Molecular basis of tumor suppression by Cdk4/6 inhibition

项目总结 视网膜母细胞瘤蛋白(Rb)途径是细胞增殖的关键调节因子，也是一个很有前途的靶点 癌症治疗学。Rb通常抑制E2F转录驱动的细胞分裂的转录程序 从而促进细胞周期停滞于G0/G1期。Rb通常被细胞周期蛋白依赖性激酶失活 (CDK)在癌细胞中的磷酸化，包括通过CDK4/6-CyCD复合体。 这一中央细胞通路中的关键未解问题包括：CDK4/6活性是如何被调节的，如何 特异性Rb磷酸化事件介导E2F激活，为什么Rb比Rb具有更强的肿瘤抑制作用 其近邻p107和p130，以及对化学CDK4/6抑制剂的耐药机制是什么。 这些抑制剂已经在临床上显示出希望，但我们需要更好地利用它们的作用方式和哪些因素 影响他们的反应。我们将把我们独特的综合专业知识应用于生化和遗传方法。 回答以前关于CDK4/6-Rb通路和肿瘤抑制的棘手问题。 我们的第一个目标是揭示癌细胞中CDK4/6-CyCD激活的机制。我们将使用结构， 生化和细胞分析研究p27蛋白在调节CDK4/6活性中的关键作用 以及细胞对CDK4/6小分子抑制剂的反应。我们的第二个目标是揭示关键分子 失活磷酸化时发生的变化和导致肿瘤的关键分子特征 对RB的抑制力。我们将研究RB中特定的CDK磷酸化事件如何导致其 细胞中的失活。我们还将探索RB中的一个小区域，我们假设该区域具有独特的肿瘤 抑制能力与p107和p130的比较。最后，我们的第三个目标是确定新的监管机构 CDK4/6-Rb通路的无偏筛选方法。这些新的监管机构可能会规定我们如何使用CDK 抑制物作为治疗药物，并创新靶向癌细胞分裂的新策略。 这些实验将解决细胞周期调控领域的基本问题，并将改变我们的 了解RB肿瘤抑制因子的功能，它是如何调节的，以及如何挽救它来阻止它 癌症生长。

PROJECT SUMMARY The retinoblastoma protein (Rb) pathway is a critical regulator of cell proliferation and a promising target for cancer therapeutics. Rb normally inhibits the transcription program for cell division driven by E2F transcription factors and thus promotes cell cycle arrest in G0/G1. Rb is commonly inactivated by Cyclin-dependent kinase (Cdk) phosphorylation in cancer cells, including by Cdk4/6-CycD complexes. Key unanswered questions in this central cellular pathway include how Cdk4/6 activity is regulated, how specific Rb phosphorylation events mediate E2F activation, why is Rb a more potent tumor suppressive than its close paralogs p107 and p130, and what are the mechanisms of resistance to chemical Cdk4/6 inhibitors. These inhibitors have shown promise in the clinic, but we need to better exploit how they act and what factors influence their response. We will apply our unique combined expertise in biochemical and genetic approaches to answer previously intractable questions about the Cdk4/6-Rb pathway and tumor suppression. Our first goal is to uncover the mechanisms of Cdk4/6-CycD activation in cancer cells. We will use structural, biochemical, and cellular assays to investigate the critical role of the p27 protein in modulating Cdk4/6 activity and the cellular response to Cdk4/6 small molecule inhibitors. Our second goal is to reveal the key molecular changes that occur upon inactivating phosphorylation and the key molecular features that confer tumor suppressor potency to Rb. We will examine how specific Cdk phosphorylation events in Rb lead to its inactivation in cells. We will also explore a small domain in Rb that we hypothesize confers unique tumor suppressive ability compared to p107 and p130. Finally, our third goal is to identify new regulators of the Cdk4/6-Rb pathway using unbiased screening approaches. These new regulators may dictate how we use Cdk inhibitors as therapeutics and innovate new strategies for targeting cancer cell division. These experiments will address fundamental issues in the field of cell-cycle regulation and will transform our understanding of Rb tumor suppressor function, how it is regulated, and how it may be rescued to arrest cancer growth.