PHARMACOLOGICAL MODULATION OF EPIGENETIC CHANGES IN AML

描述(由申请人提供)：表观遗传变化(即组蛋白去乙酰化和DNA甲基化)在恶性肿瘤细胞中肿瘤抑制基因的异常沉默中所起的作用已经得到了很好的证实。现在普遍的共识是，组蛋白去乙酰化和DNA甲基化都与急性髓系白血病的发生有关。最近的研究集中在表观遗传转录沉默的分子基础上，支持核组蛋白与DNA甲基化以动态方式相互作用的概念，以抑制对造血分化和细胞凋亡至关重要的基因。由这些机制引起的基因组沉默可以通过组蛋白脱乙酰酶(HDAC)和DNA甲基转移酶(DNMT)抑制剂的药物调节来缓解。AML的临床前工作已经证明了这些药物的体外协同作用，这增加了临床协同的希望。然而，对于这种策略抑制特定的HDAC和DNMT酶亚型的特异性或酶抑制的动力学以及这与AML患者的临床益处之间的关系还知之甚少。因此，为了了解它们的全部潜力，需要在临床试验的背景下对HDAC和DNMT抑制剂诱导的药理和生物学效应进行系统研究。在这里，我们建议探索对急性髓细胞白血病的组蛋白去乙酰化和DNA甲基化机制具有抑制活性的药物组合。我们推测，这些药物的治疗应用将恢复正常的基因表达模式，激活白血病细胞的终末分化，降低凋亡阈值，从而产生临床益处。为了验证这些假设，我们的具体目标是1)使用影响DNA甲基化机制(即地西他滨)和染色质结构(如丙戊酸)的药物在AML进行I期研究；2)对这些药物进行药代动力学和药效学研究，使药物血浆水平、染色质变化和基因重新表达与毒性和疾病反应相关联。

DESCRIPTION (provided by applicant): The role that epigenetic changes (i.e., histone deacetylation and DNA methylation) play in the aberrant silencing of tumor suppressor genes in malignant cells has been well established. There is now general consensus that both aberrant histone deacetylation and DNA methylation contribute to leukemogenesis in AML. Recent studies focused on the molecular basis of epigenetic transcriptional silencing support the concept that nuclear histones interact with DNA methylation in a dynamic way to repress genes important for hematopoietic differentiation and apoptosis. Genomic silencing induced by these mechanisms can be relieved by pharmacological modulation with histone deacetylase (HDAC) and DNA methyltransferase (DNMT) inhibitors. Preclinical work in AML has demonstrated in vitro synergy of these agents that raises the hope of clinical synergy. However, little is known about the specificity of this strategy for inhibiting specific HDAC and DNMT enzyme subtypes or the kinetics of enzyme inhibition and how this relates to clinic benefit in AML patients. Therefore, to understand their full potential, a systematic study of the pharmacological and biological effects induced by HDAC and DNMT inhibitors in the context of clinical trials is required. Here we propose to explore combination of agents with a demonstrated inhibitory activity to the histone deacetylation and DNA methylation machinery in AML. We hypothesize that the therapeutic application of these agents will restore normal patterns of gene expression, activate terminal differentiation and lower the apoptotic threshold in the leukemic cells, and thereby induce clinical benefit. To test these hypotheses, our specific aims are 1) to perform a phase I study in AML using agents that affect the DNA methylation machinery (i.e., decitabine) and chromatin structure (i.e., valproic acid); 2) to perform pharmacokinetic and pharmacodynamic studies of these agents that will allow correlations of drug plasma levels, chromatin changes and gene re-expression with toxicity and disease response.