Functional analysis of leukemic CREBBP mutations

描述（由申请人提供）：促进癌症发展及其对治疗的抗性的突变和表观遗传学改变（例如组蛋白修饰）的星座尚未完全了解。值得注意的是，最近的基因组测序研究，以确定复发性急性淋巴细胞白血病（ALL），B细胞非霍奇金淋巴瘤，膀胱移行细胞癌的突变谱已经确定了两个基因编码的组蛋白乙酰转移酶，CREB结合蛋白（CBP，CREBBP）和EP 300（p300）的KAT 3家族的病变。ALL是最常见的儿童癌症，也是本提案的重点。复发性ALL是年轻人非创伤性死亡的主要原因，对糖皮质激素的耐药性是治疗耐药ALL细胞的标志，其基础是 不太了解。在ALL中发现的CREBBP改变包括干扰或删除许多结构域的N-末端移码和终止突变，但也包括特异性影响组蛋白乙酰转移酶（HAT）结构域和参与糖皮质激素受体功能的核辅激活剂结合结构域（NCBD）的病变。长期目标是了解CREBBP突变如何促进白血病进展及其对治疗的抵抗。该提案的目的是确定CREBBP白血病突变如何影响糖皮质激素反应性转录以及白血病细胞对糖皮质激素和组蛋白脱乙酰酶抑制剂（HDACi）治疗的反应。基于申请人公开的和初步的数据，中心假设指出，在CREBBP中具有无效突变和亚型突变的白血病细胞具有改变的基因表达，其响应于糖皮质激素而减少细胞凋亡，但是这样的细胞对增加蛋白质乙酰化的药物疗法具有增加的易感性。这项研究的基本原理是，在转录“枢纽”蛋白CREBBP的某些功能结构域中发现的ALL相关突变为改变促进白血病进展和对标准疗法耐药的生物学途径提供了线索。一旦确定，CREBBP突变ALL细胞中的这些途径改变可以通过使用替代治疗来利用。三个具体目标考验中央 假说.目的1是确定突变Crebbp如何影响糖皮质激素应答基因的表达。目的2是确定Crebbp突变如何增强小鼠白血病的进展。目的3是确定CREBBP突变如何影响人类ALL异种移植物对组蛋白去乙酰化酶抑制剂和糖皮质激素的反应。这些研究的预期结果将通过确定ALL相关CREBBP突变如何影响以下因素，为ALL提供新的机制见解：1）对糖皮质激素的转录反应，2）白血病的发生和进展，3）糖皮质激素和组蛋白脱乙酰酶抑制剂的抗白血病作用。结果的转化影响将是增强基于肿瘤细胞基因型的糖皮质激素和HDACi治疗白血病的知识驱动的治疗用途。 公共卫生相关性：对抗癌治疗产生耐药性的白血病细胞是患者护理中的一个主要问题。我们发现，在治疗后复发的急性淋巴细胞白血病（ALL）中，有时会发生一种名为CREBBP的基因突变。CREBBP编码一种调节许多其他基因的蛋白质，这表明影响其靶基因的药物可能对治疗复发性ALL有效。

DESCRIPTION (provided by applicant): The constellation of mutations and epigenetic alterations (e.g. histone modifications) that promote cancer development and its resistance to treatment are incompletely understood. Significantly, recent genomic sequencing studies to define the mutational spectrum of relapsed acute lymphoblastic leukemia (ALL), B cell non-Hodgkin lymphoma, and transitional cell carcinoma of the bladder have identified lesions in the two genes encoding the KAT3 family of histone acetyltransferases, CREB-binding protein (CBP, CREBBP) and EP300 (p300). ALL is the most common childhood cancer and the focus of this proposal. Relapsed ALL is the leading cause of non-traumatic death in young people, and resistance to glucocorticoids is a hallmark of treatment resistant ALL cells, the basis of which is poorly understood. CREBBP alterations found in ALL include N-terminal frame-shift and termination mutations that disturb or delete many domains, but also lesions that specifically affect the histone acetyltransferase (HAT) domain and the Nuclear Coactivator Binding Domain (NCBD) that is involved in glucocorticoid receptor function. The long-term goal is to understand how CREBBP mutations contribute to leukemia progression and its resistance to treatment. The objective for this proposal is to determine how CREBBP leukemic mutations affect glucocorticoid-responsive transcription and the response of leukemia cells to glucocorticoid and histone deacetylase inhibitor (HDACi) therapies. Based upon the applicants' published and preliminary data, the central hypothesis states that leukemic cells with null and hypomorphic mutations in CREBBP have altered gene expression that decreases apoptosis in response to glucocorticoids, but such cells have increased susceptibility to drug therapies that increase protein acetylation. The rationale for the proposed research is that ALL-associated mutations found in certain functional domains of the transcriptional "hub" protein CREBBP provide clues to the altered biological pathways that promote leukemia progression and resistance to standard therapies. Once identified, these pathway alterations in CREBBP mutant ALL cells can potentially be exploited by the use of alternative treatments. Three specific aims test the central hypothesis. Aim 1 is to define how mutant Crebbp affects glucocorticoid-responsive gene expression. Aim 2 is to determine how Crebbp mutations enhance the progression of leukemia in mice. Aim 3 is to establish how CREBBP mutations affect the response of human ALL xenografts to histone deacetylase inhibitors and glucocorticoids. The expected outcome of these studies will provide new mechanistic insight into ALL by determining how ALL-associated CREBBP mutations impact: 1) the transcriptional response to glucocorticoids, 2) the development and progression of leukemia, and 3) the anti-leukemia effects of glucocorticoids and histone deacetylase inhibitors. The translational impact of the results will be to enhance the knowledge-driven therapeutic use of glucocorticoids and HDACi to treat leukemia based on tumor cell genotype. PUBLIC HEALTH RELEVANCE: Leukemia cells that become resistant to anti-cancer therapy are a major concern in patient care. We have found that mutations in a gene called CREBBP sometimes occur in acute lymphoblastic leukemias (ALL) that reoccur after treatment. CREBBP encodes a protein that regulates many other genes, suggesting that drugs that affect its target genes might be effective in treating relapse ALL.