Rödel Franz, Hoffmann Jörg, Distel Luitpold, Herrmann Martin, Noisternig Timmo, Papadopoulos Thomas, Sauer Rolf, Rödel Claus
Department of Radiation Oncology, Institutes of Clinical Immunology, and Pathology, University of Erlangen-Nuremberg, Erlangen, Germany.
Cancer Res. 2005 Jun 1;65(11):4881-7. doi: 10.1158/0008-5472.CAN-04-3028.
Apoptosis levels have been shown to predict tumor response to preoperative radiochemotherapy in rectal cancer. Recently, the prominent role of survivin, a structurally unique member of the inhibitor of apoptosis protein family, has been shown in colorectal cancer tumorigenesis and prognosis. In this study, we investigated whether survivin plays a direct role in mediating radiation resistance. We used short interfering RNA molecules to decrease survivin in radioresistant SW480 and intermediately radioresistant HCT-15 colorectal cancer cells. This resulted in a significant decrease of survivin mRNA and protein expression with a maximum at 24 to 48 hours after transfection. If irradiated during this sensitive period, an increased percentage of apoptotic cells and an increased caspase 3/7 activity in parallel with a decreased cell viability and a reduced clonogenic survival was shown. These effects were more pronounced in the radioresistant SW480 cell line with a radiation-induced cytotoxicity enhancement factor at 10% and 50% survival of 1.8 to 2.2 for SW480 and 1.5 to 1.7 for HCT-15, respectively. Furthermore, transfection with survivin short interfering RNA increased levels of G2-M arrest and levels of DNA double-strand breaks in irradiated cells. These observations indicate that cell cycle and DNA repair mechanisms may be associated with apoptosis induction in tumor cells that are otherwise resistant to killing by radiation. In a translational study of 59 patients with rectal cancer treated with a combination of radiotherapy and chemotherapy, increased survivin expression was inversely related to the levels of apoptosis, and was also associated with a significantly higher risk of a local tumor recurrence.
凋亡水平已被证明可预测直肠癌术前放化疗的肿瘤反应。最近，生存素作为凋亡抑制蛋白家族结构独特的成员，在结直肠癌的肿瘤发生和预后中发挥了重要作用。在本研究中，我们调查了生存素是否在介导放射抗性中起直接作用。我们使用短干扰RNA分子降低耐辐射的SW480和中度耐辐射的HCT-15结肠癌细胞中的生存素水平。这导致生存素mRNA和蛋白表达显著降低，在转染后24至48小时达到最大值。如果在这个敏感期进行照射，凋亡细胞百分比增加，半胱天冬酶3/7活性增加，同时细胞活力降低，克隆形成存活率降低。这些效应在耐辐射的SW480细胞系中更为明显，其辐射诱导的细胞毒性增强因子在10%和50%存活时，SW480分别为1.8至2.2，HCT-15为1.5至1.7。此外，用生存素短干扰RNA转染增加了受照射细胞中G2-M期阻滞水平和DNA双链断裂水平。这些观察结果表明，细胞周期和DNA修复机制可能与肿瘤细胞凋亡诱导有关，否则这些肿瘤细胞对辐射杀伤具有抗性。在一项对59例接受放疗和化疗联合治疗的直肠癌患者的转化研究中，生存素表达增加与凋亡水平呈负相关，并且也与局部肿瘤复发的显著更高风险相关。
