Lu Bo, Mu Yi, Cao Carolyn, Zeng Fenghua, Schneider Sylke, Tan Jiahui, Price Jim, Chen Jun, Freeman Michael, Hallahan Dennis E
Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Cancer Res. 2004 Apr 15;64(8):2840-5. doi: 10.1158/0008-5472.can-03-3547.
Expression of survivin is elevated in most malignancies, especially in radiation-resistant cell lines. In this study, we investigated how radiation affects survivin expression in primary endothelial cells as well as in malignant cell lines. We found that 3 Gy significantly reduced survivin protein level in human umbilical vein endothelial cells (HUVECs) but not in tumor cell lines. Flow cytometry studies suggest that the down-regulation of survivin is independent of cell cycle. In addition, survivin mRNA level was also down-regulatable by irradiation. However, it was abrogated by actinomycin D-mediated inhibition of gene transcription. Luciferase reporter gene assays suggest that irradiation suppressed the survivin promoter. p53 overexpression reduced survivin expression, but overexpression of a p53 mutant failed to abolish the radiation-induced down-regulation in HUVECs. Alteration of p53 status in Val138 lung cancer cell line also failed to restore the radiation-inducible down-regulation. Overexpression of survivin in 293 cells prevented apoptosis induced by irradiation and increased cell viability after irradiation. The inhibition of survivin using antisense oligonucleotides caused a significant decrease in cell viability of irradiated H460 lung cancer cells. These data suggest that radiation transcriptionally down-regulates survivin in HUVECs. This regulatory mechanism is defective in malignancies and is not mediated by p53. Survivin overexpression may lead to resistance to radiotherapy by inhibiting apoptosis and enhancing cell viability. The inhibition of survivin results in sensitization of H460 lung cancer cells to radiation. These studies suggest that survivin may be a target for cancer therapy.
生存素在大多数恶性肿瘤中表达上调，尤其是在耐辐射细胞系中。在本研究中，我们调查了辐射如何影响原代内皮细胞以及恶性细胞系中生存素的表达。我们发现，3 Gy剂量的辐射显著降低了人脐静脉内皮细胞（HUVECs）中生存素蛋白水平，但对肿瘤细胞系没有影响。流式细胞术研究表明，生存素的下调与细胞周期无关。此外，辐射也可下调生存素mRNA水平。然而，放线菌素D介导的基因转录抑制可消除这种下调。荧光素酶报告基因检测表明，辐射抑制了生存素启动子。p53过表达降低了生存素表达，但p53突变体的过表达未能消除HUVECs中辐射诱导的下调。Val138肺癌细胞系中p53状态的改变也未能恢复辐射诱导的下调。在293细胞中过表达生存素可防止辐射诱导的细胞凋亡，并增加辐射后的细胞活力。使用反义寡核苷酸抑制生存素可导致辐射后的H460肺癌细胞活力显著下降。这些数据表明，辐射通过转录下调HUVECs中的生存素。这种调节机制在恶性肿瘤中存在缺陷，且不受p53介导。生存素过表达可能通过抑制细胞凋亡和增强细胞活力导致放疗抵抗。抑制生存素可使H460肺癌细胞对辐射敏感。这些研究表明，生存素可能是癌症治疗的一个靶点。
