Investigations of menin function in Ewing sarcoma

项目总结 儿童癌症可以被认为是发育障碍，致癌司机劫持正常 促进肿瘤发生的发展计划。支架蛋白脑膜素是正常生活所必需的 在人类癌症中，它可以作为肿瘤抑制因子或癌基因发挥作用，这取决于 背景。薄荷素的不同功能与其通过其在基因转录调控中的作用有关。 与MLL组蛋白甲基转移酶以及与其他上下文相关的结合伙伴的相互作用。在……里面 MLL重排白血病(MLLr)，蛋白质：脑膜素和MLL融合蛋白之间的蛋白质相互作用驱动 致癌基因转录程序的表观激活。MLLr白血病对这些细胞的严重依赖 相互作用代表了一种独特的治疗脆弱性和薄荷素的小分子抑制剂：MLL 交互作用正在被开发用于白血病的定向治疗。尤文肉瘤是一种间叶性肿瘤。 推测干细胞(MSC)起源，由EWS/ETS融合驱动，最常见的是EWS/FLI1。EWS/FLI1 通过劫持正常的MSC分化启动肉瘤形成。重要的是，薄荷素在 早期间充质发育，它对谱系承诺和成骨细胞都有贡献 差异化。我们已经证明，相对于MSC，尤因肉瘤中的薄荷素过度表达，并且这种缺失 会导致致瘤性丧失。然而，薄荷素发挥其致癌作用的机制 对这些肿瘤细胞的作用尚不清楚。我们的初步数据确定了丝氨酸合成途径 (SSP)作为尤文肉瘤中薄荷素的关键下游靶点。我们已经确认SSP是超- 在尤文肉瘤中以一种脑膜素依赖的方式激活，并抑制PHGDH，即限速 SSP中的酶，导致尤文肉瘤活性的严重丧失，揭示了尤文的关键依赖 路上有肉瘤。我们的数据还表明，EWS/FLI1本身有助于PHGDH的激活和 SSP和EWS/FLI1诱导靶子集的转录依赖于膜蛋白。这些数据 共同支持薄荷素在尤文肉瘤中作为致癌中心的假设。在这 ，我们将研究薄荷素的作用机制，并检验创新假说 EWS/FLI1通过劫持脑膜素依赖的转录调控促进肿瘤的发生。在目标1中，我们将 确定Menin激活SSP的机制，并将阐明EWS/FLI1在其中的作用 进程。在目标2中，我们将依次定义SSP的关键代谢物，这些代谢物有助于肿瘤的维持 以确定尤文肉瘤细胞如此依赖这一途径的原因。在AIM 3中将定义全基因组 骨髓间充质干细胞和尤文肉瘤中薄荷素的转录靶点及其受EWS/FLI1的影响。这个 拟议的研究将促进对尤文肉瘤生物学基础的基础知识 了解EWS/FLI1如何劫持正常脑膜生理学以促进肿瘤发生。这些洞察力的目标是 将为开发新的、毒性较低的脑膜素导向疗法治疗尤因肉瘤提供机会。

PROJECT SUMMARY Pediatric cancers can be considered developmental disorders in which oncogenic drivers hijack normal developmental programs to promote tumorigenesis. The scaffolding protein menin is essential for normal development and, in human cancer, can function as a tumor suppressor or an oncogene, depending on context. The diverse functions of menin are linked to its role in regulation of gene transcription via its interaction with MLL histone methyltransferases, as well as with other context-dependent binding partners. In MLL-rearranged leukemia (MLLr), protein:protein interactions between menin and MLL-fusion proteins drive epigenetic activation of oncogenic transcription programs. A critical dependence of MLLr leukemia on these interactions represents a unique therapeutic vulnerability and small molecule inhibitors of the menin:MLL interaction are being developed for leukemia-directed therapy. Ewing sarcomas are mesenchymal tumors of presumed stem cell (MSC) origin that are driven by EWS/ETS fusions, most commonly EWS/FLI1. EWS/FLI1 initiates sarcomagenesis by hijacking normal MSC differentiation. Importantly, menin plays an essential role in early mesenchymal development, where it contributes to both lineage commitment and osteoblastic differentiation. We have shown that menin is over-expressed by Ewing sarcoma relative to MSC and that loss of menin results in loss of tumorigenicity. However, the mechanisms by which menin exerts its oncogenic effects in these tumor cells remain unknown. Our preliminary data identified the serine synthesis pathway (SSP) as a key downstream target of menin in Ewing sarcoma. We have confirmed that the SSP is hyper- activated in Ewing sarcoma in a menin-dependent manner, and that inhibition of PHGDH, the rate limiting enzyme in the SSP, results in profound loss of Ewing sarcoma viability, revealing a key dependence of Ewing sarcoma on the pathway. Our data also suggest that EWS/FLI1 itself contributes to activation of PHGDH and the SSP, and that transcription of a subset of EWS/FLI1-induced targets is dependent on menin. These data collectively support the hypothesis that menin functions as an oncogenic hub in Ewing sarcoma. In this proposal, we will investigate the mechanisms of menin function and test the innovative hypothesis that EWS/FLI1 promotes tumorigenesis by hijacking menin-dependent transcriptional regulation. In Aim 1 we will determine the mechanism by which menin activates the SSP and will elucidate the role of EWS/FLI1 in this process. In Aim 2 we will define the key metabolites of the SSP that contribute to tumor maintenance in order to determine why Ewing sarcoma cells are so dependent on this pathway. In Aim 3 will define genome-wide transcriptional targets of menin in MSC and Ewing sarcoma and how they are impacted by EWS/FLI1. The proposed studies will advance fundamental knowledge of the biologic underpinnings of Ewing sarcoma and discover how EWS/FLI1 hijacks normal menin physiology to promote oncogenesis. It is goal that these insights will provide opportunities to develop novel, and less toxic, menin-directed therapies for Ewing sarcoma.