G3BP1 Suppresses SPOP Ubiquitin Ligase to Promote Prostate Tumorigenesis

前列腺癌(PCA)在2016年估计造成26,120人死亡，是全球第二大癌症 导致男性癌症死亡的原因。最近，前列腺癌的分子特征揭示了惊人的基因组 异质性和明确的不同分子亚类，可提供对不同临床病程的洞察。 SPOP的反复突变是前列腺癌中最常见的点突变，大约发生在 10%的患者患有早期和晚期疾病。SPOP是以cullin 3为基础的底物受体 泛素连接酶，它招募雄激素受体(AR)、TRIM24和SRC-3以及其他关键调节因子 泛素化和降解，从而控制AR转录、DNA损伤修复和 肿瘤抑制。SPOPmut定义了前列腺癌的一个独特的分子类别，其特征是激活了 AR信号与DNA双链断裂(DSB)修复与转录反应(基因集)损伤 签名)类似于BRCA1失活。我们已经询问了主服务器上的TCGA RNA-seq数据集 (未经治疗)前列腺癌定义213个差异表达基因的SPOPmut转录签名， 并在独立的rna-seq队列中验证了该基因集在多个队列中的显著丰富。 SPOPmut案件。令人惊讶的是，我们还检测到了没有SPOP基因突变的原发性前列腺癌， 但表现出与SPOP突变亚类相同的基因表达特征，表明其他 在这些初级的“SPOPmut样”PCA中，事件可以表现为SPOP突变。 为了进一步了解SPOP在前列腺癌发生中的作用和调控，我们进行了 串联亲和纯化结合质谱分析，鉴定为新的SPOP-G3BP1。 结合蛋白。G3BP1不是SPOP的底物，而是SPOP泛素连接酶的有效抑制因子。 这种首创的SPOP抑制剂揭示了以前未被识别的SPOP失活方法，即 与PCa相关的SPOP基因突变无关。重要的是，我们检测到异常高水平的 Pca中的G3BP1有无SPOP突变。我们假设G3BP1的失调定义了一个 前列腺癌的新亚型具有SPOPmut样的分子特征、病理生理特征和 对AR和PARP靶向治疗药物的敏感性。此应用程序构建在独特的 前列腺癌基因组学和病理学研究团队的优势和资源互补 (Rubin)，前列腺癌患者的分子分类、临床管理和精确治疗(Barbieri)， 计算基因组学(Sboner)和基于cullin的泛素连接酶(周)。在本提案中，我们将1) 确定G3BP1异常在前列腺癌分类和潜在治疗中的临床价值 2)确定G3BP1抑制SPOP的生化机制及其作用 新发现的G3BP1-SPOP泛素信号通路在AR转录、DNA修复和前列腺中的作用 肿瘤的发生，以及3)评估G3BP高的PCa对AR和PARP靶向治疗的敏感性。

Prostate cancer (PCa) accounts for an estimated 26,120 deaths in 2016 representing the second-greatest cause of cancer death among men. Recent molecular characterization of PCa has revealed striking genomic heterogeneity and defined distinct molecular subclasses that may provide insight to the variable clinical course. Recurrent mutations in SPOP are the most common point mutations in prostate cancer, occurring in about 10% of patients across early and advanced disease. SPOP is a substrate receptor of the Cullin 3-based ubiquitin ligase, which recruits androgen receptor (AR), TRIM24 and SRC-3 and other key regulators for ubiquitination and degradation, thereby governing the threshold of AR transcription, DNA damage repair, and tumor suppression. SPOPmut defines a distinct molecular class of prostate cancer characterized by activation of AR signaling and impairment of DNA double strand break (DSB) repair with transcriptional response (gene set signature) similar to that of BRCA1 inactivation. We have interrogated the TCGA RNA-seq datasets on primary (untreated) prostate cancer to define a SPOPmut transcriptional signature of 213 differentially expressed genes, and validated in independent RNA-seq cohorts for significant enrichment of this gene set in multiple cohorts of SPOPmut cases. Surprisingly, we also detected primary prostate tumors without mutation of the SPOP gene, yet showing the same gene expression characteristics to the SPOP mutant subclass, indicating that other events can phenocopy SPOP mutations in these primary “SPOPmut-like” PCa. To further understand the function and regulation of SPOP in prostate tumorigenesis, we performed tandem affinity purification coupled with mass spectrometry analysis, and identified G3BP1 as a novel SPOP- binding protein. G3BP1 is not a substrate of SPOP, but acts as a potent inhibitor of the SPOP ubiquitin ligase. This first-in-kind SPOP inhibitor revealed previously unrecognized means of SPOP inactivation that is independent of PCa-associated SPOP gene mutations. Importantly, we detected abnormally high levels of G3BP1 in PCa either with or without SPOP mutations. We hypothesize that dysregulation of G3BP1 defines a new subclass of prostate cancer with SPOPmut-like molecular signature, pathophysiological characteristics, and sensitivity to AR- and PARP targeting therapeutics. This application is built upon the unique and complementary strengths and resources of a team of investigators in prostate cancer genomics and pathology (Rubin), molecular classification, clinical management and precision therapy of PCa patients (Barbieri), computational genomics (Sboner), and cullin-based ubiquitin ligases (Zhou). In this proposal, we will 1) determine the clinical value of G3BP1 dysregulation in PCa classification and potential therapeutic implications, 2) determine the biochemical mechanisms underlying SPOP inhibition by G3BP1 and the roles of this newly discovered G3BP1-SPOP ubiquitin signaling pathway in AR transcription, DNA repair and prostate tumorigenesis, and 3) assess the susceptibility of G3BP1high PCa to AR- and PARP-targeting therapies.