Project 3: Efficacy of MEK Inhibition in Juvenile Myelomonocytic Leukemia

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）， 侵袭性骨髓增生性肿瘤（MPN）。JMML患者的中位生存期<1年， 造血干细胞移植（HSCT），HSCT后总治愈率约为50%。我们的研究 表明NF 1在JMML患者中作为肿瘤抑制基因发挥作用，涉及过度活跃的Ras信号传导 在这种侵袭性癌症的发病机制中起着重要作用。与这一假设相一致，随后的研究发现， JMML患者的NRAS、KRAS、PTPN 11和CBL基因突变。尽管HSCT的常规使用， JMML，高达30%的患者进展为急性髓细胞白血病（AML）。与分子结构一致 JMML的遗传学，使用Mx 1-Cre转基因在JMML中消除条件突变Nf 1flox等位基因， 造血区室诱导JMML样MPN在小鼠中诱导，我们在这方面的临床前研究 遗传学上精确的小鼠模型揭示了有效和选择性MEK抑制剂的显著功效。 有趣的是，我们发现治疗并没有根除突变细胞，但调节了它们的增殖， 体内分化。在这些研究的基础上，本DHART SPORE的项目3将追求两个具体目标。 首先，我们将进行一项由研究者发起的试验，研究FDA批准的MEK抑制剂曲美替尼在复发性 和新诊断的JMML我们还将询问反应和抗性的分子机制 通过利用下一代测序技术的敏感残留疾病检测， 监测JMML标本中的突变等位基因负荷。我们假设MEK抑制将显著减少或 根除JMML儿童亚群中的JMML细胞，并将诱导临床改善而不改变 突变等位基因频率。我们进一步假设，一个完整的遗传反应将预测一个 我们将询问最初对曲美替尼有反应的患者的白血病细胞， 然后复发以确定候选耐药突变。在目标2中，我们将研究人JMML细胞， 使用以Nf 1失活为特征的MPN和AML小鼠模型来研究继发性突变 在JMML标本中鉴定的影响对曲美替尼的反应，并在功能上验证候选物 耐药机制。项目3将受益于本SPORE中的其他项目，并为其他项目提供信息， 依赖于管理、组学和生物标本/病理学核心来成功实现其 目标.

ABSTRACT – PROJECT 3 Children with neurofibromatosis type 1 (NF1) are predisposed to juvenile myelomonocytic leukemia (JMML), an aggressive myeloproliferative neoplasm (MPN). The median survival of JMML patients is <1 year without hematopoietic stem cell transplantation (HSCT), and the overall cure rate is ~50% after HSCT. Our studies showing that NF1 functions as a tumor suppressor gene in JMML patients implicated hyperactive Ras signaling in the pathogenesis of this aggressive cancer. Consistent with this hypothesis, subsequent studies uncovered mutations in the NRAS, KRAS, PTPN11, and CBL genes in JMML patients. Despite the routine use of HSCT in JMML, up to 30% of patients progress to acute myeloid leukemia (AML). Consistent with the molecular genetics of JMML, using the Mx1-Cre transgene to inactivate a conditional mutant Nf1flox allele in the hematopoietic compartment induces a JMML-like MPN is induced in mice, and our preclinical studies in this genetically accurate mouse model revealed remarkable efficacy of potent and selective MEK inhibitors. Interestingly, we found that treatment did not eradicate mutant cells, but modulated their proliferation and differentiation in vivo. Based on these studies, Project 3 of this DHART SPORE will pursue two specific aims. First, we will conduct an Investigator-initiated trial of the FDA-approved MEK inhibitor trametinib in relapsed and newly diagnosed JMML. We will also interrogate molecular mechanisms of response and resistance through the use of sensitive residual disease assays that harness next-generation sequencing technologies to monitor mutant allele burden in JMML specimens. We hypothesize that MEK inhibition will markedly reduce or eradicate JMML cells in a subset of children with JMML, and will induce clinical improvement without altering mutant allele frequency in others. We further postulate that a complete genetic response will predict a favorable outcome, and we will interrogate leukemia cells from patients who initially respond to trametinib and then relapse to identify candidate resistance mutations. In Aim 2, we will investigate human JMML cells and use mouse models of MPN and AML characterized by Nf1 inactivation to investigate how secondary mutations identified in JMML specimens influence the response to trametinib, and to functionally validate candidate mechanisms of drug resistance. Project 3 will benefit from and inform the other Projects in this SPORE, and are dependent on the Administrative, Omics, and Biospecimens/Pathology Cores for successfully achieving its goals.