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第二线粒体来源的caspase激活因子(second mitochondria-derived activator of caspases,Smac)也称为低等电点的凋亡抑制蛋白(inhibitors of apoptosis proteins,IAPs)家族直接结合蛋白,是一个从线粒体释放到细胞质中具有促凋亡活性的蛋白[1],它在凋亡信号的刺激作用下,从线粒体释放到细胞质,与IAPs结合并抑制其抗凋亡活性,从而产生促进凋亡的作用。国内外大量科学研究证实,Smac模拟活性小分子可以显著增强化疗以及放疗对肿瘤细胞的凋亡诱导效应[2-6],为未来的肿瘤治疗提供了一种新的手段。而Smac蛋白中N末端的四肽Ala-Val-Pro-Ile(以下简称AVPI)是诱导细胞凋亡的重要部分,本研究中将反式激活蛋白(transactivator,Tat)中既有穿膜特性又无细胞毒性的最小片断Tat9肽与Smac中含有AVPI的N端七肽分子合成了具有细胞穿透性的Tat-SmacN7蛋白。食管癌是人类常见的消化道恶性肿瘤之一,本研究中用Tat-SmacN7蛋白以及γ射线分别或联合处理食管癌109(esophageal carcinoma 109,EC109)细胞,观察Tat-SmacN7蛋白对EC109细胞辐射敏感性的影响。
Tat-SmacN7蛋白对食管癌109细胞辐射敏感性的影响
The effects of Tat-SmacN7 protein on radiosensitivity of esophageal carcinoma l09
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摘要:
目的 探讨Tat-SmacN7蛋白(其中,Tat:反式激活蛋白;Smac:第二线粒体来源的caspase激活因子;N7:Smac的N端含有Ala-Val-Pro-Ile的七肽)对食管癌109(EC109)细胞放疗敏感性的影响。 方法 对EC109细胞给予Tat-SamcN7、照射、以及联合处理,观察不同处理在24 h和48 h时对细胞的抑制作用,采用Western blot检测各组细胞中Smac蛋白表达水平。 结果 通过水溶性四唑盐1检测发现Tat-SmacN7单独使用对细胞的抑制作用不明显,但与Tat-SmacN7组和照射组相比,Tat-SmacN7联合放射组可以明显增强对细胞的抑制(24 h:t=16.821和9.825,P < 0.05;48 h:t=23.553和11.930,P < 0.05)。说明Tat-SmacN7能增强EC109细胞对放射的敏感性。Western blot证明了Tat-SmacN7可以使细胞内Smac蛋白表达增加。 结论 Tat-SmacN7蛋白能通过细胞高表达Smac,增强EC109细胞对辐射的敏感性。 Abstract:Objective To investigate the effects of Tat-SmacN7 protein on sensitivity of esophageal carcinoma 109(EC109) to radiation. Methods Cells were treated with Tat-SmacN7 peptides, radiation or combination, the inhibition rate of EC109 cells were detected by water-soluble tetrazolium salt-1 assay. The protein level expression of Smac was determined by Western blot. Results The cells were resistant to Tat-SmacN7 as a single agent, but it could improve the sensitization of EC109 to radiation. Compared with the Tat-SamcN7 group and the radiation group, the Tat-SmacN7 combined with radiation group was inhibited significantly(24 h:t=16.821 and 9.825, both P < 0.05; 48 h:t=23.553 and 11.930, both P < 0.05). Western blot assay showed that Tat-SmacN7 could increase the expression of Smac protein. Conclusions Tat-SmacN7 could improve the radiosensitization of EC109 cell by increasing the expression of Smac. -
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