Targeting epigenetic regulation to disrupt glioma stem cell maintenance.

描述（由申请人提供）：胶质母细胞瘤（GBM）是最致命的人类癌症之一，常规治疗只能起到缓解作用。在了解GBM遗传学和建立这些肿瘤模型方面已经取得了巨大的进步，新的靶向治疗正在测试中。不幸的是，这些进步并没有实质性地转化为改善患者的治疗效果。多种化疗药物和放射疗法已经被开发出来杀死癌细胞。然而，GBM对化疗和放疗的反应一般。显然，临床需要开发一种新的治疗策略或辅助策略来提高现有治疗的疗效。虽然没有单一的机制提供当前GBM治疗失败的原因，但包括我们自己的几个实验室已经表明，GBM肿瘤含有被称为癌症干细胞（CSCs）的干细胞样细胞。肿瘤干细胞假说认为肿瘤细胞是在一个层次结构中组织的，csc位于顶端。CSCs对细胞毒性治疗具有耐药性（Bao等）。Nature 2006)并促进肿瘤血管生成(Bao等。癌症研究2006)支持直接临床相关性。我们的团队和其他人已经表明，csc存在于血管周围和缺氧壁龛的特定功能壁龛中（Li等人）。癌症细胞2009；Lathia等人。Cell Stem Cell 2010)，靶向这些小生境可能会破坏肿瘤维持和治疗耐药性。值得注意的是，我们的研究小组发现微环境通过诱导表观遗传调节因子直接将分化的肿瘤细胞重编程为CSCs （Heddleston et al.）。《细胞死亡差异》，2012)。虽然针对癌症表观遗传调控的几种治疗方法已经开发并在临床应用（例如HDAC抑制剂和阿扎胞苷），但基于大量累积的证据表明表观遗传调控在许多疾病，特别是癌症中起着核心作用，人们对靶向这类分子重新产生了兴趣。大型制药公司和研究机构已经开发了大型项目，试图以这些分子为目标。随着表观遗传药物开发的复苏和表观遗传调控控制细胞状态的证据，我开始确定新的表观遗传靶点，这些靶点是GBM中CSC状态的关键调节因子。我进行了一项靶向RNAi筛选，重点是组蛋白去甲基化酶，这是一种关键的表观遗传修饰基因。由于表观遗传修饰和细胞状态至少部分由微环境决定，因此我利用最先进的RNAi筛选技术在功能原位微环境存在的情况下进行体内筛选。在筛选的31个组蛋白去甲基化酶基因中，确定了三个候选靶点，临床生存和基因表达数据支持它们作为治疗靶点的潜力。如何影响CSC和正常的神经祖细胞生物学通过靶向这些打击现在将被评估。

DESCRIPTION (provided by applicant): Glioblastoma (GBM) ranks among the most lethal of human cancers with conventional therapy offering only palliation. Great strides have been made in understanding GBM genetics and modeling these tumors, and new targeted therapies are being tested. Unfortunately, these advances have not substantially translated into improved patient outcomes. Multiple chemotherapeutic agents and radiation therapy have been developed to kill cancer cells. However, the response to chemotherapy and radiation in GBM is modest. There is clearly an unmet clinical need to develop either a novel treatment strategy or an adjuvant strategy to enhance efficacy of existing treatments. While no single mechanism provides for the failure of current GBM therapies, several laboratories including our own have shown that GBM tumors contain stem cell-like cells termed cancer stem cells (CSCs). The cancer stem cell hypothesis posits that tumor cells are organized in a hierarchy with CSCs at the apex. CSCs are resistant to cytotoxic therapies (Bao et al. Nature 2006) and promote tumor angiogenesis (Bao et al. Cancer Research 2006) supporting a direct clinical relevance. Our group and others have shown that CSCs reside in specific functional niches in perivascular and hypoxic niches (Li et al. Cancer Cell 2009; Lathia et al. Cell Stem Cell 2010), and targeting these niches may disrupt tumor maintenance and therapeutic resistance. Notably, our group has found that the microenvironment directly reprograms differentiated tumor cells into CSCs through the induction of epigenetic regulators (Heddleston et al. Cell Death Diff. 2012). While several therapies targeting epigenetic regulation in cancer have long been developed and in the clinic (e.g. HDAC inhibitors and Azacitidine) there has been a renewed interest in targeting this class of molecules based on the large amount of accumulating evidence that epigenetic regulation plays a central role in many diseases, particularly cancer. Major pharmaceutical companies and research agencies have developed large programs to try to target these moecules. With this resurgence of epigenetic drug development and evidence that epigenetic regulation controls cell state, I set out to identify novel epigenetic targets that are critical regulators of the CSC state in GBM. I conducted a targeted RNAi screen that focused on histone demethylases, a key class of epigenetic modifying genes. As epigenetic modifications, and therefore cell state are at least partially determined by the microenvironment, I utilized state-of-the-art RNAi screening technology to conduct the screen in vivo in the presence of a functional orthotopic microenvironment. Out of 31 histone demethylase genes screened, three candidate targets were identified, and clinical survival and gene expression data supports their potential as therapeutic targets. How CSC and normal neural progenitor biology is affect by targeting these hits will now be evaluated.