FoxO3a/MMP9信号轴在多形性恶性胶质母细胞瘤替莫唑胺耐药中的作用研究

Glioblastoma multiforme (GBM) is the most common and lethal type of primary brain cancer. Therefore addressing the challenge of GBM resistance to Temozolomide (TMZ) — a therapeutic alkylating agent used in the standard treatment of GBM—has become imperative. Since the existing mechanisms for the drug resistance fail to allow us to address the challenge, in this project we expect to find a novel TMZ-resistance mechanism by investigating the signature of Epithelial-Mesenchymal Transition (EMT) and EMT-related genes. We found that FoxO3a regulated MMP9; down-regulation of MMP9 rendered cancer cells more sensitive to TMZ as well as apoptosis induced by TMZ, and that could be subverted by overexpressing active β-catenin. Herein, we hypothesize that FoxO3a/MMP9 axis inhibits TMZ-induced apoptosis via regulation of β-catenin, thereby conferring cancer cell resistance to the drug. To test the hypothesis, 1) in GBM cells, we will investigate the signaling cascade through which FoxO3a/MMP9 axis regulates β-catenin and the influences of the signaling cascade on the drug resistance and cell apoptosis. In the established GBM xenograft model in mice, we will further investigate the roles of FoxO3a/MMP9 axis and β-catenin in the drug resistance and apoptosis. By using patient samples, we will validate FoxO3a, MMP9, β-catenin protein expressions, together with clarifying the relationship between these gene expression patterns and patient overall survivals. Aiming at providing new insight into addressing the challenge of TMZ-resistance in GBM, this study is of great significance not only for basic scientific research but also for translational medicine.

多形性恶性胶质母细胞瘤（GBM) 是最常见和最致命的神经胶质瘤，其标准药物替莫唑胺 (TMZ)的耐药问题需解决，耐药机制需完备。从GBM的上皮间叶表型转化（EMT）特性及相关分子入手我们期望找到TMZ耐药的新途径。前期工作显示：FoxO3a调控MMP9表达；下调MMP9的表达可引起GBM细胞TMZ耐药和抗凋亡能力的降低,过表达活性β-catenin可逆转下调MMP9的影响，提示FoxO3a/MMP9信号轴可能主要通过调控β-catenin抑制GBM的凋亡从而赋予GBM细胞耐药性。我们将在GBM细胞中研究FoxO3a/MMP9信号轴调控β-catenin的信号通路机制以及其与肿瘤细胞耐药和凋亡的关系；在小鼠模型中探讨该信号轴与β-catenin对GBM耐药和凋亡的作用；在GBM样本中探讨FoxO3a、MMP9、β-catenin的表达与生存期的关联。该研究将为TMZ耐药问题的解决提供新思路。

多形性恶性胶质母细胞瘤（GBM) 是最常见和最致命的神经胶质瘤，其标准药物替莫唑胺 (TMZ)的耐药问题仍未解决。因现有的耐药机制研究不足以满足这一需求，我们另辟蹊径从FoxO3a着手以期找到可能的克服GBM耐药的解决办法。首先，我们发现在U251中敲低FoxO3a可以导致肿瘤细胞增殖和侵袭能力下降，而在U87中过表达FoxO3a可以促进肿瘤增殖和侵袭。同时，我们发现FoxO3a可以特异的促进MMP9的表达，并且MMP9过表达可以抵消敲低FoxO3a给肿瘤细胞侵袭带来的影响。我们随后将研究主要集中于GBM父代肿瘤细胞以及对应的耐药株细胞上。在耐药株细胞中，我们发现FoxO3a表达水平上调。敲低FoxO3a削弱了肿瘤细胞的耐药性并伴随着核β-catenin水平的降低。随后，我们进一步研究了FoxO3a促进β-catenin入核累积的分子机制。我们采用了敲低和共表达的联合策略。在U87和U251中过表达FoxO3a 或 β-catenin可以提高肿瘤细胞耐药性。敲低FoxO3a 或 β-catenin则可削弱肿瘤细胞的耐药性。FoxO3a的过表达可恢复因FoxO3a敲低而引起的削弱的肿瘤细胞耐药性。在耐药株中敲低FoxO3a可以导致MMP9表达水平的下调，并伴随着β-catenin核累积的减少。这些结果表明FoxO3a可以通过MMP9调控β-catenin的入核累积，从而使得GBM细胞的耐药性增强。我们的工作有助于对GBM细胞TMZ机制的理解，并未其治疗提供新思路。