Cell-cycle checkpoint inhibitors as a novel anti-cancer strategy in Glioblastoma multiforme

胶质母细胞瘤（GBM）是成人中最常见和最致命的原发性恶性脑肿瘤。确定新疗法的挑战是GBM基因型行为的多样性。为了解决这个问题，Beroukhim实验室对78种GBM细胞系进行了全面的分子表征和药物筛选，这些细胞系涵盖了GBM的主要分子类别。肿瘤抑制基因TP 53的破坏的细胞系表现出对大多数化合物的不良反应，正如TP 53突变型肿瘤一般。TP 53是癌症中最常见的突变基因，因此在TP 53突变细胞中具有活性的化合物可以为大量患有耐药癌症的人提供有用的见解。幸运的是，我们发现了一种在TP 53突变细胞中更有效的CHK 1/2抑制剂（CHKi）。当肿瘤抑制基因CDKN 2A也丢失时，这种抑制剂是最有效的-大约10%的GBM患者的遗传基因。检查点激酶（CHK）是DNA损伤反应（DDR）的重要介质。它们通过在分裂前为细胞提供时间来修复DNA损伤或在损伤不可修复时启动凋亡来维持基因组的完整性。几种CHKI目前正在进行临床试验，其中一些已经显示出有希望的活性。因此，我们将研究CHKi与所有癌症（包括GBM）中两种最常见的失活肿瘤抑制因子之间的这种明显的合成致死关系。我们的具体问题是：1。TP 53和CDKN 2A的联合破坏是否会产生对CHK 1/2抑制剂的敏感性？我们将通过在GBM细胞系中应用CRISPR-CAS 9技术来生成TP 53和CDKN 2A以及组合的同基因模型，以确定TP 53和CDKN 2A的联合缺失是否使细胞对CHKi敏感。我们的读数将是细胞活力、增殖、凋亡、细胞周期进程和DDR的变化。这些实验将对决定CHKi靶向谁，帮助设计和解释未来的临床试验产生影响。评价对CHK 1/2抑制的耐药机制。癌症通常对最初有效的靶向治疗产生耐药性。确定这些耐药机制可以表明联合治疗方法，以延长响应时间。在这里，我们将采取三种方法。首先，我们将测试是否可以通过减缓细胞周期来获得抗性。其次，我们将对CHKi敏感细胞进行基因组规模的开放阅读框（ORF）筛选，以鉴定其表达产生抗性的基因。第三，我们将建立自然产生的CHKi耐药模型，并通过表征它们的表达变化和新的遗传改变的发展来评估它们是如何获得的。该项目将评估一种新的方法来治疗癌症基因组TP 53和CDKN 2A中一些最常见的基因突变的肿瘤。这些基因改变在癌症中的普遍性表明，这项工作可能会产生深远的影响。

Glioblastoma (GBM), is the most common and most lethal primary malignant brain tumor in adults. A challenge in identifying new therapies is the diversity in behavior of GBM genotypes. To address this, the Beroukhim lab conducted a comprehensive molecular characterization and drug screen on 78 GBM cell lines spanning the major molecular classes of GBM. Cell lines with disruption of the tumor suppressor gene TP53 showed poor responses to most compounds, as is true of TP53-mutant tumors in general. TP53 is the most commonly mutated gene in cancer, so compounds with activity in TP53 mutant cells could provide helpful insights for a large number of people with treatment-resistant cancers. Fortunately, we identified a CHK1/2 inhibitor (CHKi) that was more effective in TP53 mutant cells. This inhibitor was most effective when the tumor suppressor gene CDKN2A had also been lost—the genetics of about 10% of GBM patients. Checkpoint kinases (CHK) are crucial mediators of the DNA damage response (DDR). They maintain genomic integrity by providing cells time to repair DNA damage before dividing or initiate apoptosis if the damage is irreparable. Several CHKis are currently undergoing clinical trials, with some already showing promising activity. Therefore, we will investigate this apparent synthetic lethal relationship between CHKi and two of the most commonly inactivated tumor suppressors across all cancers including GBMs. Our specific questions are:1. Does joint disruption of TP53 and CDKN2A generate susceptibility to CHK1/2 inhibitors? We will generate isogenic models for TP53 and CDKN2A and the combination by applying CRISPR-CAS9 technology in GBM cell lines, to determine whether joint loss of TP53 and CDKN2A sensitizes the cells to CHKi. Our readouts will be changes in cell viability, proliferation, apoptosis, cell cycle progression and the DDR. These experiments will have implications for deciding whom to target with CHKi, aiding in design and interpretation of future clinical trials.2. Evaluate resistance mechanisms to CHK1/2 inhibition. Cancers often acquire resistance to initially effective targeted therapies. Identifying these resistance mechanisms can indicate combined treatment approaches to extend response times. Here, we will take three approaches. First, we will test if resistance can be gained by slowing down the cell cycle. Second, we will perform a genome-scale open reading frame (ORF) screen on CHKi sensitive cells to identify genes whose expression generates resistance. Third, we will generate naturally arising models of CHKi resistance and evaluate how they gained it by characterization their changes in expression and development of new genetic alterations.This project will evaluate a novel approach to treating tumors with mutations in some of the most frequently altered genes in the cancer genome TP53 and CDKN2A. The prevalence of these genetic alterations across cancers indicates that this work could have a profound impact.