Inactivation of Hdac3 in the cause, prevention, and treatment of HCC

描述（由申请人提供）：组蛋白脱乙酰酶调节染色质结构、转录、复制和DNA修复/重组。由于这些在细胞周期控制中的关键作用，HDAC已成为各种肿瘤治疗干预的重要靶点，第一个组蛋白脱乙酰酶抑制剂（HDI）已获得FDA批准。组蛋白去乙酰化酶3（Hdac 3）是染色质结构和基因表达的关键调节因子，我们的初步数据表明，它可能是HDIs的中心靶点。由于组蛋白去乙酰化酶的多方面作用，很难确定抑制这些酶如何杀死癌细胞，同时保护周围的正常组织。因此，我们着手通过含有“floxed”Hdac 3的工程小鼠来理解Hdac 3的作用。在生殖细胞系中Hdac 3的缺失导致早期胚胎死亡。此外，Hdac 3缺失甚至在体外对小鼠胚胎成纤维细胞是致命的。虽然我们用“转录偏差”来处理这种分析，但基因表达阵列分析未能确定可能解释这种凋亡的基因表达模式的诱导。相反，仔细分析细胞周期表明，凋亡需要S期进展，S期减慢。令人惊讶的是，S期DNA损伤检查点在不存在Hdac 3的情况下被激活。这一观察结果，再加上将Hdac 3与DNA修复联系起来的数据，使我们发现Hdac 3的缺失导致DNA损伤，这很可能是由于DNA复制叉停滞时发生的DNA双链断裂修复效率低下。我们现在已经开始将这些信息转化为成年小鼠体内对Hdac 3的需求。在小鼠肝脏中去除Hdac 3引起与非酒精性脂肪肝病相似的表型，这可能是由于核激素受体功能失调。最重要的是，与DNA修复缺陷和基因组不稳定性一致，Hdac 3的肝脏特异性缺失导致100%的穿透性肝细胞癌，平均HCC时间为10.2个月。我们假设Hdac 3是有效的DNA修复所必需的，Hdac 3的缺失会导致基因组不稳定，从而导致癌症的发展，但我们可以利用DNA修复中的这些缺陷来治疗癌症。该提案将进一步确定Hdac 3失活影响DNA修复，调节染色质结构和导致肝细胞癌的机制。 公共卫生相关性：组蛋白去乙酰化酶3（Hdac 3）是调控基因表达的关键因子，可能成为肿瘤治疗的靶点。本申请涉及该关键基因在肝细胞癌的病因、预防和治疗中的作用。

DESCRIPTION (provided by applicant): Histone deacetylases regulate chromatin structure, transcription, replication, and DNA repair/recombination. Because of these key roles in cell cycle control, HDACs have become an important target for therapeutic intervention in a variety of tumors and the first Histone Deacetylase Inhibitor (HDI) has received FDA approval. Histone deacetylase 3 (Hdac3) is a key regulator of chromatin structure and gene expression and our preliminary data suggests that it may be a central target of HDIs. Because of the multi-faceted action of histone deacetylases, it has been difficult to pin down how inhibiting these enzymes acts to kill cancer cells while sparing surrounding normal tissues. Therefore, we set out to understand the action of Hdac3 by engineering mice containing a "floxed" Hdac3. Deletion of Hdac3 in the germ line caused early embryonic lethality. Moreover, Hdac3 deletion was even lethal to murine embryonic fibroblasts in vitro. Although we approached this analysis with a "transcription bias", gene expression array analysis failed to identify the induction of a gene expression pattern that might explain this apoptosis. By contrast, careful analysis of the cell cycle indicated that apoptosis required S phase progression and that S phase was slowed. Surprisingly, the S phase DNA damage checkpoint was activated in the absence of Hdac3. This observation, coupled with data linking Hdac3 to DNA repair, led us to the discovery that loss of Hdac3 caused DNA damage that was most likely due to inefficient repair of the DNA double strand breaks that occur at stalled DNA replication forks. We have now begun to translate this information to the in vivo requirements for Hdac3 in adult mice. Removal of Hdac3 in the mouse liver caused a phenotype similar to non-alcoholic fatty liver disease, which was likely due to de- regulated nuclear hormone receptor functions. Most importantly, consistent with defects in DNA repair and genomic instability, the liver-specific deletion of Hdac3 caused a 100% penetrant hepatocellular carcinoma with a mean time to HCC of 10.2 months. We hypothesize that Hdac3 is required for efficient DNA repair and that loss of Hdac3 causes genomic instability that leads to cancer development, but that we can take advantage of these defects in DNA repair to treat cancer. This proposal will further define the mechanisms by which inactivation of Hdac3 affects DNA repair, regulates chromatin structure, and causes hepatocellular carcinoma. PUBLIC HEALTH RELEVANCE: Histone deacetylase 3 (Hdac3) is a key factor controlling the expression of genes, which may be a therapeutic target for cancer therapy. This application addresses the role of this key gene in the cause, prevention, and treatment of hepatocellular carcinoma.