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)是现有的最好的一线治疗药物， 但TMZ的反应取决于DNA修复基因O6-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MGMT蛋白被抑制 导致TMZ致敏和延长存活时间的表达。相比之下，MGMT非甲基化(MGMT- 嗯)GBM患者对TMZ具有抵抗力，生存时间要短得多。到目前为止，还没有 成功的治疗使MGMT-UM对TMZ易感，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能够在表观遗传上 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(GSCs)中发现一种新的表观遗传机制，涉及肿瘤抑制候选基因3 (TUSC3)，可用于重新编程MGMT-UM以恢复对TMZ的敏感性并显著延长 球基细胞瘤实验模型的存活。本应用程序的目标是了解TUSC3是如何 表观遗传调控以及TUSC3如何使GBM对TMZ敏感。我们最近发现使用这两种方法 药理学表观遗传重编程和功能获得策略：i)TUSC3启动子在 GSCs受MGMT影响；ii)TUSC3通过抑制DNA损伤显著致敏GSCs 修复和细胞周期进展；以及iii)TUSC3与TMZ协同作用，在 MGMT-M和MGMT-UM GBMS的实验模型。因此，我们将检验表观遗传学的假设 TUSC3的重新激活使GBM对TMZ敏感并延长存活时间。在目标1中，我们将确定 TUSC3是如何在GBM中进行表观遗传调控的。在目标2中，我们将确定TUSC3如何调节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 理解GBM中新的表观遗传重编程机制并有助于实现最优 为目前没有良好化疗选择的MGMT-UM GBM设计有效的试验。

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.