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女性和非裔美国女性，其一组必需基因被DNA超甲基化沉默，导致预后较差的基础表型。我们相信，促进乳腺癌发展的特定表观遗传靶点，一旦确定，将导致一种新的方法来治疗这种疾病。为此，我们利用SID诱饵破坏Sin3共抑制因子的PAH2结构域，该结构域与一小组转录因子结合，这些转录因子包含一个称为SID （mSin3A相互作用结构域）的特定基序。Sin3是一种多亚基协同抑制支架蛋白，通过募集HDAC、BP2/JARID1A（一种组蛋白H3二甲基化赖氨酸和三甲基化赖氨酸4特异性去甲基化酶）来调节转录，对DNA甲基化和其他染色质修饰剂至关重要。与HDAC抑制剂或去甲基化药物治疗相比，Sin3的PAH2结构域与有限数量的SID转录因子（包括REST、MAD1、KLF-9、-10、-11、-13和-16、UME6和HBP）结合的破坏预示着更具选择性的表观遗传效应。我们的数据表明，转染最小的SID或用编码的13个氨基酸肽（SID肽）破坏SID转录因子与Sin3A PAH2结构域的结合，在体外和体内的三阴性人和小鼠乳腺癌模型中诱导了深刻的表型变化，包括形态发生、侵袭丧失、接触抑制。这种从基础表型到分化程度更高的管腔表型的转换涉及表观遗传重编程，有助于Ecadherin、雌激素和视黄酸受体（ER和RARs）的重新表达，这为上皮/间充质转化（EMT）逆转的假设提供了支持。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没有观察到。此外，在人三阴性细胞系中，对雌激素、他莫昔芬和RAR激动剂的反应性恢复。用SID诱饵转染MMTV-myc转基因模型中产生的肿瘤获得的肿瘤细胞，并原位接种于FVB小鼠，肿瘤生长受到抑制（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，以建立临床前设计的三阴性特异性和参数。深入研究SID诱饵破坏pah2 - sin3和SID转录的机制和后果，将为理解基础表型的表观遗传调控和癌症发展中的EMT假说提供新的见解。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. PUBLIC HEALTH RELEVANCE: We have used a decoy (SID) to disrupt a specific epigenetic target which induces human triple negative breast cancer cell, morphogenesis, loss of invasion, differentiation, growth inhibition in vivo and restores sensitivity to anti-estrogen. Dissecting the mechanisms and consequences of SID decoy disruption will be studied in depth and should offer new insights in understanding epigenetic regulation of the basal phenotype and insight into breast cancer development. Successful SID decoy development offers other therapeutic options for triple negative breast cancer and also novel drugable targets.