Dissecting the Mechanisms of Tamoxifen Action

剖析他莫昔芬的作用机制

基本信息

批准号：
7774969
负责人：
Manohar Ratnam
金额：
$ 31.08万
依托单位：
UNIVERSITY OF TOLEDO HEALTH SCI CAMPUS
依托单位国家：
美国
项目类别：
财政年份：
2009
资助国家：
美国
起止时间：
2009-07-01 至 2014-04-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/7774969
关键词：
Academia Address Adjuvant Therapy Affect Agonist Animal Model Biology Breast Breast Cancer Cell Cancer cell line Case-Control Studies Cell Proliferation Cell Survival Cells Chemicals Chromatin Classification Clinical Collaborations Collection Complex Coupled Distal Effectiveness Endometrial Carcinoma Endometrial Neoplasms Estradiol Estrogen Receptors Estrogen receptor negative Estrogen receptor positive Estrogens Evaluation Exhibits Frequencies Future Gene Activation Gene Expression Gene Expression Profiling Gene Expression Regulation Gene Targeting Genes Genomics Growth Hand High Risk Woman Human In Vitro Incidence Industry Laboratories Lead Libraries Ligands Light Literature MCF7 cell Malignant Neoplasms Mammary Neoplasms Modeling Molecular Molecular Profiling Mus Nature Nuclear Receptors Outcome Pattern Pharmaceutical Preparations Physiological Physiological Effects of Drugs Physiology Positioning Attribute Postmenopause Premenopause Prevention Process Property Raloxifene Reagent Receptor Signaling Recurrence Repression Resistance Risk Role Signal Transduction Site Tamoxifen Testing Therapeutic Therapeutic Effect Time Tumor Suppression Uterus Withholding Treatment Woman Xenograft Model base cancer cell cell growth comparative experience gene repression improved in vivo malignant breast neoplasm neoplastic cell novel prevent promoter public health relevance receptor binding success tool treatment duration tumor tumor growth tumor xenograft xenoestrogen

项目摘要

DESCRIPTION (provided by applicant): Tamoxifen is a mainstay in the treatment of estrogen receptor (ER)-positive breast cancer. However, long-term treatment of women at high risk for breast cancer reduces the incidence of both invasive and non-invasive ER+ breast cancer by only about 50 percent and also modestly increases the risk of endometrial cancer. Breast tumors could also become dependent on the drug for growth. Therefore, there is considerable room for improvement over tamoxifen. The clinical limitation of tamoxifen is reflected in breast and endometrial tumor xenograft models. Understanding different molecular mechanistic aspects of tamoxifen is necessary for improving upon this drug in decreasing the incidence and recurrence of breast tumors. A remarkably under-investigated aspect of estrogen (E2) action is gene repression which is frequently prevented by tamoxifen (de-repression). We have established a novel non-classical mechanism for direct gene repression by E2 in which ER forms a TAFII30-associated co-repressor complex; tamoxifen prevents this repression by simply dissociating the complex. We have identified synthetic ER ligands that mimic tamoxifen in a variety of model promoters and genes; however, these compounds differ from tamoxifen in that they behave like E2 with respect to the above mechanism of direct gene repression. Remarkably, the new compounds not only blocked E2-stimulated MCF-7 breast tumor cell proliferation but were also antiproliferative in tamoxifen-resistant MCF-7 cells developed in vivo; they also blocked E2-stimulated growth of Ishikawa uterine endometrial cancer cells in contrast to tamoxifen. The compounds did not affect the growth of ER-negative cells. The findings beg the question of what the physiological correlates of different mechanisms of gene de- repression by tamoxifen might be, particularly in relation to the effects of tamoxifen on the incidence and growth of breast and endometrial tumors. We hypothesize that gene de-repression by tamoxifen offers distinctive mechanisms that can provide the basis for identification of mechanistic classes of ER antagonists with superior therapeutic effects in breast cancer. In other words, tamoxifen's property of de-repressing certain genes may, in itself or by association with other effects, help in creating a condition that would be permissive to the onset or success of different survival/proliferation mechanisms, thereby constraining the drug's beneficial effects in certain cell contexts; the abrogation of such a mechanism(s) in certain ER antagonists may have a net effect of indirectly suppressing cell survival/proliferation, thereby increasing the duration of tumor suppression. The ER antagonists that we have identified (as well as those we expect to identify in the future) are excellent tools to address the hypothesis since they share a common mechanistic difference related to gene repression/de- repression. Since the expected differences in gene de-repression profiles of the compounds vs. tamoxifen are relatively small, it may even be feasible to use bio-statistical analysis coupled with multiple gene knockdown approaches to ultimately relate a group of E2 targets de-repressed by tamoxifen to specific physiological effects of the drug. Regardless of the outcome, it is necessary and feasible at this time to initiate systematic studies to shed light on the nature and extent of the possible impacts of novel and uninvestigated aspects of the genomic action of tamoxifen. The mechanism-based chemical biology approach proposed here is timely because of the availability of a large collection of partially characterized ER ligands, whose classification has been limited and largely empiric. Aim 1: Further investigate molecular mechanisms of gene de-repression by tamoxifen and identify additional model genes to represent each mechanism. Aim 2: Continue to identify new mechanistic classes of ER antagonists; compare tamoxifen and the new compounds with respect to cellular effects in ER+ breast and endometrial cancer cell lines in vitro; determine differential gene repression patterns and attempt to identify critical gene targets. Aim 3: Undertake a comparative evaluation of the effects of tamoxifen and selected new reagents in relation to inhibition and latency of breast and endometrial tumors using ER+ human tumor cells in xenograft models that have previously provided the most predictive clinical information for tamoxifen and also examine uterotropic effects. PUBLIC HEALTH RELEVANCE: The drug, tamoxifen is a mainstay in suppressing the growth and decreasing the incidence/recurrence of breast cancer. To improve upon this drug, it is necessary to understand all aspects of its mechanism of action. We have discovered a new aspect of tamoxifen's molecular actions which, under the appropriate conditions, could limit the drug's effectiveness by counteracting its own ability to inhibit tumor growth. We propose to further investigate this and other mechanisms of tamoxifen action and in the process, to identify lead compounds whose properties are superior to that of tamoxifen.

