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(NF1)的儿童易患幼年粒单核细胞白血病(JMML)， 一种以造血干细胞为标准治疗的侵袭性骨髓增生性肿瘤(MPN) 移植(HSCT)。不幸的是，HSCT后的复发率很高，特别是在NF1患者。我们 发现NF1在造血细胞中具有肿瘤抑制基因的功能，并表明NF1 失活导致RAS/Raf/MEK/ERK信号失控。这项工作表明， 过度活跃的RAS信号在JMML发病机制中的作用，我们的小组和其他人随后发现 其他RAS途径基因的突变包括NRAS、KRAS、PTPN11和CBL。RAS途径突变 在诊断和复发时总是出现很高的等位基因频率。进展为急性髓系白血病 白血病(AML)发生在20%-30%的JMML患者中，并经常与以下疾病的发生有关 含有次级突变的亚克隆，最常见的是SETBP1或SH2B3。与 JMML的分子遗传学研究--用Mx1-Cre转基因灭活条件突变的Nf1flx等位基因 产生或表达致癌的KrasG12D或NrasG12D在造血细胞中诱导JMML样MPN 老鼠。我们利用这些基因工程小鼠(GEM)模型进行临床前试验和 观察MEK抑制剂对MPN Kras和Nf1突变小鼠的显著疗效。在这个初始阶段 在孢子资助周期中，我们开启了MEK抑制剂曲美替尼的国家二期临床试验 复发/难治性JMML患者(ADVL1521)并观察到患者的客观反应 到目前为止治疗过的。注册正在进行中，我们正在与核心B(OMICS)和C(病理学)合作，以 进行相关的分子和病理分析。我们还开发了灵敏的和可重现的 在我们部署要解决的当前资助期内用于监测分子反应的分析 其他翻译研究问题。最后，我们与欧洲和日本的同事合作， 将全球DNA甲基化确定为高甲基化最多样本结果的新生物标记物 预示着与基因无关的最差预后。我们将通过以下方式扩展这些新颖的观察结果 以下目标：目标1.为JMML患者进行创新的临床试验，这些试验源于我们的 实验室和临床前研究。我们将完成正在进行的ADVL1521试验，并已开发出 首次在新诊断的JMML中进行介入风险分层临床试验；以及，目标2。进行生物学和 JMML患者标本和GEM模型中有前景的治疗方法的临床前研究为临床提供信息 翻译。我们的总体目标是为婴儿和儿童开发更有效和毒性更低的疗法 通过靶向潜在的分子发病机制与JMML合作。这些研究也对 由过度活跃的RAS信号驱动的改善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.