Targeted epigenetic therapy of triple-negative breast cancer

描述（由申请人提供）：产生异常转录的多种表观遗传程序有助于乳腺癌的发展。三阴性乳腺癌，常见于年轻和非洲裔美国妇女，具有一组被DNA超甲基化沉默的必需基因，其导致预后较差的基础表型。我们相信，有助于乳腺癌发展的特定表观遗传靶点一旦确定，将导致治疗这种疾病的新方法。为此，我们使用SID诱饵靶向破坏Sin 3共阻遏物的PAH 2结构域，该结构域与一小组含有称为SID（mSin 3A相互作用结构域）的特定基序的转录因子结合。Sin 3作为一种多亚基辅阻遏物支架蛋白，通过募集HDAC、BP 2/JARID 1A来调节转录，HDAC、BP 2/JARID 1A是一种对组蛋白H3的二甲基化和三甲基化赖氨酸4具有特异性的脱甲基酶，对从头DNA甲基化和其他染色质修饰剂至关重要。Sin 3的PAH 2结构域与有限数量的SID转录因子（包括REST、MAD 1、KLF-9、-10、-11、-13和-16、UME 6和HBP）结合的破坏预测了比用HDAC抑制剂或去甲基化剂治疗更具选择性的表观遗传效应。我们的数据表明，转染最小SID或用编码的13个氨基酸的肽（SID肽）处理破坏SID转录因子与Sin 3A PAH 2结构域的结合，在体外和体内诱导三阴性人和小鼠乳腺癌模型中形态发生、侵袭丧失、接触抑制的深刻表型变化。这种从基础型到更分化的管腔表型的转变涉及表观遗传重编程，其有助于E钙粘蛋白、雌激素和视黄酸受体（ER和RAR）的重新表达，增加了对上皮/间充质转化（EMT）逆转的假设的支持。这在3个三阴性乳腺癌细胞系中观察到，但在2个ER阳性乳腺癌细胞系中未观察到。此外，在人三阴性细胞系中，恢复了对雌激素、他莫昔芬和RAR激动剂的反应性。当从MMTV-myc转基因模型中产生的肿瘤获得的肿瘤细胞用SID诱饵转染并原位接种在FVB小鼠中时，肿瘤生长被抑制（70%）。我们正在进行的研究是开发稳定的SID肽和小分子抑制剂，并在大量乳腺癌细胞系中进行体外评估，以建立三阴性特异性和临床前设计参数。将深入研究SID诱饵破坏PAH 2-Sin 3和SID转录的机制和后果，并应提供新的见解，以了解基础表型的表观遗传调控和癌症发展中的EMT假说。这为三阴性乳腺癌提供了其他治疗选择，也提供了新的药物靶点。

DESCRIPTION (provided by applicant): Multiple epigenetic programs creating aberrant transcription contribute to the development of breast cancer. Triple negative breast cancer, common in young and African American women has a group of essential genes silenced by DNA hypermethylation that contribute to the poorer prognosis basal phenotype. We believe that specific epigenetic targets that contribute to the development of breast cancer, once identified, will lead to a novel approach to the treatment of this disease. To this end we targeted the disruption of the PAH2 domain of the Sin3 co-repressor that binds to a small group of transcription factors that contain a specific motif called SID (mSin3A interaction domain) using SID decoys. Sin3 serves as a multisubunit corepressor scaffold protein that regulates transcription by recruiting HDAC, BP2/JARID1A, a demethylase specific for di- and trimethylated lysine 4 of histone H3, critical for de novo DNA methylations and other chromatin modifiers. The disruption of PAH2 domain of Sin3 binding to a limited number of SID transcription factors including REST, MAD1, KLF-9, -10, -11, -13 and -16, UME6 and HBP predicts a more selective epigenetic effect than treatment with HDAC inhibitors or demethylating agents. Our data demonstrate that transfection of the minimal SID or treatment with the encoded 13 amino acid peptide (SID peptide) disrupts SID transcription factor binding to the Sin3A PAH2 domain induces profound phenotypic changes of morphogenesis, loss of invasion, contact inhibition in triple negative human and mouse breast cancer models in vitro and in vivo. This switch from a basal to a more differentiated luminal phenotype involves epigenetic reprogramming contributing to re-expression of Ecadherin, estrogen and retinoic acid receptors (ER and RARs) adds support to the hypothesis of reversion of the Epithelial/Mesenchymal Transition (EMT). This was observed in 3 triple negative but not in 2 ER positive breast cancer cell lines. Moreover, in the human triple- negative cell lines the responsiveness to estrogen, tamoxifen and RAR agonists is restored. Tumor growth is inhibited (70%) when tumor cells obtained from the tumors generated in the MMTV-myc transgenic models were transfected with the SID decoy and inoculated orthotopically in FVB mice. Our ongoing research is to develop stable SID peptide and small molecule inhibitors and evaluate in vitro in a large number of breast cancer cell lines to establish triple negative specificity and parameters for pre-clinical design. Dissecting the mechanisms and consequences of SID decoy disruption of PAH2-Sin 3 and SID transcription will be studied in depth and should offer new insights in understanding epigenetic regulation of the basal phenotype and insight into the EMT hypothesis in cancer development. This offers other therapeutic options for triple negative breast cancer and also novel druggable targets.