Mechanism of BCL6-dependent stem cell maintenance in B cell lineage leukemia

B细胞系白血病中BCL6依赖性干细胞维持机制

• 批准号: 7979235
• 负责人: Markus Müschen
• 金额: $ 20.88万
• 依托单位: CHILDREN'S HOSPITAL OF LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7979235
• 关键词: Acute; Acute Lymphocytic Leukemia; Adjuvant; Adjuvant Therapy; Adverse effects; Affect; B-Cell Acute Lymphoblastic Leukemia; B-Cell Lymphomas; B-Lymphocytes; BCL6 gene; Biological Assay; Cancer Etiology; Cell Lineage; Cell Maintenance; Cell Survival; Cells; Child; Chronic Lymphocytic Leukemia; Chronic Myeloid Leukemia; Clinical Trials; Cytotoxic Chemotherapy; Derivation procedure; Diagnostic; Dose; Dose-Limiting; Drug resistance; Drug resistance pathway; Embryo; Frequencies; Funding; Gene Expression; Genes; Genetic; Goals; Human; In Vitro; Laboratories; Lymphoma; Maintenance; Malignant Neoplasms; Mediating; Mus; Myelogenous; NOD/SCID mouse; Oncogenes; Oncogenic; Pathway interactions; Patient Care; Patients; Peptides; Pharmaceutical Preparations; Phenotype; Play; Population; Process; Production; Program Development; Proliferating; Proto-Oncogenes; Recurrent disease; Regulation; Relapse; Reporter; Resistance; Role; Sampling; Schedule; Signal Transduction; Stem cells; Surface Antigens; Surrogate Markers; System; TP53 gene; Teenagers; Testing; Therapeutic; Toxic effect; Transcription Repressor/Corepressor; Transgenic Mice; Transgenic Organisms; Transplantation; Tyrosine Kinase Inhibitor; Validation; Work; Xenograft procedure; base; cell type; gain of function; gene repression; in vivo; inhibitor/antagonist; large cell Diffuse non-Hodgkin' s lymphoma; leukemia; leukemic stem cell; mouse model; novel; novel strategies; novel therapeutics; pre-clinical; preclinical study; prevent; programs; public health relevance; research study; response; self-renewal; senescence; stem; stem cell population

DESCRIPTION (provided by applicant): B cell lineage acute lymphoblastic leukemia (ALL) represents by far the most frequent type of malignancy in children and teenagers. Despite significant advances in ALL treatment, many patients still die because of drug- resistance or leukemia relapse. Since recent work implicated leukemia stem cells in both drug-resistance and relapse of the disease, current therapy approaches focus on leukemia stem cell eradication. In contrast to B cell lineage ALL, leukemia stem cells in myeloid lineage leukemia have been extensively characterized. Acute and chronic myeloid leukemias develop hierarchically from a phenotypically distinct stem cell population. However, recent work suggests that no such hierarchy exists in B cell lineage ALL, which precludes an unequivocal phenotypic definition of leukemia stem cells in ALL. Therefore, we propose to functionally characterize leukemia stem cells in B cell lineage ALL based on an operational definition, i.e. the ability to maintain stem cell self-renewal and overcome oncogene-induced senescence. Specifically, we will test the hypothesis that the BCL6 transcriptional repressor represents one of the critical factors in B cell lineage ALL to maintain a pool of functional leukemia stem cells. The BCL6 proto-oncogene is frequently translocated in diffuse large B cell lymphoma (DLBCL) and maintains self-renewal capacity of DLBCL cells by transcriptional repression of p53 in the lymphoma cells. However, an oncogenic function of BCL6 has not been described in other cell types so far. In preliminary studies for this proposal, we have discovered aberrant expression of BCL6 as a central component of a fundamentally novel pathway of leukemia stem cell maintenance: BCL6 prevents leukemia stem cell depletion through negative regulation of the Arf/p53/p21 pathway in B cell lineage ALL. Compared to leukemias from BCL6-/- mice, BCL6 is required for the reactivation of an early embryonic gene expression program, development of