Genomic characterization of therapeutically-relevant targets in progressive/ high-grade meningioma

脑膜瘤是最常见的原发性颅内肿瘤。虽然这些肿瘤中的许多是良性的，并且可以通过手术切除和放射治疗等标准疗法治愈，但复发仍然相对常见。不幸的是，在一线治疗失败后，目前没有标准的治疗方法来为进行性复发脑膜瘤患者提供治疗，并且在这种情况下确保持久、长期的疾病控制一直具有挑战性。这些病例需要新的治疗方法。现代基因组技术已经允许对许多不同癌症的肿瘤细胞中发现的体细胞基因突变进行广泛的表征。最近的研究已经在低级别脑膜瘤中发现了SMO、AKT1、KLF4和TRAF7突变，此外还发现了NF2失活，这是这种肿瘤的特征。另一方面，较高级别和复发性脑膜瘤具有更频繁（高达28%）的TERT启动子（TERTp）突变，这预示着更高的复发率。然而，对初始和复发性疾病的驱动基因改变的纵向基因组分析仍然不完整。在我们提出的项目中，我们将重点了解复发性脑膜瘤的临床谱中的分子改变。因此，我们研究了一大批初始诊断和复发的进行性/高级别脑膜瘤患者（n= 120）。在对匹配的初始和复发脑膜瘤对进行全外显子组测序后，我们通过建立的算法分析数据，以评估体细胞突变，拷贝数改变和重排。我们发现了新的有趣的候选基因，我们正在使用集中Sanger测序和单核苷酸基因分型的正交方法进行验证。此外，为了证实我们的发现，我们正在对大量样本进行免疫组织化学和western blot。通过对脑膜瘤细胞系（如iom - lee）、我们已经建立的患者源性脑膜瘤细胞系（MN3和MN8）和tert永生化的未转化的人类蜘蛛网膜细胞的模型进行增殖和克隆测定，我们将对最重要的候选基因进行功能表征，并评估其肿瘤转化的潜力。与原发性脑膜瘤相比，复发性脑膜瘤中缺失或扩增的基因将分别在基因上过表达或沉默，以确定这是否会导致这些模型中的表型改变。我们提出的基因组和生物学分析有可能确定导致脑膜瘤复发或恶性转化的遗传因素，这些目标可以优先考虑以最大化临床影响。因此，这项工作的成功实施将为正在进行的复发性进展性脑膜瘤的临床试验的设计和解释提供重要的信息。

Meningiomas are the most common primary intracranial tumor. Although many of these tumors are benign, and are cured with the standard therapies of surgical resection and radiation therapy, recurrence is nevertheless relatively common. After failure of frontline treatment, there is unfortunately no current standard therapy to offer patients who have progressive recurrent meningioma, and securing durable, long-term disease control in this setting has been challenging. New therapeutic approaches are needed for these cases. Modern genomic technologies have allowed for broad characterization of somatic gene mutations found in tumor cells in many different cancers. Recent work has identified SMO, AKT1, KLF4 and TRAF7 mutations in low-grade meningiomas, in addition to the well-established NF2 inactivation that is characteristic of this neoplasm. On the other hand, higher-grade and recurrent meningiomas harbor more frequently (up to 28%) TERT promoter (TERTp) mutations, which are predictive of a higher recurrence rate. However, a longitudinal genomic analysis of driver genetic alterations across the spectrum of initial and recurrent disease remains incomplete. In our proposed project, we will focus on understanding the molecular alterations across the clinical spectrum of recurrent meningiomas. Therefore, we characterized a large cohort of patients (n= 120) with progressive/higher-grade meningiomas at both initial diagnosis and recurrence. After pursuing the whole exome sequencing in matched initial and recurrent meningioma pairs, we analyzed the data by established algorithms to evaluate for somatic mutations, copy number alterations and rearrangements. We discovered new interesting candidate genes that we are validating by an orthogonal approach using focused Sanger sequencing and single-nucleotide genotyping. In addition, to confirm our findings, we are performing immunohistochemistry and western blot in large number of samples. Using proliferation and clonogenic assays in models that include meningioma cell lines (e.g. IOMM-Lee), patient-derived meningioma cell lines we have established (MN3 and MN8) and TERT-immortalized non-transformed human arachnoid cells, we will functionally characterize the most significant candidate genes and assess their potential for neoplastic transformation. Deleted or amplified genes in recurrent meningiomas, compared to primary meningiomas, will be genetically over-expressed or silenced, respectively, to determine if that results in an altered phenotype in these models. Our proposed genomic and biological analyses have the potential to identify the genetic factors that drive meningiomas to relapse or undergo malignant transformation, targets which could be prioritized to maximize clinical impact. Thus, the successful execution of this work will provide important information to facilitate the design and interpretation of ongoing clinical trials for recurrent progressive meningiomas.