The CXCR4-SDF-1 Axis in Metastatic Rhabdomyosarcoma

描述（由申请人提供）：横纹肌肉瘤（RMS）是儿童中最常见的肉瘤，并且经常浸润骨髓（BM）。 我们最近发表的数据表明，BM 微环境中分泌的基质衍生因子 1 (SDF-1) 可能在将表达 SDF-1 CXCR4 受体的 RMS 细胞导向 BM 方面发挥着至关重要的作用。 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。阐明CXCR4启动的分子机制。 由于我们观察到散射因子 (SF) 增加/引发 CXCR4 RMS 细胞对 SDF-1 梯度的趋化反应，因此我们将重点关注 RMS 转移中 SDF-1-CXCR4 和 SF-c-Met 轴之间串扰的分子机制。 我们将研究转移中哪些 SDF-1 介导的步骤受到 SF 的影响，并且根据我们的初步数据，我们将测试以下假设：SF 通过增加 CXCR4 纳入膜脂筏来调节 RMS 细胞对 SDF-1 梯度的反应性。 目标#2。确定PAX基因是否调节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，因此我们将研究 PAX 基因是否直接调节 RMS 细胞中的 CXCR4 表达。 我们将测试从 RMS 患者分离的细胞中的 CXCR4 表达是否也与 RMS 的肺泡类型以及 PAX3-和 PAX7-FKHR 融合和/或 PAX-3 和 PAX-7 野生型基因的过度表达相关。 目标#3：评估通过靶向 SDF-1-CXCR4 轴来阻断 RMS 细胞转移行为的治疗策略。 我们注意到放疗/化疗会诱导各个器官分泌 SDF-1，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。 为了控制体内 RMS 细胞自发和放疗/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采用新合成的 CXCR4 受体小分子抑制剂 (TE14013)。 这项工作对于设计阻断 SDF-1-CXCR4 轴以治疗 CXCR4 阳性癌症的策略具有相关性。

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.