The Role of Eya3 as a downstream target of EWS Fli1 in Ewings Sarcoma

描述（由申请人提供）：尤文氏肉瘤是一种侵袭性儿科骨和软组织癌症。出现转移的患者和复发的患者的预后特别差。尤文氏肉瘤是由染色体易位产生EWS/Fli 1融合蛋白驱动的。我们已经确定了发育蛋白Eya 3作为EWS/Fli 1的下游靶点。Eya 3对DNA修复很重要，也被发现是与同源框蛋白的六个家族的二分转录因子复合物的一部分。Eya/Six复合物对发育很重要，但当发育完成后不适当地表达时，会促进其他癌症中的许多致癌特性，包括增殖，存活和转移。然而，这种复合物在儿童肿瘤，特别是尤文氏肉瘤中的作用以前从未被研究过。与在其他人类肿瘤中观察到的相似，抑制尤文肉瘤细胞中的Eya 3对增殖和存活具有适度的影响。然而，我们已经发现Eya 3在尤文肉瘤中的新作用，其中Eya 3敲低显著增加尤文肉瘤细胞的化学敏感性。这可能是最近描述的Eya 3促进有效DNA修复的能力的结果。此外，由于肿瘤起始细胞（TIC）与治疗抗性（化疗抗性）癌症有关，并且由于Eya 3的结合伴侣Six 1增加乳腺癌中的TIC群体，我们进一步研究了Eya 3是否可以调节尤文肉瘤中的TIC群体。事实上，Eya 3敲低减少了肿瘤起始细胞群。该数据表明Eya 3可能通过多种且可能相互相关的机制在介导与复发性疾病相关的尤文肉瘤表型中起重要作用。该提案中概述的研究旨在更好地了解Eya 3在与尤文肉瘤复发相关的表型中的作用，试图确定新的新药靶点，当抑制时，可能会减少与尤文肉瘤相关的不良临床结局。进行的研究将使我们能够确定EWS/Fli 1调节Eya 3的机制，然后进一步评估Eya 3在调节肿瘤起始细胞群和化疗耐药性中的作用。Eya 3具有独特的酪氨酸磷酸酶结构域，以及驱动转录所需的转录激活结构域沿着其致癌伙伴Six 1。这项提案中的工作将使我们能够确定Eya 3的哪些活动对其在尤文肉瘤中的作用很重要，以便我们可以更好地指导我们用小分子抑制剂靶向Eya 3。 公共卫生相关性：尤文氏肉瘤是一种主要影响儿童的毁灭性疾病。尤因肉瘤患者的预后，特别是在复发和治疗抵抗性疾病的情况下，是很差的。我们已经确定了一种分子，Eya 3，当被抑制时，显着降低了尤文肉瘤细胞的治疗耐药特性的百分比。我们计划研究这种分子如何使尤文肉瘤细胞对治疗产生抗性，这样我们就可以设计出专门针对尤文肉瘤患者的这种分子的药物。

DESCRIPTION (provided by applicant): Ewing's sarcoma is an aggressive pediatric cancer of the bone and soft tissue. Patients that present with metastasis and patients who relapse have especially poor outcomes from this disease. Ewing's sarcoma is driven by a chromosomal translocation that produces the EWS/Fli1 fusion protein. We have identified the developmental protein, Eya3, as a downstream target of EWS/Fli1. Eya3 is important for DNA repair and is also found as part of a bipartite transcription factor complex with the Six family of homeobox proteins. The Eya/Six complex is important for development, but when inapropriately expresed after development is complete, promotes many oncogenic properties in other cancers, including proliferation, survival, and metastasis. However, the role of this complex in pediatric tumors, specificaly Ewing's sarcoma, has never before been examined. Similar to what is observed in other human tumors, inhibition of Eya3 in Ewing's sarcoma cells has a modest effect on proliferation and survival. However, we have discovered a novel role for Eya3 in Ewing's sarcoma, where Eya3 knockdown significantly increases Ewing's sarcoma cell chemosensitivity. This may be the result of the recently described ability of Eya3 to facilitate efficient DNA repair Additionally, since tumor-initiating cells (TIC) are implicated in treatment-resistant (chemoresistant) cancers, and since the binding partner of Eya3, Six1, increases TIC populations in breast cancer, we further examined whether Eya3 may modulate a TIC population in Ewing's sarcoma. Indeed, Eya3 knockdown decreases the tumor-initiating cell population. This data suggests that Eya3 may play an important role in mediating Ewing's sarcoma phenotypes associated with recurrent disease through multiple, and possibly inter- related, mechanisms. Studies outlined in this proposal aim to better understand the role of Eya3 in phenotypes associated with Ewing's sarcoma relapse, in an attempt to identify novel new drug targets that when inhibited, may reduce the poor clinical outcomes associated with Ewing's sarcoma. Studies performed will allow us to determine the mechanism of EWS/Fli1 regulation of Eya3 and then go on to further evaluate the role of Eya3 in modulating tumor-initiating cell populations and in chemoresistance. Eya3 has a unique tyrosine phophatase domain, as well as a transcriptional activation domain required to drive transcription along with its oncogenic partner, Six1. Work within this proposal will allow us to determine which activities of Eya3 are important for its roles in Ewing's sarcoma, so that we can better guide our targeting of Eya3 with small molecule inhibitors. PUBLIC HEALTH RELEVANCE: Ewing's sarcoma is a devastating disease that primarily affects children. The prognosis for Ewing's sarcoma patients, especially in the setting of recurrent and treatment-resistant disease, is poor. We have identified a molecule, Eya3, that when inhibited, significantly decreases the percentage of Ewing's sarcoma cells with treatment-resistant characteristics. We plan to study how this molecule makes Ewing's sarcoma cells resistant to treatment, so that we can design drugs to specifically target this molecule in patient suffering from Ewing's sarcoma.