Role of Estrogen Receptor alpha-p53 Interaction in Resistance to Tamoxifen Therap

描述（由申请人提供）：抗激素药物他莫昔芬被批准用于治疗早期和晚期以及早期雌激素受体（ER）阳性乳腺癌女性。已知他莫昔芬通过与雌激素受体结合而对乳腺癌细胞发挥作用，从而阻止雌激素的结合。然而，一个主要的临床问题是，大量的ER阳性乳腺肿瘤患者对他莫昔芬治疗没有反应或产生耐药性，尽管已经提出了几个合理的原因，这种耐药性的机制仍然很大程度上不清楚。ER介导雌激素促进乳腺癌细胞增殖的作用。肿瘤抑制蛋白p53通过介导细胞周期停滞和/或细胞凋亡以响应各种细胞应激物来防止肿瘤发生。这两种拮抗途径之间是否存在直接联系尚不清楚。我们的实验已经证明，ER 1与p53结合并抑制其在人乳腺癌细胞中的功能。重要的是，雌激素增强ER 1-p53相互作用，而抗激素药物他莫昔芬和氟维司群破坏相互作用。我们的回顾性临床研究结果与我们的细胞和分子观察结果相关，并且与野生型p53状态与对他莫昔芬治疗的更好反应的报告相关性一致。基于这些发现，我们推测ER 1对野生型p53的抑制可能是他莫昔芬作用的重要机制。如果肿瘤有突变的（因此功能失调的）p53，那么他莫昔芬的作用的益处就变得无关紧要了。为了检验这些假设，提出了对50名患有表达野生型p53的新诊断的ER阳性乳腺癌的绝经前妇女的先导性随机临床试验。具体目标是：（1）研究在手术前用20 mg他莫昔芬治疗4周的患者中与未治疗患者中的相互作用相比的ER-p53相互作用的状态，和（2）通过监测所选p53- 1的表达来确认p53的野生型状态并分析p53途径的功能状态。在手术前接受或未接受20 mg他莫昔芬治疗四周的患者中，肿瘤中的靶基因。这些研究将结合临床、病理学、细胞和分子生物学专业知识，在主办机构的新诊断乳腺癌患者中前瞻性进行。ER和p53的状态，它们的相互作用，以及它们在乳腺肿瘤中的后果将用免疫组化，细胞和分子方法进行分析。拟议的工作有可能带来一个范式转变，以分析对他莫昔芬治疗的耐药机制。公共卫生相关性：这项研究从一个新的角度解决了对他莫昔芬治疗的耐药性，提出了一个试点临床试验，分析他莫昔芬是否可以通过破坏ER-p53相互作用来恢复功能性肿瘤抑制基因p53。这项研究的结果将有助于制定策略，以确定谁是最受益于他莫昔芬治疗的乳腺癌患者，并避免不必要的暴露于这种药物及其众多的副作用。因此，拟议研究的结果可能会影响乳腺癌患者个体化治疗的发展。

DESCRIPTION (provided by applicant): The anti hormonal drug tamoxifen is approved for the treatment of women with early and advanced and early stage estrogen receptor (ER)-positive breast cancer. Tamoxifen is known to exert its effects on breast cancer cells by binding to the estrogen receptor, thereby preventing the binding of estrogen. However, a major clinical problem is that a large number of patients with ER-positive breast tumors either do not respond to tamoxifen therapy or develop resistance to it. Although several plausible reasons for such resistance have been suggested, the mechanisms of resistance to tamoxifen therapy remain largely unclear. ER mediates effects of estrogen in promoting proliferation of breast cancer cells. Tumor suppressor protein p53 guards against tumorigenesis by mediating cell cycle arrest and/or apoptosis in response to various cellular stressors. Whether there is a direct link between these two antagonistic pathways has remained unclear. Our experiments have demonstrated that ER1 binds to p53 and represses its function in human breast cancer cells. Importantly, estrogen enhances ER1-p53 interaction, whereas anti-hormonal drugs tamoxifen and fulvestrant disrupt the interaction. Results from our retrospective clinical studies correlate with our cellular and molecular observations and are consistent with the reported association of wild type p53 status with better response to tamoxifen therapy. Based on these findings, it is hypothesized that relieving suppression of wild type p53 by ER1 could be an important mechanism underlying tamoxifen action. The benefit of tamoxifen's effect becomes irrelevant if the tumor has mutant (and therefore dysfunctional) p53. To test these hypotheses, a pilot randomized clinical trial of 50 pre- menopausal women with newly diagnosed ER-positive breast cancer expressing wild type p53 is proposed. The Specific Aims are: (1) Investigate the status of ER-p53 interaction in patients treated with 20 mg of tamoxifen for four weeks prior to surgery as compared to the interaction in untreated patients, and (2) Confirm the wild type status of p53 and analyze the functional status of p53 pathway by monitoring expression of selected p53-target genes in tumors in patients who have or have not been treated with 20 mg tamoxifen for four weeks prior to surgery. These studies will be conducted prospectively in newly diagnosed breast cancer patients at the host institution using a combination of clinical, pathological, cellular, and molecular biology expertise. The status of ER and p53, their interaction, and its consequences in breast tumors will be analyzed with immunohistochemical, cellular, and molecular approaches. The proposed work has the potential to bring about a paradigm shift to the analysis of mechanisms underlying resistance to tamoxifen therapy. PUBLIC HEALTH RELEVANCE: This research addresses resistance to tamoxifen therapy from a novel angle by proposing a pilot clinical trial to analyze if tamoxifen can restore functional tumor suppressor p53 by disrupting ER-p53 interaction. Results from this study will help develop strategies to identify breast cancer patients who would most benefit from tamoxifen therapy, and avoid unnecessary exposure to this drug and its numerous side effects. Thus, results from the proposed study could impact the development of individualized therapy for breast cancer patients.