Characterizing and Targeting CHD4 Deficiency in Endometrial Cancer

描述(申请人提供)：子宫内膜癌是美国女性中最常见的女性生殖系统癌症之一。对于局部低度恶性子宫内膜样子宫内膜癌(EEC)患者，死亡率较低。然而，对于转移性或复发性EEC或非子宫内膜样癌的患者，如侵袭性子宫乳头状浆液性癌(UPSC)，治疗选择有限，结果非常糟糕。因此，识别子宫内膜癌中的关键基因异常对于开发新的有效的靶向治疗是至关重要的。通过分析来自癌症基因组图谱的基因测序数据，我们发现CHD4在子宫内膜癌中有很高的突变率(EEC中15%，UPSC中35%)。这种高的CHD4突变率在其他类型的肿瘤中是不存在的，这表明CHD4突变是子宫内膜癌发生的关键驱动因素。此外，我们还发现CHD4在许多子宫内膜癌细胞系中的表达显著降低，提示CHD4可能是一种新的抑癌基因，并可能成为治疗子宫内膜癌的潜在靶点。最近，越来越多的证据表明，完整的DNA损伤反应(DDR)对于维持基因组的稳定性是必不可少的，并且是癌症发展的关键障碍。有趣的是，我们最近发现CHD4在DDR中发挥关键作用，特别是在同源重组(HR)修复中。值得注意的是，我们证明了在子宫内膜癌患者中发现的具有突变的CHD4缺乏HR修复功能，这表明CHD4的DDR功能与子宫内膜癌抑制之间存在关键联系。在我们的初步研究中，我们还发现CHD4缺陷的子宫内膜癌细胞对PARP(聚[ADP-核糖]聚合酶)抑制剂更敏感，因为它们的HR修复有缺陷。所有这些耐人寻味的结果有力地表明CHD4是一种新的子宫内膜癌的肿瘤抑制因子，使用PARP抑制剂针对CHD4缺陷的子宫内膜癌构成了一种有效的靶向治疗。为了验证这一假说，我们提出了三个具体的目标：(1)评估临床子宫内膜癌组织标本中CHD4基因的异常，并确定CHD4基因缺失是否与肿瘤分级、肿瘤分期、癌症亚型和患者生存有关。(2)利用CHD4条件性基因敲除小鼠模型，确定CHD4基因缺失是否与子宫内膜癌的发生有关。这些模型将提供CHD4缺乏作为子宫内膜癌发生的驱动力的遗传学证据。(3)开发CHD4缺陷型子宫内膜癌的综合致死性治疗方法。我们将在细胞培养和小鼠模型中评估CHD4缺陷细胞对有效的PARP抑制剂的反应。我们还将结合PARP抑制剂与放射治疗以及与阿霉素或紫杉醇一起建立最佳治疗方案。综上所述，该项目不仅将有助于揭示子宫内膜癌的新分子治疗靶点，而且通过建立一种基于PARP抑制剂靶向CHD4缺陷的子宫内膜癌的新疗法，还将立即产生临床影响。

DESCRIPTION (provided by applicant): Endometrial cancer is one of the most common cancers of the female reproductive system among American women. For patients with localized low-grade endometrioid endometrial carcinoma (EEC), mortality is low. However, for patients with metastatic or recurrent EEC or nonendometrioid carcinomas, such as the aggressive uterine papillary serous carcinoma (UPSC), treatment options are limited, and outcomes are abysmal. Thus, it is critical to identify key gene aberrations in endometrial cancer for development of novel effective targeted therapy. Through analyzing gene sequencing data from The Cancer Genome Atlas, we have found a high rate of mutation of CHD4 in endometrial cancer (15% in EEC and 35% in UPSC). This high CHD4 mutation rate was not seen in other tumor types, suggesting that CHD4 aberrations are a critical driver of endometrial cancer development. In addition, we found that CHD4 expression was significantly reduced in many endometrial cancer cell lines, suggesting that CHD4 may function as a novel tumor suppressor gene and a potential therapeutic target for endometrial cancer. Recently, increasing evidence has shown that an intact DNA damage response (DDR) is essential for maintenance of genomic stability and acts as a critical barrier to cancer development. Interestingly, we have recently identified a critical role of CHD4 in DDR, particularly in homologous recombination (HR) repair. Notably, we demonstrated that CHD4 with mutations seen in endometrial cancer patients lacked HR repair function, suggesting a critical link between the DDR function of CHD4 and endometrial cancer suppression. In our preliminary studies, we also found that CHD4-deficient endometrial cancer cells were more sensitive to PARP (poly[ADP-ribose] polymerase) inhibitors because of their defective HR repair. All of these intriguing results strongly suggest that CHD4 functions as a novel tumor suppressor for endometrial cancer and that targeting CHD4 deficiency using PARP inhibitors constitutes an effective targeted therapy for CHD4-deficient endometrial cancer. Three specific aims are proposed to test this hypothesis: (1) To assess clinical endometrial cancer tissue specimens for CHD4 aberrations and determine whether CHD4 deficiency is correlated with tumor grade, tumor stage, cancer subtype, and patient survival. (2) To determine whether loss of CHD4 contributes to endometrial cancer development using our CHD4 conditional knockout mouse model. These models will provide genetic evidence for CHD4 deficiency as a driving force for endometrial cancer development. (3) To develop a novel treatment for CHD4-deficient endometrial cancer using a synthetic lethality approach. We will assess the response of CHD4-deficient cells to potent PARP inhibitors in cell culture and in the mouse models. We will also combine PARP inhibitors with radiation and with doxorubicin or paclitaxel to establish optimal therapies. In summary, this project will not only help reveal novel molecular therapeutic targets for endometrial cancer but also have immediate clinical impact by establishing a new treatment based on targeting CHD4-deficient endometrial cancer with PARP inhibitors.