Determining and targeting mechanisms controlling cancer cell division

总体汇总 Cyclin D-Cdk 4/6-Rb-E2 F通路整合内外信号调控细胞周期进程 在细胞周期的G1/S转变时。在细胞周期蛋白D-Cdk 4/6-Rb-E2 F通路中的改变在大量的 大多数人类癌症。这些改变被认为增加了癌细胞的增殖潜力。 例如，视网膜母细胞瘤（RB 1）肿瘤抑制因子的功能失活或视网膜母细胞瘤（RB 1）肿瘤抑制因子的扩增， 细胞周期蛋白D基因是一个经常性的事件，在发展中的广泛的人类癌症。单纯 一致性模型，视网膜母细胞瘤蛋白Rb在细胞周期的G1/S转换时抑制细胞增殖 通过结合和抑制E2 F转录因子。Rb对细胞生长和增殖信号的反应是 在正常细胞中被一系列细胞周期蛋白依赖性激酶复合物磷酸化和失活（第一个细胞周期蛋白 D-Cdk 4/6，然后是细胞周期蛋白E/A-Cdk 2）。Rb的磷酸化导致Rb从E2 F解离 转录因子，从而引起对DNA合成和其他关键方面重要的基因转录 细胞周期的进程。因此，认为具有组成性失活Rb的癌细胞获得增加的 增殖潜能对正常细胞和癌细胞中细胞周期蛋白D-Cdk 4/6-Rb-E2 F通路的了解导致了 已被批准用于治疗乳腺癌的特异性Cdk 4/6抑制剂的开发， 正在进行其他几种癌症的临床试验。在这个范例中，Cdk 4/6的抑制导致Rb的减少， 磷酸化，其激活Rb的细胞周期抑制功能。然而，许多肿瘤对 这些抑制剂或仅短暂地起作用。最近对患者和临床前模型的观察表明， 我们对Rb通路的理解并不像我们以前认为的那样完整。这可能解释了变量 Cdk 4/6抑制剂在临床上的应用这项提案的总体目标是获得更深层次的结构，分子， 和细胞Rb通路的理解，最终目标是帮助设计新的和改进的治疗方法， 在广泛的癌症患者中针对这一途径的策略。我们的第一个目标是确定 调控细胞周期蛋白D-Cdk 4/6-Rb-E2 F通路的机制，包括细胞周期蛋白D-Cdk 4/6如何磷酸化 Rb以及以前未知的翻译后修饰如何调节Rb和E2 F活性。我们的第二 目的是鉴定和研究Rb通路组分的新功能，包括细胞周期蛋白D的新靶点。 Cdk 4/6激酶，Rb及其家族成员p107和p130的新功能，以及新的调节机制 控制E2 F转录因子的浓度和活性。我们的第三个目标是启动 以创新方式靶向Rb通路的策略，包括抑制细胞周期蛋白D-Rb的分子 结合，刺激p107和p130的肿瘤抑制活性，并操纵E2 F稳定性。这些目标 将通过三个相互关联的项目，通过全面，协同和多学科的方法来实现。 最终，从这些研究中获得的信息可能会提供新的方法来靶向细胞周期蛋白D-Cdk 4/6-Rb。 E2 F通路改善癌症治疗。

OVERALL SUMMARY The Cyclin D-Cdk4/6-Rb-E2F pathway integrates external and internal signals to control cell cycle progression at the G1/S transition of the cell cycle. Alterations in the Cyclin D-Cdk4/6-Rb-E2F pathway are found in the vast majority of human cancers. These alterations are thought to increase the proliferative potential of cancer cells. For example, the functional inactivation of the retinoblastoma (RB1) tumor suppressor or the amplification of Cyclin D genes is a recurrent event in the development of a wide range of human cancers. In the simple consensus model, the retinoblastoma protein Rb inhibits cell proliferation at the G1/S transition of the cell cycle by binding and inhibiting E2F transcription factors. In response to cell growth and proliferative signals, Rb is phosphorylated and inactivated in normal cells by a series of Cyclin-dependent kinase complexes (first Cyclin D-Cdk4/6 and then Cyclin E/A-Cdk2). Phosphorylation of Rb results in the dissociation of Rb from E2F transcription factors thereby causing transcription of genes important for DNA synthesis and other key aspects of cell cycle progression. Thus, cancer cells with constitutively inactive Rb are thought to acquire an increased proliferative potential. Knowledge of the Cyclin D-Cdk4/6-Rb-E2F pathway in normal and cancer cells has led to the development of specific Cdk4/6 inhibitors that have been approved for the treatment of breast cancer and are in clinical trials for several other cancer types. In this paradigm, inhibition of Cdk4/6 results in decreased Rb phosphorylation, which activates Rb’s cell cycle inhibitory function. However, many tumors do not respond to these inhibitors or do so only transiently. Recent observations in patients and pre-clinical models indicate that our understanding of the Rb pathway is not as complete as we previously thought. This may explain the variable results of Cdk4/6 inhibitors in the clinic. The overall goal of this proposal is to gain a deeper structural, molecular, and cellular understanding of the Rb pathway with the ultimate goal to help design new and improved therapeutic strategies targeting this pathway in a broad range of cancer patients. Our first goal is to determine the core mechanisms regulating the Cyclin D-Cdk4/6-Rb-E2F pathway, including how Cyclin D-Cdk4/6 phosphorylates Rb and how previously unknown post-translational modifications regulate Rb and E2F activities. Our second goal is to identify and investigate new functions of Rb pathway components, including new targets of Cyclin D- Cdk4/6 kinases, new functions for Rb and its family members p107 and p130, and new regulatory mechanisms controlling the concentration and activity of E2F transcription factors. Our third goal is to initiate the development of strategies that target the Rb pathway in innovative ways, including molecules that inhibit Cyclin D-Rb association, stimulate the tumor suppressor activity of p107 and p130, and manipulate E2F stability. These goals will be achieved in three inter-related Projects via a comprehensive, synergistic and multi-disciplinary approach. Ultimately, the information gained from these studies may provide new ways to target the Cyclin D-Cdk4/6-Rb- E2F pathway to improve cancer therapy.