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(NF1)的儿童易患幼年粒单核细胞白血病(JMML)， 侵袭性骨髓增生性肿瘤(MPN)。JMML患者的中位生存期为1年。 造血干细胞移植(HSCT)，HSCT后总治愈率约为50%。我们的研究 JMML患者中NF1作为肿瘤抑制基因的功能与RAS信号的过度活跃有关 在这种侵袭性癌症的发病机制中。与这一假设一致的是，随后的研究发现 JMML患者NRAS、KRAS、PTPN11和CBL基因突变的研究尽管HSCT在 JMML中，高达30%的患者进展为急性髓系白血病(AML)。与分子上的 JMML的遗传学，使用Mx1-Cre转基因灭活条件突变的Nf1flx等位基因 造血室在小鼠体内诱导JMML样MPN，我们的临床前研究 基因准确的小鼠模型显示，有效的和选择性的MEK抑制剂具有显著的疗效。 有趣的是，我们发现，治疗并没有根除突变细胞，而是调节了它们的增殖和 体内分化。在这些研究的基础上，这个达特孢子的项目3将追求两个具体目标。 首先，我们将进行FDA批准的MEK抑制剂曲美替尼在复发性疾病中的研究人员发起的试验 和新诊断的JMML。我们还将询问反应和抗性的分子机制。 通过使用敏感的残留病检测，利用下一代测序技术 监测JMML样本中的突变等位基因负荷。我们假设抑制MEK将显著减少或 在患有JMML的儿童中根除JMML细胞，并将在不改变的情况下促进临床改善 突变等位基因频率在其他人群中。我们进一步假设，完整的遗传反应将预测 结果良好，我们将询问对曲美替尼和曲美替尼有初步反应的患者的白血病细胞 然后复发以确定候选的耐药突变。在目标2中，我们将研究人类JMML细胞和 使用以NF1失活为特征的MPN和AML小鼠模型来研究继发性突变是如何 在JMML样本中发现影响曲美替尼的反应，并从功能上验证候选药物 耐药机制。项目3将受益于该孢子中的其他项目，并告知该项目，以及 依赖于管理、OMICS和生物质学/病理学核心来成功实现ITS 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.