Development of Alkylated Hydrazides as Highly Potent and Selective Class I Histone Deacetylase Inhibitors with T cell Modulatory Properties

Histone
deacetylases (HDACs) are epigenetic regulators and additionally
control the activity of non-histone substrates. We recently demonstrated
that inhibition of HDAC8 overexpressed in various of cancers reduces
hepatocellular carcinoma tumorigenicity in a T cell-dependent manner.
Here, we present alkylated hydrazide-based class I HDAC inhibitors
in which the n-hexyl side chain attached to the hydrazide
moiety shows HDAC8 selectivity in vitro. Analysis
of the mode of inhibition of the most promising compound 7d against HDAC8 revealed a substrate-competitive binding mode. 7d marked induced acetylation of the HDAC8 substrates H3K27
and SMC3 but not tubulin in CD4+ T lymphocytes, and significantly
upregulated gene expressions for memory and effector functions. Furthermore,
intraperitoneal injection of 7d (10 mg/kg) in C57BL/6
mice increased interleukin-2 expression in CD4+ T cells and CD8+ T cell proportion with no apparent
toxicity. This study expands a novel chemotype of HDAC8 inhibitors
with T cell modulatory properties for future therapeutic applications.

组蛋白去乙酰化酶（Histone deacetylases, HDACs）是表观遗传调控因子，同时可调控非组蛋白底物的活性。我们近期的研究证实，在多种癌症中高表达的HDAC8受到抑制后，可通过T细胞依赖性途径降低肝细胞癌的致瘤性。本研究报道了一类基于烷基化酰肼的I类HDAC抑制剂，其中连接于酰肼基团的正己基侧链在体外表现出HDAC8选择性。针对最具开发潜力的化合物7d的HDAC8抑制模式分析显示，其结合方式为底物竞争性结合模式。化合物7d可显著诱导CD4+ T淋巴细胞（CD4+ T lymphocytes）中HDAC8底物H3K27与SMC3的乙酰化，却不会影响微管蛋白（tubulin）的乙酰化水平，并显著上调记忆与效应功能相关的基因表达。此外，在C57BL/6小鼠中以10 mg/kg剂量腹腔注射化合物7d，可提升CD4+ T细胞中的白细胞介素-2（interleukin-2）表达水平，并增加CD8+ T细胞的比例，且未表现出明显毒性。本研究拓展了一类具备T细胞调控特性的新型HDAC8抑制剂化学型，为未来的治疗应用提供了新的研究方向。