Woynarowski J M, Bartoszek A, Konopa J
Chem Biol Interact. 1984 May;49(3):311-28. doi: 10.1016/0009-2797(84)90105-4.
Ledakrin and seven other antitumor and cytotoxic derivatives of 1-nitro-9-aminoacridine were shown to induce DNA-single strand breaks in HeLa S3 cells as found by alkaline sucrose gradient centrifugation. The induced DNA damage is of non-random character. Some of Ledakrin -induced DNA breaks are probably generated by endonucleolytic cleavage in the course of repair processes as indicated by experiments with Novobiocin, an antibiotic preventing the incision step of DNA repair. Other Ledakrin -induced DNA breaks observed on alkaline sucrose gradients may arise from alkali-labile sites in DNA. Most of such sites seem to be converted to breaks after brief exposure to alkali. The extent of DNA damage by 1-nitro-9-aminoacridines was found to be correlated with cytotoxic activities of these compounds against HeLa S3 cells. Furthermore, Ledakrin and other derivatives seem to induce DNA-repair synthesis in HeLa S3 cells as judged by the stimulation of hydroxyurea (HU)-resistant incorporation of [3H] thymidine into DNA. The agents studied differ in their concentrations required to produce a considerable stimulation of DNA repair, whereas the maximal level of this effect is similar for all the derivatives assayed. The former values are correlated with cytotoxic activities of these compounds and seem to reflect the overall extent of DNA damage by 1-nitro-9-aminoacridines. Stimulation of DNA-repair synthesis is gradually shut off during prolonged incubation of the cells with Ledakrin or during postincubation of the cells in a drug-free medium. Such postincubation results also in the gradual accumulation of DNA-single strand breaks as observed by alkaline sucrose centrifugation. Hence, HeLa S3 cells are incapable of efficiently removing DNA damage by 1-nitro-9-aminoacridines, though the drug's action activates temporarily some repair mechanisms. The reported results suggest that overall DNA damage may contribute to the cytotoxic effects of 1-nitro-9-aminoacridines besides previously found ability of these agents to form interstrand DNA cross-links.
通过碱性蔗糖梯度离心法发现，利达克林及1-硝基-9-氨基吖啶的其他七种抗肿瘤和细胞毒性衍生物可诱导HeLa S3细胞中的DNA单链断裂。诱导产生的DNA损伤具有非随机性质。如新霉素（一种可阻止DNA修复切口步骤的抗生素）实验所示，利达克林诱导产生的一些DNA断裂可能是在修复过程中由核酸内切酶切割产生的。在碱性蔗糖梯度上观察到的其他利达克林诱导的DNA断裂可能源于DNA中的碱不稳定位点。大多数此类位点在短暂暴露于碱后似乎会转化为断裂。已发现1-硝基-9-氨基吖啶对DNA的损伤程度与这些化合物对HeLa S3细胞 的细胞毒性活性相关。此外，根据对[3H]胸腺嘧啶核苷抗羟基脲（HU）掺入DNA的刺激作用判断，利达克林和其他衍生物似乎可诱导HeLa S3细胞中的DNA修复合成。所研究的这些试剂在产生对DNA修复的显著刺激所需的浓度上有所不同，而对于所有检测的衍生物，这种效应的最大水平相似。前者的值与这些化合物的细胞毒性活性相关，似乎反映了1-硝基-9-氨基吖啶对DNA的总体损伤程度。在用利达克林长时间孵育细胞的过程中或在无药物培养基中对细胞进行孵育后，DNA修复合成的刺激作用会逐渐停止。这种孵育后结果还会导致如碱性蔗糖离心法所观察到的DNA单链断裂逐渐积累。因此，HeLa S3细胞无法有效去除1-硝基-9-氨基吖啶造成的DNA损伤，尽管该药物的作用会暂时激活一些修复机制。报告的结果表明，除了先前发现的这些试剂形成链间DNA交联的能力外，总体DNA损伤可能也会导致1-硝基-9-氨基吖啶的细胞毒性作用。
