Department of Neurosurgery, School of Medicine, Keio University, Tokyo, Japan.
J Neurosurg. 2010 Jan;112(1):33-42. doi: 10.3171/2009.3.JNS081146.
The introduction of temozolomide (TMZ) has advanced chemotherapy for malignant gliomas. A considerable number of glioblastoma cases are refractory to TMZ, however, and the development of novel chemotherapeutic regimens is needed. The authors of previous studies have revealed that hsp90 is expressed at higher levels in human neoplastic tissues, including gliomas, than in normal tissues. Heat shock protein 90 is involved in a cytoprotective mechanism against cellular stressors such as DNA damage, and the authors hypothesized that hsp90 inhibitors might act as antitumor agents against gliomas and potentiate the cytotoxicity of DNA-damaging agents.
The authors examined the cytotoxicity of an hsp90 inhibitor, 17-(allylamino)-17-demethoxygeldanamycin (17-AAG), both alone and in combination with 1 of 3 DNA-damaging agents (cisplatin, 1,3-bis(2-chloroethyl)-1-nitrosourea, and TMZ) in human glioma cell lines. The cytotoxicity of these agents to glioma cells was measured using a colony formation assay. The cell cycle phase distribution, protein expression, and number of apoptotic cells were measured using a fluorescence-activated cell sorting assay, immunoblot assays, and double staining with annexin V and propidium iodide. In an in vivo experiment, 17-AAG, cisplatin, or 17-AAG and cisplatin were administered intraperitoneally to mice with xenografted U87MG cells, and the resulting tumor volumes were measured.
The authors found that 17-AAG reduced the clonogenicity of U87MG cells, and at a low concentration (< 100 nM) potentiated the cytotoxicity of the DNA-crosslinking agents cisplatin and 1,3-bis(2-chloroethyl)-1-nitrosourea, but not that of the DNA-methylating agent TMZ. This 17-AAG-induced potentiation of DNA crosslinking agent-induced cytotoxicity was a consequence of prolonged G(2)-M arrest accompanied by the suppression of cdc2 and cdc25C and of increased apoptotic cell death accompanied by the degradation of the antiapoptosis proteins Akt and survivin. Similar effects were observed when cells were treated with radicicol, another hsp90 inhibitor. The 17-AAG-induced enhancement of DNA crosslinking agent-induced cytotoxicity was also observed in other cell lines. In addition, 17-AAG sensitized xenografted U87MG cells to cisplatin in nude mice.
Heat shock protein 90-targeted therapy may be an effective strategy for potentiating chemotherapy using DNA-crosslinking agents for TMZ-refractory gliomas.
替莫唑胺（TMZ）的引入已经推动了恶性神经胶质瘤的化疗。然而，相当数量的胶质母细胞瘤病例对 TMZ 具有抗药性，因此需要开发新的化疗方案。以前的研究作者已经表明，热休克蛋白 90（hsp90）在包括神经胶质瘤在内的人类肿瘤组织中的表达水平高于正常组织。热休克蛋白 90 参与了一种针对细胞应激物（如 DNA 损伤）的细胞保护机制，作者假设 hsp90 抑制剂可能作为针对神经胶质瘤的抗肿瘤剂，并增强 DNA 损伤剂的细胞毒性。
作者研究了 hsp90 抑制剂 17-（丙烯酰胺基）-17-去甲氧基格尔德霉素（17-AAG）单独使用和与 3 种 DNA 损伤剂（顺铂、1,3-双（2-氯乙基）-1-亚硝脲和 TMZ）中的 1 种联合使用对人神经胶质瘤细胞系的细胞毒性。使用集落形成测定法测量这些药物对神经胶质瘤细胞的细胞毒性。使用荧光激活细胞分选测定法、免疫印迹分析和用 Annexin V 和碘化丙啶双重染色测量细胞周期相分布、蛋白表达和凋亡细胞数量。在体内实验中，将 17-AAG、顺铂或 17-AAG 和顺铂腹腔内给药给荷 U87MG 细胞的异种移植小鼠，并测量由此产生的肿瘤体积。
作者发现 17-AAG 降低了 U87MG 细胞的集落形成能力，并且在低浓度（<100 nM）下增强了 DNA 交联剂顺铂和 1,3-双（2-氯乙基）-1-亚硝脲的细胞毒性，但不增强 DNA-甲基化剂 TMZ 的细胞毒性。这种 17-AAG 诱导的 DNA 交联剂诱导的细胞毒性增强是由于 G2-M 期阻滞延长伴随 cdc2 和 cdc25C 的抑制以及抗凋亡蛋白 Akt 和 survivin 的降解伴随的凋亡细胞死亡增加所致。当用另一种 hsp90 抑制剂瑞米迪辛处理细胞时，也观察到类似的效果。在其他细胞系中也观察到 17-AAG 诱导的 DNA 交联剂诱导的细胞毒性增强。此外，17-AAG 使裸鼠中的异种移植 U87MG 细胞对顺铂敏感。
针对热休克蛋白 90 的治疗可能是一种有效的策略，可通过使用 DNA 交联剂增强替莫唑胺耐药性胶质母细胞瘤的化疗。
