PROJECT 3: A High Content Clinical Trial of the MEK inhibitor Trametinib in JMML

摘要（项目3） 患有1型神经纤维瘤病（NF 1）的儿童易患青少年粒单核细胞白血病（JMML）， 一种侵袭性骨髓增生性肿瘤（MPN），其标准治疗是造血干细胞移植 移植（HSCT）。不幸的是，HSCT后复发率很高，特别是在NF1患者中。我们 发现NF1在造血细胞中起肿瘤抑制基因的作用，并表明NF1 失活导致Ras/Raf/MEK/ERK信号转导失调。这项工作表明， 过度活跃的Ras信号在JMML发病机制中的作用，我们的研究小组和其他人随后确定了 其他Ras途径基因中的突变，包括NRAS、KRAS、PTPN11和CBL。Ras途径突变 在诊断和复发时总是以高等位基因频率存在。进展为急性髓细胞性 白血病（AML）发生在20 - 30%的JMML患者中，并且经常与白血病的生长相关。 携带继发突变的亚克隆，最常见于SETBP 1或SH 2B3。符合 JMML的分子遗传学，使用Mx1-Cre转基因消除条件突变Nf1flox等位基因 在造血细胞中产生或表达致癌KrasG12D或NrasG12D诱导JMML样MPN， 小鼠我们利用这些基因工程小鼠（GEM）模型进行临床前试验， 在患有MPN的Kras和Nf1突变小鼠中观察到MEK抑制剂的显著功效。在这个初始 在SPORE的资助周期中，我们启动了MEK抑制剂曲美替尼的国家2期临床试验， 复发性/难治性JMML（ADVL 1521）患者，并在患者中观察到客观缓解 治疗至今。入组正在进行中，我们正在与Cores B（组学）和C（病理学）合作， 进行相关的分子和病理分析。我们还开发了灵敏和可重复的 在当前资助期间，我们部署了用于监测分子反应的检测， 其他翻译研究问题。最后，我们与欧洲和日本的同事合作， 确定整体DNA甲基化作为最高甲基化样本结果的新生物标志物 预示着最差的预后，与基因型无关。我们将把这些新奇的观察扩展到 目标：目标1。为JMML患者进行创新的临床试验， 实验室和临床前研究。我们将完成正在进行的ADVL 1521试验， 在新诊断的JMML中进行的第一次干预性风险分层临床试验;以及，目标2。进行生物学和 在JMML患者标本和GEM模型中进行有前景的治疗方法的临床前研究，以告知临床 翻译.我们的总体目标是为婴儿和儿童开发更有效、毒性更小的治疗方法 与JMML通过针对潜在的分子发病机制。这些研究也对 这是改善由过度活跃的Ras信号传导驱动的其他癌症治疗的根本问题。

Abstract (Project 3) Children with neurofibromatosis type 1 (NF1) are predisposed to juvenile myelomonocytic leukemia(JMML), an aggressive myeloproliferative neoplasm (MPN) for which the standard of care is hematopoietic stem cell transplant (HSCT). Unfortunately, relapse rates are high after HSCT, particularly in NF1 patients. We discovered that NF1 functions as a tumor suppressor gene in hematopoietic cells and showed that NF1 inactivation results in deregulated Ras/Raf/MEK/ERK signaling. This work suggested a central role of hyperactive Ras signaling in JMML pathogenesis, and our group and others subsequently identified mutations in other Ras pathway genes including NRAS, KRAS, PTPN11, and CBL. Ras pathway mutations are invariably present at high allelic frequency at both diagnosis and relapse. Progression to acute myeloid leukemia (AML) occurs in 20-30% of JMML patients and is frequently associated with outgrowth of subclones that harbor secondary mutations, most commonly in SETBP1 or SH2B3. Consistent with the molecular genetics of JMML, using the Mx1-Cre transgene to inactivate the conditional mutant Nf1flox allele generated or to express oncogenic KrasG12D or NrasG12D in hematopoietic cells induces a JMML-like MPN in mice. We utilized these genetically engineered mouse (GEM) models to perform preclinical trials and observed remarkable efficacy of MEK inhibitors in Kras and Nf1 mutant mice with MPN. During this initial cycle of SPORE funding, we opened a national phase 2 clinical trial of the MEK inhibitor trametinib for patients with relapsed/refractory JMML (ADVL1521) and have observed objective responses in patients treated to date. Enrollment is ongoing and we are collaborating with Cores B (Omics) and C (Pathology) to perform correlative molecular and pathologic analyses. We also developed sensitive and reproducible assays for monitoring molecular responses during the current funding period that we deployed to address additional translational research questions. Finally, we collaborated with colleagues in Europe and Japan to identify global DNA methylation as a novel biomarker of outcome with the most hypermethylated samples portending the worst prognosis independent of genotype. We will extend these novel observations through the following aims: Aim 1. To conduct innovative clinical trials for patients with JMML that emanate from our laboratory and preclinical studies. We will complete the ongoing ADVL1521 trial and have developed the first interventional risk-stratified clinical trial in newly diagnosed JMML; and, Aim 2. To perform biologic and preclinical studies of promising therapies in JMML patient specimens and GEM models to inform clinical translation. Our overall goal is to develop more effective and less toxic therapies for infants and children with JMML by targeting the underlying molecular pathogenesis. These studies also have implications for the fundamental problem of improving the treatment of other cancers driven by hyperactive Ras signaling.