Discovery and Mechanistic Study of Tailor-Made Quinoline Derivatives as Topoisomerase 1 Poison with Potent Anticancer Activity

To overcome chemical limitations
of camptothecin (CPT), we report
design, synthesis, and validation of a quinoline-based novel class
of topoisomerase 1 (Top1) inhibitors and establish that compound 28 (N-(3-(1H-imidazol-1-yl)­propyl)-6-(4-methoxyphenyl)-3-(1,3,4-oxadiazol-2-yl)­quinolin-4-amine)
exhibits the highest potency in inhibiting human Top1 activity with
an IC50 value of 29 ± 0.04 nM. Compound 28 traps Top1–DNA cleavage complexes (Top1ccs) both in the in
vitro cleavage assays and in live cells. Point mutation of Top1-N722S
fails to trap compound 28-induced Top1cc because of its
inability to form a hydrogen bond with compound 28. Unlike
CPT, compound 28 shows excellent plasma serum stability
and is not a substrate of P-glycoprotein 1 (permeability glycoprotein)
advancing its potential anticancer activity. Finally, we provide evidence
that compound 28 overcomes the chemical instability of
CPT in human breast adenocarcinoma cells through generation of persistent
and less reversible Top1cc-induced DNA double-strand breaks as detected
by γH2AX foci immunostaining after 5 h of drug removal.

为克服喜树碱（camptothecin, CPT）的化学局限性，本研究报道了一类基于喹啉的新型拓扑异构酶1（topoisomerase 1, Top1）抑制剂的设计、合成与验证，并证实化合物28（N-(3-(1H-咪唑-1-基)丙基)-6-(4-甲氧基苯基)-3-(1,3,4-恶二唑-2-基)喹啉-4-胺）在抑制人Top1活性方面活性最强，其半抑制浓度（IC50）为29 ± 0.04 nM。化合物28可在体外切割实验及活细胞中捕获Top1-DNA切割复合物（Top1ccs）。Top1-N722S的点突变无法介导化合物28诱导的Top1cc捕获，究其原因在于该突变体无法与化合物28形成氢键。与CPT不同，化合物28展现出优异的血浆血清稳定性，且并非P-糖蛋白1（P-glycoprotein 1, 通透性糖蛋白）的底物，助力其潜在抗癌活性的开发。最后，本研究证实化合物28可通过生成持续性、低可逆性的Top1cc诱导DNA双链断裂——该效应可在药物移除5小时后通过γH2AX焦点免疫染色检测到——从而克服CPT在人乳腺腺癌细胞中的化学不稳定性。