Role of autophagy in temozolomide-induced cytotoxicity for malignant glioma cells
Role of autophagy in temozolomide-induced cytotoxicity for malignant glioma cells
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DOI：
10.1038/sj.cdd.4401359
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发表时间：
2004-04-01
影响因子：
12.4
通讯作者：
Kondo, S
中科院分区：
文献类型：
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作者：
Kanzawa, T;Germano, IM;Kondo, S
自噬最初被命名为蛋白质回收的过程。它开始于将细胞质细胞器隔离在称为自噬体的膜泡中。自噬体然后与溶酶体融合，在那里内部的材料被降解和回收。然而，迄今为止，对自噬在癌症治疗中的作用知之甚少。在这项研究中，我们提出了替莫唑胺（TMZ），一种新的烷化剂，抑制恶性胶质瘤细胞的活力，以剂量依赖的方式，并诱导G2/M期阻滞。在临床可达到的剂量（100 μ M），TMZ诱导恶性胶质瘤细胞自噬，但不凋亡。TMZ处理后，微管相关蛋白轻链3（LC 3），Apg 8 p/Aut 7 p在酵母中氨基酸饥饿诱导的自噬所必需的哺乳动物同源物，被招募到自噬体膜上。当自噬在早期阶段被3-甲基腺嘌呤（一种磷脂酰肌醇3-磷酸激酶抑制剂）阻止时，不仅LC 3定位的特征模式，而且TMZ的抗肿瘤作用也被抑制。另一方面，巴弗洛霉素A1，一种液泡型H+-ATP酶的特异性抑制剂，通过抑制自噬体和溶酶体之间的融合来防止晚期自噬，通过激活caspase-3与线粒体和溶酶体膜透化来诱导细胞凋亡，从而使肿瘤细胞对TMZ敏感，而LC 3定位模式保持不变。这些结果表明TMZ诱导恶性胶质瘤细胞中的自噬。应用自噬抑制剂，如巴弗洛霉素A1，在LC 3与自噬体膜结合后起作用，有望增强TMZ对恶性胶质瘤的细胞毒性。
Autophagy is originally named as a process of protein recycling. It begins with sequestering cytoplasmic organelles in a membrane vacuole called autophagosome. Autophagosomes then fuse with lysosomes, where the materials inside are degraded and recycled. To date, however, little is known about the role of autophagy in cancer therapy. In this study, we present that temozolomide ( TMZ), a new alkylating agent, inhibited the viability of malignant glioma cells in a dose-dependent manner and induced G2/M arrest. At a clinically achievable dose (100 muM), TMZ induced autophagy, but not apoptosis in malignant glioma cells. After the treatment with TMZ, microtubule-associated protein light-chain 3 (LC3), a mammalian homologue of Apg8p/Aut7p essential for amino-acid starvation-induced autophagy in yeast, was recruited on autophagosome membranes. When autophagy was prevented at an early stage by 3-methyladenine, a phosphatidylinositol 3-phosphate kinase inhibitor, not only the characteristic pattern of LC3 localization, but also the antitumor effect of TMZ was suppressed. On the other hand, bafilomycin A1, a specific inhibitor of vacuolar type H+-ATPase, that prevents autophagy at a late stage by inhibiting fusion between autophagosomes and lysosomes, sensitized tumor cells to TMZ by inducing apoptosis through activation of caspase-3 with mitochondrial and lysosomal membrane permeabilization, while LC3 localization pattern stayed the same. These results indicate that TMZ induces autophagy in malignant glioma cells. Application of an autophagy inhibitor that works after the association of LC3 with autophagosome membrane, such as bafilomycin A1, is expected to enhance the cytotoxicity of TMZ for malignant gliomas.