TopoisomeraseI-IN-18, a derivative of Thiosemicarbazide, functions as a Topoisomerase I inhibitor, disrupting DNA synthesis and transcription. It suppresses tumor cell proliferation by inducing S phase cell cycle arrest. Additionally, it enhances mitochondria-mediated apoptosis (apoptosis), evidenced by inhibited cell migration and increased intracellular reactive oxygen species (ROS). TopoisomeraseI-IN-18 upregulates p53 protein expression, γH2AX phosphorylation, Bax expression, downregulates Bcl-2 expression, and activates the caspase cascade. This compound is applicable for lung cancer research.

Topoisomerase I-IN-18 (Compound 11d) exhibits varying antiproliferative activities across tested cancer cell lines, with IC 50 values of 59.11 μM in MCF-7, 67.63 μM in HepG-2, 44.6 μM in SGC7901, and 8.06 μM in A549, while showing minimal toxicity to normal HK-2 cells. At concentrations of 1-10 μM, Topoisomerase I-IN-18 effectively inhibits Topo I-mediated DNA supercoil relaxation in a dose-dependent manner. When used as a HY-178321 (UNC10088) Topoisomerase I inhibitor, it induces dose-dependent DNA double-strand breaks in A549 cells within 48 hours. Additionally, Topoisomerase I-IN-18 (1-10 μM, up to 48 hours) significantly hinders A549 cell migration and proliferation, suggesting potential anti-metastatic characteristics. At concentrations of 4-16 μM, it generates reactive oxygen species (ROS), induces apoptosis, and causes dose-dependent S phase arrest in A549 cells, accompanied by a decrease in G0/G1 and G2/M populations, a significant increase in γ-H2AX phosphorylation, and modulation of apoptosis-related proteins, including upregulation of p53, Bax, caspase-3, caspase-9, and downregulation of Bcl-2. Topoisomerase I-IN-18 is identified as a P-glycoprotein (P-gp) substrate and may inhibit cytochrome P450 enzymes (CYP1A2, CYP2C19, CYP2D6, and CYP3A4).