紫檀芪调节MTA1/HDAC蛋白复合物抑制肝癌细胞生长的机制

Hepatocellular carcinoma (HCC) is the most common type of liver cancer. Pterostilbene(PTER) is a stilbenoid chemically related to resveratrol and is found in blueberries and grapes.It exhibits anti-cancer, anti-hypercholesterolemia, and anti-hypertriglyceridemia properties. Metastasis-associated protein 1 (MTA1) is highly expressed in several types of human cancers and its elevated expression correlates with clinicopathological parameters of aggressive tumors MTA1 belongs to the MTA family of proteins that are critical participants of a nucleosome remodeling and deacetylation (NuRD) protein complex, which is involved in global and gene-specific transcriptional regulation, histone deacetylation, and chromatin remodeling . Other proteins in the NuRD complex are histone deacetylases 1 and 2 (HDAC1 and HDAC2). The primary function of MTA proteins is chromatin remodeling and histone and non-histone protein deacetylation, ultimately resulting in transcriptional repression.We have shown that MTA1 overexpression in cancer correlates with tumor aggressiveness and metastasis and a novel MTA1-mediated mechanism. Our results indicate a novel epigenetic mechanism that contributes to PTER anticancer activities: the inhibition of MTA1/NuRD complexes due to MTA1 decrease, which suppresses its deacetylation function and allows p53 acetylation and subsequent activation of pro-apoptotic genes. That MTA1 as a new molecular target of PTER may have important clinical applications for cancer chemoprevention and therapy. In our preliminary experiment, we found PTER causes down-regulation of MTA1 protein, increasing the PTEN expression and accumulation of Ac-PTEN. Then PTER can inhibit the growth of hepatoma. PTEN is a lipid phosphatase, converts PIP3 to PIP2 and in turn causes Akt dephosphorylation.When the PTEN enzyme is functioning properly, it acts as part of a chemical pathway that signals cells to stop dividing and can cause cells to undergo apoptosis when necessary. So we assume that PTER decrease the expression of MTA1, then destabilize MTA1/HDAC, thus allowing acetylation of PTEN on Lys402, which is in the COOH-terminal PDZ domain-binding motif. Lys402 acetylation improve the affinity of PTEN to PDZ domain-containing proteins,increasing the function of PTEN. PTER induce histone hyperacetylation and facilitating Egr-1 binding to PTEN promoter to stimulate its expression. The PI3K/Akt pathway is a major survival pathway activated in cancer. But PTEN is inhibitors of this pathway. All the results are preventing the growth of hepatoma. In this study, we design to test the hypothesis that PTER exerts its anticancer effects in hepatoma by inhibiting PTEN/PI3K/Akt pathway and explore the mechanisms. PTER is a pharmacologically safe dietary compound.Finally, we define a novel epigenetic pathway of PTER anticancer activity opens new opportunities for the development of treatment strategies based on PTER.

紫檀芪能通过多种途径抑制肿瘤的发生和发展。但其在肝癌中的作用机制尚未完全明确。我们前期研究发现：紫檀芪可下调肝癌细胞MTA1基因的表达，使MTA1/HDAC复合物结构失稳，并上调PTEN基因的表达，还导致乙酰化PTEN蛋白的积聚。据此，我们推测：紫檀芪通过下调MTA1基因，解析MTA1/HDAC复合物，提高PTEN基因启动子的乙酰化水平，进而诱导基因的表达；同时乙酰化PTEN蛋白的K402位点，增强PTEN的作用效应，从而抑制PTEN/PI3K/Akt信号转导通路，阻滞肝癌细胞生长。为验证此假说，我们使用不同剂量紫檀芪干预MTA1基因敲除的和正常的肝癌细胞，RT-PCR检测干预前后MTA1基因的表达；蛋白电泳、免疫共沉淀等技术检测相关蛋白的表达和细胞凋亡,同期进行动物实验。阐明紫檀芪调节MTA1/HDAC复合物抑制肝癌细胞生长的重要机制，为开发紫檀芪及研究肝癌的防治提供新的思路和理论依据。

肝细胞癌(HCC)是世界上最常见的癌症之一，也是人类死亡的主要原因之一。传统的化疗在治疗肝癌方面并不是很有效，而诊断往往是晚期而失去最佳的手术机会，导致大多数患者预后较差。肝细胞癌是一种多药耐药肿瘤，大多数患者对药物治疗效果不佳，包括索拉非尼因耐药而疗效较差。因此，寻找低毒、口服安全、有效的抗癌药物治疗肝癌越来越重要。近年来，我们发现PTER及其类似物(resveratrol和piceatannol)对抑制癌症有明显的影响。研究发现，pterostilbene在乳腺癌、肺癌、前列腺癌和食管癌等恶性肿瘤中均有抑制作用，但对肝癌的研究较少。Pterostilbene(PTER)是一种非常广泛的芪类化合物，是从葡萄、花生、葡萄酒等中提取的。目前，对PTER的天然模拟正在进行广泛的研究。我们讨论了pterostilbene对SMMC7721细胞侵袭、迁移、增殖、周期和凋亡的影响，从而为肝细胞癌药物治疗提供了新的靶点。对MTA家庭成员的表达水平的调查已经变得越来越普遍。MTA1是MTA家族的成员，在肿瘤的生长、侵袭和转移中起着关键作用。MTA1基因的高表达可能是肝癌手术治疗后的预后指标。以前的研究表明，MTA1蛋白和组蛋白去乙酰酶1(HDAC1)是核苷酸重构和脱乙酰(NuRD)蛋白复合物的成员。我们的研究发现，pterostilbene(PTER)具有抑制MTA1表达和抑制肿瘤生长的能力。PTER下调MTA1，降低HDAC1活性和有效浓度，导致MTA1 / HDAC复合物的不稳定，增加了PTEN的乙酰化和活化。根据我们的研究，我们认为PTER可以减少染色质修饰MTA1的表达，增加乙酰化和激活PTEN。我们研究了pterostilbene(PTER)在HCC中的抗肿瘤作用。PTER处理可下调MTA1和HDAC1的表达，提高肿瘤中Ac-PTEN的比例。结果表明，PTER可以降低MTA1的表达，使MTA1 / HDAC复合物在Lys402位点的乙酰化。我们证明PTER抑制了HCC的生长和侵袭，并有效地调节了MTA1 /HDAC/ NuRD复合物的水平，促进了HCC的PTEN乙酰化和凋亡。PTER抗癌活性的表观遗传特性为肝癌治疗开辟新前景。