Hsp70通过增加溶酶体膜稳定性在GBM放疗抵抗中的作用机制研究

Glioblastoma (GBM) has a low sensitivity to radiotherapy. Lysosomes play an important role in radioresistance of tumors, but its mechanism is still unknown. When lysosomal membrane permeates selectively, also known as lysosomal membrane permeabilization (LMP), proteolytic enzymes in lysosome will be released into cytoplasm, which will cause changes in a series of signaling pathways. As a result, cell death will occur. Our previous study showed that lysosome activity increased significantly after radiotherapy. As an important molecule to maintain the stability of lysosomal membrane, the expression of Hsp70 also increased significantly after radiotherapy. Combined use of LMP inducers significantly increased the radiosensitivity of GBM. Therefore, we speculate that radiotherapy can maintain the stability of lysosomal membrane by up-regulating Hsp70, thus cell death induced by LMP will be inhibited. In this project, we intend to study the molecular mechanism of increased lysosomal activity induced by radiotherapy. Modern techniques in molecular and cellular biology were used to observe the expression levels of Hsp70 on the radiosensitivity of GBM, and elucidate the molecular mechanism that Hsp70 promotes radioresistance by increasing the stability of lysosomal membrane. Finally, the effects of inhibiting Hsp70 on radiotherapy were verified in an animal model. This project will provide new target for the radiosensitization of GBM.

胶质母细胞瘤（GBM）对放疗的敏感性较差。溶酶体在参与肿瘤的放疗抵抗中发挥重要作用，但是具体机制未知。当溶酶体膜出现选择性通透增加，即溶酶体膜通透（LMP）发生时，溶酶体内的蛋白水解酶进入胞浆中诱发一系列信号传导通路的改变，从而激活细胞凋亡等细胞死亡机制。我们前期研究表明，放疗后溶酶体活性明显增高；作为维持溶酶体膜稳定性的重要分子，Hsp70的表达在放疗后也明显增加。而联合使用LMP诱导剂明显增加GBM的放疗敏感性。因此我们推测，放疗能够通过上调Hsp70而维持溶酶体膜稳定性，从而避免LMP诱导的细胞死亡的发生。本课题拟通过多种实验技术，探究放疗引起溶酶体活性增加的分子机制，观察Hsp70表达水平对GBM放疗敏感性的影响，阐明Hsp70通过增加溶酶体膜稳定性促进放疗抵抗的分子机制，最后在动物模型中验证抑制Hsp70对放疗的影响，为GBM的放疗增敏提供新思路。

胶质母细胞瘤（GBM）对放疗的敏感性较差。溶酶体在参与肿瘤的放疗抵抗中发挥重要作.用，但是具体机制未知。当溶酶体膜出现选择性通透增加，即溶酶体膜通透（LMP）发生时，溶酶体内的蛋白水解酶进入胞浆中诱发一系列信号传导通路的改变，从而激活细胞凋亡等细胞死亡机制。本研究我们提出诱导LMP能够增加肿瘤的放疗敏感性。在研究中我们发现，传统的抗精神药物三氟拉嗪能够诱导LMP，进一步的机制研究表明其通过STAT3导致LMP，从而产生抗肿瘤效果。我们同时还发现，双硫仑，一种戒酒药物，在GBM中能够诱导铁死亡及LMP，而抑制ROS或铁死亡水平上升后双硫仑导致的LMP显著下调。进一步的研究表明双硫仑联合放疗能明显增加GBM的DNA损伤，并导致更多的肿瘤死亡。该研究进一步证实铁死亡与LMP存在关系。FIN56，一种铁死亡诱导剂，被我们证实能够在胶质瘤细胞中诱导LMP。探索进一步的机制，我们发现转录因子EB（TFEB）在联系铁死亡和LMP中发挥关键作用。而体内外实验均证实放疗后GBM细胞中TFEB活性显著提高。TFEB作为溶酶体生物合成的关键基因，在放疗增敏中有潜在利用价值。进一步的实验还在继续。因此，诱导LMP能够增加胶质瘤的放疗敏感性。