在普遍致命的脑肿瘤胶质母细胞瘤（GBM）中，含有促瘤的胶质母细胞（GSCs）。EGFR基因扩增或突变常见于GBMs，并与预后不良相关。然而，GSCs中的EGFR变异以及它们在GSCs的维持和GBM的进展中的作用尚不清楚。我们通过生物信息学的HISAT-StringTie-Ballgown分析流程检测到了EGFR变异，并通过5' RACE、RT-PCR、核酸酶保护和北方杂交实验证实。EGFRx的功能通过神经球、细胞存活、颅内异种移植和RNA测序进行了研究。通过免疫印迹、免疫共沉淀、免疫荧光、荧光素酶报告基因、RT-PCR和CUT&Tag等实验证明了EGFRx-STAT5信号转导。 我们鉴定出了一种新的EGFR变异体（EGFRx），它专门在GSCs中表达。与缺少exon 2-7的EGFRvIII变异体不同，EGFRx的特点是缺少exon 2-14，并编码一个不具备整个细胞外配体结合结构域的EGFR蛋白质。我们观察到EGFRx具有显著的糖基化，在GSCs的自我更新、增殖和肿瘤形成中起重要作用，并且在与正常脑组织相比，脑胶质母细胞瘤中的活性较高。在机制上，EGFRx通过激酶结构域的自发非对称二聚化，在GSCs中恒定而特异性地激活STAT5。 通过对STAT5的恒定激活，EGFRx在维持GSC表型和促进GBM进展中发挥着重要作用，这表明EGFRx-STAT5信号转导是GBM的一个有前途的治疗靶点。© 2023年作者。牛津大学出版社代表神经肿瘤学会发表。版权所有。如需权限，请发送电子邮件至journals.permissions@oup.com。

Glioblastomas are universally lethal brain tumors containing tumor-propagating glioblastoma stem cells (GSCs). EGFR gene amplification or mutation is frequently detected in GBMs and is associated with poor prognosis. However, EGFR variants in GSCs and their role in the maintenance of GSCs and progression of GBM are unclear.EGFR variants were detected through bioinformatic HISAT-StringTie-Ballgown pipeline and verified through 5' RACE, RT-PCR, ribonuclease protection, and northern blotting assays. EGFRx function was investigated through neurosphere, cell viability, intracranial xenograft and RNA-seq assays. EGFRx-STAT5 signaling was investigated through western blotting, coimmunoprecipitation, immunofluorescence, luciferase reporter, RT-PCR and CUT&Tag assays.We identified a novel EGFR variant (EGFRx), that is specifically expressed in GSCs. Unlike the EGFRvIII variant, which lacks exons 2-7, EGFRx is characterized by the absence of exons 2-14, and encodes an EGFR protein that does not possess the entire extracellular ligand-binding domain. We observed that EGFRx exhibits significant glycosylation, is required for GSC self-renewal, proliferation, and tumorigenesis, and highly active in glioblastomas compared to normal brain tissue. Mechanistically, EGFRx constitutively and specifically activates STAT5 in GSCs through spontaneous asymmetric dimerization of the kinase domain.EGFRx plays essential roles in the maintenance of the GSC phenotype through constitutive activation of STAT5 and promotes GBM progression, suggesting that EGFRx-STAT5 signaling represents a promising therapeutic target for GBM.© The Author(s) 2023. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.