Silencing mammalian target of rapamycin signaling by small interfering RNA enhances rapamycin-induced autophagy in malignant glioma cells
Silencing mammalian target of rapamycin signaling by small interfering RNA enhances rapamycin-induced autophagy in malignant glioma cells
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DOI：
10.1038/sj.onc.1209992
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发表时间：
2007-03-22
期刊：
影响因子：
8
通讯作者：
Kondo, S.
中科院分区：
文献类型：
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作者：
Iwamaru, A.;Kondo, Y.;Kondo, S.
哺乳动物雷帕霉素靶蛋白（mTOR）在调节恶性胶质瘤细胞增殖中起着重要作用，mTOR特异性抑制剂如雷帕霉素类似物被认为是治疗恶性胶质瘤的有效药物。然而，单独使用mTOR抑制剂治疗恶性神经胶质瘤患者的疗效仅是适度的，这可能是因为这些药物不是作为mTOR激酶抑制剂，而是仅干扰mTOR/raptor（mTOR的调节相关蛋白）复合物的功能，因此不会干扰所有mTOR功能。本研究的目的是确定mTOR分子的整体抑制是否增强雷帕霉素对恶性胶质瘤细胞的抗肿瘤作用。我们发现，雷帕霉素诱导自噬和自噬的抑制小干扰RNA（siRNA）针对自噬相关基因Beclin 1衰减雷帕霉素敏感的肿瘤细胞中的雷帕霉素的细胞毒性，表明自噬是雷帕霉素的抗肿瘤作用的主要介质，而不是保护性反应。外源性表达的mTOR突变体干扰其激酶活性显着提高雷帕霉素诱导的自噬的发病率。此外，用siRNA沉默mTOR增强了雷帕霉素通过刺激自噬对肿瘤细胞活力的抑制作用。重要的是，不仅具有PTEN突变的雷帕霉素敏感性恶性胶质瘤细胞，而且具有野生型PTEN的雷帕霉素抗性恶性胶质瘤细胞也通过mTOR siRNA对雷帕霉素敏感。这些结果表明，雷帕霉素诱导的自噬是药物的抗肿瘤作用之一，沉默或抑制mTOR激酶活性可以增强雷帕霉素的有效性。
The mammalian target of rapamycin ( mTOR) plays a central role in regulating the proliferation of malignant glioma cells, and mTOR-specific inhibitors such as rapamycin analogs are considered as promising therapy for malignant gliomas. However, the efficacy of mTOR inhibitors alone in the treatment of patients with malignant gliomas is only modest, potentially because these agents rather than acting as mTOR kinase inhibitors instead interfere with the function of only mTOR/raptor (regulatory-associated protein of mTOR) complex and thus do not perturb all mTOR functions. The purpose of this study was to determine whether global inhibition of the mTOR molecule enhances the antitumor effect of rapamycin on malignant glioma cells. We showed that rapamycin induced autophagy and that inhibition of autophagy by small interfering RNA ( siRNA) directed against autophagy-related gene Beclin 1 attenuated the cytotoxicity of rapamycin in rapamycin-sensitive tumor cells, indicating that the autophagy was a primary mediator of rapamycin's antitumor effect rather than a protective response. Exogenous expression of an mTOR mutant interfering with its kinase activity markedly enhanced the incidence of rapamycin-induced autophagy. Moreover, silencing of mTOR with siRNA augmented the inhibitory effect of rapamycin on tumor cell viability by stimulating autophagy. Importantly, not only rapamycin-sensitive malignant glioma cells with PTEN mutations but also rapamycin-resistant malignant glioma cells with wild-type PTEN were sensitized to rapamycin by mTOR siRNA. These results indicate that rapamycin-induced autophagy is one of the agent's antitumor effects and that silencing or inhibiting mTOR kinase activity could enhance the effectiveness of rapamycin.