Targeting EWS/FLI1-driven pathways to improve therapeutic gains in Ewing's Sarcom

描述（由申请方提供）：尤文氏肉瘤家族肿瘤（ESFT）是骨和软组织的实体、高度恶性肿瘤，最常累及儿童和青少年，是年轻成人中第二常见的骨恶性肿瘤。目前的治疗包括化疗和放疗的联合治疗。然而，有两个重要的问题需要考虑：a）尽管ESFT通常对治疗有反应，但总体治愈率较低，因为这些肿瘤非常具有侵袭性，并且患者经常出现转移性疾病;和B）年轻患者暴露于高剂量化疗和/或或辐射通常与各种不良健康影响有关，在某些情况下，这些不良健康影响直到治疗完成多年后才出现。因此，需要治疗策略，以最大限度地提高治愈率，同时最大限度地减少对患者的不良晚期影响。在初步研究中，我们直接靶向EWS/FLI-1，这是已知负责大多数ESFT恶性特性的转录因子，使用设计用于阻断其活性的分子工具，单独或与化疗药物和/或放射联合使用。尽管体外和小鼠异种移植物中的实验证明这些工具有效地延迟了肿瘤生长，但很明显，同时靶向作用于EWS/FLI-1下游的其他分子对于最大化抗肿瘤活性和允许使用较低的治疗剂量是必要的，从而尽可能地减少负面的晚期效应。在这种情况下，该提议的主要目的是利用我们实验室最近建立的新的EWS/FLI-1驱动的途径（EWS/FLI-1-[小窝蛋白->1-蜗牛-E-钙粘蛋白]）来使ESFT细胞对治疗敏感，使用电离辐射（IR）作为模型抗肿瘤剂，其不遭受特异性相关的问题，所述特异性相关的问题经常使化学治疗药物的研究复杂化。由于肿瘤周围正常组织中IR相关迟发效应的程度与IR剂量直接相关，因此在儿科癌症中，重要的是采用可能治愈肿瘤的最低剂量。使用EWS细胞作为ESFT原型，我们的中心假设是（a）靶向小窝蛋白-1（CAV 1）本身和/或其与ESFT分子病理学相关的信号或调节蛋白的相互作用，（如磷脂酶D2和蛋白激酶C1）将使EWS细胞对IR更敏感，和（B）通过同时靶向也已知使EWS细胞放射增敏的其它途径的组分，如聚（ADP-核糖）聚合酶（PARP），可以进一步改善这种应答。因为我们已经将CAV 1鉴定为EWS/FLI-1的直接转录靶标和EWS细胞的致瘤性和化疗反应的关键决定因素，所以靶向CAV 1信号传导可能具有双重作用：通过低剂量IR增强对EWS细胞的杀伤并下调其肿瘤性质。

DESCRIPTION (provided by applicant): Tumors of the Ewing's sarcoma family (ESFT) are solid, highly malignant neoplasms of the bone and soft tissues that most often affect children and adolescents, being the second most common bone malignancies among young adults. Current treatment includes a combined modality with chemotherapy and radiotherapy. However, there are two important problems to consider: a) although ESFT are generally responsive to treatment, the overall cure rate is low because these tumors are very aggressive and patients frequently present with metastatic disease; and b) exposure of young patients to high doses of chemotherapy and/or radiation is frequently associated with a variety of adverse health effects that in some cases do not develop until many years after treatment completion. Consequently, treatment strategies are needed to maximize curability while simultaneously minimizing adverse late effects for the patients. In preliminary studies, we directly targeted EWS/FLI-1, the transcription factor known to be responsible for the malignant properties of most ESFT, using molecular tools designed to block its activity, either alone or in combination with chemotherapeutic drugs and/or radiation. Although experiments in vitro and in mouse xenografts demonstrated that these tools efficiently delayed tumor growth, it became clear that simultaneous targeting of additional molecules that act downstream of EWS/FLI-1 would be necessary to maximize antitumor activity and to allow the use of lower therapeutic doses, thus minimizing negative late effects as much as possible. In this context, the main objective of this proposal is to exploit a novel EWS/FLI-1-driven pathway recently established in our laboratory (EWS/FLI-1-[Caveolin->1-Snail-E-cadherin]) to sensitize ESFT cells to therapy, using ionizing radiation (IR) as a model anti-neoplastic agent that does not suffer from the specificity- related problems that frequently complicate studies with chemotherapeutic drugs. Since the extent of IR related late effects in normal tissues surrounding the tumor are directly related to the IR dose, in pediatric cancers it is important to employ the lowest dose possible to cure the tumors. Using EWS cells as the ESFT prototype, our central hypothesis is that (a) targeting caveolin-1 (CAV1) itself and/or its interactions with signaling or regulatory proteins relevant for ESFT molecular pathobiology (such as phospholipase D2 and protein kinase C1) will render EWS cells more sensitive to IR, and (b) that this response may be further improved by simultaneously targeting components of other pathways also known to radiosensitize EWS cells, such as poly (ADP-ribose) polymerase (PARP). Because we already identified CAV1 as a direct transcriptional target of EWS/FLI-1 and a key determinant of the tumorigenicity and chemotherapeutic response of EWS cells, targeting CAV1 signaling may have a dual effect: enhancing killing of EWS cells by low-dose IR and down- regulating their neoplastic properties.