De-Regulation of 5hmC/TET2 Tumor Suppressor under Anti-Estrogen Therapy

 描述（由申请方提供）：内分泌抵抗的获得是雌激素受体-α（ERα）阳性乳腺肿瘤患者内分泌治疗的常见障碍。长期以来，人们一直怀疑抗雌激素治疗放松了表观遗传机制，并在获得性ETR过程中发挥重要作用。有几项研究表明，激素操纵，表观遗传变化和内分泌抵抗力之间存在间接关系。然而，在由雌激素信号传导启动和建立的分子途径和那些控制表观遗传重编程的分子途径中仍然存在很大的差距，从而使“内分泌抗性”表型和癌症复发成为可能。本提案的目的是确定新的表观遗传因子和分子机制，其通过抗雌激素治疗的失调使ETR和癌症复发成为可能。最近发现的10 - 11易位（泰特）蛋白催化5-甲基胞嘧啶（5 mC）转化为5-羟甲基胞嘧啶（5 hmC），为DNA甲基化的动态调控提供了新的范例。我们和其他人的研究表明，TET 2的缺失促进了乳腺癌细胞中更具侵袭性的表型。令人惊讶的是，在筛选可能抑制泰特表达的途径时，我们发现雌激素E2增强了MCF-7乳腺癌细胞中TET 2的表达。相比之下，用抗雌激素药物（如他莫昔芬和氟维司群）治疗减少了相同细胞中TET 2的表达。基于这些结果，我们假设雌激素信号和抗雌激素治疗对乳腺癌的发展和ETR具有“双刃剑”效应。除了其有据可查的致癌促进功能外，雌激素信号直接上调TET 2肿瘤抑制基因。我们推测，内分泌抵抗的获得部分通过抑制TET 2的表达以及通过改变5 hmC水平。为了验证这一假设，我们将采用和开发新的分子，细胞，遗传和表观遗传方法来研究雌激素诱导的TET 2上调（Aim 1）及其对表观基因组编程/重编程（Aim 2）的影响的机制。最后，我们将研究雌激素/ERα/TET 2通路在体外和体内预防内分泌抵抗中的功能重要性（Aim 3）。如果成功，拟议研究的结果将对基础和转化乳腺癌研究以及乳腺癌辅助治疗产生巨大影响。从这项研究中获得的知识将为乳腺癌发展和抗雌激素治疗抵抗的机制提供新的理解。特别是，它还将增加一个新的观点的功能雌激素信号及其相关的表观遗传机制对乳腺癌的发展和治疗。我们预计，该项目将导致新的方向，确定不同的药物靶点，以逆转或减少内分泌抵抗的未来。

 DESCRIPTION (provided by applicant): The acquisition of endocrine resistance is a common obstacle in endocrine therapy of patients with estrogen receptor-α (ERα)-positive breast tumors. It has been long-suspected that anti-estrogen treatments deregulate the epigenetic machinery and play an important role in the acquired ETR process. There have been several studies that suggest an indirect relationship between hormonal manipulations, epigenetic changes, and endocrine resistance. However, a big gap remains in the molecular pathways that are initiated and established by estrogen signaling and those controlling epigenetic reprogramming enabling the "endocrine resistance" phenotype and cancer relapse. The goal of this proposal is to identify novel epigenetic factors and molecular mechanisms of which the deregulation by anti-estrogen therapy enables ETR and cancer relapse. The recently discovered ten-eleven translocation (TET) proteins, which catalyze 5-methylcytosine (5mC) to 5- hydorxymethylcytosine (5hmC), have provided new paradigms for the dynamic regulation of DNA methylation. The studies of ours and others have shown that the loss of TET2 promotes a more aggressive phenotype in breast cancer cells. Surprisingly, while screening for pathways that may repress TET expression, we found that estrogen E2 enhances the expression of TET2 in MCF-7 breast cancer cells. In contrast, treatment with anti- estrogen drugs, such as tamoxifen and fulvestrant, reduces the expression of TET2 in the same cells. Based on these results, we hypothesize that estrogen signaling and anti-estrogen therapy have "double edged sword" effects on breast cancer development and ETR. In addition to its well-documented oncogenic-promoting function, estrogen signaling directly up-regulates TET2 tumor suppressor genes. We hypothesize that endocrine resistance is gained in part by inhibiting the expression of TET2 as well as by altering 5hmC levels. To test this hypothesis, we will employ and develop new molecular, cellular, genetic and epigenetic approaches to investigate the mechanism underlying estrogen-induced TET2 upregulation (Aim1) and its influence on epigenomic programing/reprogramming (Aim2). Finally, we will examine the functional importance of the estrogen/ERα/TET2 pathway in preventing endocrine resistance in vitro and in vivo (Aim3). If successful, the outcomes of the proposed study will have a huge impact on basic and translational breast cancer research and on adjuvant breast cancer therapy. The knowledge acquired from this study will provide a new understanding of the mechanisms underlying breast cancer development and anti-estrogen therapy resistance. In particular, it will also add a new view of the function estrogen signaling and its associated epigenetic mechanisms have on breast cancer development and therapy. We expect that this project will lead to new directions that identify different drug targets to revers or reduce endocrine resistance in the future.