Mechanisms and targeting of aberrant Gas activation in myeloid neoplasms

项目摘要/摘要 骨髓增生异常综合征(MDS)是一种预后不佳、进展频繁的髓系肿瘤 到急性髓系白血病(AML)，没有有效的治疗方法。十年前，一项具有变革性的发展 这种疾病的潜在可能性是发现超过一半的MDS患者在 编码剪接因子(SFS，即调节前mRNA剪接的RNA结合蛋白)的基因。而当 SF突变在疾病过程中的高频率和早期发生使它们很有希望 靶点，通过剪接调节药物在治疗上利用这一点的努力在临床上并没有显示出希望 针对这些目标的测试和药物开发流水线，以及一般的MDS，目前几乎是空的。 我们建立了遗传忠实的人诱导多能干细胞(IPSC)模型 使用CRISPR基因编辑的MDS，并执行剪接(RNA-Seq)和RNA结合的综合分析 (ECLIP)搜索错误剪接的转录本，这些转录本是两个主要SF突变的直接共同目标 (SRSF2 P95L和U2AF1 S34F)。我们发现突变的SRSF2和突变的U2AF1都能引起改变 基因GNAS的剪接，促进更长异构体的产生(GNAS-L)，这反过来又产生 刺激性G蛋白的α亚基的较长形式，G⍺S(G⍺S-L)。G蛋白是关键的信号转导 分子参与许多重要的信号通路和细胞功能，包括致癌过程。 我们使用功能、生化和群体遗传学方法的初步数据支持关键作用 对于G⍺S(G⍺S-L)作为MDS驱动程序的冗长形式，揭示了SF突变驱动的新机制 MDS为MDS、AML和其他癌症开辟了一条全新的、未经探索的治疗途径 SF基因突变。 这项提议的目标是调查G⍺S作为MDS的治疗靶点，并确定 G⍺S-L.抑制信号传导的治疗干预的机会。具体来说，我们建议：(1) 评价G-⍺S直接降解(通过DTag)或抑制(通过新型环肽)的作用 剪接因子(SF)突变的MDS和AML造血细胞(原代和IPSC来源)最近使用 基于IPSC的MDS向SAML进展模型和MDS的纵向骨髓样本 进展为急性髓细胞白血病的患者；(2)G基因S-L下游细胞信号的特征和靶向 候选和无偏见的方法(反相蛋白质阵列、细胞周期分析、转录组学)；以及(3)识别 G蛋白偶联受体参与SF突变MDS和AML中GS-L的激活 聚焦CRISPR KO屏幕。 这项研究可以建立一个新的治疗靶点，可能改变MDS，AML和 可能是其他癌症。

PROJECT SUMMARY/ABSTRACT Myelodysplastic syndromes (MDS) are myeloid neoplasms with dismal prognosis, frequent progression to acute myeloid leukemia (AML) and no effective treatment. A decade ago, a development with transformative potential for this disease was the discovery that more than half of MDS patients have somatic mutations in genes encoding splicing factors (SFs, i.e. RNA binding proteins that regulate pre-mRNA splicing). While the high frequency and early occurrence during the disease course of SF mutations rendered them promising targets, efforts to therapeutically leverage this through splicing modulator drugs did not show promise in clinical testing and the drug development pipeline for these targets, and for MDS in general, is currently nearly empty. We developed genetically faithful human induced pluripotent stem cell (iPSC) models of SF-mutated MDS using CRISPR gene editing and performed integrative analyses of splicing (RNA-Seq) and RNA binding (eCLIP) to search for mis-spliced transcripts that are direct common targets of two of the main SF mutations (SRSF2 P95L and the U2AF1 S34F). We found that both mutant SRSF2 and mutant U2AF1 cause altered splicing of the gene GNAS, promoting the production of a longer isoform (GNAS-L), which in turn produces a longer form of the alpha subunit of the stimulatory G protein, G⍺s (G⍺s-L). G proteins are key signaling molecules involved in many important signaling pathways and cell functions, including oncogenic processes. Our preliminary data using functional, biochemical and population genetics approaches support a critical role for the long form of G⍺s (G⍺s-L) as an MDS driver and reveal a new mechanism by which SF mutations drive MDS that opens a completely novel and unexplored therapeutic avenue for MDS, AML and other cancers with SF gene mutations. The goal of this proposal is to investigate G⍺s as a therapeutic target for MDS and identify opportunities for therapeutic interventions that inhibit signaling by G⍺s-L. Specifically, we propose to: (1) Evaluate the effects of direct degradation (through a dTAG) or inhibition (by novel cyclic peptides) of G⍺s in splicing factor (SF)-mutated MDS and AML hematopoietic cells (primary and iPSC-derived) using recently developed iPSC-based models of MDS-to-sAML progression and longitudinal bone marrow samples from MDS patients who progressed to AML; (2) Characterize and target cell signaling downstream of Gs-L through candidate and unbiased approaches (Reverse Phase Protein Array, CyTOF, transcriptomics); and (3) Identify the G-protein coupled receptors (GPCRs) involved in Gs-L activation in SF-mutated MDS and AML through focused CRISPR KO screens. This study can establish a novel therapeutic target that may transform the treatment of MDS, AML and possibly other cancers.