Cyclin Dependent Kinase 4/6 (CDK4/6) as a Therapeutic Target in Glioblastoma

项目摘要 胶质母细胞瘤（GBM）是成人人群中最常见和最具侵袭性的原发性恶性脑癌。电流 标准治疗：肿瘤切除、电离辐射（IR）和（TMZ）对大多数患者产生最小的临床获益 由于先天或后天对治疗的抵抗。因此，靶向致癌途径的优化治疗方法 是一个迫切的需求。基因组改变导致细胞周期蛋白依赖性激酶4/6-Rb通路失调 在癌症基因组图谱分析的230例GBM病例中，有84%。这导致E2 F与监管脱钩 允许细胞分裂以及DNA损伤反应所需的基因的不受限制的转录的机制。这 指出CDK 4/6药理学抑制剂（CDK 4/6 i）作为治疗GBM的有希望的策略。因此，三个CDK 4/6 i FDA批准用于治疗乳腺癌的Abemaciclib（Abemaciclib，Ribociclib和Palbociclib）目前正在进行临床试验， GBM患者。基于先验基因组学选择GBM患者用于CDK 4/6 i治疗是Rb活性肿瘤 （野生型RB 1）和CDK 4/6扩增或CDKN 2A缺失，其编码P16 INK 4a，一种内源性抑制剂 CDK 4/6酶活性。研究指出，CDK 4/6-Rb失调是一种早期进化事件， 进展为恶性肿瘤的其他改变，并且没有足够的证据利用额外的 分子生物标志物在预测持久的患者反应。这种缺陷在临床前研究中得到了例证 在先前预测对CDK 4/6 i有反应的患者中显示出适应性抵抗。 显示GBM癌症干细胞（CSC）中Abemaciclib治疗反应的变异性的数据， 仅由CDK 4/6-Rb改变解释。我的假设是，确定驱动这些基因的分子特征， 恶性表型，并与CDK 4/6-Rb通路失调共同发生，如其他致癌基因的改变。 p53、受体酪氨酸激酶受体信号传导和MYC中的途径，以及表观遗传和转录适应 将加强我们在确定GBM患者持久应答与耐药方面的预测能力。我将测试 我的假设是通过测量一组代表性的20个基因组异质性GBM患者来源的敏感性， 与对照治疗相比，Abemaciclib和Ribociclib的CSC。我将把这种反应与他们的各种躯体反应结合起来， 基因组改变与CDK 4/6-RB轴失调共同发生。这将有助于确定基线 GBM应答与CDK 4/6 i的分子相关性。然后，我将询问CDK 4/6拷贝数的改变 扩增，存在于染色体外DNA元件，全球转录组和靶向蛋白质组学响应 CDK 4/6抑制，以确定导致GBM耐药的潜在逃逸机制。最后，为了评估 我们的研究的翻译影响，我将确定在体外观察到的表型是否在原位患者中重现- 衍生的异种移植物（PDX）。我还将确定CDK 4/6 i是否可以增强TMZ的遗传毒性作用。的结果 这项研究将为解释即将到来的临床试验结果和确定GBM患者队列提供证据 将从CDK 4/6抑制剂治疗中获益。因此，拟议的项目具有重大的翻译潜力， 与国家癌症研究所的使命保持一致，为癌症患者制定循证治疗策略。

Project Summary Glioblastoma (GBM) is the most common and aggressive primary malignant brain cancer in the adult population. Current standard of care: tumor resection, ionizing radiation (IR) and (TMZ) produce minimum clinical benefits for most patients due to innate or acquired resistance to treatment. Thus, optimization therapeutic approaches targeting oncogenic pathways in glioblastoma is an urgent need. Genomic alterations lead to dysregulation of Cyclin Dependent Kinase 4/6-Rb pathway in 84% of the 230 GBM cases profiled by The Cancer Genome Atlas. This results in the decoupling E2F from regulatory mechanisms to permit unchecked transcription of genes required for cell division as well as DNA-damage response. This points to CDK4/6 pharmacological inhibitors (CDK4/6i) as a promising strategy to treat GBM. Accordingly, three CDK4/6i (Abemaciclib, Ribociclib and Palbociclib) approved by the FDA for treatment of breast cancer are now in clinical trials for GBM patients. A priori genomics based selection of GBM patients for treatment with CDK4/6i are Rb-competent tumors (wildtype RB1), and CDK4/6 amplification or deletion of CDKN2A, which codes for P16INK4a, an endogenous inhibitor of CDK4/6 enzymatic activity. Studies point to CDK4/6-Rb dysregulation as an early evolutionary event which requires additional alterations to progress to malignancy, and there is insufficient evidence utilizing the incorporation of additional molecular biomarkers in the prediction of durable patient response. This deficiency is exemplified in preclinical studies showing adaptive resistance in patients previously predicted to respond to CDK4/6i.This is corroborated by my preliminary data showing a variability in Abemaciclib treatment response amongst GBM cancer stem cells (CSCs) that cannot be explained by CDK4/6-Rb alterations alone. My hypothesis is that the identification of molecular features driving the malignant phenotype, and co-occurring with CDK4/6-Rb pathway dysregulation, such as alterations in the other oncogenic pathways in p53, receptor tyrosine kinase receptor signaling and MYC, as well as epigenetic and transcriptional adaptation will strengthen our predictive capabilities in determining durable response versus resistance in GBM patients. I will test my hypothesis by measuring the sensitivity of a representative panel of 20 genomically heterogeneous GBM patient-derived CSCs to Abemaciclib and Ribociclib against control treatments. I will incorporate this response with their various somatic genomic alterations co-occurring with CDK4/6-RB axis dysregulation. This will enable the identification of baseline molecular correlates of GBM response with CDK4/6i. I will then interrogate the alterations in CDK4/6 copy number amplifications, present in extrachromosomal DNA elements, global transcriptome and targeted proteomics in response to CDK4/6 inhibition to identify potential escape mechanisms that lead to resistance in GBMs. Finally, to evaluate the translational impact of our studies, I will determine if the phenotypes observed in vitro are reproduced in orthotopic patient- derived xenografts (PDX). I will also determine if CDK4/6i can potentiate the genotoxic effects of TMZ. The results from this research will provide evidence towards interpreting upcoming clinical trials results and identifying GBM patient cohorts that will benefit from treatment with CDK4/6 inhibitors. Thus, the proposed project has significant translational potential, aligning with the mission of the National Cancer Institute to develop evidence-based treatment strategies for cancer patients.