The use of epigenetic therapy to activate an immune response in ovarian cancer

描述(由申请人提供)：大约每67名美国妇女中就有一人会在一生中患上皮性卵巢癌(EOC)。晚期疾病占病例的70%，令人沮丧的五年生存率不到25%。在目前的护理标准下，手术后化疗，在过去30年中，患有EOC的妇女的存活率变化很小。显然需要针对EoC的新疗法。表观遗传剂正在被探索为卵巢癌和其他实体肿瘤的新疗法。在肺癌患者中的临床成功表明，DNA甲基转移酶抑制剂5-氮杂胞苷(5-azacytidine，AZA)和组蛋白去乙酰酶抑制剂Eninostat的作用可能刺激免疫反应，靶向免疫细胞以根除肿瘤。此外，AZA已获得FDA批准用于治疗急性髓系白血病。癌症的特点是抑制染色质，包括DNA甲基化和组蛋白去乙酰化，在肿瘤抑制基因的启动子。Aza抑制DNA甲基化，Eninostat抑制组蛋白脱乙酰酶，打开染色质，导致被抑制基因的转录。在上皮性卵巢癌中，免疫基因的高表达和免疫细胞对肿瘤的侵袭预示着较好的预后。我们用AZA处理的23个EOC细胞株的初步数据显示，参与免疫反应的基因上调。这些AZA诱导的免疫基因(AIM基因)代表了天然免疫和获得性免疫的途径，从TCGA聚集性EOC肿瘤，并指示一组AIM低表达的肿瘤。在这项资助中，我建议使用AZA来刺激EOC细胞的免疫反应。这种疗法可以单独对一部分患者起作用，但应该会让更多的患者对随后的免疫疗法敏感。我推测AZA诱导的AIMS的下调将导致癌细胞死亡和宿主免疫细胞对肿瘤的募集，并能使卵巢癌细胞对随后的免疫治疗敏感。AZA激活上皮细胞免疫反应的机制尚不清楚。AZA去甲基化可导致免疫主调蛋白的重新表达。我观察到在AZA治疗下，通常沉默的RNA，如人类内源性逆转录病毒(ERV)和重复元件的转录，可能会激活免疫(病毒防御)反应。另外，AZA可诱导肿瘤表面免疫检查点配体PD-L1的表达。因此，我认为联合表观遗传免疫调节和抑制PD-1/PD-L1通路可能会导致协同抗肿瘤作用。目的1：研究AZA免疫应答的表型效应及其机制。目的2：我将确定内源性逆转录病毒和转座元件RNA是否与AZA的免疫反应有关。目的：在免疫活性高的卵巢癌小鼠模型中，先用AZA刺激免疫应答，再用抗PD-1抗体阻断免疫逃逸，评价宿主免疫细胞活化和肿瘤细胞杀伤作用。因此，我将评估表观遗传学和治疗相结合的疗效，以打破人类最致命的恶性肿瘤之一的免疫耐受。

DESCRIPTION (provided by applicant): Approximately one out of 67 U.S. women will get epithelial ovarian cancer (EOC) in her lifetime. Late-stage disease accounts for 70% of cases, with a dismal five year survival rate of less than 25%. Under the current standard of care, surgery followed by chemotherapy, survival of women with EOC has changed very little over the past three decades. Novel therapies for EOC are clearly needed. Epigenetic agents are being explored as new therapies for EOC and other solid tumors. Clinical success in patients with lung cancer suggests that the actions of the DNA methyltransferase inhibitor 5-azacytidine (AZA) and the histone deacetylase inhibitor entinostat may stimulate the immune response and target immune cells to eradicate tumors. Furthermore AZA has FDA approval for treatment of acute myeloid leukemia. Cancers are characterized by repressive chromatin, including DNA methylation and deacetylation of histones, at promoters of tumor suppressor genes. AZA inhibits DNA methylation and entinostat inhibits histone deacetylases, opening up chromatin and causing transcription of repressed genes. In EOC, higher expression of immune genes and immune cell infiltration into tumors predict better prognosis. Our preliminary data from 23 EOC cell lines treated with AZA show an upregulation of genes involved in the immune response. These AZA-Induced iMmune genes (AIM genes), representing pathways of both innate and adaptive immunity, cluster EOC tumors from TCGA and indicate a group of tumors with low AIM expression. In this grant I propose to use AZA to stimulate an immune response in EOC cells. This therapy could work alone for a subset of patients but should sensitize a larger group of patients to subsequent immune therapy. I hypothesize that an AZA-induced de-repression of AIMs will lead to cancer cell death and recruitment of host immune cells to the tumor and can sensitize ovarian cancer cells to subsequent immunotherapy. The mechanism by which AZA activates an epithelial cell immune response is unknown. Demethylation by AZA could cause re-expression of immune master regulators. I observe transcription of normally silenced RNAs such as human endogenous retroviruses (ERVs) and repetitive elements upon AZA treatment, which may activate the immune (viral defense) response. Separately, AZA can induce expression of the immune checkpoint ligand PD-L1 on tumors. Thus, I propose that combining epigenetic immune modulation with inhibition of the PD-1/PD-L1 pathway may result in synergistic anti-tumor effects against EOC tumors. Aim 1: I will determine the phenotypic effects and mechanism of the AZA immune response. Aim 2: I will determine whether endogenous retrovirus and transposable element RNAs are responsible for the AZA immune response. Aim 3: I will treat with AZA to stimulate the immune response, then an anti-PD-1 antibody to block immune evasion, in immunocompetent mouse models of ovarian cancer and assess host immune cell activation and tumor cell killing. I will thus assess the efficacy of combining epigenetic with therapy to break immune tolerance in one of the deadliest human malignancies.