PAX3/p53途径调控胶质瘤干细胞分化与凋亡的机制研究

Glioma stem cells (GSCs) are a subset of cells with the potential to initiate and maintain growth of gliomas which might be crucial for their recurrence and resistance to conventional therapies. The tumor cells differentiated from glioma stem cells have limited proliferative potential and lose their tumorigenic capacity. So the key point of target therapy of gliomas is to find the molecules which regulate the differentiation and apoptosis of GSCs. It has been reported that the dysfunction of either PAX3 or p53 is associated with glioma. The p53 is predictably one of the down stream target genes of PAX3 which has not been verified until now. Our previous studies have shown the high level of PAX3 both in malignant glioma cells and GSCs in human brains. Cell differentiation and apoptosis are induced by the down regulation of PAX3 expression and the activation of p53. Accordingly, the hypothesis is that the direct interaction between PAX3 and p53 involves in the differentiation and apoptosis of GSCs on transcriptional level. The project aims to explore the relationship between PAX3 and p53 and the mechanism of differentiation and apoptosis of GSCs by activating p53 through down-regulating the expression of PAX3. This study will offer a new regulation mechanism in the GSCs research. It will also provide a new way and theoretical basis for the clinical treatment of glioma.

胶质瘤干细胞是胶质瘤发生、发展及复发的关键细胞，同时也是临床上传统治疗手段束手无策的根本原因。干细胞分化来的肿瘤细胞仅有有限的增殖潜能，已丧失了致瘤能力。因此，靶向治疗胶质瘤的关键是找到调控胶质瘤干细胞分化和凋亡的关键分子。已有研究表明，PAX3与p53的功能异常都与胶质瘤相关，p53基因被预测是PAX3的下游靶基因之一，但至今尚未得到验证。我们的前期工作表明PAX3蛋白在人脑恶性胶质瘤及胶质瘤干细胞中高表达，下调PAX3可以诱导细胞分化及凋亡，同时激活p53的表达。据此我们提出假说：PAX3与p53在转录水平的直接相互作用调控了胶质瘤干细胞分化和凋亡过程。本课题拟探讨PAX3与p53的调控关系及其在胶质瘤干细胞分化与凋亡过程中的作用和机制。通过下调胶质瘤干细胞中PAX3的表达，激活p53的功能，促进胶质瘤干细胞分化和凋亡，为胶质瘤干细胞的研究提供新的调控机制，为胶质瘤的治疗提供新途径。

胶质母细胞瘤恶性程度高，传统的手术切除、化疗和放疗难以达到理想的治疗效果。胶质瘤干细胞（BGSCs）是其发生、发展及复发的关键细胞。前期工作中，我们发现PAX3的表达与胶质瘤患者预后密切相关，并有望成为胶质瘤治疗的新靶点，但其分子机制尚不清楚。本项目在胶质母细胞瘤中检到了PAX3与p53基因表达具有相关性。免疫荧光染色结果提示胶质瘤干细胞分化后，p53基因表达被激活。此外，PAX3能特异性地结合到p53基因启动子区域，负调控p53的转录活性。ChIP结果进一步证明 PAX3/p53调控途径参与胶质瘤干细胞分化过程。通过对BGSCs中PAX3功能进行体内外的研究发现，过表达PAX3促进BGSCs增殖、迁移能力，相反干扰PAX3的表达则抑制BGSCs增殖、迁移及体内裸鼠成瘤能力，促进凋亡。进一步研究证明PAX3对BGSCs特性的调控是部分依赖于p53通路。我们的工作为胶质瘤干细胞的诱导分化提供新的调控机制，为将来临床治疗胶质母细胞瘤提供新的治疗靶点。