Establishing that Hdac3 is a therapeutic target in a subset of B cell Lymphoma

组蛋白脱乙酰酶3(HDAC3)去乙酰化组蛋白H3和H4上的选择性赖氨酸残基以控制 染色质结构和抑制基因表达。在小鼠B细胞发育过程中，HDAC3是必需的 有效的V-D-J重组，但一旦超过这个发育阶段，缺乏HDAC3的B细胞就会存活，但 不能对抗原进行生发中心的反应。相反，这些细胞会累积 在HDAC3-/-B的表型和基因表达模式所在的生发中心的“亮区” 细胞与Foxo1-/-B细胞相匹配。这一点值得注意，因为Foxo1招募了HDAC3。而Foxo1是 通常被认为是转录激活因子，在生发中心B细胞中，在芯片序列中发现的基因 当Foxo1被删除时，与Foxo1结合的研究上调。此外，在10%的 起源于生发中心Foxo1的淋巴瘤被允许其逃逸的突变所激活 AKT的负面调控。Foxo1和HDAC3之间的融合，表明HDAC3可能发挥作用 在依赖Foxo1的弥漫性大B细胞淋巴瘤(DLBCL)中起关键作用。8种不同类型DLBCL细胞的治疗 使用选择性HDAC3抑制剂的细胞株显示，只有在Foxo1中具有激活突变的细胞才是 而含有其他常见突变的细胞，如bcl6易位，则不敏感。 此外，在CHIP-EXO研究中，该抑制物可激活与Foxo1结合的基因。这些 初步研究认为HDAC3是治疗Foxo1突变弥漫性疾病的有效靶点 大B细胞淋巴瘤。这一假说将通过制造含有B细胞淋巴瘤的小鼠来直接检验 由突变体Foxo1驱动，然后删除HDAC3。此外，我们还将精细映射Foxo1中的域 需要招募HDAC3，并使不能与HDAC3结合的突变体来测试招募 HDAC3是淋巴瘤发生和淋巴瘤细胞生存所必需的。我们还将使用尖端技术 基因组学方法，如PRO-SEQ，以确定Foxo1招募HDAC3的机制 调节基因表达。这一综合方法将最终定义HDAC3是否是 B细胞淋巴瘤的治疗靶点，并可能刺激HDAC3选择性抑制剂的进一步开发 和/或Foxo1。

Histone deacetylase 3 (HDAC3) deacetylates selective lysine residues on histone H3 and H4 to control chromatin structure and repress gene expression. During murine B cell development, Hdac3 is required for efficient V-D-J recombination, but once past this developmental stage B cells lacking Hdac3 survive, but fail to undergo a productive germinal center reaction in response to antigen. Rather, these cells accumulate in the “light zone” of the germinal center where the phenotype and gene expression pattern of Hdac3-/- B cells matched those of Foxo1-/- B cells. This is remarkable because Foxo1 recruits Hdac3. While Foxo1 is typically thought of as a transcriptional activator, in germinal center B cells, genes identified in ChIP-seq studies as bound by Foxo1 were up-regulated when Foxo1 was deleted. Moreover, in 10% of the lymphoma derived from the germinal center Foxo1 is activated by mutations that allow it to escape negative regulation by Akt. The convergence between Foxo1 and Hdac3, suggested that Hdac3 might play a key role in Foxo1-dependent diffuse large B cell lymphoma (DLBCL). Treatment of 8 different DLBCL cell lines with a selective Hdac3 inhibitor showed that only the cells with activating mutations in Foxo1 were sensitive, whereas cells containing other common mutations such as translocation of BCL6 were not. Moreover, this inhibitor caused activation of genes that were bound by Foxo1 in ChIP-exo studies. These preliminary studies lead to the hypothesis that Hdac3 is a viable therapeutic target in Foxo1 mutant diffuse large B cell lymphoma. This hypothesis will be directly tested by creating mice containing B cell lymphoma driven by mutant Foxo1 and then deleting Hdac3. In addition, we will fine map the domain in Foxo1 required for recruitment of Hdac3 and make mutants that cannot bind to Hdac3 to test whether recruitment of Hdac3 is required for lymphomagenesis and lymphoma cell survival. We will also use cutting-edge genomic methods such as PRO-seq to define the mechanism by which Hdac3 recruitment by Foxo1 regulates gene expression. This comprehensive approach will conclusively define whether Hdac3 is a therapeutic target in B cell lymphoma and may spur further development of selective inhibitors of Hdac3 and/or Foxo1.