Atrap在AngII-AT1R介导的乳腺癌三苯氧胺耐药中的作用及机制

Tamoxifen resistance, as the primary cause to the failure of breast cancer endocrine therapy, its mechanism has not been elucidated. Our previous research has demonstrated that AngII-AT1R pathway plays an important role on tumor angiogenesis, apoptosis, invasion(Cancer Letters 2013，J Cell Physiol 2014).And subsequently we discovered that AngII-AT1R pathway mediate tamoxifen resistance in breast cancer(published). Most intriguingly, our latest results showed that Atrap, one angiotensin-associated protein, is highly expressed in both breast cancer tissue and tamoxifen resistant cell lines. Since it has been proved that Atrap is involved with endocytosis, we hypothesized that Atrap may modulate AT1R endocytosis or tamoxifen resistance in breast cancer by direct interaction with AT1R. Thus we are aiming to explore how Atrap regulates AT1R endocytosis and to investigate tamoxifen sensitivity in breast cancer and AT1R with its downstream signals change by interfering Atrap expression. The study may explore the role in which Atrap plays in AngII-AT1R mediated breast cancer tamoxifen resistance and provide a new target in overcoming tamoxifen resistance in breast cancer.

三苯氧胺耐药严重影响乳腺癌治疗效果，其机制仍未阐明。课题组既往研究证实：血管紧张素II/血管紧张素II受体1（AngII-AT1R）途径在乳腺癌肿瘤血管生成、凋亡及侵袭方面发挥作用(Cancer Letters 2013，J Cell Physiol 2014)。我们前期研究证实AngII-AT1R途径介导乳腺癌三苯氧胺耐药,并率先发现血管紧张素受体相关蛋白（Atrap）在人乳腺癌组织及三苯氧胺耐药细胞系高表达。已有文献证实Atrap是内吞转运的功能蛋白。我们推测Atrap调节AT1R内吞转运或直接与AT1R相互作用参与乳腺癌三苯氧胺耐药。我们将阐明Atrap在AT1R内吞转运中的作用并通过干预Atrap表达，观察乳腺癌三苯氧胺药物敏感性和AT1R表达及下游信号通路变化。本研究将揭示Atrap在AngII-AT1R介导的乳腺癌三苯氧胺耐药中的作用及机制，为克服乳腺癌三苯氧胺耐药提供靶点。

乳腺癌是最常见的肿瘤之一，严重威胁女性健康。ATRAP在不同的组织和器官中广泛表达，尤其是在心脏和肾脏中，但其在乳腺癌中的作用和机制仍不清楚。本实验应用了大量临床样本用于检测ATRAP的表达及其与临床病理特征和预后的关系。在细胞系中进行了功能增强和功能丧失实验，并使用小鼠移植模型进行体内实验，以阐明ATRAP诱导肿瘤进展的功能和潜在机制。使用生物信息技术结合公共数据库筛选出与ATRAP相互作用的蛋白，并用免疫共沉淀（Co-IP）实验进行验证。实验结果发现，与癌旁组织相比，ATRAP在乳腺癌中普遍高表达，而且，我们发现ATRAP高表达能降低患者的无病生存期（DFS）。在功能上，ATRAP的过表达在体外促进细胞侵袭，迁移，凋亡抗性和增殖，并且，下调ATRAP提高了细胞对他莫昔芬的敏感性。从机理上讲，高水平的ATRAP能够使AKT/mTOR信号通路过度活化，并且一种特定的mTOR抑制剂抑制了ATRAP诱导的肿瘤进展。免疫共沉淀实验表明，ATRAP过表达通过直接结合并稳定Pre-B-cell leukemia homeobox 3 (PBX3)进而激活AKT/mTOR途径，诱导细胞EMT，而上调PBX3促进了低ATRAP导致的肿瘤抑制。综上所述，本研究提供了第一个证据，即ATRAP通过稳定PBX3促进乳腺癌进展，然后激活AKT/mTOR途径。所以我们提出假设：ATRAP有望作为乳腺癌患者的预后指标和治疗靶标。