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耐药性的突变和表观遗传学改变(例如，组蛋白修饰)的星座尚不完全清楚。值得注意的是，最近用于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和膀胱移行细胞癌突变谱的基因组测序研究发现，编码组蛋白乙酰转移酶KAT3家族的两个基因CREB结合蛋白(CBP，CREBBP)和EP300(P300)存在损伤。ALL是儿童最常见的癌症，也是这项提案的重点。复发的ALL是年轻人非创伤性死亡的主要原因，而对糖皮质激素的抵抗是治疗耐药的ALL细胞的标志，其基础是 人们对此知之甚少。总体而言，CREBBP的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，但也有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共激活物结合结构域(NCBD)的损伤。长期目标是了解CREBBP突变如何导致白血病进展及其对治疗的耐药性。这项建议的目的是确定CREBBP白血病突变如何影响糖皮质激素反应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物(HDACi)治疗的反应。基于申请人已发表的初步数据，中心假设指出，CREBBP零突变和亚形突变的白血病细胞改变了基因表达，减少了糖皮质激素诱导的细胞凋亡，但此类细胞对增加蛋白质乙酰化的药物治疗的敏感性增加。这项拟议研究的基本原理是，在转录“中枢”蛋白CREBBP的某些功能域中发现的所有相关突变为促进白血病进展和对标准疗法的耐药性的改变的生物途径提供了线索。一旦确定，CREBBP突变ALL细胞中的这些途径变化可能会被使用替代治疗方法所利用。三个具体目标考验着中央 假设。目的1是定义突变的CREBBP如何影响糖皮质激素反应基因的表达。目的2是确定CREBBP突变如何促进小鼠白血病的进展。目的3是确定CREBBP突变如何影响人ALL异种移植对组蛋白去乙酰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相关的CREBBP突变如何影响：1)对糖皮质激素的转录反应，2)白血病的发展和进展，以及3)糖皮质激素和组蛋白脱乙酰酶抑制剂的抗白血病作用，为ALL提供新的机制洞察。这一结果的翻译影响将是加强知识驱动的糖皮质激素和HDACi治疗基于肿瘤细胞基因型的白血病的使用。 公共卫生相关性：对抗癌治疗产生抗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，一种名为CREBBP的基因突变有时会发生在急性淋巴细胞白血病(ALL)中，治疗后会复发。CREBBP编码一种蛋白质，调节许多其他基因，这表明影响其目标基因的药物可能在治疗复发ALL方面有效。

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.