Exploiting Epigenetic Vulnerabilities In Glioblastoma Stem Cells Through Reprogramming

胶质母细胞瘤（GBM）是一种高度耐药的癌症。替莫唑胺（TMZ）是最好的一线治疗， 但TMZ反应依赖于DNA修复基因O 6-甲基鸟嘌呤DNA的启动子甲基化状态 甲基转移酶（MGMT）。MGMT甲基化（MGMT-M）GBM患者的MGMT蛋白受到抑制 这导致TMZ致敏和延长的存活。与此相反，未甲基化的MGMT（MGMT-1） UM）GBM患者对TMZ耐药，生存期短得多。到目前为止还没有 成功的治疗使MGMT-UM对TMZ敏感，因此迫切需要 MGMT-UM的新治疗策略。我们的长期目标是设计出一种策略， 将MGMT-UM GBM患者重新编程为MGMT-M GBM患者的TMZ易感性。这项建议 在GBM干细胞（GSC）中开发了一种新的表观遗传机制，涉及肿瘤抑制因子候选物3 （TUSC 3），可用于重新编程MGMT-UM，以恢复对TMZ的敏感性，并显著延长 GBM实验模型的存活率。本应用程序的目标是了解TUSC 3是如何 表观遗传学调节以及TUSC 3如何使GBM对TMZ敏感。我们最近发现， 药理学表观遗传重编程和功能获得策略，其：i）TUSC 3启动子调控， GSC受MGMT影响; ii）TUSC 3通过抑制DNA损伤显著致敏GSC 和iii）TUSC 3与TMZ协同作用，在细胞修复和细胞周期进展中产生类似的存活益处。 MGMT-M和MGMT-UM GBM的实验模型。因此，我们将测试假设，表观遗传 TUSC 3的再激活将GBM重新编程为TMZ敏感性并延长存活。在目标1中，我们将确定 TUSC 3在GBM中是如何表观遗传调节的。在目标2中，我们将确定TUSC 3如何介导TMZ GBM中的反应敏化。从这些研究中获得的机械知识将增强我们的 了解GBM中新的表观遗传重编程机制，并有助于实现最佳的 设计针对目前没有良好化疗选择的MGMT-UM GBM的有效试验。

Glioblastoma (GBM) is a highly resistant cancer. Temozolomide (TMZ) is the best first-line therapy available, but TMZ response depends on the promoter methylation status of the DNA repair gene O6-methylguanine DNA methyltransferase (MGMT). MGMT methylated (MGMT-M) GBM patients have suppressed MGMT protein expression which leads to TMZ sensitization and prolonged survival. In contrast MGMT unmethylated (MGMT- UM) GBM patients are resistant to TMZ and have much shorter survivals. So far there have been no successful treatments to render MGMT-UM susceptible to TMZ and therefore there is a desperate need for novel treatment strategies for MGMT-UM. Our long-term goal is to devise strategies that can epigenetically reprogram MGMT-UM GBM patients to the TMZ susceptibility of MGMT-M GBM patients. This proposal exploits a novel epigenetic mechanism in GBM stem cells (GSCs) involving Tumor Suppressor Candidate 3 (TUSC3) that can be used to reprogram MGMT-UM to restore sensitivity to TMZ and significantly prolong survival in experimental models of GBMs. The objective in this application is to understand how TUSC3 is epigenetically regulated and how TUSC3 sensitizes GBMs to TMZ. We recently discovered using both pharmacologic epigenetic reprogramming and gain-of-function strategies that: i) TUSC3 promoter regulation in GSCs is impacted by MGMT; ii) TUSC3 significantly sensitized GSCs through suppression of DNA damage repair and cell cycle progression; and iii) TUSC3 synergized with TMZ to produce similar survival benefits in experimental models of MGMT-M and MGMT-UM GBMs. We will therefore test the hypothesis that epigenetic reactivation of TUSC3 reprograms GBMs to TMZ sensitivity and prolonged survival. In Aim 1, we will determine how TUSC3 is epigenetically regulated in GBM. In Aim 2, we will determine how TUSC3 mediates TMZ response sensitization in GBM. Mechanistic knowledge gained from these studies will enhance our understanding of novel epigenetic reprogramming mechanisms in GBM and contribute toward the optimal design of impactful trials for MGMT-UM GBMs who currently do not have good chemotherapy options.