Selective HDAC3 Inhibitors with Potent In Vivo Antitumor Efficacy against Triple-Negative Breast Cancer

HDAC3 modulation shows promise for breast cancer, including
triple-negative
cases. Novel pyrazino-hydrazide-based HDAC3 inhibitors
were designed and synthesized. Lead compound 4i exhibited
potent HDAC3 inhibition (IC50 = 14 nM) with at least 121-fold
selectivity. It demonstrated strong cytotoxicity against triple-negative
breast cancer cells (IC50: 0.55 μM for 4T1, 0.74
μM for MDA-MB-231) with least normal cell toxicity. Metabolically
stable 4i displayed a superior pharmacokinetic profile.
A dose-dependent therapeutic efficacy of 4i was observed
in a tumor-bearing mouse model. The biomarker analysis with tumor
tissues displayed enhanced acetylation on Ac-H3K9, Ac-H3K27, and Ac-H4K12 compared to Ac-tubulin and Ac-SMC3 indicating HDAC3
selectivity of 4i in vivo. The immunoblotting study with
tumor tissue showed upregulation of apoptotic proteins caspase-3,
caspase-7, and cytochrome c and the downregulation
of proliferation markers Bcl-2, CD44, EGFR, and Ki-67. Compound 4i represents a promising candidate for targeted breast cancer
therapy, particularly for cases with triple-negative breast cancer.

组蛋白去乙酰化酶3（HDAC3）调控在乳腺癌（涵盖三阴性乳腺癌病例）的治疗中展现出应用前景。本研究设计并合成了一类基于吡嗪酰肼结构的新型HDAC3抑制剂。先导化合物4i展现出强效的HDAC3抑制活性（半数抑制浓度IC50=14 nM），且对其他靶点的选择性至少达121倍。其对三阴性乳腺癌细胞展现出强劲的细胞毒性（4T1细胞IC50为0.55 μM，MDA-MB-231细胞IC50为0.74 μM），且对正常细胞的毒性极低。代谢稳定性优异的4i还具备优良的药代动力学特性。在荷瘤小鼠模型中，4i展现出剂量依赖性的治疗功效。对肿瘤组织的生物标志物分析结果显示，与乙酰化微管蛋白（Ac-tubulin）及乙酰化SMC3蛋白（Ac-SMC3）相比，乙酰化组蛋白H3K9（Ac-H3K9）、H3K27（Ac-H3K27）及H4K12（Ac-H4K12）的乙酰化水平显著升高，这表明4i在体内具备HDAC3选择性。对肿瘤组织开展的免疫印迹实验显示，凋亡蛋白半胱氨酸天冬氨酸蛋白酶3（caspase-3）、半胱氨酸天冬氨酸蛋白酶7（caspase-7）及细胞色素c的表达水平上调，而增殖标志物Bcl-2、CD44、表皮生长因子受体（EGFR）及Ki-67的表达水平下调。综上，化合物4i是一款极具潜力的乳腺癌靶向治疗候选药物，尤其适用于三阴性乳腺癌患者。