Abstract：
The development of novel topoisomerase I (TOP1) inhibitors is crucial for overcoming the drawbacks and limitations of current TOP1 poisons. Here, we identified two potential TOP1 inhibitors, namely, FTY720 (a sphingosine 1-phosphate antagonist) and COH29 (a ribonucleotide reductase inhibitor), through experimental screening of known active compounds. Biological experiments verified that FTY720 and COH29 were nonintercalative TOP1 catalytic inhibitors that did not induce the formation of DNA-TOP1 covalent complexes. Molecular docking revealed that FTY720 and COH29 interacted favorably with TOP1. Molecular dynamics simulations revealed that FTY720 and COH29 could affect the catalytic domain of TOP1, thus resulting in altered DNA-binding cavity size. The alanine scanning and interaction entropy identified Arg536 as a hotspot residue. In addition, the bioinformatics analysis predicted that FTY720 and COH29 could be effective in treating malignant breast tumors. Biological experiments verified their antitumor activities using MCF-7 breast cancer cells. Their combinatory effects with TOP1 poisons were also investigated. Further, FTY720 and COH29 were found to cause less DNA damage compared with TOP1 poisons. The findings provide reliable lead compounds for the development of novel TOP1 catalytic inhibitors and offer new insights into the potential clinical applications of FTY720 and COH29 in targeting TOP1.
摘要：
新型拓扑异构酶I(TOP1)抑制剂的开发对于克服现有TOP1毒物的缺点和限制是至关重要的。这里,我们确定了两种潜在的TOP1抑制剂，即,FTY720（一种1-磷酸鞘氨醇拮抗剂）和COH29（一种核糖核苷酸还原酶抑制剂），通过实验筛选已知的活性化合物。生物学实验证实，FTY720和COH29是非嵌入性TOP1催化抑制剂，不会诱导DNA-TOP1共价复合物的形成。分子对接显示FTY720和COH29与TOP1具有良好的相互作用。分子动力学模拟表明，FTY720和COH29可能会影响TOP1的催化结构域，从而导致DNA结合腔大小的改变。丙氨酸扫描和相互作用熵将Arg536鉴定为热点残基。此外,生物信息学分析预测FTY720和COH29可有效治疗恶性乳腺肿瘤。使用MCF-7乳腺癌细胞的生物学实验验证了它们的抗肿瘤活性。还研究了它们与TOP1毒物的组合效应。Further,与TOP1毒物相比，发现FTY720和COH29引起的DNA损伤较少。这些发现为开发新的TOP1催化抑制剂提供了可靠的先导化合物，并为FTY720和COH29靶向TOP1的潜在临床应用提供了新的见解。
