Preventing Therapeutic Resistance in RAS-mutated Pediatric Cancers

项目总结/摘要 对于患有RAS突变肿瘤的儿科患者，测试靶向疗法的临床试验是有限的， 缺乏临床前数据。这是不幸的，因为靶向治疗有可能使一个显着的 对儿科患者发病率的影响。细胞毒性药物显著延迟儿童正常发育 导致终生后遗症。相比之下，优先攻击RAS突变肿瘤细胞的靶向疗法 虽然保留正常发育的组织可以限制不必要的后遗症， 癌症患者。不幸的是，使用MEK抑制剂的RAS突变癌细胞的单一药物靶向 或突变型RAS抑制剂在很大程度上是无效的;由于多种RTK的上调， 以及随后的WT RAS信号传导的超活化。因此，需要替代的治疗方法， 治疗RAS突变的儿科癌症为此，我们采取两种互补的方法来抑制WT RAS信号转导旨在增强RAS突变儿科癌症靶向治疗的有效性。 虽然每种方法在事后看来都是显而易见的，但都没有在RAS突变的临床前模型中进行过测试。 儿科癌症 我们首先研究了在何种程度上广泛抑制近端RTK信号传导使用抑制剂的共同 近端RTK信号传导中间体SHP 2或SOS 1增强疗效并延迟治疗抗性 在RAS突变的非CNS儿科癌细胞中的MEK或突变的RAS抑制剂。由于MEK抑制诱导 补偿RTK依赖性信号级联，与MEK共靶向RTK信号是一个有吸引力的 治疗RAS突变的儿科癌症的方法。然而，对多种RAS突变癌症的研究显示， 重新激活的特定RTK可能在细胞系或研究之间存在差异，即使在相同的癌症类型中也是如此。 因此，我们不是使用针对每个患者可能不同的特定RTK抑制剂，而是抑制共同的近端 RTK信号传导中间体SHP 2或SOS 1，并使用药理学和耐药性测定， 确定哪种药物-药物组合在增强药物杀伤和抑制治疗方面最有效 阻力然后，我们在患者来源的异种移植模型中测试最有希望的治疗组合。 作为第二种方法，我们确定突变型RAS和WT RAS联合抑制的程度， 效应子信号传导增强RAS-1中突变型RAS抑制剂的疗效并延迟对突变型RAS抑制剂的治疗抗性。 突变的非中枢神经系统儿科癌细胞。RAS蛋白显示RAF和PI 3 K途径的差异活化： HRAS有效激活PI 3 K，但激活RAF较差，而KRAS有效激活RAF，但激活RAF较差。 激活PI 3 K。由于MEK和PI 3 K途径必须被抑制以有效杀死RAS突变的 儿科癌症，我们使用突变RAS家族之间的信号差异的基本理解， 成员检查RAS突变的非CNS儿科癌细胞的合理治疗方法。然后我们 在患者来源的异种移植模型中测试最有希望的治疗组合。

Project Summary/Abstract For pediatric patients with RAS-mutated tumors, clinical trials testing targeted therapies are limited due to the paucity of preclinical data. This is unfortunate, as targeted therapies have the potential to make a significant impact on morbidity for pediatric patients. Cytotoxic agents significantly delay normal childhood development leading to lifelong sequalae. In contrast, targeted therapies that preferentially attack RAS-mutated tumor cells while sparing normal developing tissue can limit unwanted sequalae and enhance overall outcomes for pediatric cancer patients. Unfortunately, single-agent targeting of RAS-mutated cancer cells using either MEK inhibitors or mutant RAS inhibitors is largely ineffective; resistance rapidly develops due to upregulation of multiple RTKs and subsequent hyperactivation of WT RAS signaling. Thus, alternative therapeutic approaches are needed to treat RAS-mutated pediatric cancers. Toward this end, we take two complementary approaches at inhibiting WT RAS signaling designed to enhance the effectiveness of targeted therapies in RAS-mutated pediatric cancers. While each approach seems obvious in hindsight, neither has been tested in pre-clinical models of RAS-mutated pediatric cancers. We first examine the extent to which broad inhibition of proximal RTK signaling using inhibitors to the common proximal RTK signaling intermediates SHP2 or SOS1 enhances the efficacy of and delays therapeutic resistance to MEK or mutant RAS inhibitors in RAS-mutated non-CNS pediatric cancer cells. Since MEK inhibition induces compensatory RTK-dependent signaling cascades, co-targeting RTK signaling with MEK is an attractive approach to treat RAS-mutated pediatric cancers. However, studies in multiple RAS-mutated cancers revealed that the specific RTK that is reactivated can vary between cell lines or studies, even within the same cancer type. Thus, rather than using specific RTK inhibitors that may differ for each patient, we inhibit the common proximal RTK signaling intermediates SHP2 or SOS1, and use both pharmacologic and drug resistance assays to determine which drug-drug combinations are the most potent at enhancing drug killing and inhibiting therapeutic resistance. We then test the most promising therapeutic combinations in patient-derived xenograft models. As a second approach, we determine the extent to which combined inhibition of mutant RAS and WT RAS effector signaling enhances the efficacy of and delays therapeutic resistance to mutant RAS inhibitors in RAS- mutated non-CNS pediatric cancer cells. RAS proteins show differential activation of RAF and PI3K pathways: HRAS potently activates PI3K but poorly activates RAF, whereas KRAS potently activates RAF but poorly activates PI3K. Since both MEK and PI3K pathways must be inhibited for effective killing of RAS-mutated pediatric cancers, we use this fundamental understanding of signaling differences between mutant RAS family members to examine rational therapeutic approaches in RAS-mutated non-CNS pediatric cancer cells. We then test the most promising therapeutic combinations in patient-derived xenograft models.