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

 描述(申请人提供)：内分泌抵抗的获得是雌激素受体-α(ER-α)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会破坏表观遗传机制，并在获得性ETR过程中发挥重要作用。有几项研究表明，激素调节、表观遗传学变化和内分泌抵抗之间存在间接关系。然而，在由雌激素信号启动和建立的分子通路和那些控制表观遗传重编程使“内分泌抵抗”表型和癌症复发的分子通路之间仍然存在着很大的差距。这项建议的目的是确定新的表观遗传因素和分子机制，其中通过抗雌激素治疗的放松调控使ETR和癌症复发。最近发现的10-11易位(Tet)蛋白催化5-甲基胞嘧啶(5mC)为5-羟甲基胞嘧啶(5hmC)，为DNA甲基化的动态调控提供了新的范式。我们和其他人的研究表明，TET2的缺失促进了乳腺癌细胞更具侵袭性的表型。令人惊讶的是，在筛选可能抑制TET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TET2的表达。相比之下，使用抗雌激素药物，如他莫昔芬和氟维斯特，可以减少TET2在相同细胞中的表达。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生和ETR具有“双刃剑”效应。除了众所周知的致癌促进作用外，雌激素信号还可直接上调TET2肿瘤抑制基因。我们推测，内分泌抵抗部分是通过抑制TET2的表达以及改变5hmC水平而获得的。为了验证这一假说，我们将使用和开发新的分子、细胞、遗传学和表观遗传学方法来研究雌激素诱导TET2上调(Aim1)的机制及其对表观基因组编程/重编程(AIM2)的影响。最后，我们将研究雌激素/ERα/TET2通路在预防体内和体外内分泌耐药中的功能重要性(AIM3)。如果成功，这项拟议研究的结果将对基础和转化性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生和抗雌激素治疗耐药的机制提供新的理解。特别是，它还将增加一个新的观点，雌激素信号及其相关的表观遗传机制在乳腺癌的发展和治疗中的作用。我们期待这一项目将带来新的方向，确定不同的药物靶点，以逆转或减少未来的内分泌耐药。

 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.