Department of Neurosurgery, Provincial Hospital affiliated to Shandong University, Shandong University, Jinan, China.
Cancer Res. 2012 Mar 1;72(5):1221-8. doi: 10.1158/0008-5472.CAN-11-2785. Epub 2012 Jan 11.
Human tumor cell death during radiotherapy is caused mainly by ionizing radiation (IR)-induced DNA double-strand breaks (DSB), which are repaired by either homologous recombination repair (HRR) or nonhomologous end-joining (NHEJ). Although siRNA-mediated knockdown of DNA DSB repair genes can sensitize tumor cells to IR, this approach is limited by inefficiencies of gene silencing. In this study, we show that combining an artificial miRNA (amiR) engineered to target 3'-untranslated regions of XRCC2 (an HRR factor) or XRCC4 (an NHEJ factor) along with an siRNA to target the gene coding region can improve silencing efficiencies to achieve more robust radiosensitization than a single approach alone. Mechanistically, the combinatorial knockdown decreased targeted gene expression through both a reduction in mRNA stability and a blockade to mRNA translation. Together, our findings establish a general method of gene silencing that is more efficient and particularly suited for suppressing genes that are difficult to downregulate by amiR- or siRNA-based methods alone.
在放射治疗过程中，人类肿瘤细胞的死亡主要是由电离辐射（IR）诱导的 DNA 双链断裂（DSB）引起的，这些断裂可以通过同源重组修复（HRR）或非同源末端连接（NHEJ）来修复。虽然 siRNA 介导的 DNA DSB 修复基因敲低可以使肿瘤细胞对 IR 敏感，但这种方法受到基因沉默效率的限制。在这项研究中，我们表明，将针对 XRCC2（HRR 因子）或 XRCC4（NHEJ 因子）3'非翻译区的人工 miRNA（amiR）与针对基因编码区的 siRNA 结合使用，可以提高沉默效率，实现比单一方法更有效的放射增敏作用。从机制上讲，组合敲低通过降低 mRNA 稳定性和阻断 mRNA 翻译来降低靶基因表达。总之，我们的研究结果建立了一种更有效的基因沉默方法，特别适合于抑制那些难以通过 amiR 或 siRNA 单独下调的基因。
