紫杉醇下调死亡结构域沉默子表达促进白血病细胞凋亡新机制研究

Increase of leukemia cell apoptosis through the down-regulation of silencer of death domains by Paclitaxel

目的探讨紫杉醇诱导白血病细胞凋亡的信号途径及死亡结构域沉默子（SODD）分子靶向对紫杉醇化疗的增敏作用。方法采用Westernblot法检测紫杉醇对人急性淋巴细胞白血病Jurkat细胞SODD、B细胞淋巴瘤／白血病-2基因（Bcl-2）、含半胱氨酸的天冬氨酸蛋白水解酶（Caspase-3）、核转录因子（NF—xB）-P65蛋白表达的影响；构建1个载体编码3条质粒表达载体的SODD小分子干扰质粒，转染至Jurkat细胞，采用碘化丙啶（PI）标记流式细胞术检测紫杉醇对细胞的凋亡诱导率。结果紫杉醇在诱导Jurkat白血病细胞凋亡过程中能显著下调SODD及Bcl-2蛋白的表达，在该凋亡过程中Caspase-3酶原逐渐被水解剪切并促进NF—xB活化表达；通过转染SODD小分子干扰质粒的Jurkat白血病细胞对紫杉醇的凋亡敏感性显著高于对照组，差异有统计学意义（F=10．35，P〈0．05）。结论紫杉醇可有效诱导白血病细胞凋亡，SODD／Bcl-2基因调控代表了一个独特的紫杉醇类诱导的细胞凋亡信号传导通路，这条通路最终通过激活Caspase-3执行，而NF—KB在这条通路中对相关凋亡基因起反应性调节作用。小分子干扰技术抑制白血病细胞SODD表达后能显著增加紫杉醇的化疗敏感性。

Objective To explore the signaling pathway of apoptosis induced by Paclitaxel （VI＇X） in leukemia cells and the chemosensitizing effect of adding short hairpin RNA（shRNA） on VI＇X, which targets the silencer of death domains（SODD）. Methods After being treated with PTX, the expressions of SODD, B-cell lymphoma/leukemia-2 （Bcl-2） , nuclear factor kappa B （NF-KB） and Caspase-3 proteins in Jurkat cells were determined by Western blot;the shRNA-SODD vectors were constructed and transfeeted into Jurkat ceils by electroporation,and then G418 was used to select the stable tranfected cell line expressing the shRNA-SODD recombinant plasmids. The incidence of cell apoptosis induced by VI＇X was determined by flow cytometry labeled with propidium iodide. Results During the process of indu- cing apoptosis of Jurkat cells,PTX could significantly down-regulate the expressions of SODD and Bcl-2 proteins, de- grade Caspase-3 and activate NF-KB. The apoptotic sensibility of Jurkat cells transfected with shRNA-SODD to [WX was significantly increased compared with the control group, and the difference was statistically significant （F = 10.35 ,P 〈 0.05 ）. Conclusions PTX can effectively induce apoptosis of Jurkat ceils. Perhaps, SODD/Bcl-2 represents a specific apoptotie signaling pathway of PTX in leukemia cells and this apoptotic signaling pathway is Caspase-3-dependent, in which the function of NF-KB is to modulate the correlative apoptotic factors. Inhibiting the expression of SODD through transfeeting shRNA-SODD vectors can significantly increase the apoptotic sensibility of leukemia cells to PTX.