描述（由申请人提供）：他莫昔芬是治疗雌激素受体（ER）阳性乳腺癌的中流tay柱。然而，长期治疗乳腺癌高风险的女性可降低侵入性和非侵入性ER+乳腺癌的发生率仅约50％，并且适度增加了子宫内膜癌的风险。乳腺肿瘤也可能依赖于该药物的生长。因此，他莫昔芬有相当大的改进空间。他莫昔芬的临床局限性反映在乳房和子宫内膜肿瘤异种移植模型中。了解他莫昔芬的不同分子机理方面对于改善这种药物的改善需要减少乳腺肿瘤的发生率和复发。雌激素作用（E2）作用的一个明显评估的方面是基因抑制作用，该基因抑制经常被他莫昔芬（De-Repression）预防。我们已经建立了一种新型的非经典基因抑制E2的非经典机制，其中ER形成了与TAFII30相关的共抑制剂复合物。他莫昔芬通过简单地分离复合物来防止这种抑制。我们已经确定了在多种模型启动子和基因中模仿他莫昔芬的合成配体。但是，这些化合物与他莫昔芬不同，因为它们在上述直接基因抑制的机理上的行为与E2一样。值得注意的是，新化合物不仅阻塞了E2刺激的MCF-7乳腺肿瘤细胞增殖，而且在体内开发的耐他莫昔芬的MCF-7细胞中也具有抗增殖。与他莫昔芬相比，它们还阻止了Ishikawa子宫子宫内膜癌细胞的E2刺激的生长。这些化合物不影响ER阴性细胞的生长。这些发现引发了他莫昔芬不同基因抑制机制的生理相关性的问题，尤其是关于他莫昔芬对乳腺癌和子宫内膜肿瘤的发生和生长的影响。我们假设他莫昔芬的基因抑制具有独特的机制，可以为鉴定在乳腺癌中具有出色治疗作用的ER拮抗剂的机械类别提供基础。换句话说，他莫昔芬的剥夺某些基因的抑制性能本身或与其他效果相关，有助于创造一种允许的条件，该条件将允许或成功地限制了在某些细胞环境中药物的有益作用；某些ER拮抗剂中这种机制的废除可能会间接抑制细胞存活/增殖，从而增加肿瘤抑制的持续时间。我们已经确定的ER拮抗剂（以及我们希望将来会识别的拮抗剂）是解决该假设的出色工具，因为它们具有与基因抑制/抑制有关的共同机械差异。由于与他莫昔芬相对较小的化合物基因去抑制曲线的预期差异相对较小，因此使用生物统计分析以及多种基因敲低方法的生物统计分析甚至可以是可行的，以最终将一组E2靶标与他莫昔芬与该药物的特定物理学作用相关。无论结果如何，此时都有必要和可行的，以启动系统的研究，以阐明他莫昔芬基因组作用的新颖和未经资料的影响的性质和程度。此处提出的基于机制的化学生物学方法是及时的，这是因为大量部分表征的ER配体的可用性，其分类受到限制并且在很大程度上是经验性的。目标1：进一步研究他莫昔芬基因抑制基因的分子机制，并确定代表每种机制的其他模型基因。目标2：继续确定ER拮抗剂的新机械类别；比较了他莫昔芬和新化合物在体外ER+乳腺癌和子宫内膜癌细胞系中的细胞作用方面。确定差异基因抑制模式，并尝试识别关键基因靶标。 AIM 3：对他莫昔芬和选择的新试剂的影响进行比较评估，这些试剂在异种移植模型中使用ER+人类肿瘤细胞的抑制和子宫内膜肿瘤的抑制和潜伏期，这些模型以前为他提供了他莫昔芬的最预测性临床信息，并检查了他还检查了肌瘤作用。公共卫生相关性：该药物，他莫昔芬是抑制乳腺癌的发病率/复发的中流tay柱。为了改善这种药物，有必要了解其作用机理的各个方面。我们已经发现了他莫昔芬分子作用的一个新方面，在适当的条件下，该方面可以通过抵消其自身抑制肿瘤生长的能力来限制药物的有效性。我们建议进一步研究他莫昔芬作用的这种和其他机制，并在此过程中确定其性质优于他莫昔芬的铅化合物。