Deciphering the functional role of recurrent PPP2R1A mutations on endometrial metastasis

项目概述：子宫浆液性癌(USC)、子宫癌肉瘤(USC)和子宫肌肉瘤 代表最具侵袭性的子宫癌亚型，在子宫癌中所占比例不成比例 美国与癌症相关的死亡人数。这些高级别子宫癌的致命性在很大程度上是由于 这些癌症有扩散和转移的倾向，使患者缺乏有效的治疗 选择。尽管如此，这些疾病亚型转移潜能的分子驱动因素仍然存在。 不完全理解。 我们小组和其他人之前的工作已经确定了该基因内的一个反复突变的热点 编码蛋白磷酸酶2A(PP2A)的A支架亚基，PPP2R1A。这些突变， P179R和S256F仅发生在这些高级别子宫癌亚型中，而在 任何其他癌症类型。蛋白磷酸酶2A(PP2A)是一个丝氨酸/苏氨酸磷酸酶家族，其中 活性杂三聚体由催化(C)亚基、支架(A)亚基和底物组成 指导调节(B)亚单位。总体而言，PP2A被认为是一种肿瘤抑制蛋白，但某些 异源三聚体具有促癌作用。我们已经证明这些突变与子宫癌有关。 以抑制肿瘤形成的方式调节PP2A功能的肿瘤发生 异三聚体，同时保持促进肿瘤的异三聚体复合体完好无损。 我的初步数据显示，PP2A P179R和S256F突变增强了肿瘤的启动能力， 以及在体外形成3D肿瘤球体的能力。重要的是，表达这些突变的子宫癌细胞 在体内也以增加的速度形成腹膜结节，这表明这些突变可能增强了 建立腹膜腔内新的肿瘤形成模型。突变表达的条件培养液 子宫癌细胞促进肿瘤球体形成表达子宫癌细胞生长的WT，提示 突变细胞可能会为肿瘤的形成创造更宽松的肿瘤微环境。初步 数据表明，突变细胞增加了-连环蛋白的磷酸化和WNT配体的表达。 这一建议的工作假设是，反复出现的突变体P179R和S256F增强了子宫 肿瘤转移通过增加WNT信号和分泌WNT配体来实现。为了检验这一假设，我们 将开发PP2A敲入异种移植模型，以确定这些反复突变是如何促进 促进体内转移(特定目标1)。第二，机械论研究将探索 突变的子宫癌细胞，探索WNT配体，结合分泌组分析。这些研究还将 探讨PP2A缺失与WNT介导的EMT之间的联系(特异性目标2)。这项提案旨在破译 复发的PP2A𝛼突变在子宫癌转移中的功能作用 高级别子宫癌的治疗靶点(S)。

Project Summary: Uterine serous carcinomas (USC), uterine carcinosarcomas (UCS), and leiomyosarcomas represent the most aggressive subtypes of uterine cancer and account for a disproportionate number of uterine cancer related deaths in the United States. The lethality of these high-grade uterine cancers is largely due to the propensity of these cancers to disseminate and metastasize, leaving patients with a lack of effective treatment options. Despite this, the molecular drivers of the metastatic potential of these disease subtypes remain incompletely understood. Previous work by our group and others have identified a recurrent mutational hotspot within the gene encoding for the A scaffolding subunit of the protein phosphatase 2A (PP2A), PPP2R1A. These mutations, P179R and S256F, occur exclusively within these high-grade subtypes of uterine cancer and are not found in any other cancer type. Protein phosphatase 2A (PP2A), is a family of serine/threonine phosphatases, where the active heterotrimeric form is comprised of the catalytic (C) subunit, the scaffolding (A) subunit, and a substrate directing regulatory (B) subunit. In aggregate, PP2A is considered a tumor suppressor protein, but certain heterotrimers have tumor promoting roles. We have shown that these mutations contribute to uterine cancer tumorigenesis by modulating PP2A function in a manner that impairs the formation of tumor suppressive heterotrimers, while leaving tumor promoting heterotrimeric complexes intact. My preliminary data show that the PP2A P179R and S256F mutations enhance tumor initiating capacity, and the ability to form 3D tumor spheres in vitro. Importantly, uterine cancer cells expressing these mutations also form intraperitoneal nodules at an increased rate in vivo, suggesting that these mutations may enhance the establishment of new tumor formation in the peritoneal cavity. Conditioned media from the mutant expressing uterine cancer cells promoted tumor sphere formation of WT expressing uterine cancer cell growth, indicating that the mutant cells may create a more permissive tumor microenvironment for tumor formation. Preliminary data suggests that the mutant cells have increased -catenin phosphorylation and WNT ligand expression. The working hypothesis of this proposal is that the recurrent mutants, P179R and S256F, enhance uterine cancer metastasis through increased WNT signaling and secretion of WNT ligands. To test this hypothesis, we will develop PP2A A knock-in xenograft models to determine how these recurrent mutants contribute to enhanced metastasis in vivo (Specific Aim 1). Second, mechanistic studies will explore the secreted factors from the mutant uterine cancer cells, exploring WNT ligands, coupled with secretome analysis. These studies will also explore the link between loss of PP2A and WNT mediated EMT (Specific Aim 2). This proposal aims to decipher the functional role of recurrent PP2A A𝛼 mutations on uterine cancer metastasis, which may identify a new therapeutic target(s) of high-grade uterine cancers.