Karamychev V N, Panyutin I G, Kim M K, Le N, Paik C H, Carrasquillo J A, Reed M W, Neumann R D
Department of Nuclear Medicine, Warren G. Magnuson Clinical Center, National Institutes of Health, Bethesda, Maryland 20892-1180, USA.
J Nucl Med. 2000 Jun;41(6):1093-101.
We studied the fine structure of DNA damage produced by the decay of 111In incorporated into duplex and triplex DNA strands to evaluate the usefulness of this radionuclide for sequence-specific DNA cleavage.
Oligodeoxyribonucleotides (ODNs) were prepared with 111In attached by diethylenetriaminepentaacetic acid (DTPA) at the 5' end or 3' end through a long chemical linker or to an internal nucleotide position through a short linker. Subsequent formation of DNA duplexes and triplexes was confirmed by gel electrophoresis. The 111In-induced breaks were assayed in denaturing polyacrylamide gel electrophoresis with a single-nucleotide resolution.
111In-labeled oligonucleotides of high specific activity (740-1554 TBq/mmol) were synthesized. The presence of the bulky 111In-DTPA group did not impede duplex or triplex formation. Localized DNA breaks were observed in all duplexes and triplexes formed. The majority of DNA breaks in duplex formations were located within +/- 10 nucleotides from the site of attachment of the 111In-bearing linker. The yield of DNA breaks per decay was 0.38 in a duplex with internally modified ODNs. This is nearly 2 times less than the yield of DNA breaks in the same duplex with 1251 attached through the same linker. The yield of DNA breaks in the pyrimidine and purine strands of DNA triplexes with 111In attached to the triplex-forming ODNs through the linkers of different length varied from 0.05 to 0.10. The distribution of DNA breaks was wider in comparison with the duplex experiment. The lower yields of breaks per 111In decay compared with 125I may be not only the result of lower deposited energy but also of the ionic repulsion of the negatively charged 111In-DTPA group from the DNA strands.
We have shown that decay of 111In produces highly localized DNA breaks. 111In introduced into triplex- and duplex-forming ODNs through hydrocarbon linkers produces sequence-specific DNA strand breaks with an efficiency nearly comparable with that of 1251. These findings are supportive of our proposed use of 111In-ODNs for gene-specific radiotherapy.
我们研究了掺入双链和三链DNA链中的铟-111衰变所产生的DNA损伤的精细结构，以评估这种放射性核素用于序列特异性DNA切割的效用。
制备了寡脱氧核糖核苷酸（ODN），铟-111通过二乙烯三胺五乙酸（DTPA）在5'端或3'端通过长化学连接子连接，或通过短连接子连接到内部核苷酸位置。随后通过凝胶电泳确认DNA双链体和三链体的形成。在具有单核苷酸分辨率的变性聚丙烯酰胺凝胶电泳中测定铟-111诱导的断裂。
合成了高比活度（740 - 1554 TBq/mmol）的铟-111标记的寡核苷酸。庞大的铟-111 - DTPA基团的存在并不妨碍双链体或三链体的形成。在所有形成的双链体和三链体中都观察到了局部DNA断裂。双链体形成中大多数DNA断裂位于距含铟-111连接子附着位点的+/- 10个核苷酸范围内。在具有内部修饰ODN的双链体中，每次衰变的DNA断裂产率为0.38。这比通过相同连接子连接碘-125的同一双链体中的DNA断裂产率低近2倍。通过不同长度的连接子将铟-111连接到形成三链体的ODN上，DNA三链体的嘧啶和嘌呤链中的DNA断裂产率在0.05至0.10之间变化。与双链体实验相比，DNA断裂的分布更宽。与碘-125相比，铟-111每次衰变的较低断裂产率可能不仅是沉积能量较低的结果，而且是带负电荷的铟-111 - DTPA基团与DNA链之间离子排斥的结果。
我们已经表明铟-111的衰变产生高度局部化的DNA断裂。通过烃连接子引入形成三链体和双链体的ODN中的铟-111产生序列特异性DNA链断裂，其效率与碘-125几乎相当。这些发现支持我们提出的将铟-111 - ODN用于基因特异性放射治疗的用途。
