Gene targets of OLIG2 in malignant glioma stem cells

描述(申请人提供)：人类最常见的恶性胶质瘤被称为“原发胶质母细胞瘤”。这些肿瘤的特征是扩增/突变的EGFR，但通常是野生型的P53状态。P53在原发胶质瘤中的遗传完整性与这些肿瘤的侵袭性生长及其臭名昭著的辐射和细胞毒药物耐药性是不一致的。在初步研究中，我们已经找到了这一悖论的潜在解决方案。我们证明：1)基本上100%的人类恶性胶质瘤背后的CD133阳性干细胞表达bHLH转录抑制因子OLIG2；ii)OLIG2抑制P21的表达--P21是P53的可诱导靶基因；III)OLIG2对于“遗传相关”的原发胶质瘤小鼠模型的生长至关重要。我们研究计划的目的是验证OLIG2通过对抗P53的作用和抑制P21的表达来维持原代胶质瘤干细胞复制的假设。这一假设做出了可检验的预测，我们将通过对恶性胶质瘤新鲜外科分离株进行一系列实验来解决这些预测问题。我们将通过在小鼠胶质瘤模型上的实验来补充和验证对人类肿瘤干细胞的工作，这些小鼠模型模仿在原发胶质瘤和继发性胶质瘤中发现的遗传损伤(野生型EGFR，但功能丧失的p53)。具体目的如下：目的1验证P21在原发(P53阳性)胶质瘤的CD133/OLIG2阳性干细胞中不表达的预测。目的2验证抑制OLIG2基因表达将刺激原代胶质瘤干细胞P21表达和抑制恶性表型的预测。目的3验证P21对O/_/G2维持干细胞恶性表型的预测。目的4是测试其他p53诱导基因也被OLIG2抑制的预测。这些额外的OLIG2靶点可能解释了原发胶质瘤对放疗和化疗的臭名昭著的耐药性。随着时间的推移，所描述的工作可能会为人类恶性胶质瘤的治疗带来新的“可用药靶点”。

DESCRIPTION (provided by applicant): The most common form of malignant glioma in humans is termed "primary glioblastoma". These tumors are characterized by amplified/mutated EGFR but are generally wild type with respect to P53 status. The genetic integrity of P53 in primary glioma is at odds with the aggressive growth of these tumors and their notorious resistance to radiation and cytotoxic drugs. In preliminary studies, we have found a potential resolution to this paradox. We show I) that essentially 100% of the CD133 positive stem cells that underlie malignant glioma in humans express the bHLH transcription represser OLIG2, ii) that OLIG2 suppresses expression of P21 - a key cell cycle inhibitor gene that is an inducible target gene of P53 and iii) that OLIG2 is essential for growth in a "genetically relevant" murine model of primary glioma. The objective of our study plan is to test the hypothesis that OLIG2 sustains replication of primary glioma stem cells by opposing the action of P53 and suppressing the expression of P21. This hypothesis makes testable predications that we will address with a series of experiments to be conducted on fresh surgical isolates of malignant glioma. We will complement and validate the work on human tumor stem cells with experiments on murine models of glioma that emulate genetic lesions found in primary glioma and also secondary glioma (wild type EGFR but loss-of-function P53). Specific aims are as follows: Aim 1 is to test the prediction that the expression of P21 is precluded in CD133/OLIG2-positive stem cells of primary (P53 positive) gliomas. Aim 2 is to test the prediction that suppression of OLIG2 will stimulate the expression of P21 in primary glioma stem cells and suppress the malignant phenotype. Aim 3 is to test the prediction that P21 is epistatic to O/_/G2for maintenance of the malignant phenotype in stem cells for primary glioma. Aim 4 is to test the prediction that other P53-inducible genes are also suppressed by OLIG2. These additional OLIG2 targets may account for the notorious resistance of primary gliomas to radiotherapy and chemotherapy. In the fullness of time, the work described may lead to new "drugable targets" for the therapy of malignant glioma in humans.