The pathogenesis of chromosome 7q deletions in juvenile myelomonocytic leukemia

儿童恶性肿瘤经常携带染色体臂水平的拷贝数变化， 大量基因的表达水平，以及节段性改变如何促进肿瘤发生 仍然定义不清。这是我们对儿童癌症发病机制理解的一个主要空白 并阻碍了新疗法的合理设计。其中一种缺失是7号染色体的部分或全部缺失 [-7/del（7 q）]，这是儿童骨髓恶性肿瘤中最常见的细胞遗传学异常。-7/del（7 q）发生 在高达33%的幼年粒单核细胞白血病（JMML）中， 综合征/骨髓增生性肿瘤（MDS/MPN），特征为RAS通路突变和少数其他 躯体改变在骨髓恶性肿瘤中，-7/del（7 q）与治疗耐药性和不良反应相关 原因不明的预后。本提案的长期目标是了解 -7/del（7 q）的分子发病机制，并揭示JMML患者的新治疗靶点。前几 我们报道了转录因子CUX 1是一个高度保守的髓系肿瘤抑制基因， 编码在7 q上。我们证明了致癌RAS通路突变与CUX 1 肿瘤类型之间的缺失。我们最近设计了一种Cux 1敲低小鼠模型（Cux 1 low）， 发生具有人JMML特征的自发性MDS/MPN，包括所有患者中的骨髓单核细胞扩增， 造血区室浸润到非造血组织中，所有骨髓谱系中的发育不良， 和贫血。除CUX 1外，7 q缺失通常较大，并跨越其他已建立或推定的肿瘤。 抑制基因和/或骨髓调节因子。在这个建议中，我们将测试7 q是一个假设， “连续性基因综合征”区域，其中多个基因的组合剂量不平衡驱动JMML， 与致癌RAS信号传导的组合。我们将使用我们独特的小鼠模型和CRISPR/Cas9基因组 编辑以实现以下特定目标：1）确定细胞和分子机制， Cux 1敲低和Ras在JMML中协同作用; 2）定义组合剂量失衡的发病机制 JMML中的7 q基因。这项工作将通过以下方式对骨髓恶性肿瘤领域产生积极影响： 阐明7 q基因的组合缺失驱动疾病的分子机制; ii）鉴定 用于治疗JMML的新分子靶标;和iii）建立生理学上准确的小鼠模型 其中可以快速测试和优化用于人类疾病的新疗法。我们的JMML小鼠模型 将满足儿童骨髓恶性肿瘤的主要未满足需求，特别是临床前小鼠模型， 在未来的研究中筛选批准的和实验性的药物。我们的工作将揭示相关的增殖 和分化途径的治疗目标，以测试在这个模型。

Pediatric malignancies frequently harbor chromosome-arm level copy number changes that potentially impact the expression level of a large number of genes, yet how segmental alterations contribute to tumorigenesis remains poorly defined. This is a major gap in our understanding of the pathogenesis of childhood cancers and hampers the rational design of new therapies. One such deletion is loss of part or all of chromosome 7 [-7/del(7q)], the most common cytogenetic abnormality in myeloid malignancies of childhood. -7/del(7q) occurs in up to 33% of juvenile myelomonocytic leukemias (JMML), which are aggressive myelodysplastic syndrome/myeloproliferative neoplasms (MDS/MPN) characterized by RAS pathway mutations and few other somatic alterations. In myeloid malignancies, -7/del(7q) is associated with treatment resistance and a poor prognosis for reasons that are not understood. The long-term goal of this proposal is to understand the molecular pathogenesis of -7/del(7q) and to reveal new therapeutic targets for JMML patients. In previous work, we reported that the transcription factor, CUX1, is a highly conserved myeloid tumor suppressor gene encoded on 7q. We demonstrated a striking association of oncogenic RAS pathway mutations with CUX1 deletions across tumor types. We recently engineered a Cux1 knockdown mouse model (Cux1low), which develops a spontaneous MDS/MPN with features of human JMML, including myelomonocytic expansion in all hematopoietic compartments with infiltration into non-hematopoietic tissues, dysplasia in all myeloid lineages, and anemia. In addition to CUX1, 7q deletions are typically large and span other established or putative tumor suppressor genes and/or myeloid regulators. In this proposal, we will test the hypothesis that 7q is a `Contiguous gene syndrome' region, wherein combined dosage imbalance of multiple genes drives JMML, in combination with oncogenic RAS signaling. We will use our unique mouse model and CRISPR/Cas9 genome editing to achieve the following Specific Aims: 1) Identify the cellular and molecular mechanisms by which Cux1 knockdown and Ras cooperate in JMML; 2) Define the pathogenesis of combinatorial dosage imbalance of 7q genes in JMML. This work will have a positive impact on the field of myeloid malignancies by: i) elucidating the molecular mechanisms by which combinatorial loss of 7q genes drives disease; ii) identifying new molecular targets for the treatment of JMML; and iii) establishing a physiologically accurate mouse model in which novel therapies for human disease can be rapidly tested and optimized. Our mouse model of JMML will fulfill a major unmet need for childhood myeloid malignancies, specifically a preclinical mouse model for screening of approved and experimental drugs in future studies. Our work will reveal the relevant proliferative and differentiation pathways for therapeutic targets to test in this model.