Gene targets of OLIG2 in malignant glioma stem cells

描述（由申请人提供）：人类最常见的恶性神经胶质瘤形式称为“原发性胶质母细胞瘤”。这些肿瘤的特征在于扩增/突变的EGFR，但就P53状态而言通常是野生型。原发性胶质瘤中P53的遗传完整性与这些肿瘤的侵袭性生长及其对放射和细胞毒性药物的臭名昭著的抗性不一致。在初步研究中，我们已经找到了解决这一悖论的潜在方法。我们证明了：I）基本上100%的人恶性胶质瘤的CD 133阳性干细胞表达bHLH转录阻遏物OLIG 2，ii）OLIG 2抑制P21的表达，P21是一种关键的细胞周期抑制基因，是P53的诱导型靶基因，iii）OLIG 2对于原发性胶质瘤的“遗传相关”鼠模型中的生长是必需的。我们的研究计划的目的是检验OLIG 2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。这一假说提出了可检验的预测，我们将通过一系列对恶性胶质瘤新鲜手术分离株进行的实验来解决。我们将补充和验证人类肿瘤干细胞的工作与神经胶质瘤小鼠模型的实验，模拟原发性神经胶质瘤和继发性神经胶质瘤（野生型EGFR，但功能丧失P53）中发现的遗传病变。具体目标如下：目的1是验证在原发性（P53阳性）胶质瘤的CD 133/OLIG 2阳性干细胞中P21表达被排除的预测。目的2是验证抑制OLIG 2将刺激原代胶质瘤干细胞中P21的表达并抑制恶性表型的预测。目的3是验证P21对O/_（1/2）/G_2具有上位性以维持原发性胶质瘤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OLIG 2抑制的预测。这些额外的OLIG 2靶点可以解释原发性胶质瘤对放疗和化疗的臭名昭著的抗性。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“药物靶点”。

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.