Defining the non-myogenic origins of pediatric rhabdomyosarcoma

项目总结/摘要 横纹肌肉瘤（RMS）是儿童最常见的软组织肉瘤， 癌症的形式。患有高风险疾病的儿童3年生存率仅为20%， 化疗、手术和放疗的积极治疗。尽管进行了严格的临床试验， 在过去的三十年里，患有高风险横纹肌肉瘤的儿童并没有显著改变。 RMS可以发生在全身的各个部位，近40%的肿瘤发生在头部和颈部。 肿瘤位置和融合状态是关键的预后因素。RMS组织学类似于发育中的骨骼 肌肉，并已被推测起源于遗传受损的骨骼肌祖细胞。 然而，控制RMS发展和指定位置的基因仍然难以捉摸。RMS也发生在 缺乏骨骼肌的组织，如膀胱、前列腺和胆管树，表明 可能起源于骨骼肌谱系之外。目前，起源的细胞和 具体RMS位置和因此预后是未知的。我们的长期目标是阐明 确定RMS发育停滞的基础，并设计新的针对RMS的药物治疗。 在此之前，我们报道了一种新的融合阴性RMS（FN-RMS）基因工程小鼠模型 由Cre重组酶激活条件性组成型活性Smoothened（SmoM 2）等位基因引起 由脂肪蛋白2（aP 2）启动子表达。在我们的模型中，50%的小鼠在24小时内形成可见的肿瘤。 在解剖学上仅限于颈部的28天生命。也许我们的老鼠最有趣的一面 FN-RMS模型是RMS起源于肌肉外部的建议，因为aP 2-Cre在肌肉中不表达。 骨骼肌。该提案的目的是利用早期发病和解剖限制， 颈部，以识别原始细胞和指定RMS位置的因子。为了实现这一目标，我们 提出以下具体目标：1）确定Shh中肿瘤发生的发育时间和位置- 驱动FN-RMS 2)鉴定aP 2-Cre; SmoM 2小鼠中FN-RMS的起源细胞。3)定义区域特异性 的FN-RMS。利用移植，我们将确定位置特异性是否由细胞驱动 自主地在非细胞上自主地进行。我们将分离aP 2标记的早期发育细胞， 小鼠和肿瘤小鼠，以确定基因表达，表观遗传和染色质可及性差异 这些群体之间的差异有助于定位和时间特异性。我们将利用我们独特的FN- RMS小鼠模型，以确定细胞的起源，并提供深入了解发育事件促进 FN-RMS形成。这项工作将有助于阐明主要的发展Shh通路如何有助于 头颈部细胞类型的特异性允许FN-RMS。考虑到横纹肌肉瘤的广泛性 位置以及位置如何决定预后，我们推测不同的细胞来源将进一步完善 预后沿着组织学和进一步的遗传特征。

Project Summary/Abstract Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma in children and is a highly aggressive form of cancer. Children with high-risk disease suffer from a 3-year survival of only 20% despite very aggressive therapy with chemotherapy, surgery and radiation. Despite rigorous clinical trials, the survival of children suffering from high-risk rhabdomyosarcoma has not significantly changed over the last three decades. RMS can occur at locations throughout the body with nearly 40% of tumors occurring in the head and neck. Tumor location and fusion status are key prognostic factors. RMS histology resembles developing skeletal muscle and has been speculated to originate from genetically compromised skeletal muscle progenitors. However, the genes that control RMS development and specify location remain elusive. RMS also occurs in tissues devoid of skeletal muscle such as the urinary bladder, prostate, and biliary tree suggesting the possibility of origins outside of the skeletal muscle lineage. Currently, the cell of origin and the factors that specify RMS location and thus prognosis are unknown. Our long-term goal is to elucidate the mechanisms that determine the basis for developmental arrest in RMS and design novel, directed drug therapies for RMS. Previously, we reported a novel genetically engineered mouse model of fusion-negative RMS (FN-RMS) resulting from activation of a conditional, constitutively active Smoothened (SmoM2) allele by Cre recombinase expressed from the adipose protein 2 (aP2) promoter. In our model, 50% of the mice develop visible tumors by 28 days of life that are anatomically restricted to the neck. Perhaps the most intriguing aspect of our mouse FN-RMS model is the suggestion that RMS originates outside of the muscle, as aP2-Cre is not expressed in skeletal muscle. The objective of this proposal is to leverage the early onset and anatomic restriction to the neck to identify the cell of origin and factors that specify RMS location. To accomplish this objective we propose the following Specific Aims: 1) Determine developmental timing and location for oncogenesis in Shh- driven FN-RMS. 2) Identify the cell of origin of FN-RMS in aP2-Cre;SmoM2 mice. 3) Define regional specificity of FN-RMS. Using transplantation, we will determine whether the location specificity is driven cell autonomously on non-cell autonomously. We will isolate aP2-labeled, early developmental cells from normal mice and tumor mice to define how gene expression, epigenetic and chromatin accessibility differences between these populations contribute to the location and timing specificity. We will leverage our unique FN- RMS mouse model to identify the cell of origin and provide insights into the developmental events promoting FN-RMS formation. This work will help illuminate how the major developmental Shh pathway contributes to the specificity of cell types in the head and neck allowing for FN-RMS. Given the wide spectrum of RMS tumor locations and how location dictates prognosis we speculate that the varied cell of origin will further refine prognosis along with histology and further genetic characterization.