Aptamer-siRNA Chimeras Targeting HER2-Positive Breast Cancers

描述（由申请人提供）：认识到四分之一的乳腺癌表现出2型表皮生长因子受体（HER2）水平升高是乳腺癌研究中最重要的近期发现之一。HER2与晚期疾病相关，并代表快速生长、高度转移和耐药的癌症。因此，与HER2阴性乳腺癌患者相比，HER2阳性乳腺癌患者的预后更差。尽管最近在治疗方面取得了进展，但HER2阳性乳腺癌晚期患者的结局是死亡。为此提出了若干理由。原因之一是由于疾病的复杂性质而导致的对治疗的不敏感或抵抗。第二个原因是与治疗本身的非特异性相关的毒性。因此，越来越需要为HER2阳性乳腺肿瘤开发更安全，更有效的治疗方法。我们建议开发一种新的试剂，这种试剂是特异性的，可以避免HER2阳性乳腺癌的许多导致耐药性的适应性反应。这些特性将通过工程化由靶向部分（结合HER2的RNA适体）和治疗部分（针对乳腺癌特异性促存活因子的细胞毒性siRNA）组成的多功能抑制剂来实现。在与细胞表面上的HER2结合后，试剂将其治疗性货物递送到细胞中，导致癌细胞死亡。除了抑制促生存因子外，该试剂还具有通过促进其降解拮抗HER2本身活性的潜力（联合治疗）。在这个为期五年的项目中，我们建议使用啮齿动物乳腺癌模型在概念验证研究中验证这种方法。从这项工作中获得的知识将用于开发一种人类特异性治疗方式，重点是安全性和治疗效果。我们的具体目标是（1）应用尖端RNA技术抑制HER2阳性乳腺癌细胞中的促生存因子，（2）确定该试剂在啮齿动物乳腺癌模型中的有效性和安全性，以及（3）开发人类特异性试剂并评估在人类乳腺癌细胞和人类乳腺癌小鼠模型中的有效性。在这些研究完成时，我们期望我们将确定靶向HER2阳性乳腺肿瘤（以及其他HER2表达癌症）的试剂。此外，这项工作将开发可应用于建立平台技术的一般原则，用于产生针对其他癌症的靶向基因沉默疗法。这项工作的成功完成预计将为临床医生以及乳腺癌患者，包括难治性疾病患者，提供更好的治疗选择，以对抗HER2阳性乳腺癌。 公共卫生相关性：这项工作的成功完成预计将产生新的试剂，用于治疗HER2阳性乳腺癌的疗效和安全性得到改善。这些试剂可能对治疗乳腺癌患者（HER2阳性状态）具有潜在的重要影响，包括难治性疾病患者和其他HER2表达癌症患者。此外，这项工作将完善建立平台技术的一般方法，该平台技术可用于开发几种人类病理条件的新治疗方法，这些疾病将受益于靶向基因沉默。

DESCRIPTION (provided by applicant): The recognition that one out of 4 breast cancers exhibits elevated levels of the epidermal growth factor receptor type 2 (HER2) is one of the most significant recent discoveries in breast cancer research. HER2 is associated with advanced disease and typifies cancers that are fast growing, highly metastatic, and resistant to treatment. As such, patients with HER2-positive breast cancers have a worse prognosis compared to patients with HER2-negative breast cancers. Despite recent advances in treatments, the outcome for HER2-positive breast cancer patients with advanced disease is death. Several reasons have been proposed for this. One reason is insensitivity or resistance to treatment resulting from the complex nature of the disease. The second reason is toxicity associated with the non-specific nature of the treatments themselves. Therefore, there is an increasing need for developing safer, more effective treatments for HER2-positive breast tumors. We propose to develop a novel reagent that is specific and circumvents many of the adaptive responses of HER2-positive breast cancers that lead to resistance. These properties will be achieved by engineering a multifunctional inhibitor composed of a targeting moiety (an RNA aptamer that binds to HER2) and a therapeutic moiety (a cytotoxic siRNA to breast cancer specific pro-survival factors). Upon binding to HER2 on the cell-surface, the reagent will deliver its therapeutic cargo into the cells resulting in cancer cell death. In addition to inhibiting pro-survival factors, this reagent has the potential to antagonize the activity of HER2 itself by promoting its degradation (combination therapy). During the five-year project we propose to validate this approach in proof-of-concept studies using rodent models of breast cancer. The knowledge derived from this work will be used to develop a human-specific therapeutic modality with emphasis on safety and therapeutic efficacy. Our specific aims are to (1) apply cutting-edge RNA technologies to inhibit pro-survival factors in HER2-positive breast cancer cells, (2) determine efficacy and safety of this reagent in rodent models of breast cancer, and (3) develop human-specific reagents and evaluate efficacy in human breast cancer cells and in mouse models of human breast cancer. At the completion of these studies, it is our expectation that we will have identified reagents for targeting HER2-positive breast tumors (as well as other HER2-expressing cancers). In addition, this work will develop general principles that can be applied towards the establishment of a platform technology for generating targeted gene silencing therapies against other cancers. The successful completion of this work is expected to provide clinicians as well as breast cancer patients, including patients with refractory disease, with improved treatment choices for fighting HER2-positive cancers of the breast. PUBLIC HEALTH RELEVANCE: The successful completion of this work is expected to yield novel reagents with improved efficacy and safety profiles for the treatment of HER2-positive breast cancers. These reagents are likely to have a potentially important impact for treating breast cancer patients (with HER2-positive status), including patients with refractory disease, and patients with other HER2-expressing cancers. In addition, this work will refine general methods for establishing a platform technology that can be applied towards developing novel treatments for several human pathological conditions that would benefit from targeted gene silencing.