目的:基因表达的表观遗传调控在肝癌的发生发展中起着至关重要的作用;表观遗传驱动肝癌的分子机制尚不清楚.这项研究的目的是检查在侵袭性肝母细胞瘤中导致肝细胞去分化为癌细胞的分子机制,并测试这些机制的抑制是否会抑制肿瘤生长。
方法:我们分析了CCAAT/增强子结合蛋白α(C/EBPα),转录因子Sp5和组蛋白脱乙酰酶(HDAC)1途径来自新鲜肝母细胞瘤(HBL)样品的大型生物样本库,使用基于高压液相色谱的蛋白质-蛋白质复合物检查,并检查了肝细胞标记启动子上的染色质重塑和p21。在患者来源的HBL异种移植模型和培养的肝母细胞瘤细胞中,HDAC1活性受到抑制,并检查了HDAC1依赖性肝细胞标志物的表达。
结果:对生物样本库的分析表明,大部分HBL患者的致癌去磷酸化S190-C/EBPα水平升高,Sp5和HDAC1与相邻区域中这些蛋白质的量进行比较。我们发现,致癌去磷酸化-S190-C/EBPα是通过蛋白磷酸酶2A在侵袭性HBL中创建的,在细胞核内增加,并在Ser190处脱磷酸C/EBPα。C/EBPα-HDAC1和Sp5-HDAC1复合物在肝细胞中含量丰富,去分化为癌细胞。在HBL细胞中的研究表明,C/EBPα-HDAC1和Sp5-HDAC1复合物通过抑制其启动子来减少肝细胞和p21的标记。通过磺酰苯胺异羟肟酸(SAHA)和小干扰RNA介导的HDAC1抑制C/EBPα-HDAC1和Sp5-HDAC1复合物的药理学抑制增加肝细胞标志物的表达,p21,并抑制癌细胞的增殖。
结论:HDAC1介导的肝细胞标志物抑制是HBL发展的重要步骤,为通过靶向HDAC1活性产生侵袭性HBL的疗法提供背景。
OBJECTIVE: Epigenetic regulation of gene expression plays a critical role in the development of liver cancer; however, the molecular mechanisms of epigenetic-driven liver cancers are not well understood. The aims of this study were to examine molecular mechanisms that cause the dedifferentiation of hepatocytes into cancer cells in aggressive hepatoblastoma and test if the inhibition of these mechanisms inhibits tumor growth.
METHODS: We have analyzed CCAAT/Enhancer Binding Protein alpha (C/EBPα), Transcription factor
Sp5, and histone deacetylase (HDAC)1 pathways from a large biobank of fresh hepatoblastoma (HBL) samples using high-pressure liquid chromatography-based examination of protein-protein complexes and have examined chromatin remodeling on the promoters of markers of hepatocytes and p21. The HDAC1 activity was inhibited in patient-derived xenograft models of HBL and in cultured hepatoblastoma cells and expression of HDAC1-dependent markers of hepatocytes was examined.
RESULTS: Analyses of a biobank showed that a significant portion of HBL patients have increased levels of an oncogenic de-phosphorylated-S190-C/EBPα,
Sp5, and HDAC1 compared with amounts of these proteins in adjacent regions. We found that the oncogenic de-phosphorylated-S190-C/EBPα is created in aggressive HBL by protein phosphatase 2A, which is increased within the nucleus and dephosphorylates C/EBPα at Ser190. C/EBPα-HDAC1 and
Sp5-HDAC1 complexes are abundant in hepatocytes, which dedifferentiate into cancer cells. Studies in HBL cells have shown that C/EBPα-HDAC1 and
Sp5-HDAC1 complexes reduce markers of hepatocytes and p21 via repression of their promoters. Pharmacologic inhibition of C/EBPα-HDAC1 and
Sp5-HDAC1 complexes by Suberoylanilide hydroxamic acid (SAHA) and small interfering RNA-mediated inhibition of HDAC1 increase expression of hepatocyte markers, p21, and inhibit proliferation of cancer cells.
CONCLUSIONS: HDAC1-mediated repression of markers of hepatocytes is an essential step for the development of HBL, providing background for generation of therapies for aggressive HBL by targeting HDAC1 activities.