Signaling from multiple receptor tyrosine kinases (RTK) contributes to therapeutic resistance in glioblastoma (GBM). Heparan sulfate (HS), present on cell surfaces and in the extracellular matrix, regulates cell signaling via several mechanisms. To investigate the role for HS in promoting RTK signaling in GBM, we generated neural progenitor cells deficient for HS by knockout of the essential HS-biosynthetic enzyme Ext1, and studied tumor initiation and progression. HS-null cells had decreased proliferation, invasion, and reduced activation of multiple RTKs compared with control. In vivo tumor establishment was significantly decreased, and rate of tumor growth reduced with HS-deficient cells implanted in an HS-poor microenvironment. To investigate if HS regulates RTK activation through platelet-derived growth factor receptor α (PDGFRα) signaling, we removed cell surface HS in patient-derived GBM lines and identified reduced cell surface PDGF-BB ligand. Reduced ligand levels were associated with decreased phosphorylation of PDGFRα, suggesting HS promotes ligand–receptor interaction. Using human GBM tumorspheres and a murine GBM model, we show that ligand-mediated signaling can partially rescue cells from targeted RTK inhibition and that this effect is regulated by HS. Indeed, tumor cells deficient for HS had increased sensitivity to EGFR inhibition in vitro and in vivo. Implications: Our study shows that HS expressed on tumor cells and in the tumor microenvironment regulates ligand-mediated signaling, promoting tumor cell proliferation and invasion, and these factors contribute to decreased tumor cell response to targeted RTK inhibition.

中文翻译：

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Ext1合成的硫酸乙酰肝素调节受体酪氨酸激酶信号传导并促进GBM对EGFR抑制剂的抵抗


来自多种受体酪氨酸激酶 (RTK) 的信号传导有助于胶质母细胞瘤 (GBM) 的治疗耐药。硫酸乙酰肝素 (HS) 存在于细胞表面和细胞外基质中，通过多种机制调节细胞信号传导。为了研究 HS 在促进 GBM 中 RTK 信号传导中的作用，我们通过敲除必需的 HS 生物合成酶 Ext1 生成了缺乏 HS 的神经祖细胞，并研究了肿瘤的发生和进展。与对照相比，HS 缺失细胞的增殖、侵袭和多种 RTK 的激活减少。将缺乏 HS 的细胞植入缺乏 HS 的微环境中，体内肿瘤的建立显着减少，肿瘤生长率降低。为了研究 HS 是否通过血小板源性生长因子受体 α (PDGFRα) 信号传导调节 RTK 激活，我们去除了患者来源的 GBM 系中的细胞表面 HS，并鉴定了减少的细胞表面 PDGF-BB 配体。配体水平降低与 PDGFRα 磷酸化降低相关，表明 HS 促进配体-受体相互作用。使用人类 GBM 肿瘤球和鼠 GBM 模型，我们表明配体介导的信号传导可以部分拯救细胞免受靶向 RTK 抑制，并且这种效应受 HS 调节。事实上，HS 缺陷的肿瘤细胞在体外和体内对 EGFR 抑制的敏感性增加。意义：我们的研究表明，肿瘤细胞和肿瘤微环境中表达的 HS 调节配体介导的信号传导，促进肿瘤细胞增殖和侵袭，这些因素导致肿瘤细胞对靶向 RTK 抑制的反应降低。