The CXCR4-SDF-1 Axis in Metastatic Rhabdomyosarcoma

描述（申请人提供）：横纹肌肉瘤（Rhabdomyosarcoma， RMS）是儿童中最常见的肉瘤，通常浸润骨髓（BM）。我们最近发表的数据表明，基质衍生因子-1 （SDF-1）在骨髓微环境中分泌，可能在引导表达SDF-1受体CXCR4的RMS细胞进入骨髓中发挥关键作用。为了研究RMS转移的机制，并开发一种新的治疗方法来阻断RMS中的SDF-1-CXCR4轴，我们提出了三个目标。目标# 1。目的：阐明CXCR4启动的分子机制。由于我们观察到散射因子（SF）增加/启动CXCR4+ RMS细胞对SDF-1梯度的趋化反应，我们将重点研究SDF-1-CXCR4和SF-c- met轴之间串扰在RMS转移中的分子机制。我们将研究哪些SDF-1介导的转移步骤受到SF的影响，并且基于我们的初步数据，我们将验证SF通过增加CXCR4在膜脂筏中的包合来调节RMS细胞对SDF-1梯度的反应性的假设。目标# 2。确定PAX基因是否调控CXCR4的表达。由于在RMS细胞系中，CXCR4的表达与肺泡RMS以及PAX3-FKHR和PAX7-FKHR基因的表达相关，我们将研究PAX基因是否直接调控CXCR4在RMS细胞中的表达。我们将测试从RMS患者分离的细胞中CXCR4的表达是否也与RMS的肺泡型、PAX3-和PAX7-FKHR融合和/或PAX-3和PAX-7野生型基因的过表达相关。目标3。通过靶向SDF-1-CXCR4轴来评估阻断RMS细胞转移行为的治疗策略。我们注意到放射/化疗诱导各种器官的SDF-1分泌，并创造一个“允许转移”的环境。因此，我们假设SDF-1-CXCR4轴可能在逃避治疗的肿瘤细胞的扩散中发挥作用。为了在体内控制RMS细胞的自发和放射/化疗诱导的转移行为，我们将在人类RMS异种移植免疫缺陷小鼠模型中使用新合成的CXCR4受体小分子抑制剂（TE14013）。这项工作将有助于设计阻断SDF-1-CXCR4轴的策略来治疗cxcr4阳性癌症。

DESCRIPTION (provided by applicant): Rhabdomyosarcoma (RMS) is the most common sarcoma in children and very often infiltrates the bone marrow (BM). Our recently published data show that stromal derived factor-1 (SDF-1), which is secreted within the BM microenvironment, may play a crucial role in directing to the BM the RMS cells that express the receptor for SDF-1, CXCR4. To investigate the mechanisms operating in the metastasis of RMS and develop a new therapeutic approach to blocking the SDF-1-CXCR4 axis in RMS, we propose three aims. Aim #1. To elucidate the molecular mechanisms of CXCR4 priming. Since we observed that scatter factor (SF) increases/primes the chemotactic response of CXCR4+ RMS cells to an SDF-1 gradient, we will focus on molecular mechanisms of crosstalk between the SDF-1-CXCR4 and SF-c-Met axes in RMS metastasis. We will investigate which SDF-1-mediated steps in metastasis are influenced by SF and, based on our preliminary data, we will test the hypothesis that SF by increasing inclusion of CXCR4 into membrane lipid rafts modulates the responsiveness of RMS cells to SDF-1 gradient. Aim #2. To determine whether PAX genes regulate the expression of CXCR4. Since in RMS cell lines the expression of CXCR4 correlates with alveolar RMS and expression of the PAX3-FKHR and PAX7-FKHR genes, we will investigate whether PAX genes directly regulate CXCR4 expression in RMS cells. We will test whether CXCR4 expression in cells isolated from RMS patients also correlates with the alveolar type of RMS, and with PAX3- and PAX7-FKHR fusion and/or overexpression of PAX-3 and PAX-7 wild-type genes. Aim # 3. To assess therapeutic strategies to block the metastatic behavior of RMS cells by targeting the SDF-1-CXCR4 axis. We noticed that radio-/chemotherapy induces SDF-1 secretion in various organs and creates a "metastasis-permissive" environment. Thus we hypothesize that the SDF-1-CXCR4 axis may play a role in the spread of tumor cells that have escaped therapy. To control the spontaneous and radio-/chemotherapy-induced metastatic behavior of RMS cells in vivo, we will employ the newly synthesized small-molecular inhibitor of the CXCR4 receptor (TE14013) in a human RMS xenotransplant-immunodeficient mouse model. This work will be of relevance for designing strategies to block the SDF-1-CXCR4 axis to treat CXCR4-positive cancers.