Sedelnikova O A, Panyutin I G, Thierry A R, Neumann R D
Department of Nuclear Medicine, Warren G. Magnuson Clinical Center, National Institutes of Health, Bethesda, Maryland 20892-1180, USA.
J Nucl Med. 1998 Aug;39(8):1412-8.
We investigated the distribution, stability and radiotoxicity of 125I-oligodeoxyribonucleotides (125I-ODN) in human fibrosarcoma HT-1080 cells to study the radiotoxic effects of the Auger electron emitter 125I delivered to the cells by ODN.
We delivered 125I-ODN into the cells via complexing with a liposomal delivery system. To assess the intracellular distribution and stability of 125I-ODN delivered by the liposomal delivery system, we used autoradiography, fluorescent and confocal microscopy and electrophoresis. To study the radiotoxicity of the unbound 125I-ODN, we used a clonogenic assay. The radiotoxicity of 125I-ODN delivered by the liposomal delivery system was compared with that of freely diffusible 125I-antipyrine, membrane-excluded 125I-bovine serum albumin and DNA incorporated 125I-deoxyuridine (125I-UdR).
Oligodeoxyribonucleotides accumulated in the cell nucleus within a few hours of incubation. On the basis of the number of decays at 37% survival, 125I-ODN are 2 times more radiotoxic than 125I-antipyrine, which is freely diffusible into cells, and 8 times more radiotoxic than 125I-bovine serum albumin, which remains outside cells. However, the radiotoxicity of unbound 125I-ODN is almost 3 orders of magnitude lower than that of DNA-incorporated 125I-UdR. The 125I-ODN are not significantly degraded by intracellular nucleases during the time of uptake incubation.
The dramatic difference in radiotoxicity between 125I-ODN and 125I-UdR confirms that, despite the nuclear localization, 125I-ODN are not bound to or incorporated within the genomic DNA. Our data demonstrate that the radiotoxicity of Auger electron emitters is determined by the radiation dose delivered to nuclear DNA, not necessarily to the nucleus. Therefore, relatively high intracellular concentrations of unbound 125I-ODN can be achieved without causing significant cell death.
我们研究了125I-寡脱氧核糖核苷酸（125I-ODN）在人纤维肉瘤HT-1080细胞中的分布、稳定性和放射毒性，以研究由ODN递送至细胞的俄歇电子发射体125I的放射毒性作用。
我们通过与脂质体递送系统复合将125I-ODN递送至细胞内。为了评估由脂质体递送系统递送的125I-ODN在细胞内的分布和稳定性，我们使用了放射自显影、荧光和共聚焦显微镜以及电泳技术。为了研究未结合的125I-ODN的放射毒性，我们使用了克隆形成试验。将脂质体递送系统递送的125I-ODN的放射毒性与可自由扩散的125I-安替比林、膜排斥的125I-牛血清白蛋白以及掺入DNA的125I-脱氧尿苷（125I-UdR）的放射毒性进行了比较。
寡脱氧核糖核苷酸在孵育数小时内积聚在细胞核中。基于37%存活率时的衰变次数，125I-ODN的放射毒性是可自由扩散进入细胞的125I-安替比林的2倍，是留在细胞外的125I-牛血清白蛋白的8倍。然而，未结合的125I-ODN的放射毒性比掺入DNA的125I-UdR低近3个数量级。在摄取孵育期间，125I-ODN不会被细胞内核酶显著降解。
125I-ODN与125I-UdR在放射毒性上的显著差异证实，尽管定位于细胞核，但125I-ODN并未与基因组DNA结合或掺入其中。我们的数据表明，俄歇电子发射体的放射毒性取决于递送至核DNA的辐射剂量，而不一定是递送至细胞核的剂量。因此，可以实现相对较高的细胞内未结合125I-ODN浓度而不引起显著的细胞死亡。
