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

项目摘要 胶质母细胞瘤(GBM)是成人中最常见、最具侵袭性的原发恶性脑癌。当前 护理标准：肿瘤切除、电离辐射(IR)和电离辐射(TMZ)对大多数患者的临床益处最小 由于先天或后天对治疗产生抵抗力。因此，针对致癌途径的优化治疗方法 治疗胶质母细胞瘤是当务之急。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%的人患有这种疾病。这导致了E2F与监管脱钩 允许细胞分裂所需基因的无节制转录以及DNA损伤反应的机制。这 指出CDK4/6药物抑制剂(CDK4/6i)是治疗GBM的一种有前途的策略。相应地，三个CDK4/6i FDA批准的治疗乳腺癌的药物(阿贝西利、利波西利和帕波西利)目前正在进行临床试验 GBM患者。基于先验基因组学的CDK4/6I治疗的GBM患者是RB活性肿瘤 (野生型RB1)和编码内源抑制物p16INK4a的CDKN2A的CDK4/6扩增或缺失 CDK4/6酶活性的变化。研究指出，CDK4/6-Rb失调是一种早期进化事件，需要 更多的改变进展为恶性肿瘤，并且没有足够的证据利用合并其他 分子生物标记物在预测患者持久反应中的作用。这一缺陷在临床前研究中得到了例证。 在先前预测对CDK4/6有反应的患者中显示适应性抵抗。这一点得到了我的初步证实 数据显示，在GBM癌症干细胞(CSCs)中，阿贝米利治疗反应的变异性不能 仅用CDK4/6-Rb改变来解释。我的假设是，分子特征的识别推动了 恶性表型，并与CDK4/6-Rb通路异常共存，如其他致癌基因的改变 P53、受体酪氨酸激酶受体信号通路和MYC，以及表观遗传和转录适应 将增强我们在确定GBM患者的持久反应与耐药性方面的预测能力。我要测试一下 我的假设是通过测量20名遗传异质性的GBM患者衍生的代表性小组的敏感度 CSCs至Abemaciclib和Ribociclib对照处理。我会把这一反应与他们的各种体型结合起来 与CDK4/6-Rb轴异常共存的基因组改变。这将使识别基线成为可能 GBM反应与CDK4/6I的分子相关性然后我会询问CDK4/6拷贝数的变化 存在于染色体外DNA元件、全球转录组和靶向蛋白质组学中的扩增 抑制CDK4/6以确定导致GBM耐药的潜在逃逸机制。最后，为了评估 我们研究的翻译影响，我将确定体外观察到的表型是否在原位患者中重现- 衍生异种移植物(PDX)。我还将确定CDK4/6i是否可以增强TMZ的遗传毒性作用。结果来自于 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。 这将受益于CDK4/6抑制剂的治疗。因此，拟议的项目具有巨大的翻译潜力， 与国家癌症研究所为癌症患者制定循证治疗战略的使命相一致。

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.