β-catenin contributes to cordycepin-induced MGMT inhibition and reduction of temozolomide resistance in glioma cells by increasing intracellular reactive oxygen species
β-catenin contributes to cordycepin-induced MGMT inhibition and reduction of temozolomide resistance in glioma cells by increasing intracellular reactive oxygen species
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DOI：
10.1016/j.canlet.2018.07.040
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发表时间：
2018-01-01
期刊：
影响因子：
9.7
通讯作者：
Zhao, Gang
中科院分区：
文献类型：
--
作者：
Bi, Yiming;Li, Han;Zhao, Gang
多形性胶质母细胞瘤（GBM）是人类最具侵袭性的肿瘤之一，预后差。替莫唑胺（TMZ）是用于治疗GBM的主要烷化剂。然而，一些GBM患者对TMZ具有耐药性。因此，迫切需要更有效的治疗选择。虫草素（COR）是一种具有抗肿瘤作用的天然化学物质，但其作用机制尚不清楚。一些证据表明，O-6-甲基鸟嘌呤DNA甲基转移酶（MGMT）修复受损的DNA，并有助于胶质瘤对TMZ的耐药性。Wnt/β-catenin途径调节MGMT基因表达。然而，虫草素是否通过下调β-连环蛋白通路和增加胶质瘤细胞对TMZ的化疗敏感性来抑制MGMT表达仍不清楚。在本研究中，我们发现虫草素抑制胶质瘤细胞的活力，诱导凋亡，细胞周期阻滞，活性氧（ROS）的过度产生和还原谷胱甘肽（GSH）在体外。此外，虫草素显着减少肿瘤体积和延长中位生存期的荷瘤大鼠体内。我们还发现，虫草素抑制MGMT表达和增强化疗敏感性TMZ在体外和体内胶质瘤细胞，伴随着下调p-GSK-3 β和β-连环蛋白。此外，MGMT的过表达逆转了虫草素和TMZ的协同作用。用CHIR-99021或β-连环蛋白的过表达对GSK-3 β的药理学抑制逆转了虫草素诱导的细胞活力降低、β-连环蛋白和MGMT下调、细胞凋亡增加和TMZ抗性降低。此外，我们发现β-连环蛋白通过减少GSH来调节虫草素诱导的ROS过度产生。用N-乙酰-L-半胱氨酸（NAC）抑制ROS的产生不仅挽救了细胞活力的降低，而且消除了β-连环蛋白和MGMT的抑制，防止了胶质瘤细胞凋亡，并逆转了虫草素和TMZ的协同作用。综上所述，我们证明β-连环蛋白通过增加细胞内ROS而有助于虫草素诱导的MGMT抑制和胶质瘤细胞中TMZ抗性的降低。这些结果表明，虫草素可能是一种新的药物，以改善GBM的治疗，特别是在TMZ耐药GBM与高MGMT表达。
Glioblastoma multiforme (GBM) is one of the most aggressive human tumors, and it has a poor prognosis. Temozolomide (TMZ) is the primary alkylating agent used to treat GBM. Nevertheless, a number of GBM patients are resistant to TMZ. Therefore, there is an urgent need for more effective therapeutic options. Cordycepin (COR) is a natural chemical with anti-tumor effects, although its mechanism of action is poorly understood. Several lines of evidence suggest that O-6-methylguanine DNA methyltransferase (MGMT) repairs damaged DNA and contributes to drug resistance to TMZ in gliomas. The Wnt/beta-catenin pathway regulates MGMT gene expression. However, whether cordycepin inhibits MGMT expression by downregulating the beta catenin pathway and augmenting chemosensitivity to TMZ in glioma cells remains unclear. In the present study, we found that cordycepin inhibited the viability of glioma cells and induced apoptosis, cell cycle arrest, overproduction of reactive oxygen species (ROS) and reduction of glutathione (GSH) in vitro. Moreover, cordycepin significantly reduced tumor volume and prolonged median survival of tumor-bearing rats in vivo. We also found that cordycepin inhibited MGMT expression and augmented chemosensitivity to TMZ in glioma cells in vitro and in vivo, accompanied by downregulation of p-GSK-3 beta and beta-catenin. Moreover, overexpression of MGMT reversed the synergistic effect of cordycepin and TMZ. Pharmacological inhibition of GSK-3 beta with CHIR-99021 or overexpression of beta-catenin reversed cordycepin-induced reduction of cell viability, downregulation of beta-catenin and MGMT, increase of apoptosis and reduction of TMZ resistance. Furthermore, we found that beta-catenin regulated cordycepin-induced overproduction of ROS by decreasing GSH. Inhibition of ROS production with N-acetyl-L-cysteine (NAC) not only rescued the reduction of cell viability but also eliminated beta-catenin and MGMT inhibition, prevented glioma cells apoptosis and reversed the synergistic effect of cordycepin and TMZ. Taken together, we demonstrated that beta-catenin contributed to cordycepin-induced MGMT inhibition and reduction of TMZ resistance in glioma cells via increasing intracellular ROS. These results indicate that cordycepin may be a novel agent to improve GBM treatment, especially in TMZ-resistant GBM with high MGMT expression.