Distal chromosome 6q harbors a haploinsufficient tumor suppressor gene that regulates PI3K signaling in glioblastoma

Glioblastoma is a universally fatal disease characterized by remarkable molecular heterogeneity. Prognostic biomarkers in glioblastoma have implications for patient management and drug development but are currently limited. In this study, we analyzed exome-wide human glioblastoma somatic copy number alteration data and discovered cytoband 6q27 as an independent poor prognostic marker across multiple glioblastoma datasets. We then combined CRISPR-Cas9 data, human spatial transcriptomic data, and human and mouse RNA sequencing data to nominate PDE10A as a potential haploinsufficient tumor suppressor in the 6q27 region. Mouse glioblastoma modeling using the RCAS/tv-a system confirmed that Pde10a suppression induced an aggressive glioma phenotype in vivo. Cell culture analysis showed that decreased Pde10a expression led to increased Pi3k/Akt signaling, a response blocked by selective Pi3k inhibitors. Single nucleus RNA sequencing from our mouse gliomas in vivo, in combination with cell culture validation showed that Pde10a suppression was associated with a proneural to a mesenchymal transition that exhibited increased cell adhesion and decreased cell migration. PDE10A loss was associated with unmethylated MGMT promoter status in human glioblastoma and resistance to temozolomide and radiation therapy in vitro. Our results indicate that patients with glioblastoma harboring PDE10A loss have worse outcomes, increased resistance to standard-of-care therapy, and potentially increased sensitivity to PI3K inhibition. Overall design: We targeted Pde10a with shRNAs in mouse neural stem cells deficient in Cdkn2a

胶质母细胞瘤（Glioblastoma）是一种普遍致命的疾病，以显著的分子异质性为典型特征。胶质母细胞瘤的预后生物标志物对患者管理与药物开发具有重要指导价值，但目前可用的此类标志物仍较为匮乏。本研究分析了全外显子组范围的人类胶质母细胞瘤体细胞拷贝数变异（somatic copy number alteration）数据，在多组胶质母细胞瘤数据集中鉴定出细胞带6q27作为独立不良预后标志物。随后，本研究结合CRISPR-Cas9数据、人类空间转录组学（spatial transcriptomic）数据以及人类与小鼠的RNA测序数据，将6q27区域的PDE10A候选为潜在的单倍剂量不足型肿瘤抑制基因。利用RCAS/tv-a系统构建的小鼠胶质母细胞瘤模型证实，Pde10a抑制会在体内诱导出侵袭性胶质瘤表型。细胞培养分析显示，Pde10a表达下调会增强PI3K/Akt信号通路活性，该效应可被选择性PI3K抑制剂阻断。针对我们体内小鼠胶质瘤的单细胞核RNA测序结果结合细胞培养验证表明，Pde10a抑制与前神经元型-间充质转化相关，该转化表现为细胞黏附能力增强、细胞迁移能力下降。在人类胶质母细胞瘤中，PDE10A缺失与O6-甲基鸟嘌呤-DNA甲基转移酶（MGMT）启动子未甲基化状态相关，且在体外实验中表现出对替莫唑胺与放射治疗的耐药性。本研究结果提示，携带PDE10A缺失的胶质母细胞瘤患者预后更差、对标准治疗方案的耐药性更强，且可能对PI3K抑制治疗具有更高的敏感性。实验整体设计：我们在Cdkn2a缺陷型小鼠神经干细胞中利用短发夹RNA（shRNAs）靶向抑制Pde10a。