Sensitization by Radio-Chemotherapy in Targeting Therapy for Survival Signal Transduction Pathways against Head and Neck Cancers

NBS1是DNA双链断裂（DSBs）修复的必需基因，可能在同源重组修复和非同源末端连接修复中发挥重要作用。在这项研究中，我们研究了通过小干扰RNA （siRNA）抑制NBS1表达是否可以增强不同TP53状态的癌细胞的辐射敏感性。我们使用了TP53基因状态不同的人舌癌细胞（SAS/neo携带野生型TP53或SAS/mp53携带突变型TP53）。将表达靶向NBS1基因的siRNA的DNA盒转染到这些细胞系中。Western blotting分析NBS1及其他蛋白的细胞水平。我们发现转染DNA盒后，SAS/neo和SAS/mp53的辐射敏感性增强。在转染NBS1- sirna的细胞中，我们观察到NBS1蛋白的组成表达减少，辐射诱导的磷酸化NBS1蛋白积累减少。此外，辐射诱导的转录因子NF-kB的表达被NBS1-siRNA抑制。在TP53野生型细胞中转染NBS1-siRNA后，x射线敏感性增强，在TP53突变细胞中敏感性更加明显。我们的数据表明，辐射致敏是由于nbs1 - sirna介导的DNA修复和/或x射线通过NF-kB诱导的细胞存活信号通路的抑制。siRNA靶向似乎是一种新的辐射增敏剂，特别是在人类TP53突变癌细胞中。

NBS1 is essential for the repair of DNA double-strand breaks (DSBs) and may play a important role in the homologous recombination repair and nonhomologous end joining repair. In this study, we examined whether suppressed NBS1 expression by small interference RNA (siRNA) could enhance radiation sensitivity in cancer cells with different TP53 status. We used human tongue cancer cells differing in TP53 gene status (SAS/neo bearing wild-type TP53 or SAS/mp53 bearing mutant TP53). A DNA cassette expressing siRNA targeted for the NBS1 gene was transfected into those cell lines. Cellular levels of NBS1 and other proteins were analyzed using Western blotting. We found that the radiation sensitivity of SAS/neo and SAS/mp53 was enhanced by transfection of the DNA cassette. In the NBS1-siRNA-transfected cells, we observed decreased constitutive expression of NBS1 protein and decreased radiation-induced accumulation of phosphorylated NBS1 protein. In addition, radiation-induced expression of the transcription factor NF-kB was suppressed by NBS1-siRNA. Enhanced X-ray sensitivity after NBS1-siRNA transfection was achieved in TP53 wild-type cells and sensitivity was even more pronounced in TP53 mutant cells. Our data suggest that the sensitization to radiation results from NBS1-siRNA-mediated suppression of DNA repair and/ or X-ray-induced cell survival signaling pathways through NF-kB. siRNA targeting appears to be a novel radiation-sensitizing agent, particularly in human TP53 mutant cancer cells.