drug-resistance, leukemia cell colony formation and leukemia-initiation in serially transplanted NOD/SCID mice in B cell lineage but not myeloid lineage leukemia. A novel retro-inverso BCL6 peptide inhibitor (RI-BPI) strongly synergized with tyrosine kinase inhibitors in the treatment of B cell lineage ALL cells in vitro and in vivo. This proposal will test the hypothesis that BCL6-dependent self-renewal represents a critical requirement for stem cell maintenance in B cell lineage ALL. Based on the discovery of BCL6 as a key component of a fundamentally novel pathway of stem cell self-renewal in various subtypes of ALL, we propose three Aims to develop these findings towards application in patient care: (1) To test the hypothesis that aberrant expression of BCL6 in leukemia cells prevents Arf/p53-mediated senescence and promotes stem cell quiescence, (2) To identify transcriptional targets of BCL6 in primary human leukemia cells and their contribution to self-renewal signaling and (3) To validate BCL6-BPI as a therapy adjuvant for targeted eradication of leukemia stem cells. PUBLIC HEALTH RELEVANCE: Despite significant advances in the treatment of leukemia over the past four decades, the rate of long-term survival has reached a plateau and still large numbers of leukemia patients die, mostly because of relapse and drug-resistance, which was recently attributed to the persistence of leukemia stem cells. If a therapy succeeds in eradicating leukemia stem cells, de novo initiation of the disease (relapse) is no longer possible. Therapeutic progress in recent clinical trials has likely been stalled, partly because current cytotoxic therapy approaches target proliferating bulk leukemia cells rather than quiescent leukemia stem cells. We now discovered that BCL6, a factor known to play a central role in B cell lymphomas, also plays a key role in the maintenance of leukemia stem cells. Since leukemia stem cells represent the origin of relapse and drug-resistance in leukemia in many cases, the identification of BCL6 as a target for leukemia stem cell eradication holds great promise. BCL6 is a master regulatory factor that controls the production of many different important genes. BCL6 was not previously known to be involved in leukemias. In preliminary studies for this proposal, we have discovered aberrant expression of BCL6 as a central component of a fundamentally novel pathway of leukemia stem cell self-renewal and drug-resistance in a wide array of human leukemias, some of which are still difficult to treat. In these leukemias, drug-treatment results in aberrant production of BCL6 by the leukemia cells, which appears to allow leukemia stem cell to self-renew and become resistance against drug-treatment. Recently a drug has been developed that can attach to BCL6 and block its cancer-causing activities. We found that this BCL6 inhibitor, which is called RI-BPI, has strong synergistic activity when combined with conventional drug- treatment, which opens up a powerful new therapeutic strategy for leukemia stem cell eradication through targeted inhibition of BCL6. Based on the discovery of BCL6 as a key component of a novel pathway of drug-resistance and stem cell self-renewal in a wide array of leukemias, we propose three Aims to develop these findings towards application in patient care: (1) To test the hypothesis that aberrant expression of BCL6 in human leukemia cells promotes leukemia stem cell survival, (2) To determine the frequency and phenotype of BCL6-dependent leukemia stem cells in human B cell ALL and (3) To validate a the role of the BCL6 inhibitor RI-BPI as a therapy for targeted eradication of leukemia stem cells. Since RI-BPI is currently going through the process of approval for use in clinical trials, we expect to be able to test the power of this approach in clinical trials by the end of the funding period.

