THE ROLE OF STAT3 SIGNALING IN CHILDHOOD SARCOMAS

信号转导子和转录激活子3（STATs）的组成性激活通常是 在三种最常见的儿童肉瘤的细胞系和患者样本中检测到， 横纹肌肉瘤、骨肉瘤和尤文氏肉瘤。组成型STAT3信号传导参与 通过刺激细胞增殖，介导免疫逃避，促进血管生成， 从而产生抗药性。该项目的中心假设是组成性STATS信号传导是 这些儿童肉瘤的生存和肿瘤发生所需的和关键的，因此，抑制 STATS活性代表了治疗干预的可行方法。这一假设得到了我们的支持。 数据表明，显性阴性形式的STATS，STATS小干扰RNA（siRNA）， 小分子变构STATS抑制剂LLL12可抑制儿童乳腺癌细胞增殖并诱导其凋亡 肉瘤细胞系。我们已经开发了LLL12的类似物LY5，其表现出几个优点，包括 增强对STATS的特异性，增加效力，如在较低药物浓度下的生物活性所证明的 本发明提供了更高浓度、更大的溶解度和预测的口服生物利用度以及更简单的合成方法。的 本建议的目标是在这些初步研究结果的基础上，确定负责STATS的信号 激活儿童肉瘤，并评估LY5的疗效使用的研究与肿瘤 细胞系、儿童肉瘤的小鼠模型（异种移植物、原位肿瘤和转移性肿瘤），以及 自发性骨肉瘤的犬模型。我们的长期目标是使用联合治疗， STAT选择性抑制剂与iGF-1 R（项目3）和NF-κ B（项目1）抑制剂， 改善儿童肉瘤预后。研究的具体目标如下：（1）调查 负责肉瘤细胞中STATS激活的分子机制; 2）评估抑制功效 新型STAT选择性小分子抑制剂LY5对体外肉瘤细胞和小鼠肉瘤的作用 体内模型;和3）确定STATS抑制的生物活性和临床毒性， 自发性犬骨肉瘤 相关性（参见说明）： 在儿童肉瘤中经常检测到STATS的组成性激活， 在体外抑制肿瘤细胞生长和在小鼠异种移植模型中抑制肿瘤生长。本构 STATS信号传导对肉瘤细胞的存活至关重要，并可作为治疗靶点。因此，我们认为， STATS靶向治疗的评价对儿童肉瘤的治疗具有重要意义。

The constitutive activation of Signal Transducer and Activator of Transcription 3 (STATS) is frequently detected in cell lines and patient samples of the three most frequently occurring childhood sarcomas, rhabdomyosarcoma, osteosarcoma, and Ewing's sarcoma. Constitutive STAT3 signaling participates in tumorigenesis by stimulating cell proliferation, mediating immune evasion, promoting angiogenesis, and conferring drug resistance. The central hypothesis of this project is that constitutive STATS signaling is required and critical for survival and tumorigenesis in these childhood sarcomas and as such, inhibition of STATS activity represents a viable approach for therapeutic intervention. This hypothesis is supported by our data demonstrating that a dominant negative form of STATS, STATS small interfering RNA (siRNA), and the small molecule allosteric STATS inhibitor LLL12 can inhibit proliferation and induce apoptosis of childhood sarcoma cell lines. We have developed an analog of LLL12, LY5, that exhibits several advantages including enhanced specificity for STATS, increased potency as evidenced by biologic activity at lower drug concentrations, greater solubility and predicted oral bioavailability, and a simpler method for synthesis. The objectives of this proposal are to build on these initial findings and identify the signals responsible for STATS activation in childhood sarcomas, and evaluate the efficacy of LY5 using a combination of studies with tumor cell lines, mouse models of childhood sarcomas (xenografts, orthotopic tumors and metastatic tumors), and a canine model of spontaneous osteosarcoma. Our long-term objective is to use combined therapy of a STATS-selective inhibitor with iGF-1R (Project 3) and NF-kappa B (Project 1) inhibitors and ultimately improve outcome for childhood sarcomas. The following specific aims will be studied: 1) Investigate the molecular mechanisms responsible for STATS activation in sarcoma cells; 2) Evaluate the inhibitory efficacy of the novel STATS-selective small molecular inhibitor, LY5 on sarcoma cells in vitro and mouse sarcoma models in vivo; and 3) Determine the biologic activity and clinical toxicities of STATS inhibition in spontaneous canine osteosarcoma. RELEVANCE (See instructions): Constitutive activation of STATS is frequently detected in childhood sarcomas and blocking STATS activity inhibits tumor cell growth in vitro and suppresses tumor growth in mouse xenograft models. Constitutive STATS signaling is crucial to the survival of sarcoma cells and may serve as a therapeutic target. Therefore, the evaluation of targeted STATS therapy is relevant and significant to the childhood sarcoma treatments.