Topoisomerase II inhibitor 3 (Compound 6 h) is an acridone derivative acting as a Type II DNA topoisomerase (topo II) inhibitor. It specifically targets topo IIα/β subtypes, with IC50 values of 0.17 μM for topo IIα and 0.23 μM for topo IIβ, causing significant DNA damage and inducing apoptosis by triggering the loss of mitochondrial membrane potential [1].

Topoisomerase II inhibitor 3 (Compound 6 h) is a potent topo IIα/β inhibitor, causing significant DNA damage and apoptosis by disrupting mitochondrial membrane potential. It is effective against topo IIα and IIβ with IC50 values of 0.17 μM and 0.23 μM, respectively, and induces dose-dependent double-strand breaks (DSBs) in DNA. Anti-proliferative activity was evaluated across various cell lines, including human breast cancer MDA-MB-231, lung cancer A549, acute myelogenous leukemia KG1, and rat myocardial H9C2 cells, at 100 μM over 12 hours. The most notable effects were observed in MDA-MB-231 cells (IC50: 0.42 μM), A549 cells (IC50: 1.10 μM), and KG1 cells (IC50: 0.15 μM), while H9C2 cells were much less affected (IC50 >20 μM). Further analysis confirmed substantial mitochondrial membrane potential (MMP) loss in MDA-MB-231 cells treated with 0.5-10 μM for 24 hours.