Inducing transcriptional reprogramming of leukemic B-cells by facilitating transcription factors binding to nascent decondensed chromatin

通过促进转录因子与新生脱浓缩染色质结合来诱导白血病 B 细胞的转录重编程

基本信息

批准号：
10408669
负责人：
David Deming
金额：
$ 4.68万
依托单位：
THOMAS JEFFERSON UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2021
资助国家：
美国
起止时间：
2021-05-01 至 2023-04-30
项目状态：
已结题

项目摘要

Project Summary/Abstract B cell acute lymphoblastic leukemia (B-ALL) consist of Leukemic Blast Cells (LBCs) that become arrested at distinct stages of B cell development because of underlying alterations in transcriptional and epigenetic programming. The inability to differentiate confers a capacity for unlimited self-renewal and increased proliferative capability. Based on the successes in the treatment of the APL leukemia with ATRA and arsenic, leading to cell maturation and senescence, the differentiation-based therapies became a popular, but rarely successful, therapeutic strategy. We propose that this strategy has been unsuccessful due to a gap in the knowledge of the underlying mechanism through which transcriptional reprogramming occurs. My new strategy is based on our group’s recent observations that differentiation of normal hematopoietic progenitor cells (HPCs) is dependent on their ability to transiently decondense their post-replicative chromatin upon induction with lineage specifying cytokines. At the early stages of DNA replication, this decondensed state of nascent chromatin offers a window of opportunity for lineage-specific transcription factors (TFs) to overcome the barrier of the condensed structure of nucleosomes at repressed genes and to bind and activate their target sites. Preliminary results indicate that B-ALL LBCs have lost the inherent ability to open nascent chromatin, thus creating a barrier in their transcriptional reprogramming that differentiation-based therapies cannot overcome. In this proposal, to overcome this barrier of condensed nascent chromatin and to reprogram LBCs, I will utilize the following approach. First, I will pharmacologically ablate H3K27me3 to decondense nascent chromatin by inhibiting H3K27me3 histone methyltransferases EZH1/2. Second, I will use small molecules to activate inducible transcription factors, which can then readily bind to their target genes due to the decondensed structure of nascent chromatin. Cancers are commonly known to accumulate mutations in inducible TFs and receptors; thus, screens of small molecule inducers for a variety of TFs/receptors will be performed to determine the best possible inducer for distinct subtypes of B-ALL. Preliminary results provide strong indications that induction by novel small molecule ligands/inducers may lead to transcriptional reprogramming in B-ALL LBCs, which results in an almost complete loss of viability of these cells. This strategy has also shown significant promise in increasing the efficacy of and in decreasing the effective dosages of clinical standard of care drugs, such as steroid hormones. Furthermore, my results indicate that synchronization of B-ALL cells into the entry of the S-phase greatly increase the efficiency of our reprogramming strategy. Overall, our conceptual advance is in that we are not attempting to induce hematopoietic differentiation of LBCs, but rather through decondensing nascent chromatin induce transcriptional reprogramming to aberrant lineages, which may lead to terminal maturation, and thus to senescence, reduced proliferation, and cell death.

项目摘要/摘要 B细胞急性淋巴细胞白血病（B-all）由白血病细胞（LBC）组成，该细胞被捕在由于转录和表观遗传学的基本变化，B细胞发育的不同阶段编程。无法区分供认无限自我更新和增加的能力增殖能力。基于用ATRA和砷治疗APL白血病的成功，导致细胞成熟和感受，基于分化的疗法变得流行，但很少成功的治疗策略。我们建议，由于差距了解转录重编程的潜在机制。我的新策略基于我们小组最近的观察结果，即正常造血祖细胞（HPC）的分化取决于它们在诱导后瞬时解除复制后染色质的能力谱系指定细胞因子。在DNA复制的早期阶段，这种新生染色质的反应状态为谱系特异性转录因子（TFS）提供了机会窗口，以克服障碍核小体在反射基因处的凝结结构并结合和激活其目标位点。初步的结果表明，B-All LBC失去了打开新生染色质的遗传性，从而产生了障碍在他们的转录重新编程中，基于分化的疗法无法克服。在此提案中克服这种凝结的新生染色质和重编程LBC的障碍，我将利用以下方法。首先，我将通过抑制药物烧蚀H3K27me3对染色质脱离新生染色质 H3K27me3 Hisstone甲基转移酶EZH1/2。其次，我将使用小分子激活诱导转录因子，然后由于结构的解剖结构，可以轻松地与其靶基因结合新生染色质。众所周知，癌症是在诱导型TF和接收器中积累突变的；因此，将对各种TF/受体进行小分子诱导剂的筛选，以确定最佳 B-all的不同亚型诱导者。初步结果提供了有力的迹象，表明新型小型诱导分子配体/诱导剂可能导致B-All LBC中的转录重编程，这几乎导致这些细胞的生存能力完全丧失。该策略在提高效率方面还显示了巨大的希望在降低护理药物（例如立体激素）临床标准的有效剂量的过程中。此外，我的结果表明，B all细胞同步到S期的进入大大增加了我们重编程策略的效率。总体而言，我们的概念进步是我们没有试图诱导LBC的造血分化，而是通过反应新生的染色质诱导转录重编程对异常谱系，这可能导致终末成熟，从而导致衰老，减少增殖和细胞死亡。