描述（由申请人提供）：B细胞谱系急性淋巴细胞白血病（ALL）代表了迄今为止儿童和青少年最常见的恶性类型。尽管在所有治疗方面取得了重大进展，但许多患者仍然因耐药性或白血病复发而死。自最近的工作暗示了白血病干细胞在疾病的抗药性和复发中，目前的治疗方法着重于白血病干细胞消除。与B细胞谱系相比，偶然谱系白血病中的白血病干细胞已得到广泛的特征。急性和慢性髓样白血病从表型不同的干细胞种群分层发展。然而，最近的工作表明，在B细胞谱系中不存在这样的层次结构，这完全排除了白血病干细胞的明确表型定义。因此，我们建议根据操作定义，即维持干细胞自我更新并克服致癌基因诱导的衰老的能力，从而在功能上表征B细胞谱系中的白血病干细胞。具体而言，我们将检验以下假设：Bcl6转录阻遏物代表B细胞谱系中所有的关键因素之一，以维持功能性白血病干细胞池。 Bcl6原始癌基因经常在扩散的大B细胞淋巴瘤（DLBCL）中易位，并通过在淋巴瘤细胞中p53的转录抑制来维持DLBCL细胞的自我更新能力。但是，到目前为止，在其他细胞类型中尚未描述BCl6的致癌功能。在该提案的初步研究中，我们发现BCl6的异常表达是白血病干细胞维持的根本新途径的核心组成部分：BCL6通过ARF/p53/p21途径在B细胞谱系中的ARF/p53/p21途径的负调控来阻止白血病干细胞的消耗。与Bcl6 - / - 小鼠的白血病相比，BCL6是早期胚胎基因表达程序的重生需要的，在B细胞谱系中串行移植的NOD/SCID小鼠中的药物耐药性，耐药性细胞菌落形成和白血病的启动所必需的。一种新型的恢复性BCL6肽抑制剂（RI-BPI）与酪氨酸激酶抑制剂在B细胞谱系治疗所有细胞的体外和体内都具有强烈的协同作用。该建议将检验以下假设：Bcl6依赖性自我更新代表了B细胞谱系中干细胞维持的关键要求。 基于将BCL6的发现作为所有亚型的干细胞自我更新的根本新途径的关键组成部分，我们提出三个旨在将这些发现发展为患者护理中的应用：（1）测试以下假设，即在白血病细胞中BCL6在dycection和persistion dements tostients tostients tostients tarts inf arf/p53介导的靶点（2）中的靶向（2）原发性人白血病细胞及其对自我更新信号的贡献，以及（3）验证Bcl6-BPI作为靶向根除白血病干细胞的疗法辅助药物。 公共卫生相关性：尽管在过去的四十年中，白血病的治疗方面取得了重大进展，但长期生存的速度已经达到了高原，并且仍大量的白血病患者死亡，这主要是由于复发和抗药性，这最近归因于白血病干细胞的持久性。如果疗法成功地消除了白血病干细胞，则不再可能从头开始疾病（复发）。在最近的临床试验中，治疗进展可能已经停滞不前，部分原因是目前的细胞毒性治疗方法靶向增殖的大量白血病细胞，而不是静态的白血病干细胞。现在，我们发现BCL6是已知在B细胞淋巴瘤中起核心作用的因素，在维持白血病干细胞中也起着关键作用。由于白血病干细胞代表了许多情况下白血病复发和抗药性的起源，因此将BCl6鉴定为白血病干细胞消除的靶标具有很大的希望。 BCL6是控制许多不同重要基因的产生的主要调节因素。 BCl6以前不涉及白血病。在该提案的初步研究中，我们发现Bcl6的异常表达是白血病干细胞自我更新和耐药性众多白血病的根本新颖途径的核心组成部分，其中一些仍然难以治疗。在这些白血病中，药物治疗导致白血病细胞异常产生BCL6，这似乎使白血病干细胞可以自我更新并成为对药物治疗的耐药性。最近，已经开发出一种可以附着在BCL6上并阻止其引起癌症的活动的药物。我们发现，该BCL6抑制剂（称为RI-BPI）与常规药物治疗结合使用时具有强大的协同活性，该抑制剂通过靶向抑制BCL6开辟了一种强大的白血病干细胞消除白血病的治疗策略。 Based on the discovery of BCL6 as a key component of a novel pathway of drug-resistance and stem cell self-renewal in a wide array of leukemias, we propose three Aims to develop these findings towards application in patient care: (1) To test the hypothesis that aberrant expression of BCL6 in human leukemia cells promotes leukemia stem cell survival, (2) To determine the frequency and phenotype of BCL6-dependent人类B细胞中的白血病干细胞和（3）验证A BCl6抑制剂RI-BPI的作用是针对靶向根除白血病干细胞的疗法。由于RI-BPI目前正在批准临床试验的批准过程，因此我们希望能够在临床试验中测试这种方法的能力。