Selective targeting of ependymoma progenitor cells via BMI1 inhibition

项目摘要 室管膜瘤（EPN）是致命的50%的儿童，并没有看到任何治疗 30多年来的改善。标准治疗仍然仅限于手术、放射治疗， 以及在有限的情况下进行化疗。在过去的十年里，我们对 通过对患者样本的分子分析，EPN的分子生物学已经得到了发展 但这些进展未能改善结果。基因组研究明确定义了 包括后颅窝A和B以及幕上亚组的多个亚组。 尽管取得了这些进展，EPN的异质性仍然是一个问题。为了解决这个 问题，我们对EPN患者样本进行了单细胞RNA测序分析， 鉴定了一个未分化的祖细胞群体，其表达高水平的 多能细胞标记物。同时，我们进行了一个无偏的表观基因组范围的RNAi， 筛选靶向410个染色质调节因子，以鉴定新的表观遗传调节因子 用于EPN细胞生长。我们鉴定了Polycomb阻遏复合物1（PRC 1）蛋白 BMI 1作为一个顶级命中，当耗尽或化学抑制严重抑制EPN 细胞生长有趣的是，BMI 1在未分化人群中表达最高， 通过我们的scRNA-seq识别并与更差的结果相关。重要的是 BMI 1的功能意义以前没有在EPN中进行过评价。我们 假设BMI 1高表达促进了细胞的去分化和自我更新， UEC亚群，从而将细胞锁定在高度致瘤性干细胞样状态。 为了解决我们的假设，我们将首先研究BMI 1功能对PFA的抑制作用， 肿瘤细胞自我更新和体外侵袭性PFA亚群的分化。我们 然后将建立用新的小分子靶向BMI 1的治疗功效 EPN中的抑制剂。这项工作完成后，BMI 1将在以下方面发挥直接作用： EPN干细胞分化并为在人类中使用BMI 1抑制剂提供依据 儿科临床试验

PROJECT SUMMARY Ependymoma (EPN) is fatal in 50% of children and has not seen any therapeutic improvements in over 30 years. Standard therapy remains limited to surgery, radiation, and chemotherapy in limited situations. In the past decade our understanding of the molecular biology of EPN has been advanced by molecular analysis of patient samples but these advances have failed to improve outcomes. Genomic studies clearly define multiple subgroups including Posterior fossa A and B as well as supratentorial subgroups. Despite these advances the heterogeneity in EPN remains a problem. To address this problem, we performed single cell RNA sequencing analysis of EPN patient samples and identified an undifferentiated progenitor population that expresses high levels of pluripotent cell markers. In parallel we performed an unbiased epigenome-wide RNAi screen targeting 410 chromatin regulators to identify novel epigenetic regulators critical for EPN cell growth. We identified the Polycomb repressive complex 1 (PRC1) protein BMI1 as a top hit, that when depleted or chemically inhibited severely suppressed EPN cell growth. Interestingly BMI1 is most highly expressed in the undifferentiated population identified by our scRNA-seq and associated with worse outcomes. Importantly the functional significance of BMI1 has not previously been evaluated in EPN. We hypothesize that high expression of BMI1 promotes de-differentiation and self-renewal of the UEC subpopulation, thereby locking the cells in a highly tumorigenic stem-like state. To address our hypothesis, we will first investigate the inhibition of BMI1 function on PFA tumor cell self-renewal and differentiation of aggressive PFA subpopulations in vitro. We will then establish the therapeutic efficacy of targeting BMI1 with novel small molecule inhibitors in EPN in vivo. Completion of this work will establish a direct role for BMI1 in EPN stem cell differentiation and provide justification for use of BMI1 inhibitors in human pediatric clinical trials.