Antony Smitha, Agama Keli K, Miao Ze-Hong, Takagi Kazutaka, Wright Mollie H, Robles Ana I, Varticovski Lyuba, Nagarajan Muthukaman, Morrell Andrew, Cushman Mark, Pommier Yves
Laboratory of Molecular Pharmacology, National Cancer Institute, NIH, Bethesda, MD 20892-4255, USA.
Cancer Res. 2007 Nov 1;67(21):10397-405. doi: 10.1158/0008-5472.CAN-07-0938.
Camptothecin (CPT) derivatives are effective anticancer drugs, especially against solid tumors. As CPTs are chemically unstable and have clinical limitations, we have synthesized indenoisoquinolines as novel topoisomerase I (Top1) inhibitors. We presently report two indenoisoquinoline derivatives, NSC 725776 and NSC 724998, which have been selected for therapeutic development. Both are potent Top1 inhibitors and induce Top1 cleavage at unique genomic positions compared with CPT. Consistent with Top1 poisoning, protein-linked DNA breaks were detected in cells treated with NSC 725776 and NSC 724998 at nanomolar concentrations. Those drug-induced protein-linked DNA breaks persisted longer after drug removal than those produced by CPT. Studies in human cells in culture show that NSC 725776 and NSC 724998 exert antiproliferative activity at submicromolar concentrations. Furthermore, NSC 725776 and NSC 724998 show cross-resistance in cells deficient or silenced for Top1, which is consistent with their selective Top1 targeting. Similar to other known Top1 inhibitors, NSC 725776-treated and NSC 724998-treated cells show an arrest of cell cycle progression in both S and G(2)-M and a dependence on functional p53 for their cytotoxicity. Dose-dependent gamma-H2AX foci formation was readily observed in cells treated with NSC 725776 and NSC 724998. These gamma-H2AX foci were detectable at pharmacologically relevant doses for up to 24 h and thus could be used as biomarkers for clinical trials (phase 0).
喜树碱（CPT）衍生物是有效的抗癌药物，尤其对实体瘤有效。由于CPT在化学上不稳定且存在临床局限性，我们合成了茚并异喹啉作为新型拓扑异构酶I（Top1）抑制剂。我们目前报告了两种茚并异喹啉衍生物，NSC 725776和NSC 724998，它们已被选用于治疗开发。两者都是强效的Top1抑制剂，与CPT相比，能在独特的基因组位置诱导Top1切割。与Top1中毒一致，在以纳摩尔浓度用NSC 725776和NSC 724998处理的细胞中检测到蛋白质连接的DNA断裂。这些药物诱导的蛋白质连接的DNA断裂在药物去除后持续的时间比CPT产生的断裂更长。在培养的人类细胞中的研究表明，NSC 725776和NSC 724998在亚微摩尔浓度下发挥抗增殖活性。此外，NSC 725776和NSC 724998在Top1缺陷或沉默的细胞中显示出交叉耐药性，这与其选择性靶向Top1一致。与其他已知的Top1抑制剂类似，用NSC 725776和NSC 724998处理的细胞在S期和G（2）-M期均显示细胞周期进程停滞，并且其细胞毒性依赖于功能性p53。在用NSC 725776和NSC 724998处理的细胞中很容易观察到剂量依赖性的γ-H2AX焦点形成。这些γ-H2AX焦点在药理学相关剂量下长达24小时均可检测到，因此可作为临床试验（0期）的生物标志物。
