临床上主要使用大剂量阿糖胞苷联合其它药物治疗复发/难治性急性T淋巴细胞白血病（T-ALL），但仍存在反应率低，预后差的问题。为了寻找新的联合治疗靶点，我们前期利用基于CRISPR/Cas9技术的sgRNA文库进行了高通量遗传筛选，结果发现敲除NF90-NF45核因子复合体可以与阿糖胞苷联合致死Jurkat T-ALL细胞。本课题拟根据NF90-NF45优先分布于细胞核仁的事实，首先研究NF90-NF45是否能够调控rDNA基因的转录和核糖体发生过程以及其具体分子机制；然后评价NF90-NF45过度激活引起的rDNA基因转录和核糖体发生异常是否是造成阿糖胞苷耐药性的重要原因；最后拟在细胞和动物模型上评价rDNA转录特异性抑制剂CX-5461联合低剂量阿糖胞苷治疗T-ALL的有效性。本研究的成功有望为复发/难治性T-ALL提供一个治疗新靶标和一种新的联合治疗方案。

High-dose cytarabine in combination with other drugs is the frontline therapy for relapsed/refractory acute T-cell lymphocytic leukemia (T-ALL), but the response rate is low with poor prognosis. Earlier we performed a CRISPR/Cas9 based high-throughput genetic screen in a T-ALL cell line-Jurkat cells, to search for proteins whose deletion synergize with cytarabine. We found that knockout of NF90-NF45, a nuclear protein complex, shows strong synergy with cytarabine to kill Jurkat cells. Based on the observation that NF90-NF45 is preferentially localized in the nucleoli, in this study, we will first investigate the role and underlying mechanism of NF90-NF45 in regulating ribosomal DNA (rDNA) transcription and ribosome biogenesis. Next, we will address if cytarabine resistance is associated with overactivation of NF90-NF45 and consequent dysregulation of rDNA transcription and ribosome biogenesis. Finally, we will evaluate the efficacy of combination therapy consisting of low-dose cytarabine and CX-5461, a specific inhibitor of rDNA transcription in vitro and in T-ALL animal models. As a summary, this study holds promise to reveal a new drug target and a combination therapy to benefit relapsed/refractory T-ALL patients.