DDX5调控NOTCH介导的转录参与急性T淋巴细胞白血病的发病

Acute lymphocytic leukemia (ALL) is the most common malignancy of childhood, especially the T cell acute lymphocytic leukemia (T-ALL). However, the pathogenesis of T-ALL remains unclear. In T-ALL, Notch signaling pathway is hyperactive. The MAML family are the essential components of the Notch transcription activation complex. Currently, the molecular basis underlying the MAML1 co-activation function that regulating Notch signal remains very limited. Our previous research showed that DDX5, an ATP-dependent RNA helicase, as a component of the MAML1 protein complex as well as the Notch transcription complex. Given a role for DDX5, we thus reasoned that DDX5 might be a critical regulator for Notch-mediated T-ALL. Then we validated the interaction between MAML1 and DDX5 in vitro and in vivo using molecular biology assays..In this study, we will knowdown DDX5 to identify the expression of Notch target signature, along with the cell proliferation and survival in T-ALL cells. Depend on the animal model, we will investigate the impact of DDX5 on the cell proliferation of leukemia whose Notch pathway are active and interpose the time point of DDX5 which overexpression. Our findings thus revealed a critical role of DDX5 as a transcriptional regulator for Notch-madiated T-ALL pathogenesis and has the potential as a drug target in the Notch mutated T-ALL.

急性淋巴细胞白血病（ALL）居儿童恶性肿瘤之首，以急性T淋巴细胞白血病（T-ALL）为主，致病机制至今未明。在T-ALL中，Notch通路过度激活，MAML家族是Notch转录激活复合物的主要成员，但MAML1调控Notch信号通路的分子机制尚未阐明。我们前期研究发现DDX5既是MAML1蛋白复合物的成员又是Notch转录复合物的成员，推断DDX5在Notch介导转录的T-ALL中有重要作用。体内外实验显示DDX5与MAML1、NOTCH1相互作用。.本项目拟在T-ALL细胞中靶向下调DDX5表达及对Notch通路和白血病细胞增殖和凋亡的影响，进一步在动物模型研究DDX5对T-ALL中肿瘤细胞增殖的影响，并选取DDX5高表达时间点进行干预，结果有助于揭示DDX5作为转录调控子参与Notch活化的T-ALL的发病机制，探索应用调控DDX5作为靶点治疗Notch活化的T-ALL的可能性。

DDX5是DEAD-box家族成员之一，是ATP依赖的RNA解旋酶，可能参与了NOTCH1调控的T-ALL的发病。本研究通过体内和体外实验观察了DDX5与MAML1的关系，结果发现，（1）DDX5与MAML1相互作用，并与Notch活化的T-ALL中内源性NOTCH1转录激活复合物有关。（2）慢病毒调节的短发夹RNA knock down DDX5导致Notch靶基因的表达降低，细胞增殖减慢，细胞凋亡加速。（3）在裸鼠中，DDX5的缺失抑制了白血病移植瘤的生长。这些研究结果提示，在白血病细胞中，DDX5在促进有效的Notch调节的转录中扮演重要角色，表明DDX5在NOTCH1调节的T-ALL的发病中作用显著。因此，在白血病中，DDX5将是Notch调制的信号通路中的一个潜在的新的作用靶点。