HDAC抑制剂通过STAT3/AKT/EMT信号轴抗三阴乳腺癌转移和复发的作用机制研究

Tumor metastasis is responsible for more than 90% of cancer-associated mortalities and represents a vital clinical challenge. Accumulating evidence demonstrates that important roles for histone deacetylase (HDAC) in tumor tumorigenesis, metastasis and relapse, highlighting them as attractive targets for antitumor drug development. In our early studies, we screened small molecules that possess anti-HDAC activity from the compound library by experiment breast cancer animal model, we found that two HDAC inhibitors, SB939 and 4SC-202, strongly suppressed human triple-negative breast cancer (TNBC) metastases to the lung in vivo. Most of importantly, both of them displayed more potent anti-tumor activity compared with SAHA. Western blot and immunohistochemistry analysis assays further revealed that SB939 upregulated the levels of Ac-H3 and E-cadherin, inhibited tumor cell proliferation (PCNA) and induced apoptosis (cleaved-caspase 3) through suppressed the phosphorylation and activation of STAT3 and AKT, implying that SB939 and 4SC-202 may be two efficient tumor metastasis inhibitors. Therefore, through working on different platforms that are in vitro, ex vivo and in vivo models, we systematically investigated and compared the biological activities of these two compounds on angiogenesis, growth and tumor metastasis of TNBC. These findings may pave a way to better reveal the novel functions and its molecular basis for the anticancer action, and thus provide a scientific basis for molecular targeted therapy.

肿瘤转移是患者治疗失败、复发和死亡的首要原因。研究表明：组蛋白去乙酰化酶（HDAC）是治疗肿瘤转移和复发的重要靶标。项目前期通过体内乳腺癌转移模型作为评价系统，筛选出SB939和4SC-202两个对TNBC肺转移具有较高抑制作用的HDAC小分子抑制剂。初步发现SB939在显著降低转移灶中PCNA表达的同时上调cleaved-caspase的表达，且Ac-H3、HDAC1、p-STAT3、p-AKT以及E-cadherin蛋白表达均发生明显改变，但在非TNBC细胞中未观察到相似的实验效果，提示SB939和4SC-202很可能具备抗TNBC肺转移的新功能和抑制HDAC介导STAT3/ AKT /EMT信号通路的新机理。课题组拟通过细胞水平、蛋白水平以及整体动物模型多种途径阐明其抗TNBC的抑瘤功效，为肿瘤个体化治疗提供科学依据，为研制具有我国自主知识产权的肿瘤生物治疗药物奠定理论基础。

肿瘤转移是导致乳腺癌患者死亡的主要原因。在临床治疗中由于其发病机制的复杂性及个体差异性，目前并没有根治性的抗乳腺癌的药物。随之表观遗传学的深入研究，发现组蛋白去乙酰化酶（HDACs）广泛参与到肿瘤发生的过程中，并渐渐成为了肿瘤治疗的热点。本文中我们鉴定出一种一种新型羟肟酸类HDAC抑制剂pracinostat(SB939)，研究发现SB939能够抑制乳腺癌的侵袭和转移。.实验结果表明SB939可抑制乳腺癌细胞（MDA-MB-231、MCF-7、T47D）的增殖，其IC50分别为10.32、30.98、5.34µmol/L，但对乳腺正常上皮细胞的IC50为81.58，结果提示SB939能剂量依懒性的抑制乳腺癌细胞的增殖且在该剂量下对正常乳腺上皮细胞毒性不明显。细胞划痕、小室侵袭实验及3D基质胶实验结果表明SB939可呈浓度依赖性的抑制乳腺癌细胞的迁移和侵袭，其半数抑制浓度IC50均为0.1-0.5µmol/L。Western blot研究表明SB939在浓度为1µmol/L时可明显降低HDACs的表达水平，并可上调组蛋白H3和H4的乙酰化水平，同时可下调信号转导和转录激活因子3（Signal Transducer and Activator of Transcription 3，STAT3）的磷酸化水平并逆转EMT相关标记物的表达，增加E-cadherin蛋白的表达，减低N-cadherin、Vimentin的表达以及降低调控EMT的转录因子β-catenin表达水平。在乳腺癌皮下荷瘤模型和自发性转移模型研究中，我们发现SB939在25mg/kg可抑制体内肿瘤的生长以及肿瘤转移活性，但不影响裸鼠的正常体重指标且SB939对乳腺癌生长和转移的抑制效果优于SAHA阳性对照组。以上结果提示：SB939可以通过IL-6/STAT3通路逆转EMT从而抑制乳腺癌的转移，有望成为治疗乳腺癌的候选药物。

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