Department of Pharmacology, School of Medical Sciences, University of New South Wales, Sydney, Australia.
PLoS One. 2011;6(9):e25150. doi: 10.1371/journal.pone.0025150. Epub 2011 Sep 22.
DNA topoisomerase I (Top1) is over-expressed in tumour cells and is an important target in cancer chemotherapy. It relaxes DNA torsional strain generated during DNA processing by introducing transient single-strand breaks and allowing the broken strand to rotate around the intermediate Top1-DNA covalent complex. This complex can be trapped by a group of anticancer agents interacting with the DNA bases and the enzyme at the cleavage site, preventing further topoisomerase activity. Here we have identified novel Top1 inhibitors as potential anticancer agents by using a combination of structure- and ligand-based molecular modelling methods. Pharmacophore models have been developed based on the molecular characteristics of derivatives of the alkaloid camptothecin (CPT), which represent potent antitumour agents and the main group of Top1 inhibitors. The models generated were used for in silico screening of the National Cancer Institute (NCI, USA) compound database, leading to the identification of a set of structurally diverse molecules. The strategy is validated by the observation that amongst these molecules are several known Top1 inhibitors and agents cytotoxic against human tumour cell lines. The potential of the untested hits to inhibit Top1 activity was further evaluated by docking into the binding site of a Top1-DNA complex, resulting in a selection of 10 compounds for biological testing. Limited by the compound availability, 7 compounds have been tested in vitro for their Top1 inhibitory activity, 5 of which display mild to moderate Top1 inhibition. A further compound, found by similarity search to the active compounds, also shows mild activity. Although the tested compounds display only low in vitro antitumour activity, our approach has been successful in the identification of structurally novel Top1 inhibitors worthy of further investigation as potential anticancer agents.
DNA 拓扑异构酶 I（Top1）在肿瘤细胞中过度表达，是癌症化疗的重要靶点。它通过引入瞬时单链断裂来松弛 DNA 处理过程中产生的扭转应变，并允许断裂的链围绕中间的 Top1-DNA 共价复合物旋转。该复合物可以被一组与 DNA 碱基和酶在切割位点相互作用的抗癌剂捕获，从而阻止进一步的拓扑异构酶活性。在这里，我们通过使用结构和基于配体的分子建模方法相结合，鉴定了新型 Top1 抑制剂作为潜在的抗癌剂。基于生物碱喜树碱（CPT）衍生物的分子特征开发了药效团模型，这些衍生物是有效的抗肿瘤剂和主要的 Top1 抑制剂。生成的模型用于美国国立癌症研究所（NCI）化合物数据库的计算机筛选，导致鉴定了一组结构多样的分子。该策略通过观察到其中包括几种已知的 Top1 抑制剂和对人肿瘤细胞系具有细胞毒性的试剂得到验证。通过对接进入 Top1-DNA 复合物的结合位点进一步评估未经测试的命中物抑制 Top1 活性的潜力，从而选择了 10 种化合物进行生物学测试。由于化合物的可用性有限，仅对 7 种化合物在体外进行了 Top1 抑制活性测试，其中 5 种显示出轻度至中度的 Top1 抑制作用。通过与活性化合物的相似性搜索发现的进一步化合物也显示出轻度活性。尽管测试的化合物在体外仅显示出低抗肿瘤活性，但我们的方法成功地鉴定了结构新颖的 Top1 抑制剂，值得进一步研究作为潜在的抗癌剂。
