Cooperating pathways in glioblastoma stem cells

摘要 胶质母细胞瘤（GBM）是最常见和最致命的脑癌。不幸的是， 可悲的是，在过去的30年里，治疗进展甚微。手术带来的好处不大， 血脑屏障（BBB）限制了药物的进入，GBM细胞对放射和主要的化疗有抗性， 替莫唑胺迄今为止，GBM的靶向治疗在试验中取得了令人失望的结果。的挑战 开发有效的GBM治疗方法的内在因素已经变得越来越清楚，包括 对标准治疗的抗性，药物输送到肿瘤中，干细胞样GBM细胞亚群 （GSC），以及GBM的遗传复杂性和分子适应性。 GBM肿瘤显示出分化状态的细胞等级，其中GSC保持动态平衡 自我更新和分化之间的关系。无数的分子信号通路对于 正常脑发育在胶质瘤的发生和发展中也起重要作用。我们之前 证明MET受体酪氨酸激酶信号传导是GSC的关键调节剂。最近的研究 暗示各种神经递质信号可以通过维持肿瘤的生长和进展来促进肿瘤的生长和进展， 干细胞状态 我们最近的研究和初步数据发现，多巴胺受体亚型2（DRD 2），一个关键的 多巴胺信号受体，通过调节GSC的干细胞状态促进GBM生长。 出乎意料的是，DRD 2在临床GBM样本中高度表达，在GSC中优先表达， 与正常脑组织相比。DRD 2促进GBM的增殖和克隆形成 细胞通过激活MET。这一发现是高度相关的，因为MET信号转导经常在细胞中过度活跃。 GBM作为肿瘤干细胞表型和GBM放射抗性的关键调节因子， GBM的治疗靶点。重要的是，DRD 2敲低或FDA批准的DRD 2拮抗剂介导的 DRD 2抑制有效灭活致癌信号传导途径，减少GSC的克隆生长， 并在原位异种移植模型中阻碍GBM生长。此外，我们发现了一种强协同抗- MET抑制剂和DRD 2拮抗剂组合在GBM亚组中的肿瘤作用。该项目将 询问MET-DRD 2信号在GSC自我更新和GBM进展中的作用，并阐明MET-DRD 2信号在GSC自我更新和GBM进展中的作用。 在分子水平上的致癌DRD 2信号传导机制（目标1），并测试FDA- 批准的抗精神病药物和新的抑制肽，可以特异性地阻断 DRD 2和MET（目标2），并确定这些靶向试剂单独或与 在临床前患者GBM来源的原位肿瘤模型中与标准疗法组合， 预测治疗反应的生物标志物（目标3）。我们预计，完成这些拟议的 这些研究将为癌症干细胞生物学提供一个新的范例，并提供一种新的有效的治疗方法。 这种方法可能会导致转化为改进的疗法。

ABSTRACT Glioblastoma (GBM) is the most common and the most lethal brain cancer. Unfortunately, there has been tragically little therapeutic progress over the last 30 years. Surgery provides modest benefit, the blood-brain barrier (BBB) limits drug access, and GBM cells are resistant to radiation and to the leading chemotherapy, temozolomide. Targeted therapies for GBM have yielded disappointing results in trials to date. The challenges inherent in developing effective GBM therapeutic approaches have become increasingly clear, and include resistance to standard treatments, drug delivery into the tumor, a subpopulation of stem-like GBM cells (GSCs), and genetic complexity and molecular adaptability of GBM. GBM tumors display a cellular hierarchy of differentiation states, in which GSCs maintain a dynamic balance between the state of self-renewal and differentiation. A myriad of molecular signaling pathways crucial for the normal brain development also play important roles in glioma initiation and progression. We previously demonstrated that MET receptor tyrosine kinase signaling is a crucial regulator of GSCs. Recent studies have implicated that various neurotransmitter signaling can promote tumor growth and progression via maintaining stem cell state. Our recent studies and preliminary data have discovered that dopamine receptor subtype 2 (DRD2), a key receptor of dopamine signaling, promoted GBM growth via regulating the stem cell state of GSCs. Unexpectedly, DRD2 was highly expressed in clinical GBM specimens, with preferential expression in GSCs, compared to normal brain tissue. Mechanistically, DRD2 facilitated proliferation and clonogenic growth of GBM cells via activation of MET. This finding is highly relevant because MET signaling is frequently hyperactive in GBMs as a key regulator of cancer stem phenotype and GBM radio-resistance, and it is a well-recognized therapeutic target in GBM. Importantly, DRD2 knockdown or an FDA-approved DRD2 antagonist-mediated DRD2 inhibition potently inactivated oncogenic signaling pathways, diminished clonogenic growth of GSCs, and impeded GBM growth in orthotopic xenograft models. Furthermore, we found a strong synergistic anti- tumor effect by combination of MET inhibitor and DRD2 antagonist in a subset of GBM. This project will interrogate the roles of MET-DRD2 signaling in GSC self-renewal and GBM progression, and elucidate the mechanisms of oncogenic DRD2 signaling at the molecular level (Aim 1), and test therapeutic efficacy of FDA- approved antipsychotic drugs and novel inhibitory peptides that can specifically block the interaction between DRD2 and MET (Aim 2), and determine therapeutic efficacies of these targeting reagents alone or in combination with standard therapies in preclinical patient GBM-derived orthotopic tumor models and identify the biomarkers that predict therapeutic response (Aim 3). We anticipate that completion of these proposed studies will yield a new paradigm for cancer stem cell biology and provide a novel and effective therapeutic approach, which may lead to the translation into improved therapies.