDX模型，在最近的高危RMS临床中使用的密集多药方案迅速失效 协议(ARST0431)。因此，本项目的目标是：1)确定先天和后天抗性的机制 在RAS驱动的ERMS中联合靶向RAF和MEK，以促进更有效的临床结果。 使用DNA和RNA测序，我们将识别与抗药性和 验证和定义先天和后天抵抗2型RAF和MEK抑制剂的机制 在ERMS中；2)评估如何将该方法整合到当前的临床化疗方案中 SMT实验设计。我们的研究将告知生物标记物对2型RAF+MEK抑制剂的反应 与化疗相比，如何对这种组合进行排序，以优化对 RMS PDX/CDX模型，因此直接影响RAS驱动的ERMS的临床试验设计。

Summary Despite the use of aggressive chemo-radiation therapy, children with high-risk rhabdomyosarcoma (RMS) including advanced or metastatic embryonal RMS (ERMS) with RAS mutations, have very poor outcomes (20- 30% survival at 5 years from diagnosis) with no significant improvement over the last 30 years. Further, current multimodality therapies are associated with life-long life-threatening sequelae. This project focuses on developing less-genotoxic, targeted therapy for RAS-mutant ERMS. Preliminary data support rapid translation of vertical targeting of the MAPK pathway as a therapeutic approach in ERMS. The proposed aims are based upon the following observations: (i) In RAS-driven ERMS, resistance to MEK inhibitors is a consequence of pathway reactivation through CRAF; (ii) Combination of new generation type 2 RAF inhibitors with MEK inhibitors cause dramatic regressions of most RAS-mutant ERMS PDX models but are not curative. Consequently, both intrinsic and acquired resistance will be a barrier for long-term curative outcomes; (iii) Innovative single mouse testing (SMT) experimental design shows that, consistent with their high-risk classification, RAS-mutant ERMS PDX/CDX models, rapidly fail intensive multidrug regimens used in the most recent high-risk RMS clinical protocol (ARST0431). Therefore, this project aims to: 1) define mechanisms of innate and acquired resistance to co-targeting RAF and MEK in RAS-driven ERMS with the goal to facilitate more impactful clinical outcomes. Using DNA and RNA sequencing, we will identify genomic/epigenomic changes associated with resistance and validate and define mechanisms of innate and acquired resistance to combining type 2 RAF and MEK inhibitors in ERMS; 2) evaluate how this approach can be integrated into current clinical chemotherapy protocols using the SMT experimental design. Our studies will inform biomarkers of response to type 2 RAF + MEK inhibitors combination and how this combination can be sequenced relative to chemotherapy to optimize responses of RMS PDX/CDX models, thus directly impacting clinical trials design for RAS-driven ERMS.