Cyclin E: Implications for targeted therapy in HER2-overexpressing breast cancer

描述（由申请人提供）：长期目标是确定HER2调节周期蛋白E表达的机制，并为申请人作为医生科学家的职业生涯做好准备，申请人将在奖励期完成之前提交R01申请。职业发展计划强调获得技术技能和扩大有关知识基础，以促进向独立过渡。该研究计划调查了我们的新发现，即HER2和cyclin E的过表达与乳腺癌的侵袭性表型相关，HER2下调导致cyclin E表达降低。假设：HER2在乳腺癌细胞中作用于cyclin E的上游，调节cyclin E及其低分子量（LMW）形式的产生，这可能预测HER2靶向治疗的反应或作为第二个治疗靶点。目的：1)明确HER2调控LMW cyclin E的机制2)建立HER2和cyclin E过表达对靶向治疗应答的影响3)评价HER2和cyclin E过表达对乳腺癌患者预后的预测意义。研究设计：我们将利用等基因MCF-7系统确定HER2对细胞周期蛋白E转录和降解的影响。利用76N等基因乳腺上皮细胞模型系统确定HER2通过改变弹性蛋白酶：弹力蛋白比例对LMW同种异构体产生的影响。其次，我们将使用MCF- 7细胞模型，稳定转染flag标记的cyclin E构建物，代表cyclin E和LMW形式，并与HER2共转染，以研究cyclin E对HER2和cyclin E靶向治疗的影响。结果将在体内使用her2过表达的乳腺癌异种移植模型得到证实。最后，我们将分析HER2， FL和LMW cyclin E在我们机构治疗的患者乳腺组织标本中的表达。表达水平与临床结果相关。相关性：我们的研究将使我们了解HER2调节cyclin E及其LMW形式表达的机制。深入了解这两种已知的乳腺癌预后不良因素之间的关系，将决定确定细胞周期蛋白E水平是否具有临床实用性，以预测对her2靶向治疗的反应，或作为治疗剂的第二靶点。这一知识将为确定her2过表达乳腺癌患者使用靶向治疗的治疗策略提供策略。

DESCRIPTION (provided by applicant): The long term goals are to define the mechanism by which HER2 regulates cyclin E expression and to prepare the applicant for a career as a physician scientist who will submit an R01 application prior to completion of the award period. The career development plan emphasizes acquisition of technical skills and expansion of relevant knowledge base to facilitate the transition to independence. The research plan investigates our novel finding that overexpression of HER2 and cyclin E is associated with an aggressive phenotype of breast cancer and that HER2 downregulation results in decreased cyclin E expression. Hypothesis: HER2 acts upstream of cyclin E in breast cancer cells regulating the generation of cyclin E and its low molecular weight (LMW) forms, which may predict response to HER2-targeted therapy or serve as a 2nd therapeutic target. Aims: 1) Identify mechanisms by which HER2 regulates LMW cyclin E 2) Establish the effect of HER2 and cyclin E overexpression on response to targeted therapy 3) Evaluate the prognostic and predictive significance of HER2 and cyclin E overexpression in breast cancer patients. Study Design: We will establish the effects of HER2 on cyclin E transcription and degradation using an isogenic MCF-7 system. The effects of HER2 on the generation of LMW isoforms by altering the elastase:elafin ratio will be determined using the 76N isogenic breast epithelial cell model system. Second, we will use a model of MCF- 7 cells stably transfected with FLAG-tagged cyclin E constructs representing cyclin E and the LMW forms and cotransfected with HER2 to investigate the effects of cyclin E on HER2- and cyclin E-targeted therapies. Results will be confirmed in vivo using an HER2-overexpressing breast cancer xenograft model. Finally, we will analyze expression of HER2, FL and LMW cyclin E in breast tissue specimens collected from patients treated at our institution. Expression levels will be correlated with clinical outcome. Relevance: Our studies will allow us to understand the mechanism by which HER2 regulates expression of cyclin E and its LMW forms. Insight into the relationship between these two known poor prognostic factors in breast cancer will determine if there is clinical utility in determining cyclin E levels to either predict response to HER2-targeted therapy or serve as a 2nd target for therapeutic agents. This knowledge will provide a strategy to determine treatment strategies using targeted therapy in patients with HER2-overexpressing breast cancer.