Topoisomerase II inhibitor 3 (Compound 6 h) is an acridone derivative that acts as a Type II DNA topoisomerase (topo II) inhibitor. It specifically inhibits the topo IIα/β subtypes, with an IC50 value of 0.17 μM for topo IIα and 0.23 μM for topo IIβ. This compound elicits significant DNA damage and induces apoptosis by triggering the loss of mitochondrial membrane potential [1].

Topoisomerase II inhibitor 3 (Compound 6 h) serves as a potent inhibitor for topo IIα/β, causing significant DNA damage and apoptosis through the disruption of mitochondrial membrane potential. This compound is effective against both the topo IIα and IIβ subtypes, with IC50 values of 0.17 μM and 0.23 μM, respectively. It also induces double-strand breaks (DSBs) in DNA in a dose-dependent manner. In terms of anti-proliferative activity, it has been 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 a concentration of 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), KG1 cells (IC50: 0.15 μM), whereas H9C2 cells were significantly less affected (IC50 >20 μM). Further apoptosis analysis in MDA-MB-231 cells, treated with concentrations ranging from 0.5-10 μM for 24 hours, confirmed the substantial loss of mitochondrial membrane potential (MMP).