Development of first-in-class histone acetyltransferase (HAT) activators for precision targeting of epigenetic derangements in lymphoma

弥漫性大B细胞淋巴瘤（DLCBL）是最常见的淋巴瘤类型，影响约30，000例患者 每年。最近对DLBCL分子发病机制的了解将这种疾病分为两种分子机制， 亚型：生发中心（GC）和ABC亚型。ABC-DLCBL的靶向分子特征是在最后的 的发展阶段，但这种成功尚未实现更常见的GC-DLCBL。GC是一个 淋巴结的一个区室，负责通过体细胞超突变产生高亲和力抗体 和类切换重组。表观遗传修饰剂，如EZH 2、组蛋白乙酰转移酶（HAT）和表观遗传修饰剂。 转录抑制因子Bcl 6是B细胞发育所必需的，允许必要的诱变和沉默 体细胞超突变所必需的肿瘤抑制因子这种生理状态部分是通过 组蛋白乙酰化减少和甲基化增加，从而导致转录抑制状态。 影响这些表观遗传和转录修饰因子HAT、EZH 2和Bcl 6的突变已被鉴定为 GC衍生淋巴瘤的驱动事件。 鉴于表观遗传功能障碍在GC衍生的B细胞淋巴瘤发病机制中的重要性， 我们假设，如果HAT等位基因的失活突变对GC-DLBCL至关重要，那么激活HAT等位基因的药物可能会导致GC-DLBCL的发生。 野生型酶应显示治疗效果。此外，我们认为， 表观遗传机制与HAT激活剂和其他表观遗传修饰剂（HDAC和EZH 2抑制剂） 可诱导深刻的表观遗传修饰，导致程序性细胞死亡的协同诱导。最后， 如果特定基因如EP 300的突变状态和表达水平与对HAT的应答相关， 激活剂或组合的表观遗传疗法，则NanoString表达组可以开发为 生物标志物的反应。 本提案的目标将通过解决以下具体目标进行评估：（1）描述 HAT激活剂YF 2通过测定与HAT酶的结合及其对细胞中乙酰化的功能作用， 免费检测。(2)确定HAT激活剂与临床上可用的表观遗传 细胞系和小鼠中的修饰剂。表观遗传修饰剂将包括HDAC和EZH 2抑制剂。 HAT激活剂与表观遗传修饰剂联合应用对翻译后蛋白表达的影响 将确定下游靶标的修饰（甲基化、乙酰化）和基因表达。（三） 询问EP 300的突变状态和淋巴瘤细胞系的表观遗传基因特征，以告知精确度 用HAT活化剂靶向。将确定候选人的基础基因突变和表达谱 在淋巴瘤细胞系中的表观遗传和转录调节剂，并将与HAT激活剂的IC 50相关 和联合表观遗传疗法的协同系数。如果我们接受这些假设， 代表了直接靶向突变的机会，如HAT和EZH 2，它们驱动GC-DLBCL。

Diffuse large B-cell lymphoma (DLCBL) is the most common type of lymphoma affecting ~30,000 patients annually. Recent insights into the molecular pathogenesis of DLBCL has divided this disease into two molecular subtypes: germinal center (GC) and ABC subtypes. Targeting molecular features of ABC-DLCBL are in the final stages of development, but such success has not been realized for the more common GC-DLCBL. The GC is a compartment of the lymph node responsible for generating high affinity antibodies via somatic hyper-mutation and class switch recombination. Epigenetic modifiers such as EZH2, histone acetyltransferases (HATs), and the transcriptional repressor, Bcl6, are essential to B-cell development allowing for requisite mutagenesis and silencing of tumor suppressors necessary for somatic hypermutation. This physiologic state is partly achieved by decreased acetylation and increased methylation of histones enforcing a transcriptionally repressed state. Mutations affecting these epigenetic and transcriptional modifiers, HATs, EZH2 and Bcl6, have been identified as driving events in GC-derived lymphomas. Given the critical importance of epigenetic dysfunction in the pathogenesis of GC-derived B-cell lymphomas, we hypothesize that if inactivating mutations in HAT alleles are crucial to GC-DLBCL then drugs activating the wild-type enzyme should demonstrate therapeutic effect. In addition, we believe that combined targeting of epigenetic machinery with HAT activators and other epigenetic modifying agents (HDAC and EZH2 inhibitors) may induce profound epigenetic modification leading to synergistic induction of programmed cell death. Finally, if mutational status and expression levels of specific genes such as EP300 correlate with response to HAT activators or combined epigenetic therapy, then a NanoString expression panel may be developed as a biomarker for response. The objectives of this proposal will be evaluated by addressing the following specific aims: (1) Characterize the HAT activator YF2 by determining binding to HAT enzymes and its functional effects on acetylation in cell- free assays. (2) Determine the effects of HAT activators in combination with clinically available epigenetic modifying agents in cell lines and mice. Epigenetic modifying agents will include HDAC and EZH2 inhibitors. The effects of HAT activators in combination with epigenetic modifying agents on post-translational modifications (methylation, acetylation), and gene expression of downstream targets will be determined. (3) Interrogate the mutational status of EP300 and epigenetic gene signatures of lymphoma cell lines to inform precision targeting with HAT activators. Basal gene mutation and expression profiles will be determined for candidate epigenetic and transcriptional modifiers in lymphoma cell lines and will be correlated to the IC50 of HAT activators and the synergy coefficients of combined epigenetic therapy. Should we accept these hypotheses, this would represent an opportunity to directly target mutations, such as HAT and EZH2, which drive GC-DLBCL.