Contextual Glioblastoma Screening For Efficacious Radiation Sensitizers

描述（由申请人提供）：尽管经过数十年的研究，多形性胶质母细胞瘤（GBM）患者的预后仍然极差。目前新诊断的胶质母细胞瘤的标准治疗是在可行的范围内进行手术切除，然后进行辅助放疗和替莫唑胺化疗。原位GBM肿瘤细胞被认为是放射抗性的，这被经典地认为是细胞固有的特性。但最近的 研究指出了两种非经典机制对GBM中的辐射抗性的贡献：胶质母细胞瘤干细胞（GSC）和肿瘤微环境（TME）。虽然GSC采用确定的分子机制导致辐射抗性，但这些机制在体内显著增强，表明强烈的TME影响。鉴于GBM中的非经典辐射抗性由TME调节，因此不能在细胞培养物中进行放射增敏剂的测试。相反，需要新型测试平台，既提供考虑到TME的适当生物背景，又允许快速药物测试。GBM中的肿瘤间异质性使这种测试进一步复杂化。四个主要的分子GBM亚型，具有不同的异质性的鉴定激发了这样的关注，如果特定的放射增敏剂是有效的，但不是在一个亚型，这种异质性可能混淆药物测试。在这里，我们建议实施一种新的方法来筛选上下文GBM反应放射增敏剂使用器官型培养的人GBM手术标本，以评估分子和细胞反应的辐射原位。基于我们的临床前研究和当前GBM临床试验的知识，我们建议评估TGF β抑制作为增加GBM放射敏感性的手段，以验证该测试平台。拟议的实验是基于这样的假设，即对辐射的反应是通过抑制TGF β以减少辐射诱导的双链DNA断裂（DSB）的识别和修复的形式增强的。我们预测，抑制TGF β信号传导将防止观察到的辐射诱导的器官型培养物中GSC患病率的增加，如功能性克隆形成测定和肿瘤起始潜力所测量的。重要的是，我们将评估TGF β抑制剂作为放射增敏剂在代表先前描述的所有分子亚型的人类GBM标本中的相对功效。 我们认为，这种方法保留了TME和GSC对离体GBM放射生物学的贡献，将允许通过以下方法进行有效的药物筛选： 结合药物功效的细胞和功能读数，以及通过检查GBM的不同分子亚型中的药物作用。重要的是，我们设想这种方法成为发现可应用于其他脑肿瘤的放射增敏剂的范例。

DESCRIPTION (provided by applicant): The prognosis for patients with glioblastoma multiforme (GBM) remains extremely poor despite decades of research. The current standard of care for newly diagnosed glioblastoma is surgical resection to the extent feasible, followed by adjuvant radiotherapy and temozolomide chemotherapy. GBM tumor cells in situ are considered to be radioresistant, which is classically thought to be a cell-intrinsic property. However, recent studies point to the contribution of two non-classical mechanisms that contribute to radiation resistance in GBM: glioblastoma stem cells (GSCs) and the tumor microenvironment (TME). While GSCs employ defined molecular mechanisms that lead to radioresistance, these mechanisms are dramatically potentiated in vivo, suggesting a strong TME influence. Given that non-classical radioresistance in GBM is modulated by the TME, it follows that testing of radiosensitizing agents cannot be performed in cell culture. Instead, novel testing platforms are required that both provide appropriate biological context that takes into account the TME, as well as allow for rapid drug testing. Such testing is further complicated by intertumoral heterogeneity in GBM. The identification of four major molecular GBM subtypes that have different prognoses motivates concerns that such heterogeneity may confound drug testing if specific radiosensitizing agents are efficacious in one subtype but not others. Here we propose to implement a novel approach to screen contextual GBM response to radiosensitizers using organotypic culture of human GBM operative specimens to evaluate the molecular and cellular response to radiation in situ. Based on our preclinical studies and the knowledge of current GBM clinical trials, we propose to evaluate TGF� inhibition as a means to increase GBM radiosensitivity to validate this testing platform. The proposed experiments are based on the hypothesis that response to radiation is enhanced by inhibition of TGF� in the form of decreased recognition and repair of radiation-induced double-stranded DNA breaks (DSBs). We predict that inhibition of TGF� signaling will prevent the observed radiation-induced increase in the prevalence of GSCs in organotypic cultures, as measured by functional clonogenic assays and tumor initiation potential. Importantly, we will evaluate the relative efficacy of TGF� inhibitors as radiosensitizers in human GBM specimens representing all molecular subtypes previously described. We posit that this approach, which preserves TME and GSC contributions to GBM radiobiology in an ex vivo setting, will allow for efficient drug screening by incorporating both cellular and functional readouts for drug efficacy, as well as by examining drug effects in distinct molecular subtypes of GBM. Importantly, we envision this approach becoming a paradigm for discovery of radiosensitizing agents that can be applied to other brain tumors.